Molecular screening of Enterococcus virulence determinants and potential for genetic exchange between food and medical isolates

Molecular epidemiology of antibiotic-resistant Enterococcus spp. from the farm-to-fork continuum in intensive poultry production in KwaZulu-Natal, South Africa

The poultry industry is among the main protein suppliers worldwide. Thus, this study determined the antibiotic resistance and virulence profiles of Enterococcus spp. along the farm-to-fork production chain of an intensive poultry system in the uMgungundlovu District, Kwazulu-Natal, South Africa. Overall, 162 samples along the continuum (growth phase, transport and post-slaughter) were evaluated for the presence of Enterococcus spp. using selective media, biochemical tests and polymerase chain reaction (PCR). Resistance profiles were assessed by Kirby-Bauer disk diffusion method following the WHO-AGISAR recommended antibiotics panel for Enterococcus spp. Antibiotic resistance and virulence genes were detected using real-time PCR. Clonal relatedness was evaluated by REP-PCR. Overall, 131 isolates were recovered across the continuum, (34% E. faecalis, 32% E. faecium, 2% E. gallinarum and 32% other Enterococcus spp.). Resistance to tetracycline (79%), erythromycin (70%), nitrofurantoin (18%), ampicillin (15%), streptomycin (15%), chloramphenicol (10%), ciprofloxacin (4%), tigecycline (4%), gentamicin (4%), teicoplanin (3%) was observed among all Enterococcus spp.; no vancomycin resistance (0%) was recorded. Also, 24% of E. faecium were resistant to quinupristin-dalfopristin. Twenty-four multidrug resistance (MDR) antibiograms were observed across all species; E. faecium (43%) showed the highest frequency of MDR. The most frequently observed antibiotic resistomes were tetM (76%) and ermB (66%) while smaller percentages were noted for aph(3')-IIIa (12%) and vanC1 (1%). Virulence genes efaAFs (100%), cpd (96%) and gelE (80%) were more prevalent in E. faecalis. Clonality revealed that isolates along the continuum were highly diverse with major REP-types consisting of isolates from the same sampling point. This study highlights the diversity of MDR Enterococcus in the food chain with isolates harbouring resistance and virulence genes. These could be reservoirs for the potential transfer of pathogenic enterococci carrying these genes from poultry to humans through the food chain continuum, thus, underscoring the need for routine antibiotic resistance surveillance in food animals.

Virulence Factor Genes Incidence among Enterococci from Sewage Sludge in Eastern Slovakia following Safety Aspect

The sewage sludges represent a potential health hazard because of the quantity of different microbiota detected in sewages. Among microbiota detected in sewages, also belong representatives of the phylum Firmicutes. In the past, environmental enterococci in addition to coliforms were widely used as indicators of faecal contamination. Regarding the enterococcal strains as potential pathogenic bacteria, their pathogenicity is mainly caused by production of virulence factors. Therefore, the aim of the study was to analyse incidence of virulence factors in enterococci from cows' dung water. Species identification of 24 enterococci using MALDI-TOF MS system allotted 23 strains to the species Enterococcus faecium with highly probable species identification and E. faecalis EEV20 with a score value meaning secure genus identification/probable species identification. Enterococci were absent of cytolysin A gene, hyaluronidase gene, and element IS gene. It can be concluded that they are not invasive which is very important from safety aspect. The most frequently detected gene was adhesin E. faecium (efaAfm, in 22 E. faecium strains and in one E. faecalis). Adhesin efaAfs gene was detected in E. faecalis EEV20 and in two E. faecium. GelE gene was present in three strains. E. faecium EF/EC31 was absent of virulence factor genes.

Presence of Virulence Genes in Enterococcus Species Isolated from Meat Turkeys in Germany Does Not Correlate with Chicken Embryo Lethality

Virulence-associated traits have frequently been studied in enterococci and are considered to contribute towards the pathogenicity of infections. In the present study, Enterococcus isolates were collected during diagnostic investigations from meat turkeys in Germany. Twenty-eight isolates of three different Enterococcus species were analyzed for five selected putative virulence traits to understand their potential role in the pathogenicity using the chicken embryo lethality assay. Ten E. faecalis, ten E. faecium, and eight E. gallinarum isolates were examined for the presence of common virulence genes and their phenotypic expression, namely, the cytolysin operon, five individual cyl genes (cylL_L, cylL_S, cylM, cylB, and cylA), gelatinase (gelE), hyaluronidase (hyl_Efm), aggregation substance (asa1), and enterococcal surface protein (esp). The Enterococcus isolates showed significant species-dependent differences in the presence of genotypic traits (p < 0.001 by Fisher's exact test; Cramer's V = 0.68). At least one gene and up to three virulence traits were found in E. faecalis, while six E. faecium isolates and one E. gallinarum isolate did not display any virulence-associated pheno- or genotype. More than half of the Enterococcus isolates (n = 15) harbored the gelE gene, but only E. faecalis (n = 10) expressed the gelatinase activity in vitro. The hyl_Efm gene was found in five E. gallinarum isolates only, while seven isolates showed the hyaluronidase activity in the phenotypic assay. In Cramer's V statistic, a moderate association was indicated for species (V ≤ 0.35) or genotype (V < 0.43) and the results from the embryo lethality assay, but the differences were not significant. All E. gallinarum isolates were less virulent with mortality rates ranging between 0 and 30%. Two E. faecalis isolates were highly virulent, harboring the whole cyl-operon as well as gelE and asa1 genes. Likewise, one E. faecium isolate caused high embryo mortality but did not harbor any of the investigated virulence genes. For the first time, Enterococcus isolates of three different species collected from diseased turkeys were investigated for their virulence properties in comparison. The results differed markedly between the Enterococcus species, with E. faecalis harboring the majority of investigated genes and virulence traits. However, the genotype did not entirely correlate with the phenotype or the isolates' virulence potential and pathogenicity for chicken embryos.

Influence of the Type of Diet on the Incidence of Pathogenic Factors and Antibiotic Resistance in Enterococci Isolated from Faeces in Mice

A comparative study on potential risks was carried out in a collection of 50 enterococci isolated from faeces of mice fed a standard or a high-fat diet enriched with extra virgin olive oil, refined olive oil or butter, at the beginning, after six weeks and after twelve weeks of experiments. Strains were biochemically assessed and genetically characterized. E. faecalis and E. casseliflavus were the most frequently isolated species in any diet and time points. Apart from the fact of not having isolated any strain from the virgin olive oil group during the last balance, we found statistically significant differences p<0.05 among the diets in the percentage of antibiotic resistance and in the presence of the enterococcal surface protein gene (esp), as well as a tendency p<0.1 for the presence of the tyrosine decarboxylase gene (tdc) to increase over time in the group of isolates from the standard diet. When the resistance of the strains to virgin or refined olive oil was studied, only the group of enterococci from high fat diets showed a significantly higher percentage of resistance to refined olive oil p<0.05, while both types of oil equally inhibited those isolated from the standard diet p>0.05.

Investigation of Lactic Acid Bacteria Isolated from Giant Panda Feces for Potential Probiotics In Vitro

The present study aimed to isolate an optimal lactic acid bacterial strain from the feces of healthy giant pandas. The strain exhibited good stability at low pH and high bile salt concentrations, activity against pathogens relevant to pandas, and antibiotic susceptibility. In the current study, 25 isolates were obtained from de Man, Rogosa, and Sharpe agar. Two (E21 and G83) and eight (E1, E2, E16, E18, E21, E69, E70, and G83) isolates demonstrated good performance at pH 2.0 and bile 2% (w/v), respectively. Three isolates (G83, G88, and G90) possessed better antimicrobial effect on enterotoxigenic Escherichia coli CVCC196 (ETEC) than the rest. One isolate (G83) strongly affected Salmonella, whereas three (G83, G87, and G88) exhibited inhibitory activity against Staphylococcus aureus. All isolates were multi-drug resistant. These isolates were identified as Lactobacillus (5 isolates) and Enterococcus (20 isolates) by 16S rRNA sequencing. Virulence genes were detected in Enterococcus isolates. Isolate G83 was identified as Lactobacillus plantarum and was considered as the best probiotic candidate among all of the experimental isolates. This study provided necessary and important theoretical guidance for further experiments on G83 in vivo.

Isolation of Enterococcus faecium, characterization of its antimicrobial metabolites and viability in probiotic Minas Frescal cheese

The aim of this study was to isolate Enterococcus faecium from raw milk samples, to characterize its antimicrobial metabolites, and to evaluate its viability in a probiotic Minas Frescal cheese. For this, antagonist activity against Listeria monocytogenes, safety aspects and biochemical, genotypic, and probiotic characteristics of the isolates were evaluated. Minas Frescal cheese was manufactured with the isolate that showed the best characteristics in vitro, and its viability in the product was evaluated. It was observed that of the 478 lactic acid bacteria isolates, only isolate E297 presented antagonist activity, genes encoding for enterocin production and absence of virulence factors. Besides that, E297 presented probiotic characteristics in vitro, and maintained its viability (8.09 log CFU mL^-1) for 14 days of cold storage, when it was added to cheese. Therefore, isolate E297 can be considered a promising microorganism for the manufacture of probiotic foods, especially Minas Frescal cheese.

Biofilm formation capacity and presence of virulence factors among commensal Enterococcus spp. from wild birds

Enterococci are opportunistic pathogens that can form biofilms during infections and many virulence determinants are involved in this process. Although the virulence factors are often analysed in Enterococcus spp. from humans and food animals, little is known about gut enterococcal isolates from wild birds. Therefore, the determination of virulence factors among enterococci isolated from wild birds may provide new information about a possible source of infection for humans and animals or vice versa via the environment. We analysed different phenotypic and genotypic traits in enterococci from wild birds related to potential virulence in humans and animals and to evaluate biofilm formation and its relationship to virulence genes. The E. faecalis isolates were characterised by greater frequency of biofilm formation in BHI than E. faecium. There was a correlation between hydrophobicity and biofilm formation in BHI broth in E. faecalis. None of the isolates was haemolytic. The presence of some adhesion and gelatinase genes was detected in biofilm-positive isolates. The enterococcal pathogenic factors (esp, hyl, and cyl operon genes) did not seem to be necessary or sufficient for production of biofilm by analysed bacteria. Enterococcus species isolated from wild birds should be considered as a possible source of some virulence determinants.

[Isolation of enterocin-producing Enterococcus hirae strains from the intestinal content of the Patagonian mussel (Mytilus edulis platensis)]

Two bacteriocin-producing lactic acid bacterial strains were isolated from the intestinal content of the Patagonian mussel and characterized by phenotypic and molecular tests. The isolates were identified as Enterococcus hirae and named E. hirae 463Me and 471Me. The presence of the enterocin P gene was identified in both strains by PCR techniques, while enterocin hiracin JM79 was detected only in the 471Me strain. Both strains were sensitive to clinically important antibiotics and among the virulence traits investigated by PCR amplification, only cylL_l and cylL_s could be detected; however, no hemolytic activity was observed in the blood agar test. Cell free supernatants were active against all Listeria and Enterococcus strains tested, Lactobacillus plantarum TwLb 5 and Vibrio anguilarum V10. Under optimal growth conditions, both strains displayed inhibitory activity against Listeria innocua ATCC 33090 after 2h of incubation. E. hirae 471Me achieved a maximum activity of 163840AU/ml after 6h of incubation, while the same value was recorded for E. hirae 463Me after 8h. In both cases, the antagonist activity reached its maximum before the growth achieved the stationary phase and remained stable up to 24h of incubation. To our knowledge, this is first report of the isolation of bacteriocinogenic E. hirae strains from the Patagonian mussel. The high inhibitory activity and the absence of virulence traits indicate that they could be applied in different biotechnological areas such as food biopreservation or probiotic formulations.

Evaluation of Bile Salt Hydrolases, Cholesterol-Lowering Capabilities, and Probiotic Potential of Enterococcus faecium Isolated From Rhizosphere

Bile salt hydrolase (BSH) activity, hypo-cholesterolemic effect, and probiotic properties have been reported for Enterococcus strains isolated from animal and human gut and fermented foods but not for strains isolated from environmental niches, like aquatic and terrestrial plants, soil, and water. The present study is the first report on isolation of Enterococcus faecium from rhizospheric soils that harbor the bsh gene, remove cholesterol in vitro, and possess essential and desirable probiotic attributes. Fifteen samples were collected from different sites located in northern, southern, and central regions of India, of which five yielded pure colonies that were named LR2, LR3, ER5, LR13, and VB1. These were identified by 16S rRNA gene sequencing as E. faecium and evaluated for BSH activity, cholesterol-lowering potential in vitro, and probiotic properties. Our results indicated that all the strains were capable of surviving the harsh conditions of the gastrointestinal tract and did not harbor any of the virulence genes. Though all strains showed the presence of bsh and potential for cholesterol removal, E. faecium strain LR13 showed a remarkable cholesterol removal capability and vancomycin susceptibility and possessed most of the desirable and essential attributes of a probiotic. Hence, it seems to be a fairly promising probiotic candidate that needs to be further evaluated in in vivo studies, especially for its hypo-cholesterolemic potential.

Molecular screening of beneficial and safety determinants from bacteriocinogenic lactic acid bacteria isolated from Brazilian artisanal calabresa

Despite of the beneficial relevance of several lactic acid bacteria (LAB) in the food industry, micro-organisms belonging to this group can determine spoilage in food products and carry a number of virulence and antibiotic resistance-related genes. This study aimed on the characterization of beneficial and safety aspects of five bacteriocinogenic LAB strains (Lactobacillus curvatus 12-named L. curvatus UFV-NPAC1), L. curvatus 36, Weissela viridescens 23, W. viridescens 31 and Lactococcus garvieae 36) isolated from an artisanal Brazilian calabresa, a traditional meat sausage. Regarding their beneficial aspects, all tested isolates were positive for mub, while EF226-cbp, EF1249-fbp and EF2380-maz were detected in at least one tested strain; none of the isolates presented map, EFTu or prgB. However, evaluated strains presented a variable pattern of virulence-related genes, but none of the strains presented gelE, cylA, efsA, cpd, int-Tn or sprE. Moreover, other virulence-related genes evaluated in this study were detected at different frequencies. L. curvatus 12 was generated positive results for ace, ccf, int, ermC, tetL, aac(6')-Ie-aph(2″)-Ia, aph(2″)-Ib, aph(2″)-Ic, bcrB, vanB and vanC2; L. curvatus 36: hyl, asa1, esp, int, ermC, tetK, aph(3')-IIIa, aph(2'')-Ic and vanC2; L. garvieae 32: asa1, ant(4')-Ia, aph(2'')-Ib, catA, vanA and vanC1; W. viridescens 23: esp, cob, ermB, aph(3')-IIIa, aph(2'')-Ic, vanA, vanB and vanC2; W. viridescens 31: hyl, esp, ermC, aph(3')-IIIa, aph(2'')-Ib, aph(2'')-Ic, catA, vanA and vanB. Despite presenting some beneficial aspects, the presence of virulence and antibiotic resistance genes jeopardize their utilization as starter or biopreservatives cultures in food products. Considering the inhibitory potential of these strains, an alternative would be the use of their bacteriocins as semi-purified or pure technological preparation. SIGNIFICANCE AND IMPACT OF THE STUDY: The food industry has a particular interest in using bacteriocinogenic lactic acid bacteria (LAB) as starter, probiotics and/or biopreservatives in different food products. Characterization of additional beneficial features is important to identify new, multifunctional potential probiotic strains. However, these strains can only be applied in food products only after being properly characterized according their potential negative aspects, such as virulence and antibiotic resistance genes. A wide characterization of beneficial and safety aspects of bacteriocinogenic LAB is determinant to guide the proper utilization of these strains, or their purified bacteriocins, by the food industry.

Bacteriocinogenic Lactococcus lactis subsp. lactis 3MT isolated from freshwater Nile Tilapia: isolation, safety traits, bacteriocin characterisation, and application for biopreservation in fish pâté

This work was aimed to screen bacteriocin-producing LAB from freshwater fish, select a prominent strain and evaluate its safety, characterise the bacteriocin produced, and evaluate its potential to be used as biopreservatives. Isolate 3MT showed the ability to produce bacteriocin-like substances and was identified as Lactococcus lactis subsp. lactis. This strain proved to be free from virulence factors as well as biogenic amine production and antibiotic resistance patterns. The bacteriocin produced displayed high resistance to heat, pH, detergents, and its partial purification led to a 4.35-fold increase in specific activity. Moreover, this bacteriocin showed the ability to inhibit the growth of Vibrio sp. 1T1 in fish pâté stored at 10 °C for 20 days, without altering its sensory properties. The bacteriocin can be used successfully as a preservative to improve the hygienic quality and enhance the shelf life of fish paté in particular and food products in general. Lactococcus lactis subsp. lactis strain 3MT can also be safely used as a protective culture.

Enterococci: Between Emerging Pathogens and Potential Probiotics

Enterococci are ubiquitous microorganisms that could be found everywhere; in water, plant, soil, foods, and gastrointestinal tract of humans and animals. They were previously used as starters in food fermentation due to their biotechnological traits (enzymatic and proteolytic activities) or protective cultures in food biopreservation due to their produced antimicrobial bacteriocins called enterocins or as probiotics, live cells with different beneficial characteristics such as stimulation of immunity, anti-inflammatory activity, hypocholesterolemic effect, and prevention/treatment of some diseases. However, in the last years, the use of enterococci in foods or as probiotics caused an important debate because of their opportunistic pathogenicity implicated in several nosocomial infections due to virulence factors and antibiotic resistance, particularly the emergence of vancomycin-resistant enterococci. These virulence traits of some enterococci are associated with genetic transfer mechanisms. Therefore, the development of new enterococcal probiotics needs a strict assessment with regard to safety aspects for selecting the truly harmless enterococcal strains for safe applications. This review tries to give some data of the different points of view about this question.

PreliminaryIn VitroEvaluation of the Probiotic Potential of the Bacteriocinogenic StrainEnterococcus lactisPMD74 Isolated from Ezine Cheese

Ezine cheese is a nonstarter and long-ripened cheese produced in the Mount of Ida region of Çanakkale, Turkey, with a protected designation of origin (PDO) status. The nonstarter fermented foods serve as sources for the isolation of novel strains. The present study aimed to report the novelty of the bacteriocinogenicEnterococcus lactisPMD74 strain and thein vitroassessment of its potential as a probiotic candidate. Additionally, the present study aimed to describe the technological and safety-related properties of the aforementioned strain. The strain exhibited high viability at pH 3.0, in the presence of pepsin, pancreatin, and bile salts (0.3% and 0.5%), and considerable survival passage through the stimulated digestion tests. The strain PMD74 exhibited substantial autoaggregative (41%) and coaggregative properties, which increased as a function of time. The highest coaggregation percentage was obtained withSalmonella entericaserotype Typhimurium SL1344 (23%), followed byStaphylococcus aureusATCC 6538 (10.3%) andEscherichia coliATCC 26922 (7.4%), respectively. The strain PMD74 was able to inhibit the growth of a number of Gram-positive bacteria, includingListeria monocytogenes,Lactobacillus sake,Staphylococcus aureus, andE. faecalis. The antimicrobial activity of the proteinaceous compound was calculated as 6400 AU·mL−1by the critical dilution method againstE. faecalisATTC 29212.γ-Hemolytic PMD74 was observed to be sensitive to vancomycin, ampicillin, penicillin, gentamicin, tetracycline, chloramphenicol, and tylosin. Among the four genes tested,E. lactisPMD74 was observed to be positive for three virulence determinants,ace,sprE, andgelE, and negative foresp. The amino acid decarboxylase activities were detected negative for histidine, tyrosine, and ornithine.E. lactisPMD74 was classified as a low acidifier, which suggested its possible role as an adjunct culture.E. lactisPMD74 exhibited considerable survival ability (8.86 log CFU·mL−1) in the acidic condition of fermented milk for a four-week-long storage period.

Detailed Soluble Proteome Analyses of a Dairy-Isolated Enterococcus faecalis: A Possible Approach to Assess Food Safety and Potential Probiotic Value

Enterococci are common inhabitants of the gastrointestinal tracts of humans and animals and thanks to their capability to tolerate different environmental conditions and their high rates of gene transfer, they are able to colonize various ecological niches, as food matrices. Enterococcus faecalis bacteria are defined as controversial microorganisms. From one side they are used as food starters, bio-control agents and probiotics to improve human or animal health. From the other side, in the last two decades enterococci have emerged as important nosocomial pathogens, because bearing high-level of resistance to antibiotics and several putative virulence factors. In this study, the soluble proteome quantitation data (LC-MS/MS) of the food-isolated strain E. faecalis D27 (dairy-isolate) was compared with the soluble proteome quantitation data of the pathogenic E. faecalis UW3114 (urinary tract infection isolate) and with the one of the health promoting strain E. faecalis Symbioflor1, respectively. The comparison of cytosolic protein expression profiles highlighted statistically significant changes in the abundance of proteins mainly involved in specific metabolic pathways, nutrient transport, stress response, and cell wall modulation. Moreover, especially in the dairy isolate and the clinical isolate, several proteins with potential pathogenic implications were found, such as serine proteases, von Willebrand factor, serine hydrolase with beta lactamase activity, efflux transporter, and proteins involved in horizontal gene transfer. The analysis of the extracellular proteome provided interesting results concerning proteins involved in bacterial communication, such as pheromones and conjugative elements and also proteins able to interact with human components. The phenotypic characterization evaluating (i) biofilm formation (ii) hemolytic activity on blood agar plates (iii) protease activity (iv) gelatinase (v) antibiotic resistance pattern, enabled us to elucidate the risks associated with the poor characterized foodborne E. faecalis D27.

Antimicrobial Resistance and Virulence Genes in Enterococcus faecium and Enterococcus faecalis from Humans and Retail Red Meat

The emergence of antimicrobial-resistant and virulent enterococci is a major public health concern. While enterococci are commonly found in food of animal origin, the knowledge on their zoonotic potential is limited. The aim of this study was to determine and compare the antimicrobial susceptibility and virulence traits of Enterococcus faecalis and Enterococcus faecium isolates from human clinical specimens and retail red meat in Slovenia. A total of 242 isolates were investigated: 101 from humans (71 E. faecalis, 30 E. faecium) and 141 from fresh beef and pork (120 E. faecalis, 21 E. faecium). The susceptibility to 12 antimicrobials was tested using a broth microdilution method, and the presence of seven common virulence genes was investigated using PCR. In both species, the distribution of several resistance phenotypes and virulence genes was disparate for isolates of different origin. All isolates were susceptible to daptomycin, linezolid, teicoplanin, and vancomycin. In both species, the susceptibility to antimicrobials was strongly associated with a food origin and the multidrug resistance, observed in 29.6% of E. faecalis and 73.3% E. faecium clinical isolates, with a clinical origin (Fisher's exact test). Among meat isolates, in total 66.0% of E. faecalis and E. faecium isolates were susceptible to all antimicrobials tested and 32.6% were resistant to either one or two antimicrobials. In E. faecalis, several virulence genes were significantly associated with a clinical origin; the most common (31.0%) gene pattern included all the tested genes except hyl. In meat isolates, the virulence genes were detected in E. faecalis only and the most common pattern included ace, efaA, and gelE (32.5%), of which gelE showed a statistically significant association with a clinical origin. These results emphasize the importance of E. faecalis in red meat as a reservoir of virulence genes involved in its persistence and human infections with reported severe outcomes.

Antimicrobial Resistance, Virulence Determinants, and Biofilm Formation of Enterococcus Species From Ready-to-Eat Seafood

Enterococcus species form an important population of commensal bacteria and have been reported to possess numerous virulence factors considered significantly important in exacerbating diseases caused by them. The present study was designed to characterize antibiotic-resistant and virulent enterococci from ready-to-eat (RTE) seafood. A total of 720 RTE shrimp samples comprising sauced shrimp (n = 288), boiled shrimp (n = 216), and smoked shrimp (n = 216) obtained from open markets in Delta State, Nigeria, were assessed. Standard classical methods and polymerase chain reaction (PCR) were used in identifying the Enterococcus species. Potential virulence factors (β-hemolysis, gelatinase activity, S-layer, and biofilm formation) were assessed using standard procedures. The antibiotic susceptibility profile of the identified enterococci isolates was assayed using the Kirby–Bauer disc diffusion method. PCR was further used to screen selected antibiotic resistance and virulence genes. Prevalence of Enterococcus species from shrimp varieties is as follows: sauced, 26 (9.03%); boiled, 6 (2.78%); and smoked, 27 (12.50%), with an overall prevalence of 59 (8.19%) based on the occurrence of black hallow colonies after incubation. Enterococcus species detected include E. faecalis, 17 (28.8%); E. faecium, 29 (49.2%); E. gallinarum, 6 (10.2%); E. casseliflavus, 2 (3.4%); E. hirae, 3 (5.1%); and E. durans, 2 (3.4%). Biofilm occurrence among the shrimp varieties is as follows: 19/26 (73.1%) for sauced shrimps, 5/6 (83.3%) for boiled shrimps, and 16/27 (59.3%) for smoked shrimps. The phenotypic expression of the enterococci virulence revealed the following: S-layer, 59 (100%); gelatinase production, 19 (32.2%); and β-hemolysis, 21 (35.6%). An average of 3–11 virulence genes were detected in the Enterococcus species. The resistance profile of Enterococcus species is as follows: erythromycin, 29 (49.2%); vancomycin, 22 (37.3%); and tetracycline, 27 (45.8%). The frequency of occurrence of antibiotic resistance genes from the phenotypic resistant enterococci isolates to the macrolide, glycopeptide, and tetracycline antibiotics is as follows: ermA, 13/29 (44.8%); vanA, 14/22 (63.6%); tetA, 14/27 (51.9%); tetM, 15/27 (55.6%); ermB, 4/29 (13.8%); and vanB, 5/22 (22.7%). Findings from this study reveal the antibiotic resistance of enterococci strains of such species as E. durans, E. casseliflavus, E. gallinarum, and E. hirae. This study further revealed that RTE food products are reservoirs of potential virulent enterococci with antibiotic-resistant capabilities. This provides useful data for risk assessment and indicates that these foods may present a potential public health risk to consumers.

Probiotics: If It Does Not Help It Does Not Do Any Harm. Really?

Probiotics per definition should have beneficial effects on human health, and their consumption has tremendously increased in the last decades. In parallel, the amount of published material and claims for their beneficial efficacy soared continuously. Recently, multiple systemic reviews, meta-analyses, and expert opinions expressed criticism on their claimed effects and safety. The present review describes the dark side of the probiotics, in terms of problematic research design, incomplete reporting, lack of transparency, and under-reported safety. Highlighted are the potential virulent factors and the mode of action in the intestinal lumen, risking the physiological microbiome equilibrium. Finally, regulatory topics are discussed to lighten the heterogeneous guidelines applied worldwide. The shift in the scientific world towards a better understanding of the human microbiome, before consumption of the probiotic cargo, is highly endorsed. It is hoped that better knowledge will extend the probiotic repertoire, re-confirm efficacy or safety, establish their efficacy and substantiate their beneficial effects.

Genomic and Functional Characterization of Enterococcus mundtii QAUEM2808, Isolated From Artisanal Fermented Milk Product Dahi

Microbial strains with a unique combination of technological and bioactive properties are preferred for industrial applications. The present study was conducted to evaluate the potential use of Enterococcus mundtii QAUEM2808 (NCBI Accession Number: LSMC00000000) in milk fermentation. This strain was isolated from Dahi, an indigenous fermented milk product of South-East Asia. The in vitro study confirmed the acidification ability as well as the proteolytic, cellulolytic, and amylolytic enzyme activities of this strain. It also produced a substantial amount of the folate in laboratory media and no physiological dysfunctions in laboratory animals was observed in feeding trials. All these properties were confirmed by in silico genome analysis. The Enterococcus mundtii QAUEM2808 genome consisted of a single, circular chromosome comprising 2,957,300-bp, 2,587 genes with GC content of 38.5%. Moreover, 16t RNAs, 1, 3 (16S, 23S) rRNAs, 4 ncRNAs, and 91 pseudo genes were also predicted. The majority of genome encode genes for protein, amino acids, carbohydrate, cell wall DNA and RNA metabolisms including all genes required for conversion of lactose to lactic acid. It also exhibited antimicrobial activity against E. coli ATCC 10536, S. aureus ATCC 6538, P. aeruginosa ATCC 9027, and L. monocytogenes ATCC 13932 and was found to be sensitive to commonly used antibiotics. The in silico analysis revealed the presence of genes for mundaticin and enterocin production, and CRISPER regions, however, the genes for antibiotic resistance were absent. No genes related to the pathogenicity island and prophages were detected by genome mining. Therefore, it could be inferened that Enterococcus mundtii QAUEM2808 has the potential to be used in milk fermentation as adjunct culture.

The Influence of Heat-Killed Enterococcus faecium BGPAS1-3 on the Tight Junction Protein Expression and Immune Function in Differentiated Caco-2 Cells Infected With Listeria monocytogenes ATCC 19111

Listeria monocytogenes, the common foodborne pathogenic bacteria species, compromises the intestinal epithelial barrier, leading to development of the listeriosis, a severe disease especially among immunocompromised individuals. L. monocytogenes infection usually requires antibiotic treatment, however, excessive use of antibiotics promotes emergence of antibiotic resistance and the destruction of gut microbiota. Probiotics, including lactic acid bacteria (LAB), have been repeatedly proven as an alternative approach for the treatment of various infections. We have analyzed the potential of Enterococcus faecium BGPAS1-3, a dairy isolate exhibiting strong direct antilisterial effect, to modulate the response of differentiated Caco-2 intestinal epithelial cells to L. monocytogenes ATCC 19111 infection. We showed that the molecule with antilisterial effect is a bacterial cell-wall protein that is highly resistant to the high-temperature treatment. When we tested the antilisterial potential of heat-killed BGPAS1-3, we found that it could prevent tight junction disruption in differentiated Caco-2 monolayer infected with L. monocytogenes ATCC 19111, induce antilisterial host response mechanisms, and stimulate the production of protective TGF-β in intestinal epithelial cells. We also showed that the modulation of MyD88 dependent TLR2 and TLR4 pathways by BGPAS1-3 are involved in host response against L. monocytogenes ATCC 19111. Since heat-killed BGPAS1-3 possess strong antilisterial effects, such postbiotic could be used as a controllable and safe therapeutic.

In vitro treatment of Enterococcus faecalis with calcium hydroxide impairs phagocytosis by human macrophages

OBJECTIVE

Monocyte-derived macrophages (MDMs) ability to phagocytize and produce nitric oxide (NO) was tested against root-canal strains of Enterococcus faecalis submitted to alkaline stress. Root-canal strains were also compared with urine Enterococci.

MATERIALS AND METHODS

Enterococcus faecalis were stressed with alkaline-BHI broth and incubated in vitro at a cell/bacteria ratio of 1:5. Phagocytosis was analyzed by fluorescence microscopy using acridine orange stain, and NO concentration was measured in supernatants.

RESULTS AND CONCLUSIONS

Alkaline-stress significantly impaired MDMs phagocytosis of E. faecalis strains analyzed, except in ATCC4083 isolated from a pulpless tooth, but NO production was unchanged. Comparison of different strains showed the urine isolate had higher NO levels than root canal strains. Alterations in the bacterial cell wall structures after alkaline-stress possibly made bacteria less recognizable and phagocytized by MDMs but did not affect their ability to activate NO production. Furthermore, root canal strains elicited different responses by immune cells compared with strains from urine. Clinically, impaired phagocytosis of E. faecalis could contribute to their persistence in root canal systems previously treated with calcium hydroxide.

Probiotic Properties of Enterococcus Isolated From Artisanal Dairy Products

The present study focused on probiotic characterization and safety evaluation of Enterococcus isolates from different artisanal dairy products. All the isolates exhibited inhibitory activity against several food spoilage bacteria and food-borne pathogens, including Shigella flexneri, Staphylococcus aureus, Listeria monocytogenes, Yersinia enterocolitica, Klebsiella pneumoniae, Escherichia coli, and Bacillus subtilis. The PCR results indicated the presence of at least one enterocin structural gene in all the tested strains. The Enterococcus isolates were further evaluated regarding their safety properties and functional features. The isolates were susceptible to vancomycin, gentamycin, and chloramphenicol. The results of PCR amplification revealed that all the tested isolates harbored none of the tested virulence genes except E. faecalis (ES9), which showed the presence of esp gene. The Enterococcus isolates showed cholesterol lowering properties. The selected isolates showed a high tolerance to low pH, and toward bile salts. They also demonstrated hydrophobicity activity, auto-aggregation, and adhesion ability to the human intestinal Caco-2 cell line. These properties may contribute the bacteria colonizing the gut. This study revealed that the Enterococcus isolates, especially E. durans ES11, ES20 and ES32, might be excellent candidates for production of functional foods to promote health benefits.

Inhibition of Clostridium difficile in Mice Using a Mixture of Potential Probiotic Strains Enterococcus faecalis NM815, E. faecalis NM915, and E. faecium NM1015: Novel Candidates to Control C. difficile Infection (CDI)

This study is aimed at the isolation, identification, and characterization of potential probiotic strains capable of inhibiting Clostridium difficile in vitro and in vivo. Twenty isolates were isolated from infant fecal samples and screened against C. difficile using their cell-free supernatant. Only three isolates showed maximum inhibition from 56.05 to 60.60%, thus they were characterized for probiotic properties and safety. The results obtained approved their tolerance to the gastrointestinal tract conditions and safety profile. They were identified by sequencing 16S rRNA as Enterococcus faecalis NM815, E. faecalis NM915, and Enterococcus faecium NM1015. For in vivo evaluation, a viable mixture of these three strains (10⁹ CFU/mL) was administrated to a group of mice (treated group) in daily dose for 14 days, then followed by challenge with viable C. difficile (10⁵ CFU/mL) in daily dose for 7 days, then a second administration of a viable mixture of the three strains was done daily for 7 days. In addition, the control group was administered PBS buffer only and the untreated group received PBS buffer instead of the probiotic mixture before and after the challenge with C. difficile. The results obtained from histological analysis confirmed the effectiveness of our three potential probiotic strains which expressed inhibition of C. difficile and maintained the structural integrity of the liver and intestinal cells.

In Silico and Experimental Data Claiming Safety Aspects and Beneficial Attributes of the Bacteriocinogenic Strain Enterococcus faecalis B3A-B3B

This study aimed at comparing the genome of Enterococcus faecalis B3A-B3B, a bacteriocinogenic strain recently isolated from a healthy Iraqi infant to those of Enterococci of clinical and beneficial grades. The putative genes gelE, cpd, efaAfm, ccf, agg, and cob coding for virulence factors were detected in B3A-B3B strain, which meanwhile resulted to be non-cytotoxic, non-hemolytic, devoid of inflammatory effects, and sensitive to most of the antibiotics tested except for clindamycin and trimethoprim, which resistance is usually ascribed to intrinsic nature. B3A-B3B strain was remarkable for its hydrophobicity, auto-aggregation, adhesion to human Caco-2 cells, and survival in simulated gastrointestinal conditions, and cholesterol assimilation fulfilling therefore key beneficial attributes.

Occurrence of enterococci harbouring clinically important antibiotic resistance genes in the aquatic environment in Gauteng, South Africa

The development of antibiotic resistance and dissemination of its determinants is an emerging public health problem as it compromises treatment options of infections that were, until recently, treatable. Investigation of outbreaks of vancomycin resistant enterococci (VRE) suggests that the environment serves as a significant reservoir for antibiotic resistance genes (ARGs). However, there is a paucity of data regarding the presence of ARGs in the water sources in South Africa. In this study, water samples collected from wastewater treatment plants (WWTPs), surface water and hospital sewage were screened for enterococci harbouring genes conferring resistance to four classes of antibiotics. Enterococci isolates harbouring ARGs were detected in raw influent and treated wastewater discharge from WWTPs and hospital sewage water. Plasmid and transposon encoded ermB (macrolide), tetM and tetL (tetracycline) as well as aph(3')-IIIa (aminoglycosides) genes were frequently detected among the isolates, especially in E. faecalis. The presence of enterococci harbouring ARGs in the treated wastewater suggest that ARGs are discharged into the environment where their proliferation could be perpetuated. Among the enterococci clonal complexes (CCs) recovered from wastewater were E. faecium CC17 (ST18), which is frequently associated with hospital outbreaks and a novel E. faecalis sequence type (ST), ST780.

Molecular and phenotypic characterization of enterococci isolated from broiler flocks in Turkey

The aim of this study was to determine the antimicrobial resistance, resistance mechanisms implicated, and virulence genes (asa1, gelE, cylA, esp, and hyl) of Enterococcus spp. isolated from broiler flocks in Turkey. In addition, clonality of ampicillin and vancomycin-resistant enterococci was also investigated using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Out of 430 cloacal swab samples investigated, 336 (78.1%) Enterococcus spp. was isolated. The most frequently identified species were E. faecalis (87.8%), E. faecium (8.3%), E. durans (2.4%), E. casseliflavus (0.9%), and E. hirae (0.6%). The most common resistance was against tetracycline (81.3%), erythromycin (77.1%), ciprofloxacin (56.8%), and chloramphenicol (46.4%). Fifty (14.9%) isolates showed high-level gentamicin resistance (HLGL) phenotype. Ampicillin and vancomycin resistance were observed in 3.3% and 1.5% of the isolates, respectively. Two hundred eighty-three isolates were positive for the presence of virulence genes. Among the virulence genes tested, only gelE, asa1, esp, and cylA genes were detected. The most prevalent virulence gene was gelE (234, 69.6%), followed by asa1 (160, 47.6%), esp (37, 11%), and cylA (2, 0.6%). In conclusion, this study revealed that commensal enterococci from broiler flocks showed high rate of resistance to antimicrobials including clinically important antimicrobials for humans. The main underlying reason for high resistance could be attributed to the inappropriate and widespread use of antimicrobials. Therefore, there is an urgent need to develop control strategies to prevent the emergence and spread of antimicrobial resistance.

Enterococcus faecium TIR-Domain Genes Are Part of a Gene Cluster Which Promotes Bacterial Survival in Blood

Enterococcus faecium has undergone a transition to a multidrug-resistant nosocomial pathogen. The population structure of E. faecium is characterized by a sharp distinction of clades, where the hospital-adapted lineage is primarily responsible for bacteremia. So far, factors that were identified in hospital-adapted strains and that promoted pathogenesis of nosocomial E. faecium mainly play a role in adherence and biofilm production, while less is known about factors contributing to survival in blood. This study identified a gene cluster, which includes genes encoding bacterial Toll/interleukin-1 receptor- (TIR-) domain-containing proteins (TirEs). The cluster was found to be unique to nosocomial strains and to be located on a putative mobile genetic element of phage origin. The three genes within the cluster appeared to be expressed as an operon. Expression was detected in bacterial culture media and in the presence of human blood. TirEs are released into the bacterial supernatant, and TirE2 is associated with membrane vesicles. Furthermore, the tirE-gene cluster promotes bacterial proliferation in human blood, indicating that TirE may contribute to the pathogenesis of bacteremia.

Prevalence of virulence determinants and antibiotic resistance patterns of Enterococcus faecalis strains in patients with community-acquired urinary tract infections in Iran

The aim of this study was to characterize virulence factors and antibiotic resistance patterns in E. faecalis strains obtained from community-acquired urinary tract infections. A total of 70 E. faecalis isolates from Labbafinejad Hospital in Tehran were collected. Antibiotic resistance and virulence determinants were examined by phenotypic and molecular methods. Among 70 E. faecalis isolates, efba (97.1%), ace (95.7%), and gelE (94.3%) were the most prevalent virulence genes. The most common antibiotic resistance pattern was tetracycline (88.6%) and minocycline (87.1%). Multi-drug resistant phenotype was detected among 10% of them. Our results showed capability of E. faecalis strains for infection of the urinary tract in community. Involvement of virulence determinants in the pathogenesis of community acquired E. faecalis strains was proposed due to their high prevalence rates. Food producing animals were proposed as their environmental reservoirs, due to dominance of tetracycline resistance phenotype among them.

Co-occurrence of antimicrobial resistance and virulence determinants in enterococci isolated from traditionally fermented fish products

OBJECTIVES

Fermented foods frequently consumed in Northeast India can act as a reservoir for disseminating pathogenic organisms. Enterococci are often responsible for contamination of food products. This study investigated the antimicrobial resistance and co-existing virulence determinants of enterococci found in traditionally processed foods in India.

METHODS

A total of 38 enterococci isolates identified as Enterococcus faecalis isolated from fermented fish samples from retail markets of Northeast India were selected for screening of pathogenic traits.

RESULTS

Of the 38 isolates, 8 (21%) were able to hydrolyse gelatin and 13 (34%) showed protease activity. Screening for haemolytic activity of the isolates showed no positive test on sheep blood. The presence of virulence genes (gelE, agg, esp, cpd, efaAfs and cylA) was investigated by PCR. gelE, agg and esp were present in 17, 13 and 4 isolates, respectively. cpd and efaAfs were found in all isolates, whereas cylA was not detected. High resistance percentages to various antibiotics included kanamycin (63%), vancomycin and gentamicin (58%), tetracycline (53%) and rifampicin (50%). The vanA genotype was confirmed in 15 multidrug- and vancomycin-resistant strains.

CONCLUSION

The simultaneous occurrence of virulence determinants and antimicrobial resistance in enterococci prevalent in the fermented fish products studied poses a potential threat of transmission to humans through the food chain. This study highlights the importance of E. faecalis as a reservoir of antimicrobial resistance and virulence factors and their potential transfer to humans. The findings reopen the issue of food safety regarding enterococci prevalent in traditionally processed fish products in the region.

In vitro Assessment of the Probiotic Properties and Bacteriocinogenic Potential of Pediococcus pentosaceus MZF16 Isolated From Artisanal Tunisian Meat "Dried Ossban"

Pediococcus pentosaceus MZF16 has been isolated from artisanal Tunisian meat so called "Dried Ossban," an original ecological niche, and identified by MALDI-TOF mass spectrometry and 16S rDNA sequencing. This bacterium showed a high tolerance to gastric stress conditions, and toward bile salts. P. pentosaceus MZF16 also demonstrated a hydrophobic surface profile (high adhesion to xylene), autoaggregation, and adhesive abilities to the human intestinal Caco-2/TC7 cell line. These properties may help the bacterium colonizing the gut. Furthermore, MZF16 was found to be resistant to gentamycin and chloramphenicol but did not harbor any transferable resistance determinants and/or virulence genes. The data also demonstrated absence of cytotoxicity of this strain. Conversely, P. pentosaceus MZF16 can slightly stimulate the immune system and enhance the intestinal epithelial barrier function. Moreover, this bacterium has been shown to be highly active against Listeria spp. due to bacteriocin production. Characterization of the bacteriocin by PCR amplification, sequencing and bioinformatic analyses revealed that MZF16 produces a bacteriocin 100% identical to coagulin, a pediocin-like inhibitory substance produced by Bacillus coagulans. To our knowledge, this is the first report that highlights the production of a pediocin 100% identical to coagulin in a Pediococcus strain. As coagulin, pediocin MZF16 has the consensus sequence YYGNGVXCXXXXCXVXXXXA (X denotes any amino acid), which confirms its belonging to class IIa bacteriocins, and its suitability to preserve foods from Listeria monocytogenes development. According to these results, P. pentosaceus MZF16 can be proposed as a probiotic and bioprotective agent for fermented foods, including Tunisian dry meat and sausages. Further investigations will aim to study the behavior of this strain in meat products as a component of functional food.

Safety Aspect of Enterococcus faecium FL31 Strain and Antibacterial Mechanism of Its Hydroxylated Bacteriocin BacFL31 against Listeria monocytogenes

In previous work we have isolated and identified a new strain called Enterococcus faecium FL31. The active compound secreted by this strain, "BacFL31", has been purified and characterized. In the present study, safety aspect, assessed by microbiological and molecular tests, demonstrated that Enterococcus faecium FL31 was susceptible to relevant antibiotics, free of hemolytic, gelatinase, DNase, and lipase activities. In addition, it did not harbor virulence and antibiotic resistance genes. Combined SYTOX Green dye and UV-absorbing experiments, along with released extracellular potassium and transmembrane electrical potential measurements, showed that pure BacFL31 at a concentration of 1×MIC (50 μg/mL) could damage cytoplasmic membrane of the pathogen Listeria monocytogenes ATCC19117. The same concentration causes the leakage of its intracellular constituents and leads to the destruction of this pathogenic microorganism. In summary, this work reflected characteristics of Enterococcus faecium FL31 strain and its bacteriocin in terms of functional and safety perspectives.

Antimicrobial resistance of Enterococcus faecium strains isolated from commercial probiotic products used in cattle and swine

Probiotics, an antibiotic alternative, are widely used as feed additives for performance benefits in cattle and swine production systems. Among bacterial species contained in probiotics, Enterococcus faecium is common. Antimicrobial resistance (AMR), particularly multidrug resistance, is a common trait among enterococci because of their propensity to acquire resistance and horizontally transfer AMR genes. Also, E. faecium is an opportunistic pathogen, and in the United States, it is the second most common nosocomial pathogen. There has been no published study on AMR and virulence potential in E. faecium contained in probiotic products used in cattle and swine in the United States. Therefore, our objectives were to determine phenotypic susceptibilities or resistance to antimicrobials, virulence genes (asa1, gelE, cylA, esp, and hyl) and assess genetic diversity of E. faecium isolated from commercial products. Twenty-two commercially available E. faecium-based probiotic products used in cattle (n = 13) and swine (n = 9) were procured and E. faecium was isolated and species confirmed. Antimicrobial susceptibility testing to determine minimum inhibitory concentrations was done by micro-broth dilution method using National Antimicrobial Resistance Monitoring Systems Gram-positive Sensititre panel plate (CMV3AGPF), and categorization of strains as susceptible or resistant was as per Clinical Laboratory and Standards Institute's guidelines. E. faecium strains from 7 products (3 for swine and 4 for cattle) were pan-susceptible to the 16 antimicrobials tested. Strains from 15 products (6 for swine and 9 for cattle) exhibited resistance to at least one antimicrobial and a high proportion of strains was resistant to lincomycin (10/22), followed by tetracycline (4/22), daptomycin (4/22), ciprofloxacin (4/22), kanamycin (3/22), and penicillin (2/22). Four strains were multidrug resistant, with resistant phenotypes ranging from 3 to 6 antimicrobials or class. None of the E. faecium strains were positive for any of the virulence genes tested. The clonal relationships among the 22 E. faecium strains were determined by pulsed-field gel electrophoresis (PFGE) typing. A total of 10 PFGE patterns were observed with 22 strains and a few of the strains from different probiotic products had identical (100% Dice similarity) PFGE patterns. In conclusion, the E. faecium strains in a few commercial probiotics exhibited AMR to medically-important antimicrobials, but none contained virulence genes.

Human-origin probiotic cocktail increases short-chain fatty acid production via modulation of mice and human gut microbiome

The gut bacteria producing metabolites like short-chain fatty acids (SCFAs; e.g., acetate, propionate and butyrate), are frequently reduced in Patients with diabetes, obesity, autoimmune disorders, and cancers. Hence, microbiome modulators such as probiotics may be helpful in maintaining or even restoring normal gut microbiome composition to benefit host health. Herein, we developed a human-origin probiotic cocktail with the ability to modulate gut microbiota to increase native SCFA production. Following a robust protocol of isolation, characterization and safety validation of infant gut-origin Lactobacillus and Enterococcus strains with probiotic attributes (tolerance to simulated gastric and intestinal conditions, adherence to intestinal epithelial cells, absence of potential virulence genes, cell-surface hydrophobicity, and susceptibility to common antibiotics), we select 10 strains (5 from each genera) out of total 321 isolates. A single dose (oral gavage) as well as 5 consecutive doses of this 10-strain probiotic cocktail in mice modulates gut microbiome and increases SCFA production (particularly propionate and butyrate). Inoculation of these probiotics in human feces also increases SCFA production along with microbiome modulation. Results indicate that human-origin probiotic lactobacilli and enterococci could ameliorate gut microbiome dysbiosis and hence may prove to be a potential therapy for diseases involving reduced SCFAs production in the gut.

Evaluating the Safety of Potential Probiotic Enterococcus durans KLDS6.0930 Using Whole Genome Sequencing and Oral Toxicity Study

Enterococcus durans KLDS6.0930 has previously been shown to have probiotic potential. However, being a potential clinical pathogen, it becomes necessary to evaluate its safety status for novel potential probiotic use. The purpose of this study is to systematically evaluate the safety of E. durans KLDS6.0930 based on its genomics, phenotypic characteristics and oral toxicity. The complete genome of E. durans KLDS6.0930 was sequenced and analyzed for safety-related genes. Antibiotic susceptibility and the production of harmful metabolites were tested. A 28-day repeated oral dose toxicity test was implemented in rats. In vitro, E. durans KLDS6.0930 was resistant to five antibiotics, with intrinsic resistances to four antibiotics and no identified genes for the last. E. durans KLDS6.0930 was not hemolytic and virulence factors were non-functional in its genome. E. durans KLDS6.0930 produced a small amount of tyramine and phenethylamine; genes encoding tyramine decarboxylase were identified. In addition, genotype and phenotype analyses showed that the strain did not have the ability to generate D-lactic acid, indole, or nitroreductase. In vivo, E. durans KLDS6.0930 did not induce adverse effects on the organs, hematological and serum biochemical parameters, or cecal bacterial populations in the oral toxicity test. These results indicate that E. durans KLDS6.0930 can be safely used as a potential probiotic for human consumption and animal feed.

The unravelled Enterococcus faecalis zoonotic superbugs: Emerging multiple resistant and virulent lineages isolated from poultry environment

This study aimed to investigate the zoonotic potential by virtue of phylogenetic analysis, virulence and resistance gene profiles of Enterococcus faecalis originating from poultry environment. The ERIC, BOX and RAPD PCR analysis showed the clustering of E. faecalis strains (n = 74) into five groups (G1-G5) and fifteen sub-clusters (B1-B15), which share 50%-80% similarities with ATCC E. faecalis and clinical strains of human infection. E. faecalis strains harboured seven enterocins genes including ent1097 (85%), entB (84%), enterolysinA (51%), entSEK4 (51%), entL50 (31%), entA (25.7%) and ent1071 (14.9%). The highest prevalence of gelE-sprE (90%), lip-fl (90%) followed by cylL (62%), hyl (60%), katA (16%) and cylA (5.4%) was observed in poultry isolates. The fsr operon and gelE-sprE was co-associated in 66.2% strains. E. faecalis also harboured biofilm and endocarditis-associated genes, including efaAfs (97%), ebp-pilli (ebpABC and srtC 69.9%-80%), asa1 (71%), agg (55%), ace (54%) and esp-Tim (3%). Despite all found sensitive to vancomycin, 98.6% strains were multi-drug resistant to five to twelve tested antimicrobials. An increased-level of resistance (≥32 μg/ml) was observed to ampicillin (8.1%), meropenem (21.6%), chloramphenicol (73.4%), erythromycin (90.5%), tetracycline (100%) and high-level resistance to kanamycin (79.7%) and gentamicin (52.7%). The multi-drug resistant E. faecalis (MDRe.f) were carried pbp4 (90%), tetL (90%), tetM (70%), ermB (81%), cat (52.7%), acc6-aph2 (58.1%), aaph(3)-III (49.9%), gyrA (97%) and parC (98%) genes. Moreover, these MDRe.f were also harboured, hospital-associated marker IS16 (58%) and pheromone responsive genes, that is ccf (88%), cpd (74%), cob (62%) and eep (66%). Thus, regardless of the distinct phylogenetic background of E. faecalis of poultry origin, ATCC E. faecalis and clinical strains of human origin, we found major similarities in virulence, resistance gene profiles and mobile genetic elements (IS16 and pheromone responsive plasmids), supporting the zoonotic/reverse zoonotic risk associated with this organism.

Compatibility and safety of five lectin-binding putative probiotic strains for the development of a multi-strain protective culture for poultry

The ban on the use of antibiotics as feed additives for animal growth promotion in the European Union and United States and the expectation of this trend to further expand to other countries in the short term have prompted a surge in probiotic research. Multi-species probiotics including safe and compatible strains with the ability to bind different nutritional lectins with detrimental effects on poultry nutrition could replace antibiotics as feed additives. Lactobacillus salivarius LET201, Lactobacillus reuteri LET210, Enterococcus faecium LET301, Propionibacterium acidipropionici LET103 and Bifidobacterium infantis CRL1395 have proved to be compatible as evaluated through three different approaches: the production and excretion of antimicrobial compounds, growth inhibition by competition for essential nutrients and physical contact, and a combination of both. The safety of P. acidipropionici LET103 was confirmed, since no expression of virulence factors or antibiotic resistance was detected. The innocuity of E. faecium LET301 should be further evaluated, since the presence of genes coding for certain virulence factors (gelE, efaAfm and efaAfs) was observed, albeit no expression of gelE was previously detected for this strain and there are no reports of involvement of efaAfm in animal pathogenicity. Finally, a combination of the five strains effectively protected intestinal epithelial cells of broilers from the cytotoxicity of mixtures of soybean agglutinin, wheat germ agglutinin and concanavalin A. To our knowledge, this is the first time that a combination of strains is evaluated for their protection against lectins that might be simultaneously present in poultry feeds.

Evaluation of Probiotic Properties and Safety of Enterococcus faecium Isolated From Artisanal Tunisian Meat "Dried Ossban"

Enterococcus faecium strains were isolated from an original biotope, artisanal dried Tunisian meat “Dried Ossban,” and evaluated for safety and capacity as probiotics. Gram-positive, catalase negative, and bacteriocin-producing bacteria were screened using selective microbiological media. All isolates were identified by phenotypic and molecular tools. Five E. faecium strains (MZF1, MZF2, MZF3, MZF4, and MZF5) were selected and further assessed for their probiotic properties. They were found to be resistant to the physiological concentrations of bile salts, and the harsh conditions of the gastrointestinal tract, and showed autoaggregation and adhesion ability. All these isolates possess at least one enterocin and could efficiently inhibit the growth of Listeria innocua HPB13. The analysis of their safety profile revealed for almost all the strains the absence of cytotoxicity and virulence determinants, and susceptibility to clinically important antibiotics such as vancomycin. These data suggest that these bacteria, isolated from “Dried Ossban,” do not present a risk to human health, and may be considered as interesting candidates for future use as probiotics and bioprotective cultures for application in the food and/or feed industries.

The Genus Enterococcus: Between Probiotic Potential and Safety Concerns-An Update

A considerable number of strains belonging to different species of Enterococcus are highly competitive due to their resistance to wide range of pH and temperature. Their competitiveness is also owed to their ability to produce bacteriocins recognized for their wide-range effectiveness on pathogenic and spoilage bacteria. Enterococcal bacteriocins have attracted great research interest as natural antimicrobial agents in the food industry, and as a potential drug candidate for replacing antibiotics in order to treat multiple drugs resistance pathogens. However, the prevalence of virulence factors and antibiotic-resistance genes and the ability to cause disease could compromise their application in food, human and animal health. From the current regulatory point of view, the genus Enterococcus is neither recommended for the QPS list nor have GRAS status. Although recent advances in molecular biology and the recommended methods for the safety evaluation of Enterococcus strains allowed the distinction between commensal and clinical clades, development of highly adapted methods and legislations are still required. In the present review, we evaluate some aspects of Enterococcus spp. related to their probiotic properties and safety concerns as well as the current and potential application in food systems and treatment of infections. The regulatory status of commensal Enterococcus candidates for food, feed, probiotic use, and recommended methods to assess and ensure their safety are also discussed.

Safety of Lactobacillus plantarum ST8Sh and Its Bacteriocin

Total DNA extracted from Lb. plantarum ST8Sh was screened for the presence of more than 50 genes related to production of biogenic amines (histidine decarboxylase, tyrosine decarboxylase, and ornithine decarboxylase), virulence factors (sex pheromones, gelatinase, cytolysin, hyaluronidase, aggregation substance, enterococcal surface protein, endocarditis antigen, adhesion of collagen, integration factors), and antibiotic resistance (vancomycin, tetracycline, erythromycin, gentamicin, chloramphenicol, bacitracin). Lb. plantarum ST8Sh showed a low presence of virulence genes. Only 13 genes were detected (related to sex pheromones, aggregation substance, adhesion of collagen, tetracycline, gentamicin, chloramphenicol, erythromycin, but not to vancomycin, and bacitracin) and may be considered as indication of safety for application in fermented food products. In addition, interaction between Lb. plantarum ST8Sh and drugs from different groups were determined in order to establish possible application of the strain in combination with commercial drugs. Cytotoxicity of the semi-purified bacteriocins produced by Lb. plantarum ST8Sh was depended on applied concentration-highly cytotoxic when applied at 25 μg/mL and no cytotoxicity at 5 μg/mL.