ARTICLE | doi:10.20944/preprints201808.0272.v1
Subject: Life Sciences, Microbiology Keywords: Staphylococcus aureus, meat, raw milk, antibiotics; antibiotic resistance genes
Online: 15 August 2018 (13:58:11 CEST)
Background: Staphylococcus aureus (S. aureus) occasionally threatens the life of the host as a persistent pathogen even though it is normal flora of humans and animals. We characterized drug resistance in S. aureus isolated from animal carcasses and milk samples from the abattoirs and dairy farms in the Eastern Cape Province. Methods: A 1000 meat swab samples and 200 raw milk samples were collected from selected abattoirs and dairy farms in the Eastern Cape Province, South Africa. S. aureus was isolated and positively identified using biochemical tests and confirmed by molecular methods. Antibiotic susceptibility test against 14 different antibiotics was performed against all isolates. Antibiotic resistance genes were also detected. Results: Of the 1200 samples collected, 134 (11.2%) samples were positive for S. aureus. Resistance ranged from 71.6% for penicillin G to 39.2% for tetracycline. Resistance gene (blaZ) was detected in 13 (14.9%), while msrA was found in 31 (52.5%) of S. aureus isolates. Conclusions: The present result shows the potential dissemination of multidrug-resistant S. aureus strains in the dairy farms and abattoirs in the Eastern Cape. Therefore, this implies that the organism may rapidly spread through food and pose serious public health risk
ARTICLE | doi:10.20944/preprints202103.0024.v1
Subject: Life Sciences, Biochemistry Keywords: Methicillin-resistant Staphylococcus aureus; Multidrug resistance; mecA gene; Frozen chicken meat; Bangladesh
Online: 1 March 2021 (13:56:33 CET)
Infections by methicillin-resistant Staphylococcus aureus (MRSA) are continuously expanding within the community. Chicken meat is usually contaminated by MRSA, and this contaminated chicken meat is an important source of foodborne infections in humans. In this study, a cross-sectional supershop survey was conducted to determine the prevalence and antimicrobial resistance pattern of MRSA in 113 domestic frozen chicken meat samples purchased from nine branded supershops available in five divisional megacities of Bangladesh. The study also focused on the determination of methicillin resistance gene in MRSA isolates. S. aureus was identified by standard culture-based and molecular methods, and subjected to antimicrobial susceptibility testing. MRSA was screened by cefoxitin disk diffusion test. Methicillin resistance gene was identified by PCR. Of samples, 54.9% were positive for S. aureus, and, of these, 37.1% isolates were identified as MRSA. All the isolates were multidrug resistant (MDR): 52.2% were resistant to 6−8 antimicrobial classes, and 47.8% isolates to 9−12 classes. Three (3.2%) isolates of S. aureus were possible extensively drug resistant. The highest rates of resistance were observed against cefoxitin (100%), followed by nalidixic acid, ampicillin and oxacillin (97.7%), colistin (91.3%), amoxicillin-clavulanic acid and amoxicillin (87%), penicillin-G and cloxacillin (82.6%), oxytetracycline (78.3%) and cefixime (73.9%). Screening of methicillin resistance gene revealed that 43.5% isolates of MRSA were positive for mecA gene. The high prevalence of MDR MRSA in frozen chicken meat samples in this study emphasizes the need for better sanitary education of food handlers in hygienic practices focusing on their potential role as reservoirs and spreaders of MRSA.
REVIEW | doi:10.20944/preprints202301.0045.v1
Subject: Medicine & Pharmacology, Cardiology Keywords: Infective Endocarditis, Staphylococcus Aureus Infection, Staphylococcus Aureus Immunity, Staphylococcus Aureus Cytotoxin, Biofilm resistance.
Online: 4 January 2023 (02:43:20 CET)
Staphylococci sp. have become the primary pathogens implicated in infective endocarditis, especially within high-income nations. Coupled with the increasing burden of healthcare with aging populations and the protracted course the infections may take, these infections contribute to a significant challenge for healthcare. A systematic review was conducted using relevant search criteria from PubMed, Ovid’s version of MEDLINE, and EMBASE, and data were tabulated from randomized controlled trials (RCT), observational cohort studies, meta-analysis, and basic research articles. The review was registered with the OSF register of systematic reviews and followed the PRISMA reporting guidelines. 35 studies met the inclusion criteria and were included in the final systematic review. The role of Staphylococcus aureus and its interaction with the protective shield and host protection functions is identified and highlighted in several studies. The interaction between infective endocarditis pathogens, vascular endothelium, and blood constituents is also explored giving rise to the potential use of antiplatelets as preventative and/or curative agents. Several factors allow Staphylococcus aureus infections to proliferate within the host with numerous promoting and perpetuating agents. The complex interaction with the hosts' innate immunity also potentiates its virulence. Ameliorating these molecular pathways may serve as a therapeutic avenue for the prevention and treatment of these infections in the near future.
Subject: Life Sciences, Microbiology Keywords: branched-chain amino acid; ion-pair reversed-phase liquid chromatography; mastitis; dairy cow; staphylococcus aureus
Online: 18 September 2019 (16:51:46 CEST)
The early diagnosis of mastitis represents an essential factor for a prompt detection of the animal for further actions. In fact, if not culled, infected cows must be segregated from the milking herd and milked last, or milked with separate milking units. Besides microbiological analysis, the somatic cell count (SCC) commonly used as predictor of intramammary infection, frequently lead to a misclassification of milk samples. To overcome these limitations, more specific biomarkers are continuously evaluated. Total amino acid content increases significantly in mastitic milk compared to normal one. Bovine mastitis can arise as a result of infection of the mammary gland by Staphylococcus aureus. Multiplication of this bacterium within the mammary gland is required for infection to persist. S. aureus requires branched-chain amino acids (BCAAs: isoleucine, leucine, valine) for protein synthesis, branched-chain fatty acids synthesis and environmental adaptation by responding to their availability via transcriptional regulators. The importance of BCAAs for S. aureus physiology necessitates that it either synthesize them or scavenge them from the environment. Increase of BCAAs in composite milk has been postulated to be linked to mammary infection by S. aureus. In the present work, we demonstrated, by a direct ion-pairing reversed-phase method based on the use of the evaporative light-scattering detector (IP-RP-HPLC-ELSD), applied to 65 composite cow milk samples, a correlation between the concentration of isoleucine and leucine and S. aureus load.
REVIEW | doi:10.20944/preprints202212.0348.v1
Subject: Medicine & Pharmacology, General Medical Research Keywords: antibiotic; biofilm; infections; Staphylococcus aureus; therapeutic antibiofilm
Online: 20 December 2022 (03:24:37 CET)
Staphylococcus aureus is a microorganism frequently associated with implant-related infections, owing to its ability to produce biofilms. These infections are difficult to treat because antimicrobials must cross the biofilm to effectively inhibit bacterial growth. Although some antibiotics can penetrate the biofilm and reduce the bacterial load, it is important to understand that the results of routine sensitivity tests are not always valid for interpreting the activity of different drugs. In this review, a broad discussion on the genes involved in biofilm formation, quorum sensing, and antimicrobial activity in monotherapy and combination therapy is presented that should benefit researchers engaged in optimizing the treatment of infections associated with S. aureus biofilms.
ARTICLE | doi:10.20944/preprints202301.0033.v2
Subject: Life Sciences, Microbiology Keywords: Staphylococcus aureus; clinical mastitis; antibiotic resistance (AR) prevalence; AR phenotype; AR genotype; recent trend
Online: 22 January 2023 (06:50:19 CET)
This study was aimed to examine the recent trends of antibiotic resistance (AR) prevalence in Staphylococcus aureus isolated from milk of animals with clinical mastitis in areas of the Abruzzo and Molise regions in central Italy. Fifty-four S. aureus isolates could be obtained from routine testing for clinical mastitis agents carried out in the author institution in years 2021 and 2022. These were analyzed for phenotypic resistance to eight antibiotics recommended for testing by European norms and belonging to the antibiotic classes used for mastitis treatment in milk producing animals. Moreover, the presence of 14 transferable genetic determinants encoding resistance to the same antibiotics was analyzed by qPCR tests developed in this study. Phenotypic resistance to non-β-lactams was infrequent, with only one 2022 isolate resistant to clindamycin. However, low level resistance to the β-lactam cefoxitin was observed in 59.2% isolates in both years making these isolates classifiable as methicillin resistant. The AR genotypes detected were blaZ gene (50% 2021 isolates and 44.4% 2022 isolates), ermC/T- aphA3-blaZ (one 2021 isolate), ant6-ermC/T-aphA3-blaZ (one 2021 isolate), ermB-blaZ (one 2022 isolate) and mecA-mph (one 2022 isolate). An interview to the veterinarians who conferred the samples, regarding antimicrobials prescribed for mastitis treatment and criteria of usage, indicated a possible causal relation with the AR test results. The low prevalence of AR genotypes, not increasing in time, most probably reflecting the reported management of antibiotic therapies in farms. However, the frequently observed cefoxitin resistance needs to be explained genotypically, further monitored and limited by modifying antibiotic usage practices. The identification of a mecA positive isolate in 2022 suggests to investigate further if this genotype is emerging locally.
ARTICLE | doi:10.20944/preprints201911.0063.v2
Subject: Life Sciences, Microbiology Keywords: contamination; pathogens; bacteria; escherichia coli; staphylococcus aureus; hygiene; shigella; salmonella; milk processing; foodborne infection; cfu
Online: 13 November 2019 (10:37:25 CET)
Pasteurized milks are still causing food borne illness. Milk contamination can occur at any stage from its way from cow to our tables. Usually milk is pure and sterile when produced in udder of a healthy cow. Like humans, cow are reservoirs of bacteria which are harmless to humans and some cows can harbour few bacteria that are harmful to humans even though they are not harmful to the cow. Milk can be contaminated during or after milking. Also, cow feeds can be contaminated with mycotoxins such as aflatoxins produced by the fungi, Aspergillus flavus. Four types of aflatoxins are known which are; aflatoxin B1, B2, G1, G2. Cows comsuming feeds contaminated with aflatoxin B1 leads to secretion in the milk of aflatoxin M1 and M2 causing aflatoxicosis. Microbial contamination of milk and dairy products is a universal problem and foodborne infections accounting for 20 million cases annually in the world have been identified as an important public health and economic problem in developed as well as developing nations. The main objective of this study was to determine milk microbial quality in Kicukiro district. The specific objectives are to identify bacteria pathogens in milk collected in Kicukiro district, to compare milk quality among sectors of Kicukiro district, to compare milk processed by industries and home-processed milk. The methodology employed in this research was cross-sectional and experimental as the study began with collection of raw data and went through laboratory analysis from July–August, 2018. The findings showed that 59.56% of the milk fell within Grade I – Grade III (< 200,000 ≤ 2,000,000 cfu/ml) and 40.42 % of the milk samples were not within the acceptable limit of total count quality as per COMESA and EAS, non-lactobacilli and fungi were present in most samples as examined through microscope and no Staphylococcus aureus was present in any sample as examined by catalase and coagulase tests.
ARTICLE | doi:10.20944/preprints202108.0451.v1
Subject: Life Sciences, Microbiology Keywords: Staphylococcus aureus; antibiotic resistance; biofilms; antimicrobial peptides; ciprofloxacin; combined effect
Online: 23 August 2021 (14:21:08 CEST)
Staphylococcus aureus can develop resistance by mutation, tranfection or biofilm formation. Resistance was induced in S. aureus by growth in sub-inhibitory concentrations of ciprofloxacin for 30 days. The ability of the antimicrobials to disrupt biofilms was determined using crystal violet and live/dead staining. Effects on the cell membranes of biofilm cells was evaluated by measuring release of dyes and ATP and nucleic acids. S. aureus did not develop resistance to the AMPs but resistance increased to ciprofloxacin by 128 times after 30 passages. Only peptides reduced biofilms of ciprofloxacin resistant cells. The antibiofilm effect of melimine with ciprofloxacin was more (27%) than with melimine alone at 1X MIC (p < 0.001). Similarly, at 1X MIC the combination of Mel4 and ciprofloxacin produced more (48%) biofilm disruption than Mel4 alone (p < 0.001). Combinations of either of the peptides with ciprofloxacin at 2X MIC released 66 nM ATP, more than either peptide alone (p 0.005). At 2X MIC, only melimine in combination with ciprofloxacin released DNA/RNA which was 3 times more than released by melimine alone (p = 0.043). These results suggest the potential use of melimine and Mel4 with conventional antibiotics for the treatments of S. aureus biofilms.
ARTICLE | doi:10.20944/preprints202207.0105.v1
Subject: Medicine & Pharmacology, Veterinary Medicine Keywords: Melaleuca armillaris; essential oil; erythromycin; Staphylococcus aureus; synergism; mastitis
Online: 7 July 2022 (04:05:55 CEST)
Staphylococcus aureus frequently causes subclinical mastitis around the world with high impact in milk industry and public health. Essential oils (EO) are recognized antimicrobials that can be synergistic with antibiotics. The main objective of this study was evaluating the essential oil (EO) of Melaleuca armillaris as an adjuvant of erythromycin (ERY) for the alternative treatment of bovine mastitis caused by S. aureus. The Minimum Inhibitory and Bactericidal Concentrations (MIC and MBC) of EO, ERY, and its combinations were established against S. aureus at different pHs (7.4, 6.5 and 5.0), emulating extra and intracellular conditions. Sensible (N=3) and resistant (N=3) strains to ERY and S. aureus ATCC 29213 as control were used. Math models were applied to described the antibacterial activity of EO and combinations EO-ERY. The EO was bactericidal against all the strains independently of the pH with a slightly improvement in acid conditions. The synergism between EO and ERY was estimated by the Fractional Inhibitory Concentration Index (FIC) and by mathematical modeling of the bacterial killing data. Synergism was observed with ERY, where combinations had bactericidal activity also even with pH modification. M. armillaris EO is an interesting adjuvant for ERY, being a promissory option for further analysis of intracellular efficacy against S. aureus.
REVIEW | doi:10.20944/preprints202010.0412.v1
Subject: Life Sciences, Biochemistry Keywords: Human Osteoblast; MG-63; Staphylococcus aureus; internalization mechanisms
Online: 20 October 2020 (12:08:32 CEST)
Bacterial internalization is a strategy that non-intracellular microorganisms use to escape the host immune system and survive inside the human body. Among bacteria species, Staphylococcus aureus showed ability to interact and infect osteoblasts causing osteomyelitis as well as bone and joint infection, while also becoming increasingly resistant to antibiotic therapy and a reservoir of bacteria that can make the infection difficult to cure. Despite being a serious issue in orthopedic surgery, little is known about the mechanisms that allow bacteria to enter and survive inside the osteoblasts, also due to the lack of consistent experimental models. In this review, we describe the current knowledge about S. aureus internalization mechanisms and various aspects of the interaction between bacteria and osteoblasts (e.g. best experimental conditions, bacteria-induced damages and immune system response), focusing on studies performed using the MG-63 osteoblastic cell line, so far the best model for the study of this phenomenon.
ARTICLE | doi:10.20944/preprints202106.0149.v1
Subject: Life Sciences, Biochemistry Keywords: vaccine; Staphylococcus aureus; T cell response; mastitis; bovine
Online: 7 June 2021 (07:54:02 CEST)
Staphylococcus aureus mastitis remains a major challenge for dairy farming. Here, 24 mice were immunized and divided into four groups: G1: control; G2: Granulocyte Macrophage Colony-Stimulating Factor (GM-CSF) DNA vaccine; G3: F0F1 ATP synthase subunit α (SAS), succinyl-diaminopimelate (SDD), and cysteinyl-tRNA synthetase (CTS) recombinant proteins; and G4: SAS+SDD+CTS plus GM-CSF DNA vaccine. The lymphocyte subpopulations and the intracellular interleukin-17A (IL-17A) and interferon-γ production in the draining lymph node cells were immunophenotyped by flow cytometry. The immunophenotyping and lymphocyte proliferation was determined in spleen cells cultured with and without S. aureus stimulus. Immunization with S. aureus recombinant proteins generated memory cells in draining lymph nodes. Immunization with the three recombinant proteins plus GM-CSF DNA led to an increase in the percentage of IL-17A+ cells among overall CD44+ (memory), T CD4+, CD4+ T CD44+ CD27-, γδ TCR, γδ TCR+ CD44+ CD27+ and TCRVγ4+ cells. Vaccination with S. aureus recombinant proteins associated with GM-CSF DNA vaccine downregulates TH2 immunity. Immunization with the three recombinant proteins plus the GM-CSF DNA led to a proliferation of overall memory T, CD4+ and CD4+ TEM cells upon S. aureus stimulus. This approach fostered type 3 immunity, suggesting the development of a protective immune response against S. aureus.
CASE REPORT | doi:10.20944/preprints202212.0128.v1
Subject: Medicine & Pharmacology, Cardiology Keywords: infective endocartidis; methicillin-resistant Staphylococcus aureus; mitral valve
Online: 7 December 2022 (10:47:17 CET)
Infective endocarditis (IE) is a life-threatening condition caused by infection within the endocardium of the heart, and commonly involves the valves. The subsequent cascading inflammation leads to the appearance of a highly friable thrombus that is large enough to become lodged within the heart chambers. As a result, fever, fatigue, heart murmurs, and embolization phenomena may be seen in patients with IE. Embolization results in the seeding of bacteria, and obstruction of circulation, causing cell ischemia. Of concern, bacteria with the potential to gain pan-drug resistance, such as methicillin-resistant Staphylococcus aureus (MRSA), are increasingly being identified as the causative agent of IE in hospitals and among intravenous drug abusers. We retrospectively reviewed de-identified clinical data to summarize the clinical course of a patient with MRSA isolated using an automated blood culture system. At the time of presentation, the patient showed a poor consciousness level, and the calculated Glasgow scale was 10/15. A high-grade fever with circulatory shock indicated an occult infection, and a systolic murmur was observed with peripheral signs of embolization. This case demonstrated the emerging threat of antimicrobial resistance in the community, and revealed clinical findings of IE that may be helpful to clinicians for the early recognition of the disease. The management of such cases requires a multi-specialty approach, which is not widely available in small island developing states like the Maldives.
ARTICLE | doi:10.20944/preprints202211.0159.v1
Subject: Medicine & Pharmacology, Nursing & Health Studies Keywords: care wound; wound diabetic; honey; staphylococcus aureus
Online: 9 November 2022 (01:07:32 CET)
Background : Diabetic wounds are very easy to experience complications in the form of infection due to bacterial invasion, and sugar conditions blood which tall encourage the growth of bacteria.Bacteria that can cause infection in diabetic wounds wrong one is staphylococci aureus . Wound diabetes can treated with honey. Honey contains antibacterial , antioxidant and hydrogen peroxide properties that help kill bacteria dangerous. Objective : The purpose of this study was to determine the effect of the wound dressing contains honey against bacterial colonization Staphylococcus aureus on wound diabetic . Methods : The research design used is pre-experimental with o ne-group pre-test and post-test design . Sampling method using consecutive sampling as many as 7 respondents. Results : Analysis data use test dependent t-test and obtained score p value 0.000 ( p value < = 0.05), so could concluded there is influence care wound use honey to colonization bacteria Staphylococcus aureus in wounds diabetic Diabetes Mellitus patients in the region work Public health center Banjarmasin . Conclusion : best Use honey as product care wound because nature the antibacterial which could prevent infection and speed up process healing wound .
ARTICLE | doi:10.20944/preprints202109.0193.v1
Subject: Life Sciences, Microbiology Keywords: bioassay; chromatography; folkloric medicine; methicillin-resistant Staphylococcus aureus; Senna alata; spectroscopy
Online: 13 September 2021 (07:21:28 CEST)
Senna alata (Linn) Roxb. plant is widely used to manage various infections in folkloric medicine. Methicillin-resistant Staphylococcus aureus (MRSA) infection continues to be a major global public health problem. This study aims to investigate the bioactive components of S. alata leaves active against MRSA. The leaves of S. alata were sequentially extracted and fractionated using standard methods and screened for activities against MRSA. The diethyl ether active thin layer chromatography (TLC) spot was subjected to infrared (IR) and gas chromatography-mass spectroscopic (GC-MS) studies. The aqueous extract and diethyl ether fraction of S. alata leaves elicited the highest activity against the MRSA. The GC-MS analysis of the fraction produced 15 eluates; only the sub-fraction 13 was effective. The TLC analysis of the sub-fraction 13 revealed three spots; only the second spot produced activity. The GC-MS result of the spot showed six peaks. The spectral results for peak 3 match the data from the IR study suggestive of 9-octadecenoic acid methyl ester. Senna alata leaves possess bioactive compounds closely related to 9-octadecenoic acid methyl ester with potent antibacterial activity against MRSA.
ARTICLE | doi:10.20944/preprints201804.0078.v1
Subject: Life Sciences, Microbiology Keywords: membrane fatty acids composition; Staphylococcus aureus; staphyloxanthin; membrane fluidity; metabolic regulation
Online: 6 April 2018 (11:37:53 CEST)
Fatty acids play a major role in determining membrane biophysical properties. Staphylococcus aureus produces branched-chain fatty acids (BCFAs) and straight-chain fatty acids (SCFAs), and can incorporate exogenous SCFAs and straight-chain unsaturated fatty acids (SCUFAs). Many S. aureus strains produce the triterpenoid pigment staphyloxanthin, and the balance of BCFAs, SCFAs and staphyloxanthin determines membrane fluidity. Here, we investigated the relationship of fatty acid and carotenoid production in S. aureus using a pigmented strain (Pig1), its carotenoid-deficient mutant (Pig1ΔcrtM) and the naturally non-pigmented Staphylococcus argenteus that lacks carotenoid biosynthesis genes and is closely related to S. aureus. Fatty acid compositions in all strains were similar under a given condition indicating that staphyloxanthin does not influence fatty acid composition. Strain Pig1 had decreased membrane fluidity as measured by fluorescence anisotropy than the other strains under all conditions indicating that staphyloxanthin helps maintain membrane rigidity. We could find no evidence for correlation of expression of crtM and fatty acid biosynthesis genes. Supplementation of medium with glucose increased SCFA production and decreased BCFA and staphyloxanthin production, whereas acetate-supplementation also decreased BCFAs but increased staphyloxanthin production. We believe that staphyloxanthin levels are influenced more through metabolic regulation than responding to fatty acids incorporated into the membrane.
ARTICLE | doi:10.20944/preprints202201.0378.v1
Subject: Medicine & Pharmacology, General Medical Research Keywords: staphylococcus aureus; infective endocarditis; clinical prediction rules; echocardiography
Online: 25 January 2022 (10:41:47 CET)
Background. It is unclear whether the use of clinical prediction rules is sufficient to rule out infective endocarditis (IE) in patients with Staphylococcus aureus bacteremia (SAB) without an echocardiogram evaluation, either transthoracic (TTE) and/or transesophageal (TEE). Our primary purpose was to test the usefulness of PREDICT, POSITIVE and VIRSTA scores to rule out IE without echocardiography. Our secondary purpose was to evaluate whether not performing an echocardiogram evaluation is associated with higher mortality. Methods. We conducted a unicentric retrospective cohort including all patients with a first SAB episode from January 2015 to December 2020. IE was defined according to modified Duke criteria. We predefined threshold cut-off points to consider that IE was ruled out by means of the mentioned scores. To assess 30-day mortality, we used a multivariable regression model considering performing an echocardiogram as covariate. Results. Out of 404 patients, IE was diagnosed in 50 (12.4%). Prevalence of IE within patients with negative PREDICT, POSITIVE and VIRSTA scores was: 3.6% (95% CI 0.1-6.9%), 4.9% (95% CI 2.2-7.7%), and 2.2% (95% CI 0.2-4.3%), respectively. Patients with negative VIRSTA and negative TTE had an IE prevalence of 0.9% (95% CI 0-2.8%). Performing an echocardiogram was independently associated with lower 30-day mortality (OR 0.24 95%CI 0.10-0.54, p=0.001). Conclusion. PREDICT and POSITIVE scores were not sufficient to rule out IE without TEE. In patients with negative VIRSTA score, it was doubtful if IE could be discarded with a negative TTE. Not performing an echocardiogram was associated with worse outcomes, which might be related to presence of occult IE. Further studies are needed to assess the usefulness of clinical prediction rules in avoiding echocardiographic evaluation in SAB patients.
ARTICLE | doi:10.20944/preprints202102.0061.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Staphylococcus aureus; Melaleuca armillaris; essential oil; Gompertz model; Sigmoid model; antibacterial
Online: 1 February 2021 (16:02:30 CET)
Essential oils (EO) are a great antimicrobial resource against bacterial resistance in public health. Math models are useful describing the growth, survival, and inactivation of microorganisms against antimicrobials. We evaluated the antimicrobial activity of M. armillaris EO obtained from plants placed in the province of Buenos Aires (Argentina) against Staphylococcus aureus. Minimum Inhibitory and Bactericidal Concentrations were close and decreased slightly acidifying the medium from pH 7.4 to 6.5 and 5.0. This result was also evidenced by applying a sigmoid model, where the time and EO concentration necessaries to achieve 50% of the maximum effect decreased when medium was acidified. Moreover, at pH 7.4, applying the Gompertz model, we found that subinhibitory concentrations of EO decreased the growth rate and the maximum population density, and increased the latency period respect to the control. Additionally, we established physicochemical parameters for quality control and standardization of M. armillaris EO. Mathematical modelling allowed us to estimate key parameters in the behavior of S. aureus and Melaleuca armillaris EO at different pHs. This is interesting in situations where the pH changes are relevant, such as the control of intracellular infections in public health or the development of preservatives for food industry.
ARTICLE | doi:10.20944/preprints202011.0306.v1
Subject: Life Sciences, Biochemistry Keywords: Staphylococcus aureus; osteoblast-like cells; internalization; inflammation; immune system; host-pathogen interaction; cytokines
Online: 10 November 2020 (12:06:04 CET)
Staphylococcus aureus is a Gram-positive bacterium causing a range of mild to life-threatening infections including bone infections such as osteomyelitis. S. aureus is able to invade and persist within non-professional phagocytic cells such as osteoblasts. In the present study four different S. aureus strains, 2SA-ST239-III, 5SA-ST5-II, 10SA-ST228-I, and 14SA-ST22-IVh were tested for their ability to modulate cell viability in MG-63 osteoblast-like cells following a successful invasion and persistence. Methicillin-sensitive S. aureus (MSSA) ATCC-12598-ST30 was used as control. Despite the demonstrated similar abilities of internalization and persistence of ATCC-12598-ST30, 2SA-ST239-III, and 14SA-ST22-IVh strains in MG-63 osteoblast-like cells under our experimental conditions, we demonstrated that the decrease in cell viability was due to the different behavior of the considered strains, with the number of intracellular bacteria playing a limited role. We focused our attention on different cellular biochemical functions related to inflammation, cell metabolism, and oxidative stress during osteoblast infections. We were able to show that: 1) ATCC-12598-ST30 and 2SA-ST239-III were the only two clones able to persist and maintain their number into the cellular hostile environment during the entire period of infection; 2) 2SA-ST239-III was the only clone able to significantly increase the gene expression (3 and 24 h) and protein secretion (24 h) of both interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) in MG-63 osteoblast-like cells; 3) the same clone determined a significant up-regulation of transforming growth factor-β1 (TGF-β1) and the metabolic marker glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNAs at 24 h post infection; 3) neither the MSSA nor the four MRSA strains induced oxidative stress phenomena in MG-63 cells, although a very different expression pattern towards nuclear factor E2-related factor 2 (Nrf2) and its downstream gene heme oxygenase 1 (HO-1) activation was observed among the different clones. Our results can open a new way of considering therapies, going in the direction of an individualized therapeutic strategy that should take into account the difference existing between MSSA and MRSA as well as the distinctive features of the different clones. Not only, therefore, a different antibiotic approach but also a starting point for considering different host factors, i.e. the modulation of specific cytokines such as IL-6, TNF-α, and TGF-β1.
ARTICLE | doi:10.20944/preprints201912.0308.v1
Subject: Biology, Other Keywords: Staphylococcus aureus; bacteriophage; Kayvirus genus; endolysin; virulence determinants; vancomycin
Online: 23 December 2019 (13:10:05 CET)
Staphylococcal bacteriophages of Kayvirus genus are candidates for therapeutic applications. One of their proteins, Tgl, is slightly similar to staphylococcal virulence factors, secreted autolysins of lytic transglycosylase motifs, IsaA and SceD. We show that Tgl is also a lytic enzyme secreted by bacterial transport system and localizes to cell peripheries, like IsaA and SceD. It caused lysis of E. coli cells expressing the cloned tgl gene, but could be overproduced when depleted of signal peptide. S. aureus cells producing Tgl lysed in the presence of nisin, which mimics the action of phage holin. In vitro, Tgl protein was able to destruct S. aureus cell walls. The production of Tgl decreased S. aureus tolerance to vancomycin, unlike the production of SceD, which is associated with the decreased sensitivity to vancomycin. In the genomes of kayviruses, the tgl gene is located a few genes away from gene lysK, encoding the major endolysin. While lysK is a late phage gene, tgl can be transcribed by a host RNA polymerase, as are phage early genes. Taken together our data indicate that tgl is a part of kayviruses lytic module and encodes an additional endolysin which can act in concert with LysK in cell lysis.
ARTICLE | doi:10.20944/preprints201811.0445.v1
Subject: Life Sciences, Microbiology Keywords: Contamination, Escherichia coli, fecal coliforms, Nakawa, Salmonella, Staphylococcus aureus
Online: 19 November 2018 (10:19:56 CET)
This study evaluated the microbial safety of vended boiled, pasteurized and UHT milk sold in Nakawa, Kampala-Uganda. 15 milk samples were analyzed; 2 samples had Salmonella, 5 had S. aureus with a count of 1.66 0.02 log10CFU/ml. E. coli was detected in 8 samples with 1.0 0.02 to 3.0 0.01log10CFU/ml count. A high load of 3.0 CFU/ml was obtained in 3 samples with E. coli. Four E. coli positive samples had a contamination load of 2.0 0.015log10 CFU/ml of which one was pasteurized milk. Only a pasteurized milk showed a low E. coli load at 1.0 0.02log10 CFU/ml. All UHT milk had no microbial contamination. Both boiled and pasteurized milk had Salmonella, S. aureus and E. coli in levels above the set threshold limits. Milk consumers in Nakawa stand a potential public health risk of food poisoning reflected by presence of Salmonella, S. aureus and E. coli in some milk sold in the area.
ARTICLE | doi:10.20944/preprints201912.0164.v1
Subject: Life Sciences, Microbiology Keywords: biofilm; co-culture; Staphylococcus aureus; SaOS-2; biomaterials; implanted devices
Online: 12 December 2019 (05:24:29 CET)
Biofilm-mediated infection is a major cause of bone prosthesis failure. The lack of molecules able to act in biofilms has driven research aimed at identifying new anti-biofilm agents via chemical screens. However, to be able to accommodate a large number of compounds, the testing conditions of these screenings end up being typically far from the clinical scenario. In this study, we assess the potential applicability of three anti-biofilm compounds (based on natural compounds) as part of implanted medical devices by testing them on in vitro systems that more faithfully resemble the clinical scenario. To that end, we used a competition model based on the co-culture of SaOS-2 mammalian cells and Staphylococcus aureus (collection and clinical strains) on a titanium surface. Additionally, we studied whether these derivatives of natural compounds enhance the previously proven protective effect of pre-incubating the titanium surface with SaOS-2 cells. Out of the three tested leads, one showed the highest potential, and can be regarded as a promising agent for incorporation into bone implants. This study emphasizes and demonstrates the importance of using meaningful experimental models, where potential antimicrobials ought to be tested for protection of biomaterials in translational applications.
Subject: Medicine & Pharmacology, Allergology Keywords: DPTM; Methicillin-resistant Staphylococcus aureus (MRSA); Antibacterial activity; Murine skin wound model; MIC
Online: 12 April 2021 (12:18:08 CEST)
Staphylococcus aureus (S. aureus) is a major human pathogen that requires new antibiotics with unique mechanism. A new pleuromutilin derivative, 14-O-[(4,6-Diaminopyrimidine-2-yl) thioacetyl] mutilin (DPTM), has been synthesized and proved as a potent antibacterial agent using in vitro and in vivo assays. In the present study, DPTM was further in vitro evaluated against Methicillin-resistant Staphylococcus aureus (MRSA) isolated from dairy farms and outperformed tiamulin fumarate, a pleuromutilin drug used for veterinary. Moreover, a murine skin wound model caused by MRSA infection was established and the healing effect of DPTM was investigated. The results showed that DPTM could promote the healing of MRSA skin infection, reduce the bacterial burden of infected skin MRSA and decrease the secretion of IL-6 and TNF-α inflammatory cytokines in plasma. These results provided the basis for further in-depth drug targeted studies of DPTM as a novel antibacterial agent.
REVIEW | doi:10.20944/preprints202104.0244.v1
Subject: Life Sciences, Biochemistry Keywords: Staphylococcus aureus; MRSA; genome-scale metabolic models; model-driven discovery; strain-specific models
Online: 8 April 2021 (14:25:31 CEST)
Staphylococcus aureus is a high-priority pathogen causing severe infections with high morbidity and mortality worldwide. Many S. aureus strains are methicillin-resistant (MRSA) or even multi-drug resistant. It is one of the most successful and prominent modern pathogens. An effective fight against S. aureus infections requires novel targets for antimicrobial and antistaphylococcal therapies. Recent advances in whole-genome sequencing and high-throughput techniques facilitate the generation of genome-scale metabolic models (GEMs). Among the multiple applications of GEMs is drug-targeting in pathogens. Hence, comprehensive and predictive metabolic reconstructions of S. aureus could facilitate the identification of novel targets for antimicrobial therapies. This review aims at giving an overview of all available GEMs of multiple S. aureus strains. We downloaded all 114 available GEMs of S. aureus for further analysis. The scope of each model was evaluated, including the number of reactions, metabolites, and genes.Furthermore, all models were quality-controlled using Mᴇᴍᴏᴛᴇ, an open-source application with standardized metabolic tests. Growth capabilities and model similarities were examined. This review should lead as a guide for choosing the appropriate GEM for a given research question. With the information about the availability, the format, and the strengths and potentials of each model, one can either choose an existing model or combine several models to create models with even higher predictive values. This facilitates model-driven discoveries of novel antimicrobial targets to fight multi-drug resistant S. aureus strains.
ARTICLE | doi:10.20944/preprints201812.0362.v1
Subject: Keywords: Antibiotic resistance, efflux pump inhibitors, Escherichia coli, efflux pumps, multidrug resistance, Staphylococcus aureus
Online: 31 December 2018 (09:55:32 CET)
Bacterial antibiotic resistance has become a major global health concern. One of the main reasons for the development of multi-drug resistance properties in bacteria is due to the bacterial efflux pump systems. They are important transport proteins, mainly involved in the removal of toxic substrates like antibiotics from inner cell environment. These pumps are responsible for the intrinsic ability of bacteria to get resistant to the antibiotic. Various types of efflux pumps are present in the Gram-positive and Gram-negative bacteria. Plant-derived products like Capsaicin, Olympicin A, and Indirubicin were found to be inhibitors of an efflux pump in Staphylococcus aureus similarly Ursolic acid derivatives; Daidzein and Lanatoside C were plant-derived inhibitors of an efflux pump in Escherichia coli. In this review detail information have been provided about efflux pump inhibitors that have been found to be effective in the Gram-positive bacteria and Gram-negative bacteria. The aim of this review is to focus on the role of plant-derived compounds as effective efflux pumps inhibitors with reference to mainly Staphylococcus aureus and Escherichia coli.
ARTICLE | doi:10.20944/preprints201705.0041.v1
Subject: Life Sciences, Microbiology Keywords: core-shell; disinfection; Escherichia coli; nanoparticles; pathogens; silver; solar-photocatalysis; Staphylococcus aureus; water; zinc oxide
Online: 4 May 2017 (11:32:16 CEST)
Water borne pathogens present a threat to human health and their disinfection from water poses a challenge, prompting search for newer methods and newer materials. Disinfection of Gram-negative bacterium Escherichia coli and Gram-positive coccal bacterium Staphylococcus aureus in aqueous matrix was achieved within 60 and 90 minutes respectively at 35⁰C using solar-photocatalysis mediated by sonochemically synthesized Ag@ZnO core-shell nanoparticles. The efficiency of the process increased with increase in temperature and at 55⁰C the disinfection could be achieved in 45 and 60 min respectively for the two bacteria. A new ultrasound assisted chemical precipitation technique was used for the synthesis of Ag@ZnO core-shell nanoparticles. The characteristics of the synthesized material were established using physical techniques. The material remained stable even at 400o C. Disinfection efficiency of the Ag@ZnO core-shell nanoparticles was confirmed in case of real world water samples from pond, river, municipal tap and was found to be better than that of pure ZnO and TiO2 (Degussa P25). When the nanoparticle based catalyst was recycled and reused for subsequent disinfection experiments, its efficiency did not change remarkably even after three cycles. The sonochemically synthesized Ag@ZnO core-shell nanoparticles have a good potential for application in solar photocatalytic disinfection of water borne pathogens.
ARTICLE | doi:10.20944/preprints201904.0059.v1
Subject: Keywords: methicillin-resistant Staphylococcus aureus; methicillin-sensitive Staphylococcus aureus; statistics; superbug; hormone; prevention
Online: 5 April 2019 (11:46:16 CEST)
In California, an average of 41,900 patients are diagnosed annually with Staphylococcus bacterial infection; out of these, 24,090 patients have methicillin-resistant Staphylococcus aureus (MRSA) infection and 17,810 patients have methicillin-sensitive Staphylococcus aureus (MSSA) infection. The aim of this paper is to find out whether there is a significant difference in strain dominancy and in what direction. The paper gathered and analyzed data for period of five years of infection rate due to Staphylococcus aureus. This study indicates that a significant difference in dominancy exists, the MRSA infection rate (an average of five years period) is 1.35 times higher than the MSSA infection rate (P-value < 0.05, CI: 95%), but the gap between the two infection rates is decreasing. The infection rate of both MRSA and MSSA is in a path of decline.
ARTICLE | doi:10.20944/preprints201810.0293.v1
Subject: Medicine & Pharmacology, Other Keywords: MRSA, MSSA, Staphylococcus aureus, mortality, gender, Methicillin-resistant Staphylococcus aureus, infectious disease, prevention
Online: 15 October 2018 (09:35:59 CEST)
Average of 41,900 patients are diagnosed annually with staphylococcus bacterial infection in California, 24,089 patients have Methicillin-resistant Staphylococcus Aureus (MRSA) and 17,810 patients have Methicillin-Sensitive Staphylococcus (MSSA). This paper demonstrates that there is a difference in mortality rate due to staphylococcus infection between males and females (P-value<0.05, CI 95%). Male patient diagnosed with S. aureus has 1.3 chance of mortality incidence than female patient. In addition, MRSA infection rate is 1.4 times MSSA infection (P-value<0.05, CI 95%), but the gap of infection is decreasing; however, mortality of both infections combined are more than threefold greater compared to three decades ago.
REVIEW | doi:10.20944/preprints202207.0126.v1
Subject: Medicine & Pharmacology, Cardiology Keywords: Infective Endocarditis; Staphylococcus Aureus; Biofilm; Immune response; Fibronectin
Online: 7 July 2022 (10:00:18 CEST)
Infective endocarditis remains an illness that carries a significant burden to healthcare resources. In recent times, there has been a shift from Streptococcus sp to Staphylococcus sp as the primary organism of interest. This has significant consequences given the virulence of Staphylococcus and its propensity to form a biofilm, rendering non-surgical therapy ineffective. In addition, antibiotic resistance has affected treatment of this organism. The cohorts at most risk for Staphylococcal endocarditis are the elderly patients with multiple comorbidities. The innovation of transcatheter technologies alongside other cardiac interventions such as implantable devices have contributed to the increased risk attributable to this cohort. We examine the role of the heart team for diagnosis and treatment of this condition. In addition, we examine the determinants of virulence of Staphylococcus aureus, the interaction with hosts immunity and the discovery and emergence of a potential vaccine. We also examine the potential role of prophylactic antibiotics during dental procedures. With increasing rates of transcatheter device implantations, there is a projected increment of endocarditis especially in this high-risk group. A high index of suspicion is needed alongside early initiation of therapy and referral to the heart time to improve outcomes.
ARTICLE | doi:10.20944/preprints202211.0039.v1
Subject: Life Sciences, Genetics Keywords: Staphylococcus aureus, MRSA ST239, osteomyelitis, genome features, adaptation; chronic infection
Online: 2 November 2022 (03:34:29 CET)
Abstract. The increasing frequency of isolation of methicillin-resistant Staphylococcus aureus (MRSA) limits the chances of effective antibacterial therapy of staphylococcal diseases and results in development of persistent infection such as bacteremia and osteomyelitis. The aim of this study was to identify features of the MRSAST239 0943-1505-2016 (SA943) genome, that contribute to the formation of both acute and chronic musculoskeletal infections. The analysis was performed using comparative genomics data of the dominant epidemic S. aureus lineages namely ST1, ST8, ST30, ST36, ST239. SA943 genome encodes proteins that provide resistance to the host immune system, suppress immunological memory and form biofilms. The molecular mechanisms of adaptation responsible for development of persistent infection were as follows: amino acid substitution in PBP2 and PBP2a, providing resistance to ceftaroline; loss of a large part of prophage DNA and restoration of nucleotide sequence of beta-hemolysin, that greatly facilitates escape of phagocytosed bacteria from phagosome and formation of biofilms; dysfunction of the AgrA system due to the presence of psm-mec and several amino acid substitutions in the AgrC; partial deletion of nucleotide sequence in genomic island vSAβ resulting in the loss of two proteases of Spl - operon; deletion of SD repeats in SdrE amino acid sequence.
ARTICLE | doi:10.20944/preprints201706.0057.v1
Subject: Life Sciences, Microbiology Keywords: antimicrobial peptides; lipopeptides; cyclic lipopeptides Staphylococcus aureus; biofilm; culture media
Online: 13 June 2017 (06:09:47 CEST)
Staphylococcus aureus bacteria are one of the leading microorganisms responsible for nosocomial infections as well as being the primary causative pathogen of skin and wound infections. Currently, the therapy of staphylococcal diseases faces many difficulties, due to a variety of mechanisms of resistance and virulence factors. Moreover, a number of infections caused by S. aureus is connected with biofilm formation that impairs effectiveness of the therapy. Short cationic lipopeptides that are designed on the basis of the structure of antimicrobial peptides structure are likely to provide a promising alternative to conventional antibiotics. Despite the fact that many research groups have proved a high antistaphylococcal potential of lipopeptides, the lack of unified protocols in determination of antimicrobial activity may be the reason of inconsistency of the results. The aim of this study was to learn how the use of various bacteriological media as well as solvents may affect activity of lipopeptides and their cyclic analogs.
ARTICLE | doi:10.20944/preprints202007.0342.v1
Subject: Keywords: Propolis; Soxhlet; Anthraquinone; antibacterial activity; Proteus Mirabilis; Klebsiella Pneumonia; Staphylococcus Qureus
Online: 16 July 2020 (06:19:30 CEST)
Different products from a unique Propolis extract, Propolis (bee glue), an of resinous consistency produced by bees, has been used as indigenous medicine for the treatment of several diseases in some contrary. Safety assessment of propoils extracts with respect to antimicrobial activity against three bacterial isolates, Proteus Mirabilis , Klebsiella Pneumonia and Staphylococcus Qureus.The result showed that the main composition of the extract was Anthraquinone, the last one was responsible for the biological activity of the extract. FT-IR, UV results showed more than eight peaks for represent the main fine composition of the extract. The present study also showed that the extract has antibacterial activity against three bacterial isolates
ARTICLE | doi:10.20944/preprints202208.0059.v1
Subject: Biology, Other Keywords: Staphylococcus epidermidis; metabolic network validation; minimal cut sets; knock-outs; systems biology
Online: 2 August 2022 (09:33:09 CEST)
Increasingly, systems biology is gaining relevance in basic and applied research. The combination of computational biology with wet lab produces a synergy that results in an exponential increase in knowledge of biological systems. The study of microorganisms such as Staphylococcus epidermidis RP62A enables the researcher to understand better its metabolic network, which allows the design of effective strategies to treat infections caused by this species or others. S. epidermidis is the second cause of infection in patients with joint implants, so treating its proliferation seems vital for public health. There are different approaches to the analysis of metabolic networks. Flux Balance Analysis (FBA) is one of the most widespread streams. It allows the study of large metabolic networks, their structural properties, the optimization of metabolic flux, and the search for intervention strategies to modify the state of the metabolic network. This work presents the validation of the Staphylococcus epidermidis RP62A metabolic network model elaborated by Díaz-Calvo et al.. Then, we elaborate further on the network analysis’s essential reactions, classifying them. Finally, we introduce some proposals to intervene in the network and design knock-outs.
CASE REPORT | doi:10.20944/preprints202007.0219.v1
Subject: Medicine & Pharmacology, Pediatrics Keywords: Preterm infant; Necrotizing pneumonia; Methicillin-Resistant Staphylococcus Aureus (MRSA); Pneumatoceles; Linezolid; Vancomycin; Rifampicin
Online: 11 July 2020 (02:10:45 CEST)
Necrotizing pneumonia due to Methicillin-Resistant Staphylococcus Aureus (MRSA) is devastating and difficult to treat in preterm infants. We report a case of severe MRSA necrotizing pneumonia in a preterm infant. As an add-on rescue therapy to vancomycin, linezolid rapidly cured this case after the failure of vancomycin plus rifampicin. This rapid cure suggests that adjunctive rather than rescue linezolid may be considered in such cases.
ARTICLE | doi:10.20944/preprints202104.0086.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: DNA sensor; point of care diagnostics; methicillin-resistant Staphylococcus aureus; label free biosensor; AC electrokicetics
Online: 5 April 2021 (10:11:51 CEST)
Biosensors have shown great potential in realizing rapid, low cost and portable on-site detection for diseases. This work reports the development of a new bioelectronic sensor called AC electrokinetics-based capacitive (ABC) biosensor, for the detection of genomic DNA (gDNA) of methicillin-resistant Staphylococcus aureus (MRSA). The ABC sensor is based on interdigitated microelectrodes biofunctionalized with oligonucleotide probes. It uses a special AC signal for direct capacitive monitoring of topological change on nanostructured sensor surface, which simultaneously induce dieletrophoretic enrichment of target gDNAs. As a result, rapid and specific detection of gDNA/probe hybridization can be realized with high sensitivity. It requires no signal amplification such as labelling, hybridization chain reaction, or nucleic acid sequence-based amplification. This method involves only simple sample preparation. After optimization of nano-structured sensor surface and signal processing, the ABC sensor demonstrated fast turnaround of results (~10 s detection), excellent sensitivity (a detection limit of 4.7 DNA copies /µL MRSA gDNA) and high specificity, suitable for point of care diagnosis. As a bioelectronic sensor, the developed ABC sensors can be easily adapted for detection of other infectious agents.
ARTICLE | doi:10.20944/preprints202008.0106.v1
Subject: Life Sciences, Microbiology Keywords: citrus pectin; lemon; grapefruit; IntegroPectin; flavonoids; citrus terpenes; polyphenols; antimicrobial resistance; Staphylococcus aureus; Pseudomonas aeruginosa
Online: 5 August 2020 (03:34:49 CEST)
Grapefruit and lemon pectin obtained from the respective waste citrus peels via hydrodynamic cavitation in water only are powerful, broad-scope antimicrobial alternatives to antibiotics against Gram-negative and -positive pathogens. Dubbed IntegroPectin, these pectic polymers functionalized with citrus flavonoids and terpenes show superior antimicrobial activity when compared to commercial citrus pectin. Similarly to commercial pectin, lemon IntegroPectin determined ca. 3 log reduction of Staphylococcus aureus cells, while an enhanced activity of commercial citrus pectin was detected in the case of Pseudomonas aeruginosa cells with a minimal bactericidal concentration (MBC) of 15 mg mL-1. Although grapefruit and lemon IntegroPectin share equal MBC in the case of P. aeruginosa cells, grapefruit IntegroPectin shows boosted activity upon exposure of S. aureus cells with a 40 mg mL-1 biopolymer concentration being sufficient to achieve complete killing of the bacterial cells. Insight on the mechanism of action of these biocompatible antimicrobials and their effect on bacterial cells, at the morphological level, were obtained indirectly through Fourier Transform Infrared spectroscopy and directly through scanning electron microscopy. In the era of antimicrobial resistance, these results are of great societal and sanitary relevance as they open new avenues to develop innovative antimicrobials for the treatment of polymicrobial infections unlikely to develop drug resistance.
ARTICLE | doi:10.20944/preprints202106.0050.v1
Subject: Keywords: Montivipera bornmuelleri snake venom; F1F0-ATPase; Staphylococcus epidermidis; Escherichia coli; antibacterial activity; HCT116 cells; anticancer activity
Online: 2 June 2021 (07:21:59 CEST)
In this work, we pursued the biological characterization of the venom of Montivipera born-muelleri, a viper from the Lebanese mountains. In relativity to its antibacterial potential, the in-hibitory effect of this venom on the F1F0-ATPase enzymes of Gram-positive Staphylocoocus epider-midis and Gram-negative Escherichia coli bacteria was examined. In order to determine the de-gree of cytotoxicity of the venom on the HCT116 human colon cancer cell lines, the biological MTT proliferation and cell viability test were implemented. After validation of the enzymatic F1F0-ATPase model by the spectrophotometric method, using quercetin as the reference ligand, re-sults revealed that M. bornmuelleri venom is able to inhibit the activity of the enzyme of these two bacteria with a concentration of the order of 100-150 µg/mL. In addition, a venom concentration of 10 µg/mL was sufficient to kill the totality of HCT116 cell lines cultivated in vitro. These data show that M. bornmuelleri venom is a mixture of diverse molecules presenting activities of interest and is a potential source to explore in order to discover new drug candidates.
ARTICLE | doi:10.20944/preprints202102.0312.v1
Subject: Life Sciences, Biochemistry Keywords: raw milk stretched cheeses; lactic acid bacteria; coliform bacteria; Escherichia coli; Staphylococcus aureus; yeasts and moulds
Online: 12 February 2021 (15:26:35 CET)
To evaluate the behaviour of the relevant microbial populations during stretched cheese production, the quantitative microbiological analysis was performed during the critical steps of the preparation. The obtained data distributions proved statistically significant increases in all indicators, on average by 4.55 ± 0.64 log CFU/g of presumptive lactococci counts, 4.06 ±0.61 of lactobacilli, 1.53 ± 0.57 log CFU/g of coliforms, 2.42 ± 0.67 log CFU/g of Escherichia coli, 1.53 ± 0.75 log CFU/g of yeasts and moulds, and 0.99 ± 0.27 log CFU/g of presumptive Staphylococcus aureus, from the early stage of milk coagulation until curd ripening (0–24 h). The following steaming/stretching process caused reductions in viable counts with the most significant inactivation effect on coliform bacteria, including E. coli (-4.0 ± 1.0 log CFU/g). Total viable counts and yeasts and moulds showed 2 and almost 3 log reduction (-2.2 ± 1.1 log CFU/g and -2.6 ± 0.9 log CFU/g), respectively. The lowest decreases in presumptive S. aureus counts were estimated at the level of -1.50 ± 0.64 log CFU/g. The counts of yeasts and moulds showed the best indicatory function during the entire storage period of vacuum-packaged cheeses at 6 °C.
ARTICLE | doi:10.20944/preprints202201.0131.v1
Subject: Medicine & Pharmacology, General Medical Research Keywords: methicillin-resistant Staphylococcus aureus; Matrix-Assisted Laser Desorption/Ionization Time-of-Flight; antibiotic susceptibility test; artificial intelligence
Online: 10 January 2022 (19:01:57 CET)
Combining Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) spectra data and artificial intelligence (AI) has been introduced for rapid prediction on antibiotic susceptibility test (AST) of S. aureus. Based on the AI predictive probability, the cases with probabilities between low and high cut-offs are defined as “grey zone”. We aimed to investigate the underlying reasons of unconfident (grey zone) or wrong predictive AST. A total 479 S. aureus isolates were collected, analyzed by MALDI-TOF, and AST prediction, standard AST were obtained in a tertiary medical center. The predictions were categorized into the correct prediction group, wrong prediction group, and grey zone group. We analyzed the association between the predictive results and the demographic data, spectral data, and strain types. For MRSA, larger cefoxitin zone size was found in the wrong prediction group. MLST of the MRSA isolates in the grey zone group revealed that uncommon strain types composed 80%. Amid MSSA isolates in the grey zone group, the majority (60%) was composed of over 10 different strain types. In predicting AST based on MALDI-TOF AI, uncommon strains and high diversity would contribute to suboptimal predictive performance.
ARTICLE | doi:10.20944/preprints202108.0081.v1
Subject: Life Sciences, Biochemistry Keywords: heteroaromatic stilbene derivatives; antimicrobial activity; Staphylococcus aureus; Enterococcus faecalis; Escherichia coli; Pseudomonas aeruginosa; Acinetobacter baumannii; Klebsiella pneumoniae.
Online: 3 August 2021 (13:32:14 CEST)
The widespread use of antibiotics has led to a gradual increase in drug-resistant bacterial infections, which severely weakens the clinical efficacy of antibacterial therapies. In recent decades, stilbenes aroused great interest because of their high bioavailability, as well as for their manifold biological activity. Our research efforts are focused on synthetic heteroaromatic stilbene deriva-tives as they represent a potentially new type of antibiotic with a wide antibacterial spectrum. Herein, a preliminary molecular modeling study and a versatile synthetic scheme allowed us to define eight heteroaromatic stilbene derivatives with potential antimicrobial activity. In order to evaluate our compound’s activity spectrum and antibacterial ability, Minimum Inhibitory Con-centration (MIC) and Minimum Bactericidal Concentration (MBC) tests have been performed on Gram-positive and Gram-negative ATCC strains. Compounds PB4, PB5, PB7 and PB8 showed the best values in terms of MIC and were also evaluated for MBC, which however was found to be greater than MIC, confirming a bacteriostatic activity. For all compounds, we evaluated toxici-ty on colon-rectal adenocarcinoma cells tumor cells (CaCo2), once established that the whole se-lected set was more active than 5-Fluorouracil in reducing CaCo-2 cells viability. To the best of our knowledge, the biological assays have shown for these derivatives an excellent bacteriostatic activity, compared to similar molecular structures previously reported, thus paving the way for a new class of antibiotic compounds.
ARTICLE | doi:10.20944/preprints202001.0182.v1
Subject: Chemistry, Medicinal Chemistry Keywords: dinoflagellate; Karenia mikimotoi; glycolipids; monogalactosyldiacylglycerol; monogalactosylmonoacylglycerol; polyunsaturated fatty acid methyl ester; Staphylococcus aureus; Escherichia coli; Candida albicans; anti-inflammatory activity
Online: 17 January 2020 (09:18:08 CET)
A New monogalactosyldiacylglycerol (MGDG), a known monogalactosylmonoacylglycerol (MGMG) and a known polyunsaturated fatty acid methyl ester (PUFAME) were isolated from the marine dinoflagellate Karenia mikimotoi. The planar structure of the glycolipids was elucidated using MS and NMR spectroscopic analyses and comparisons to the known glycolipid to confirm its structure. The isolation of PUFAME strongly supports the polyunsaturated fatty acid fragment of these glycolipids. The relative configuration of the sugar was deduced by comparisons of 3JHH values and proton chemical shifts with those of known glycolipids. All isolated compounds MGDG, MGMG and PUFAME (1-3) were evaluated for their antimicrobial and anti-inflammatory activity. All compounds modulated macrophage responses, with compound 3 exhibiting the greatest anti-inflammatory activity.