REVIEW | doi:10.20944/preprints202202.0248.v1
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: lactobacilli infections; update; case reports; virulence traits; safety implications
Online: 21 February 2022 (08:54:37 CET)
probiotics. However, these bacteria caused rare infections mostly in diabetic and immunocompromised subjects in presence of risk factors such as prosthetic hearth valves and dental procedures or caries. The scope of this survey was re-assessing the pathogenic potential of lactobacilli based on the infection case reports published in the last three years. In 2019, 2020 and 2021 17, 15 and 16 cases, respective-ly,.including endocarditis, bacteremia and other infections, were reported. These annual numbers are higher than observed previously. Lacticaseibacillus rhamnosus (13 cases), comprising strain GG (ATCC 53103) with established applications in healthcare, L. paracasei (7 cases), Lactobacillus acidophilus (5 cas-es), L. jensenii (5 cases), Lactiplantibacillus plantarum (3 cases), L. paraplantarum, L. delbrueckii subsp. del-brueckii, L. gasseri, L. paragasseri, Limosilactobacillus fermentum and L. reuteri (1 case each) were involved. Virulence characterization of two strains that caused infections, a derivative of L. rhamnosus GG and L.paracasei LP10266, indicated that increased biofilm forming capacity favors pathogenicity and it is determined by variable genetic traits. This survey highlighted that strains of lactobacilli able to cause infections were little characterized genet-ically. Instead, to avoid that these bacteria become a hazard, genetic stability should be periodically re-evaluated by whole genome sequencing (WGS) to ensure that only non-pathogenic variants are ad-ministered to vulnerable individuals.
REVIEW | doi:10.20944/preprints201904.0188.v1
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: Lactobacillus species; opportunistic pathogens; infections; risk factors; predisposing factors; virulence
Online: 16 April 2019 (12:45:22 CEST)
Microorganisms belonging to the Lactobacillus genus are naturally associated or deliberately added to fermented food products and are widely used in probiotic food additives and supplements. Moreover these bacteria normally colonize mouth, gastrointestinal (GI) tract and female genitourinary tract of humans. They exert multiple beneficial effects and are regarded as safe microorganisms. However, infections caused by lactobacilli, mainly endocarditis, bacteremia and pleuropneumonia occasionally occur. The relevance of Lactobacillus spp. as opportunistic pathogens in humans and related risk factors and predisposing conditions are illustrated in this review article with more emphasis on the species L. rhamnosus, that has been more often involved in infection cases. The methods used to identify this species in clinical samples, to distinguish strains and to evaluate traits that can be associated to pathogenicity, as well as future perspectives for improving the identification of potentially pathogenic strains are outlined.
ARTICLE | doi:10.20944/preprints202204.0029.v1
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: Lacticaseibacillus species; probiotic potential; genetic traits; presence in genomes
Online: 6 April 2022 (04:54:20 CEST)
This study aimed to exploring the intra-species distribution of genetic characters that favor the persistence in the gastrointestinal tract (GIT) and host interaction of bacteria belonging to the species Lacticaseibacillus genus. These bacterial species comprise commercial probiotics with the widest use among consumers and strains naturally occurring in GIT and in fermented food. Since little is known on the distribution of genetic traits for adhesion capacity, polysaccharide production, biofilm formation, utilization of substrates critically important for survival in GIT, that influence probiotic characteristics, a list of genetic determinants involved in such functions was created by a search for specific genes involved in the above aspects in the genome the extensively characterized probiotic L. rhamnosus GG. The presence/absence and variability of each gene in other Lacticaseibacillus spp. genomes was assessed by alignment with the publicly available fully annotated genome sequences. Eighty-two gene loci were compared, and 49 of these were found to be absent in some genomes in a species or strain-specific mode. A set of genes was found to be conserved, indicating that all strains of the genus may exert some probiotic effects. Among the variable loci a taurine utilization operon and a α-L-fucosidase were examined for presence/absence in 26 strains isolated from infant feces by PCR based tests. Results were variable among the isolates, though their common origin indicated the capacity to survive in the intestinal niche. This study indicated that the capacity to exert probiotic actions of Lacticaseibacillus spp. depends on a conserved set of genes and is enhanced by variable genetic factors whose role is only in part elucidated. The selection of strains of the most promising probiotic candidates to be used in food is feasible by analyzing presence/absence of a set of variable traits.
ARTICLE | doi:10.20944/preprints202211.0381.v1
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: fermented sausage; Ventricina del Vastese; traditional production; coagulase negative staphylo-cocci; hazardous genetic traits; antibiotic resistance
Online: 21 November 2022 (07:31:16 CET)
Ventricina del Vastese is a traditional dry fermented sausage from Central Italy not yet charac-terized for occurrence, identity and safety of coagulase negative staphylococci (CNS), a bacterial group technologically important for this kind of products. Therefore, in this study, 98 CNS isolates from four manufacturers were differentiated by Repetitive element palindromic PCR (Rep-PCR) and identified by 16S rRNA gene sequencing. These were examined for genes encoding biogenic amine (BA) production, resistance to aminoglycosides, β-lactams and tetracyclines and staphylococcal enterotoxins (SEs). Staphylococcus succinus (55%) predominated, followed by S. xylosus (30%), S. epidermidis (7.4%), S. equorum (3.1%), S. saprophyticus (3.1%) and S. warneri (1%). One S. succinus subsp. casei isolate was slightly β-hemolytic. SEs and the histidine decarboxylase gene hdcA were not detected, while the tyrosine decarboxylase gene tdcA was detected in four S. xylosus isolates. A blaZ beta-lactamase gene and tetracycline resistance genes tetK (six isolates) and tetA (one isolate also bearing tetK) were found, respectively. However, fewer hazardous and AR traits compared to CNS examined in other studies were found, as a probable consequence of using meat from animals reared in conditions that allow to minimize pathogen circulation and antibiotic use. Therefore, appropriate production conditions can reduce these threats.
ARTICLE | doi:10.20944/preprints202001.0341.v1
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: Listeria spp.; food; food contact surfaces; genotyping; virulence genes; toxin-antitoxin system mazEF
Online: 29 January 2020 (03:42:54 CET)
This study aimed to evaluate the hazards posed by foodborne bacteria of the Listeria genus by analyzing prevalence, diversity and virulence of Listeria spp. in food and food manufacturing plants. Seventy five isolates obtained from the routine analysis of 653 samples by three diagnostic laboratories in Northern Italy were genotipically differentiated by Repetitive Extragenic Palindrome (rep) PCR with the GTG5 primer, identified by sequencing the 16S rRNA gene and examined by specific PCR tests for the presence of L. monocytogenes virulence determinants occasionally found to occur in other species of the genus. The identity of the amplification products was confirmed by sequencing. Fifty seven isolates were identified as L. innocua, 12 as L. monocytogenes, 5 as L. welshimeri and one as L. seeligeri. All L. monocytogenes isolates belonged to the serotype 1/2a and were predicted to be virulent for the presence of the inlJ internalin gene. Potentially virulent strains of L. innocua, L. seeligeri and L. welshimeri, carrying the L. monocytogenes inlA gene and/or hly gene, were identified, and most isolates were found to possess the toxin-antitoxin system mazEF for efficient adaptation to heat shock. Results indicated the need to reinforce food contamination prevention measures against all Listeria species by efficiently defining their environmental distribution.
REVIEW | doi:10.20944/preprints202208.0036.v1
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: Listeria ivanovii; pathogenicity; virulence characters; environmental distribution; occurrence in food
Online: 2 August 2022 (04:41:19 CEST)
Listeria ivanovii and L. monocytogenes, are the only pathogenic species of the genus Listeria and share many virulence factors and mechanisms of pathogenicity. L. ivanovii shows host tropism towards small ruminants and rodents and much lower virulence for humans compared to L. monocytogenes. However, severe infections caused by L. ivanovii, resulting in bacteremia, abortion and stillbirth, occasionally occurred in immunocompromised persons and in pregnant women, while in immunocompetent hosts L. ivanovii can cause gastroenteritis. In this review the updated knowledge on virulence aspects and distribution of L. ivanovii in the environment and in food are summarized. Recent research on its virulence characters at genome level gave indications on how pathogenicity evolved in this bacterial species. As for L. monocytogenes, L. ivanovii infections occur after the ingestion of contaminated food, so an overview of reports regarding its distribution in the food products was carried out to obtain indications on the categories of foods exposed to contamination by L. ivanovii. It was found that a wide variety of food products can be a source of this microorganism and that, like L. monocytogenes, L. ivanovii is able to persist in the food production environment. Studies on its ability to grow in enrichment and isolation media suggested that its occurrence in nature might be underestimated. Moreover, virulence varies among strains for differences in virulence character regulation, presence/absence of genetic regions and the possible instability of a Listeria pathogenicity genomic island, LIPI-2, which is unique to L. ivanovii. We can conclude that L. ivanovii, as a possible pathogen for animals and humans, requires more focused investigations regarding its occurrence in the environment and in food and on intra-species variability of pathogenic potential.
REVIEW | doi:10.20944/preprints202303.0301.v1
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: traditional dry fermented sausages; protection policy; desired microbiota; lactic acid bacteria; coagulase negative staphylococci; autochthonous cultures; safety; sensory quality
Online: 16 March 2023 (09:02:51 CET)
Traditional dry fermented meat products are obtained artisanally in many countries, where they represent a gastronomic heritage well distinguished from industrial counterparts. This food category is most often obtained from red meat, a food commodity that is under attack because of evidences of increased risk of cancer and degenerative diseases with high consumption. However, traditional fermented meat products are intended for moderate consumption and gastronomic experience and, as such, their production must be continued also to safeguard culture and economy of the geographical areas of origin. In this review, the main risks attributed to these products are considered and how these risks are minimized by following precise production norms, respectful of the ancient manufacturing processes is described. Moreover, results obtained in studies reporting use of autochthonous microbial cultures of lactic acid bacteria (LAB), coagulase negative staphylococci (CNS), Debaryomyces hansenii and Penicillium nalgiovense to improve safety and quality of traditional fermented meats are summarized. The role of these products as a source of microorganisms that can be beneficial to the host are also considered. From the results of the studies reviewed here it appears that the development of autochthonous cultures for these foods ensure safety and stabilize sensory characteristics with possibility to be extended to the large variety of traditional productions.