Background: Staphylococcus aureus (S. aureus) is an opportunistic pathogen and a predominant cause of life-threatening nosocomial infections. Drug resistance in S. aureus is attributed to production of biofilm, which is controlled largely by bacterial quorum sensing (QS) systems. Methodology: In vitro analysis of biofilm inhibition assay was performed using crystal violet staining assay, swarming motility, light microscopy and growth curve analyses. Identification of the major constituents of I. verum fruit extract was performed by GC-MS. Ligand-protein interaction was analyzed by molecular docking investigations. Results: The methanol extract of I. verum inhibited the growth of MRSA at the concentration of 4.8 mg/ml. At the sub-inhibitory concentration (2.4mg/ml), the extract showed significant reduction in biofilmogenesis. Light microscopy analysis confirmed the antibiofilm activity as well as the efficacy in disturbing biofilm architecture. A reduced swarming motility was observed at the lowest concentration of 2.4mg/ml. GC-MS analysis revealed anethol (AL) as the major constituent. The molecular docking analysis attributes the antibiofilm activity to an active ligand AL, which strongly interacted with the active site residues of AgrA and SarA proteins of S. aureus. Conclusion: We report the activities of I. verum to be immensely interfering with QS system and biofilm formation in MRSA.

Transparent materials used for facial protection equipment provide protection against microbial infections caused by viruses and bacteria, including multidrug-resistant strains. However, transparent materials used for this type of application are made of materials that do not possess antimicrobial activity. They just avoid direct contact between the person and the biological agent. Therefore, healthy people can get infected through contact of the contaminated material surfaces and this equipment constitute an increasing source of infectious biological waste. Furthermore, infected people can transmit microbial infections easily because the protective equipment do not inactivate the microbial load generated while breathing, sneezing, or coughing. In this regard, the goal of this work consisted of fabricating a transparent face shield with intrinsic antimicrobial activity that could provide extra-protection against infectious agents and reduce the generation of infectious waste. Thus, a single-use transparent antimicrobial face shield composed of polyethylene terephthalate and an antimicrobial coating of benzalkonium chloride has been developed for the next generation of facial protective equipment. The antimicrobial coating was analyzed by atomic force microscopy and field emission scanning electron microscopy with elemental analysis. This is the first facial transparent protective material capable of inactivating enveloped viruses such as SARS-CoV-2 in less than one minute of contact, and the methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis. Bacterial infections contribute to severe pneumonia associated with the SARS-CoV-2 infection, and their resistance to antibiotics is increasing. Our extra protective broad-spectrum antimicrobial composite material could also be applied for the fabrication of other facial protective tools such as such as goggles, helmets, plastic masks and space separation screens used for counters or vehicles. This low-cost technology would be very useful to combat the current COVID-19 pandemic and protect health care workers from multidrug-resistant infections in developed and underdeveloped countries.

Wound infections evidently appeared in times of World War I that accounted a significant mortality and morbidity rate among injured soldiers. Currently, around 11 million people worldwide require medical treatment for wound infections and 300,000 die every year due to untreated wound infection. The extensive use of antibiotics to treat wound infection leads to emerging new microbial strains that are resistant to many antibiotics. There is a growing concern on the emergence and re-emergence of drug-resistant pathogens such as multi-resistant bacterial strains. Hence, the development of new antimicrobial compounds or the modification of those that already exist to improve antibacterial activity is a high priority area of research. During the past few decades, nanotechnology has arisen with new promising technology for synthesis of nanobiomaterials. Metallic nanoparticles (NPs) are considered as new alternative treatment with superior antibacterial activity. In this study, new formulation of titanium oxide (TiO2) NPs with different sizes were synthesized and characterized. Genotoxicity, mutagenicity and antibacterial activities of TiO2 NPs against the causative agents of wound infection were investigated. Antibacterial activity of TiO2 NPs was conducted against three ATCC ® bacterial strains: methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli and Pseudomonas aeruginosa. The results clearly illustrate a superior antibacterial activity of all newly formulated TiO2 NPs against the most causative agents of wound infection. Most of our TiO2 NPs showed non-genotoxic and non-mutagenic results at the maximum concentrations. Findings of this study will enhance the future of the therapeutic strategies against the resistant pathogenic strains that cause wound infections.

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.

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.

The emergence of multidrug-resistant bacterial strains, especially in the clinical setting, has renewed interest in alternative treatment methods. The utilization of prokaryotic viruses in phage therapy has demonstrated potential as a novel treatment method against multidrug-resistant bacterial infections. As the post-antibiotic era quickly approaches, the development and standardization of phage therapy is critically relevant to public health. This review serves to highlight the development of phage therapy against methicillin-resistant Staphylococcus aureus (MRSA), an antibiotic-resistant bacterial strain responsible for severe clinical infections.

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.

Staphylococcus aureus (S. aureus), particularly Methicillin-resistant S. aureus (MRSA), is a life-threatening pathogen that causes a variety of infections in hospital and community settings. It poses a significant risk and challenge for global health that hinders our ability to control and treat bacterial infections. Recently, the emergence and spread of variant strains of bacteria, misuse of the limited available options of effective antibiotics, spread of fake drugs, and climate change that increased the contact between humans and animals’ populations carrying different bacterial has significantly increased the incidence of Multi-Drug Resistance strains (MDR). This in turn, has created a severe problem in the infection control treatment of S. aureus infected patients. Treatment options for MRSA infection are increasingly limited and complicated. Unfortunately, different strains of MRSA are showing tolerance and resistance toward vancomycin, which is the standard of care for complicated MRSA. Therefore, it is crucial now to invest developing new effective anti-biotics and synergies, develop and implement national action plans for the management of an-tibiotic resistance, as well as improving our understanding of the antimicrobial resistance mechanisms. Here, in this review we explain the main mechanisms of antibiotic resistance in MRSA and describes different approaches to manipulate it in MRSA, providing a basis for de-signing effective drugs, and shedding some light on the evolution of S. aureus.

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.

The changing epidemiology of Staphylococcus aureus has created several gaps in its population structure and emergence of strains. Two global shifts in the aftermath of the past methicil-lin-resistant S. aureus (MRSA) pandemic are: a rise in healthcare-associated infections and evolu-tion of cutaneous and soft tissue infections with high morbidities and mortalities. Furthermore, bitter lessons from COVID-19 showed S. aureus necrotizing-pneumonia and skin conditions ag-gravating Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) and Monkeypox manifestations. Limited data and paucity of high-quality evidence exist for many key clinical questions. Using clinical microbiology, molecular characterization, hospital data on age and in-fection sites, and antibiograms, we have investigated S. aureus infection patterns. We showed that age-specific distribution in both intensive care unit (ICU) and non-ICU revealed highest infection rates (94.7%) in senior-patients >50 years; most were MRSA (81.99%). However, specific distribu-tions of geriatric MRSA and MSSA rates were 46.5% and 4.6% in ICU and 35.48% and 8.065% in non-ICU, respectively. Intriguingly, age groups 0-20 years showed uniquely similar MRSA pat-terns in ICU and non-ICU patients (13.9%, 9.7%, respectively) and MSSA in ICU (11.6%). In age groups 20-50 years, MRSA were 2-fold in non-ICU (35%) than ICU (18.6%). Interestingly, highly significant association was found between infection-site and age-groups (P-value .000). Skin in-fections remained higher in all ages; pediatrics 32.14%, adults 56%, and seniors 25% while res-piratory infections were lower in pediatrics (14.3%) and adult 17%), and highest in seniors (38%). Blood and “other” sites in pediatrics recorded (28.6%; 25%, respectively), slightly lower in adults (18.6%; 8.6%) and seniors (14%); 22.8%), respectively. Further, significant association existed between infection-site and MRSA (Chi-Square Test, P-value .002). The common cutaneous infec-tions across all age-groups and the significant association of MRSA to geriatric-respiratory infec-tions have a high potential for skin-carriage as reservoir for endogenous infection. The similar frequencies of both lineages in youth in all settings imply MSSA-carriage as potential evolutionary origins for MRSA. These findings have important clinical implications for strategic planning in patient management and S. aureus control particularly in age-specific infections and vigilance for potential viral coinfections.

From the hospital wastewater, a novel bacteriophage was isolated and characterized. According to characterization properties, this bacteriophage belongs to the Siphoviridae family, the maximum bacteriophage titer was recorded at 37°C and a pH of 7.2, had a 44,789 bp linear double-strand DNA genome, and within the genome sequence, there are 61 genes, all of which are encoded into proteins. Although this bacteriophage does not have any virulence factors or antimicrobial resistance genes and had specific lytic activity against some antimicrobial resistance S. aureus clinical isolates.

Due to the rapid emergence of multi drug resistant (MDR) pathogens against which current an-tibiotics are no longer functioning, severe infections are becoming practically untreatable. Con-sequently, the discovering of new classes of effective antimicrobial agents with novel modes of action is becoming increasingly urgent. The bioactivity of Cannabis sativa, an herbaceous plant used for millennia for medicinal and recreational purposes, is mainly due to its content in phytocan-nabinoids (PCs). Among the 180 PCs detected, cannabidiol (CBD), Δ8 and Δ9-tetrahydrocannabinols (Δ8-THC and Δ9-THC), cannabichromene (CBC), cannabigerol (CBG), cannabinol (CBN) and some their acidic precursors have demonstrated from moderate to potent antibacterial effects against Gram-positive bacteria (MICs 0.5–8 µg/mL), including methicillin-resistant Staphylococcus aureus (MRSA), epidemic MRSA (EMRSA), as well as fluoroquinolones and tetracycline-resistant strains. Particularly, the not psychotropic CBG was also capable to inhibit MRSA biofilm formation, to eradicate that mature, and to rapidly exterminate MRSA persiters cells. On this scenario, CBG, as well as other minor not psychotropic PCs, such as CBD, and CBC could represent promising compounds for developing novel antibiotics with high therapeutic potential. Anyway, further studies are necessary, needing abundant quantities of such PCs, scarcely provided naturally by Cannabis plants. Here, after an extensive overture on cannabinoids including their reported an-timicrobial effects, aiming at easing the synthetic production of the necessary amounts of CBG, CBC and CBD for further studies, we have, for the first time, systematically reviewed the synthetic pathways utilized for their synthesis, reporting both reaction schemes and experimental details.

Of late, the focus has been shifted towards quorum sensing inhibitors which reduce bacterial virulence and lower the probability of resistance and refining infections. In this work, meta-bromo-thiolactone (mBTL), a potent quorum and virulence inhibitor against Staphylococcus aureus and MRSA phenotypes, was formulated in chitosan nanoparticles (ChNPs) using ionic gelation method. mBTL-loaded-ChNPs were characterized for particle size, polydispersity index, zeta potential. Morphology was visualized by Transmission Electron Microscopy (TEM), drug release profile and antibiofilm analysis using Confocal Laser Scanning Microscope (CLSM) and Scanning Electron Microscopy (SEM) were performed. Synthesized mBTL-loaded-CNPs showed homogenized nano-size particles ranging from 158+1.3 to 284+5.6 nm with spherical particles that exhibited sustainable release profile over 48 hr at 37 °C. These findings revealed successful preparation of mBTL-loaded-ChNPs, that further showed effective antibiofilm activity at MIC50 (0.5 mg/mL) where all strains displayed reduced biofilm formation compared to untreated strains. CLSM results showed a significant reduction in the number of viable cells, indicating the effectiveness of m-BTL as an antibacterial agent. SEM analysis permitted visualization of biofilm structure in relation to the spatial localization of important biofilm matrix components, the formed biofilms were clearly distinguished in the SEM images. Bacterial cells in the control group were enclosed in thick biofilms. In contrast, there was a considerable reduction in biofilm production when mBTL was present, where bacterial cells seemed less ordered and more scattered with no detectable biofilms. In conclusion, mBTL-loaded-ChNPs is a potential alternative treatment to overcome antimicrobial resistance and condensed MRSA infections.

Post-COVID-19 bacterial infections are a significant threat to global health, mainly due to the overuse and misuse of antibiotics. The review highlights the importance of using antibiotics judiciously and following appropriate guidelines and recommendations. The article also examines the potential indirect contribution of steroids to antibiotic resistance through immune suppression in severe cases of COVID-19. Anti-microbial resistance (AMR) is one of the leading causes of death worldwide that continues as a silent pandemic caused by the major AMR superbug includes Carbapenem-resistant Acinetobacter baumannii (CRAB), Methicillin-resistant Staphylococcus aureus (MRSA), Carbapenem-resistant Enterobacterales (CRE), Extended-spectrum Beta Lactamase producing Enterobacterales (ESBL) which is resistant to cephalosporin and Multidrug-resistant (MDR) Pseudomonas aeruginosa. Ongoing surveillance and monitoring of antibiotic use and resistance helped to minimize the risk of antibiotic resistance and shrink it from pandemic to endemic.

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.

Discovery and development of effective strategies to treat emerging and often drug resistant strains of viral and microbial pathogens presents one of the greatest challenges of the 21st century. Despite nearly a century of progress in developments in antimicrobial and antiviral therapies, infectious diseases still account for a substantial proportion of deaths worldwide, including over 100 million globally in the recent pandemic to date. In recent decades, the plague of antimicrobial resistance also represents an additional and alarming signal for both human and animal healthcare and signals a renewed sense of urgency in addressing this issue. This has made the search for novel classes of antibiotics, antivirals and therapeutics found to be capable of bypassing the microbial and viral resistance mechanisms necessary to in order to replenish our current arsenal of antimicrobial and antiviral drugs and update our therapeutic regimens. In addition, the tremendous impact exerted by viral infections and related pathologies on our lives during the recent decade has forced scientists to acknowledge the opportunities and challenges associated with tackling infectious diseases by developing effective antiviral agents endowed with novel mechanisms of action. The discovery of new antimicrobial/antiviral agents, as well as the repurposing of existing drugs and therapeutic options will be crucial to fight the ever-increasing resistance of “superbugs”, pathogenic fungi, viruses, and parasites. Proponents of modern biophoton therapy proposed in this paper can trace its origins to the Russian scientist Alexander Gurwitsch, who a century ago observed ultra-weak emissions of light emerging from an onion root and soon found additional living tissues to be emanating similar energetic phenomena, thus energizing research which continues to the present day and projected toward the development of useful applications of the new-found biological photonic phenomena. The purpose of the present paper is to introduce the past experiences, potential applications and highly successful outcomes of biophotonic therapy as an option to treat infectious diseases including HIV, Hepatitis C, MRSA, and others, with emphasis on efficacy of using biophotonic therapies to treat and ameliorate the drug resistant variants of the above infectious agents, including potential applications for the current COVID-19 pandemic and in preparation for the emergence of the next epidemic or pandemic.

The urgent global health challenge posed by methicillin-resistant Staphylococcus aureus (MRSA) infections demands effective solutions. Antimicrobial peptides (AMPs) represent promising tools of research of new antibacterial agents and LyeTx I mn∆K, a short synthetic peptide based on the Lycosa erythrognatha spider venom, is a good representative. This study focused on analyzing some antimicrobial activities of LyeTx I mn∆K, including minimum inhibitory and bactericidal concentrations, synergy and resensitization assays, lysis activity, the effect on biofilm, and the bacterial death curve in MRSA. Additionally, its characterization was conducted through isothermal titration calorimetry, dynamic light scattering, calcein release, and finally, efficacy in a mice wound model. The peptide demonstrating remarkable efficacy against planktonic cells and biofilms of MRSA, outperforms vancomycin in terms of rapid bactericidal action and anti-biofilm effects. The mechanism involves significant membrane damage. Interactions with bacterial model membranes, including those with lysylphosphatidylglycerol (LysylPOPG) modifications, highlight versatility and selectivity of this compound. Also, the peptide has the ability to sensitize resistant bacteria to conventional antibiotics, showing potential for combinatory therapy. Furthermore, using an in vivo model, was showed that a formulated gel containing the peptide proved superior to vancomycin in treating MRSA-induced wound in mice. Together the results highlight LyeTx I mnΔK as a promising prototype for the development of effective therapeutic strategies against superficial MRSA infections.

Antimicrobial resistance is a major public health concern. Rodents and shrews live in closer proximity to humans and animals and serve as reservoirs for the transmission of several diseases, including AMR pathogens. There is no data available from India on surveillance of AMR bacteria in rodents and shrews. In this study, bacterial pathogens viz, Staphylococcus sp, Escherichia coli and Salmonella sp were isolated from rodents and shrews and genetic elements conferring antimicrobial resistance in the pathogens were screened by PCR. Bacterial pathogens in the oropharyngeal and anal swabs collected from the rodents and shrews trapped (n=100) were cultured on selective media such as Mannitol salt, Mac Conkey and Xylose lysine deoxycholate media to isolate Staphylococcus sp., E. coli and Salmonella sp. respectively. A total of 76 (80%) S. aureus and 19 (20%) Staphylococcus non aureus were isolated. E. coli was isolated in 89 samples and among the Salmonella sp (n=59), 16 (27%) were S. enteritidis and 29 (49.1%) were S. typhimurium. In S. aureus isolates, mec A and mec C (MRSA) were detected in 40 (52.6%) and 6 (7.9%) isolates respectively. Also, 7 (36.84%) and 1 (5.3%) Staphylococcus non aureus isolates were tested to harbour mec A and mec C genes. A total of 77 (86.5%) E. coli isolates had genes encoding ESBL [TEM in 21 (23.59%), SHV in 45 (50.6%) and CTXM in 11 (12.4%)]. Among the 45 pathogenic Salmonella sp, 44 (97.78%) harboured AMR genes [tet in 13 (28.9%), sul3 & sul4 in 20 (44.4%) and qnrA in 11 (24.4%)]. Thirty-eight animals harboured more than one zoonotic pathogen and 21 with multi-drug resistant genes. Our findings signify that these rodents and shrews may serve as sentinels to screen environment spillover of AMR pathogens and also act as reservoir to transmit MRSA, ESBL, Salmonella sp. human/animals. Also these animals aid in the transfer of antimicrobial resistance genetic elements to non-pathogenic organisms.

The wound management sector has attracted considerable attention due to the increasing challenge posed by antimicrobial resistance (AMR) and the specialized care required for chronic wounds. Effective wound care involves selecting appropriate dressings tailored with antimicrobial agents to prevent bacterial infection. Among various types of wound dressings, fibers and electrospun fibers, with their unique characteristics, have emerged as innovative new materials. However, the rise of AMR necessitates the exploration of new antimicrobial agents for wound dressings, particularly for addressing bacterial pathogens like methicillin-resistant Staphylococcus aureus (MRSA). Endophytic fungi, known for producing diverse bioactive compounds, including novel antibacterial agents, represent a promising source of such new agents. This study tested thirty-two endophytic fungi from thirteen distinct Australian native plants for their antibacterial activity against S. aureus, the most common wound-associated bacteria. Ethyl acetate (EtOAc) extracts from fungal culture filtrates exhibited inhibitory effects against both methicillin-sensitive S. aureus ATCC 25923 and MRSA strains M173525 and M180920. DNA sequence analysis was employed for fungal identification, with EtOAc extracts from the most active sample, EL 19 (Chaetomium globosum), selected for further bactericidal and antibiofilm testing against the chosen bacteria. Biofilm of S. aureus ATCC 25923 was reduced by 55% by EtOAc extracts of EL 19 at 1/2 × MIC. To demonstrate the potential application in wound dressing materials, three different concentrations of the extract were incorporated into Polycaprolactone fiber mats through electrospinning, with resultant inhibition of S. aureus ATCC 25923 being observed. This research underscores the potential of endophytic fungi from Australian plants as sources of substances effective against common wound pathogens. Further exploration of the responsible compounds and their mechanisms could facilitate the development of wound dressings effective against MRSA and innovative biofilm-resistant electrospun fibers, contributing to the global efforts to combat AMR.

The presence of Staphylococcus aureus in six dry-cured meat-processing facilities was investigated. S. aureus was detected in 3.8% of surfaces from five facilities. Prevalence was clearly higher during processing (4.8%) than after cleaning and disinfection (1.4%). Thirty eight isolates were typified by PFGE and MLST. Eleven sequence types (STs) were defined by MLST. ST30 (32%) and ST12 (24%), were the most abundant. Enterotoxin genes were detected in 53% of isolates. The enterotoxin A gene (sea) was present in all ST30 isolates, seb in one ST1 isolate and sec in two ST45 isolates. Sixteen isolates harbored the enterotoxin gene cluster (egc) with four variations in the sequence. The toxic shock syndrome toxin gene (tst) was detected in 82% of isolates. Regarding the antimicrobial resistance, twelve strains were susceptible to all the antibiotics tested (31.6%). However, 15.8% were resistant to three or more antimicrobials, and therefore multidrug-resistant. Our results showed that, in general, efficient cleaning and disinfection procedures were applied. Nonetheless, the presence of S. aureus with virulence determinants and resistance to antimicrobials, and particularly multidrug resistant MRSA ST398 strains might represent a potential health hazard for consumers, even though the pathogen was not isolated from final products.

The purpose of the present study was to investigate anti-staphylococcal activity of liposomal daptomycin, against four biofilm-producing S. aureus and S. epidermidis clinical strains, three of which are methicillin resistant. Neutral and negatively charged Daptomycin-loaded liposomes were prepared by three methods thin film hydration (TFH), DRV and microfluidic mixing (MM), and characterized for drug encapsulation (EE%), size distribution, zeta-potential, vesicle stability, drug release and drug integrity. Interestingly, whilst drug loading in THF and DRV nanosized (by extrusion) vesicles was around 30-35, very low loading (~4%) was possible in MM vesicles, requiring further explanatory investigations. Liposomal encapsulation protected daptomycin from degradation and preserve its bioactivity. Quantitative microtiter plate (crystal violet, CV), methylthiazoltetrazolium (MTT), and growth curve (GC) assays evaluated antimicrobial activity of neutral and negative charge daptomycin-liposomes towards planktonic bacteria and biofilms. Neutral liposomes exhibited dramatically enhanced inhibition of bacteria growth (compared to free drug) for all species studied, while negative charged liposomes were totally inactive. Biofilm prevention and treatment studies revealed high antibiofilm activity of liposomal daptomycin. Neutral liposomes were more active for prevention and negative charge ones for treating established biofilms. Planktonic bacteria as well as matured biofilms of low daptomycin susceptible MRSE and MRSA strains were almost completely eradicated by liposomal-daptomycin indicating the need for their further exploration as antimicrobial therapeutics.

Programmed death ligand 1 (PD-L1) is a co-inhibitory molecule expressed on the surface of various cell types, known for its suppressive effect on T cells through interaction with PD-1. Neutrophils also express PD-L1, and its expression is elevated in specific situations; however, the immunobiological role of PD-L1+ neutrophil has not been fully characterized. Here, we report that PD-L1-expressing neutrophils increased in methicillin-resistant Staphylococcus aureus (MRSA) infection are highly functional in bacterial elimination and supporting inflammatory resolution. The frequency of PD-L1+ neutrophils was dramatically increased in MRSA-infected mice, and this population exhibited enhanced activity in bacterial elimination compared to PD-L1- neutrophils. An administration of PD-L1 monoclonal antibody did not impair PD-L1+ neutrophil function suggesting that PD-L1 expression itself does not influence neutrophil activity. However, PD-1/PD-L1 blockade significantly delayed liver inflammation resolution in MRSA-infected mice, as indicated by increased plasma alanine transaminase (ALT) level and frequencies of inflammatory leukocytes in the liver implying that neutrophil PD-L1 suppresses the inflammatory response of these cells during the acute phase of MRSA infection. Our results reveal that elevated PD-L1 expression can be a marker for enhanced anti-bacterial function of neutrophils. Moreover, PD-L1+ neutrophils are an indispensable population attenuating inflammatory leukocyte activities assisting in a smooth transition into the resolution phase in MRSA infection.