Indication for Co-evolution of Lactobacillus johnsonii with its hosts

Lactobacillus johnsonii CPN23 vis-à-vis Lactobacillus acidophilus NCDC15 Improves Gut Health, Intestinal Morphometry, and Histology in Weaned Wistar Rats

The present investigation was carried out with the aim to establish the comparative efficacy of a canine-sourced probiotic meant for canine feeding and a conventional dairy-sourced probiotic. For this purpose, canine-origin Lactobacillus johnsonii CPN23 and dairy-origin Lactobacillus acidophilus NCDC15 were evaluated for potential probiotics health benefits in the rat model. Forty-eight weaned Wistar rats enrolled in this experiment of 8 weeks were fed a basal diet and divided into three dietary treatments. Rats of group I enrolled as control (CON) were given MRS placebo at 1 mL/head/day, while rats of group II (LAJ) and III (LAC) were administered with overnight MRS broth grown-culture of L. johnsonii CPN23 and L. acidophilus NCDC15, respectively, at 1 mL/head/day (108 cfu/mL). The average daily gain and net gain in body weight were significantly higher (p < 0.05) in LAJ and LAC than in CON. Fecal and digesta biochemical attributes altered (p < 0.05) positively in response to both probiotics. Total fecal and pooled digesta SCFAs were higher (p < 0.05) in both LAJ and LAC than in CON. The microbial population in cecal and colonic digesta responded (p < 0.05) positively to both probiotics. The diameter of intestinal segments was higher (p < 005) in LAJ as compared to CON. The number and height of villi in jejunum tended to be higher in LAJ as compared to CON. The humoral immune response to sheep erythrocytes as well as chicken egg-white lysozyme was higher in LAJ as compared to CON. Overall, the results of the study have demonstrated the effectiveness of the canine-sourced L. johnsonii CPN23 as a potential probiotic, with a comparatively better response than the dairy-sourced L. acidophilus NCDC15. It could thus be recommended for use in feeding dogs to help augment their health.

The Effects of Lactobacillus johnsonii on Diseases and Its Potential Applications

Lactobacillus johnsonii has been used as a probiotic for decades to treat a wide range of illnesses, and has been found to have specific advantages in the treatment of a number of ailments. We reviewed the potential therapeutic effects and mechanisms of L. johnsonii in various diseases based on PubMed and the Web of Science databases. We obtained the information of 149 L. johnsonii from NCBI (as of 14 February 2023), and reviewed their comprehensive metadata, including information about the plasmids they contain. This review provides a basic characterization of different L. johnsonii and some of their potential therapeutic properties for various ailments. Although the mechanisms are not fully understood yet, it is hoped that they may provide some evidence for future studies. Furthermore, the antibiotic resistance of the various strains of L. johnsonii is not clear, and more complete and in-depth studies are needed. In summary, L. johnsonii presents significant research potential for the treatment or prevention of disease; however, more proof is required to justify its therapeutic application. An additional study on the antibiotic resistance genes it contains is also needed to reduce the antimicrobial resistance dissemination.

Evidence of host specificity in Lactobacillus johnsonii genomes and its influence on probiotic potential in poultry

To date, the selection of candidate strains for probiotic development in production animals has been largely based upon screens for desired phenotypic traits. However, increasing evidence indicates that the use of host-specific strains may be important, because coevolution with the animal host better prepares a bacterial strain to colonize and succeed in its respective host animal species. This concept was applied to Lactobacillus johnsonii in commercial poultry production because of its previous correlation with enhanced bird performance. Using 204 naturally isolated chicken- and turkey-source L. johnsonii, we demonstrate that there is a strong phylogenetic signal for coevolution with the animal host. These isolates differ phenotypically, even within host source, and these differences can be correlated with certain L. johnsonii phylogenetic clades. In commercial turkey poults, turkey-specific strains with strong in vitro phenotypes performed better early in life than strains lacking those phenotypes. A follow-up performance trial in broiler chickens demonstrated that chicken-specific strains result in better overall bird performance than nonchicken-specific strains. Collectively, this work provides evidence for the impact of host adaptation on a probiotic strain's potential. Furthermore, this top-down approach is useful for screening larger numbers of isolates for probiotic candidates.

Lactobacillus rhamnosus attenuates Thai chili extracts induced gut inflammation and dysbiosis despite capsaicin bactericidal effect against the probiotics, a possible toxicity of high dose capsaicin

Because of a possible impact of capsaicin in the high concentrations on enterocyte injury (cytotoxicity) and bactericidal activity on probiotics, Lactobacillus rhamnosus L34 (L34) and Lactobacillus rhamnosus GG (LGG), the probiotics derived from Thai and Caucasian population, respectively, were tested in the chili-extract administered C57BL/6 mice and in vitro experiments. In comparison with placebo, 2 weeks administration of the extract from Thai chili in mice caused loose feces and induced intestinal permeability defect as indicated by FITC-dextran assay and the reduction in tight junction molecules (occludin and zona occludens-1) using fluorescent staining and gene expression by quantitative real-time polymerase chain reaction (qRT-PCR). Additionally, the chili extracts also induced the translocation of gut pathogen molecules; lipopolysaccharide (LPS) and (1→3)-β-d-glucan (BG) and fecal dysbiosis (microbiome analysis), including reduced Firmicutes, increased Bacteroides, and enhanced total Gram-negative bacteria in feces. Both L34 and LGG attenuated gut barrier defect (FITC-dextran, the fluorescent staining and gene expression of tight junction molecules) but not improved fecal consistency. Additionally, high concentrations of capsaicin (0.02-2 mM) damage enterocytes (Caco-2 and HT-29) as indicated by cell viability test, supernatant cytokine (IL-8), transepithelial electrical resistance (TEER) and transepithelial FITC-dextran (4.4 kDa) but were attenuated by Lactobacillus condition media (LCM) from both probiotic-strains. The 24 h incubation with 2 mM capsaicin (but not the lower concentrations) reduced the abundance of LGG (but not L34) implying a higher capsaicin tolerance of L34. However, Lactobacillus rhamnosus fecal abundance, using qRT-PCR, of L34 or LGG after 3, 7, and 20 days of the administration in the Thai healthy volunteers demonstrated the similarity between both strains. In conclusion, high dose chili extracts impaired gut permeability and induced gut dysbiosis but were attenuated by probiotics. Despite a better capsaicin tolerance of L34 compared with LGG in vitro, L34 abundance in feces was not different to LGG in the healthy volunteers. More studies on probiotics with a higher intake of chili in human are interesting.

Milk oligosaccharide-mediated cross-feeding between Enterococcus gallinarum and lactobacilli in the gut microbiota of infant rats

We investigated bacteria that have a nutritional symbiotic relationship with respect to milk oligosaccharides in gut microbiota of suckling rats, with specific reference to sialyllactose (SL) degrading Enterococcus gallinarum. Our next generation sequencing analysis of the colonic contents of 12-day-old suckling rats revealed that almost half of the bacteria in the microbiota belonged to the Lactobacillaceae family. Major Lactobacillus species in the contents were identified as L. johnsonii, L. murinus, and L. reuteri. We then monitored changes in numbers of the above Lactobacillus species, E. gallinarum, and the bacteria belonging to the family Enterobacteriaceae (i.e., enterobacteria) in the colonic contents of infant rats at 7, 12, 21, 28, and 35 days of age by using real-time PCR assays targeting these bacterial groups. The 7-day-old infant rats had a gut microbiota in which enterobacteria were predominant. Such dominance was replaced by L. johnsonii and the concomitant E. gallinarum markedly increased in those of 12 and 21 days of ages. During this period, the number of enterobacteria declined dramatically, but that of L. reuteri surged dramatically. Our separate in vitro experiment showed that supplementation of culture media with SL promoted the growth of L. johnsonii and E. gallinarum, with marked production of lactic acid. These findings revealed possible milk oligosaccharide-mediated cross-feeding between E. gallinarum and L. johnsonii, with the former degrading SL to release lactose to be utilized by the latter.

Polar bear-adapted Ursidibacter maritimus are remarkably conserved after generations in captivity

Most species in the bacterial family of Pasteurellaceae colonize one specific host species. Vertebrates of very different evolutionary descent including fish, turtles, marsupials, eutherians and birds are colonized by different members of Pasteurellaceae. This one-to-one microbial-host species partnership makes Pasteurellaceae species valuable candidates to study biodiversity, bacterial-host co-evolution and host adaptation, and their widespread distribution across vertebrates provide the possibility to collect a wide array of data, where wildlife species are essential. However, obtaining samples from wild animals comes with logistic, technical and ethical challenges, and previous microbiota studies have led to the presumption that captive animals are poor models for microbial studies in wildlife. Here, we show that colonization of polar bears by Ursidibacter maritimus is unaffected by factors related to captivity, reflecting a deep symbiotic bond to the host. We argue that the study of ecological and evolutionary principles in captive wildlife is possible for host-adapted taxa such as those in the Pasteurellaceae family. Moreover, studying captive, often trained animals protects wild populations from the stress associated with obtaining samples.

Non-Viable Lactobacillus johnsonii JNU3402 Protects against Diet-Induced Obesity

In this study, the role of non-viable Lactobacillus johnsonii JNU3402 (NV-LJ3402) in diet-induced obesity was investigated in mice fed a high-fat diet (HFD). To determine whether NV-LJ3402 exhibits a protective effect against diet-induced obesity, 7-week-old male C57BL/6J mice were fed a normal diet, an HFD, or an HFD with NV-LJ3402 for 14 weeks. NV-LJ3402 administration was associated with a significant reduction in body weight gain and in liver, epididymal, and inguinal white adipose tissue (WAT) and brown adipose tissue weight in HFD-fed mice. Concomitantly, NV-LJ3402 administration to HFD-fed mice also decreased the triglyceride levels in the plasma and metabolic tissues and slightly improved insulin resistance. Furthermore, NV-LJ3402 enhanced gene programming for energy dissipation in the WATs of HFD-fed mice as well as in 3T3-L1 adipocytes with increased peroxisome proliferator-activated receptor-γ (PPARγ) transcriptional activity, suggesting that the PPARγ pathway plays a key role in mediating the anti-obesity effect of NV-LJ3402 in HFD-fed mice. Furthermore, NV-LJ3402 administration in HFD-fed mice enhanced mitochondrial levels and function in WATs and also increased the body temperature upon cold exposure. Together, these results suggest that NV-LJ3402 could be safely used to develop dairy products that ameliorate diet-induced obesity and hyperlipidemia.

PCR-based screening, isolation, and partial characterization of motile lactobacilli from various animal feces

BACKGROUND

Most lactobacilli found in animal intestines are generally non-motile, but there are few exceptions. Our previous work showed that Lactobacillus agilis BKN88, which is a highly motile strain originating from a chicken, takes advantage of motility in gut colonization in murine models, and thus motile lactobacilli likely have unique ecological characteristics conferred by motility. However, the ecology and habitat of gut-derived motile lactobacilli are still rarely understood. In addition, the limited availability of motile Lactobacillus isolates is one of the major obstacles for further studies. To gain insight into the ecology and habitat of the motile lactobacilli, we established a routinely applicable detection method for motile lactobacilli using PCR and subsequent selective isolation in semi-solid MRS medium for the collection of additional motile lactobacilli from animal feces.

RESULTS

We applied the PCR detection using motile lactobacilli-specific primers, based on the motor switch protein gene (fliG) of flagella, to 120 animal feces, followed by selective isolation performed using 45 animal feces. As a result, motile lactobacilli were detected in 44 animal feces. In the selective isolation, 29 isolates of L. agilis and 2 isolates of L. ruminis were obtained from 8 animal species.

CONCLUSIONS

These results indicated that motile lactobacilli are distributed in different animal species. Moreover, phylogenetic analysis of the L. agilis isolates suggests co-evolution with the host, and adaptation to a particular environmental niche.

Comparative genomic analysis of Proteus spp. isolated from tree shrews indicated unexpectedly high genetic diversity

Proteus spp. are commensal gastrointestinal bacteria in many hosts, but information regarding the mutual relationships between these bacteria and their hosts is limited. The tree shrew is an alternative laboratory animal widely used for human disease research. However, little is known about the relationship between Proteus spp. and tree shrews. In this study, the complete genome sequencing method was used to analyse the characteristics of Proteus spp. isolated from tree shrews, and comparative genomic analysis was performed to reveal their relationships. The results showed that 36 Proteus spp. bacteria were isolated, including 34 Proteus mirabilis strains and two Proteus vulgaris strains. The effective rate of sequencing was 93.53%±2.73%, with an average GC content of 39.94%±0.25%. Briefly, 3682.89±90.37, 2771.36±36.01 and 2832.06±42.49 genes were annotated in the NCBI non-redundant nucleotide database (NR), SwissProt database and KEGG database, respectively. The high proportions of macrolide-, vancomycin-, bacitracin-, and tetracycline-resistance profiles of the strains were annotated in the Antibiotic Resistance Genes Database (ARDB). Flagella, lipooligosaccharides, type 1 fimbriae and P fimbriae were the most abundantly annotated virulence factors in the Virulence Factor Database (VFDB). SNP variants indicated high proportions of base transitions (Ts), homozygous mutations (Hom) and non-synonymous mutations (Non-Syn) in Proteus spp. (P<0.05). Phylogenetic analysis of Proteus spp. and other references revealed high genetic diversity for strains isolated from tree shrews, and host specificity of Proteus spp. bacteria was not found. Overall, this study provided important information on characteristics of genome for Proteus spp. isolated from tree shrews.

Comparative Genomics Analysis of Lactobacillus ruminis from Different Niches

Lactobacillus ruminis is a commensal motile lactic acid bacterium living in the intestinal tract of humans and animals. Although a few genomes of L. ruminis were published, most of them were animal derived. To explore the genetic diversity and potential niche-specific adaptation changes of L. ruminis, in the current work, draft genomes of 81 L. ruminis strains isolated from human, bovine, piglet, and other animals were sequenced, and comparative genomic analysis was performed. The genome size and GC content of L. ruminis on average were 2.16 Mb and 43.65%, respectively. Both the origin and the sampling distance of these strains had a great influence on the phylogenetic relationship. For carbohydrate utilization, the human-derived L. ruminis strains had a higher consistency in the utilization of carbon source compared to the animal-derived strains. L. ruminis mainly increased the competitiveness of niches by producing class II bacteriocins. The type of clustered regularly interspaced short palindromic repeats /CRISPR-associated (CRISPR/Cas) system presented in L. ruminis was mainly subtype IIA. The diversity of CRISPR/Cas locus depended on the high denaturation of spacer number and sequence, although cas1 protein was relatively conservative. The genetic differences in those newly sequenced L. ruminis strains highlighted the gene gains and losses attributed to niche adaptations.

A novel probiotic, Lactobacillus johnsonii 456, resists acid and can persist in the human gut beyond the initial ingestion period

Probiotics are considered to have multiple beneficial effects on the human gastrointestinal tract, including immunomodulation, pathogen inhibition, and improved host nutrient metabolism. However, extensive characterization of these properties is needed to define suitable clinical applications for probiotic candidates. Lactobacillus johnsonii 456 (LBJ 456) was previously demonstrated to have anti-inflammatory and anti-genotoxic effects in a mouse model. Here, we characterize its resistance to gastric and bile acids as well as its ability to inhibit gut pathogens and adhere to host mucosa. While bile resistance and in vitro host attachment properties of LBJ 456 were comparable to other tested probiotics, LBJ 456 maintained higher viability at lower pH conditions compared to other tested strains. LBJ 456 also altered pathogen adhesion to LS 174T monolayers and demonstrated contact-dependent and independent inhibition of pathogen growth. Genome analyses further revealed possible genetic elements involved in host attachment and pathogen inhibition. Importantly, we show that ingestion of Lactobacillus johnsonii 456 over a one week yogurt course leads to persistent viable bacteria detectable even beyond the period of initial ingestion, unlike many other previously described probiotic species of lactic acid bacteria.

The evolution of ecological facilitation within mixed-species biofilms in the mouse gastrointestinal tract

The eco-evolutionary interactions among members of the vertebrate gut microbiota that ultimately result in host-specific communities are poorly understood. Here we show that Lactobacillus reuteri coexists with  species that belong to the Lactobacillus johnsonii cluster (L. johnsonii, L. gasseri, and L taiwanensis) in a taxonomically wide range of rodents, suggesting cohabitation over evolutionary times. The two dominant Lactobacillus species found in wild mice establish a commensalistic relationship in gastric biofilms when introduced together into germ-free mice in which L. reuteri facilitates colonization of L. taiwanensis. Genomic analysis revealed allopatric diversification in strains of both species that originated from geographically separated locations (Scotland and France). Allopatry of the strains resulted in reduced formation of mixed biofilms in vitro, indicating that interspecies interactions in gastric Lactobacillus-biofilms are the result of an adaptive evolutionary process that occurred in a biogeographical context. In summary, these findings suggest that members within the vertebrate gut microbiota can evolve inter-dependencies through ecological facilitation, which could represent one mechanism by which host-specific bacterial communities assemble across vertebrate species and an explanation for their spatial and biogeographic patterns.

The Genomic Basis of Lactobacilli as Health-Promoting Organisms

Lactobacilli occupy a unique position in human culture and scientific history. Like brewer’s and baker’s yeast, lactobacilli have been associated with food production and preservation for thousands of years. Lactobacillus species are used in mixed microbial cultures, such as the classical Lactobacillus bulgaricus / Streptococcus thermophilus inoculum for yogurt fermentation, or combinations of diverse lactobacilli/yeasts in kefir grains. The association of lactobacilli consumption with greater longevity and improved health formed the basis for developing lactobacilli as probiotics, whose market has exploded worldwide in the past 10 years. The decade that followed the determination of the first genome sequence of a food-associated species, Lactobacillus plantarum , saw the application to lactobacilli of a full range of functional genomics methods to identify the genes and gene products that govern their distinctive phenotypes and health associations. In this review, we will briefly remind the reader of the range of beneficial effects attributed to lactobacilli, and then explain the phylogenomic basis for the distribution of these traits across the genus. Recognizing the strain specificity of probiotic effects, we review studies of intraspecific genomic variation and their contributions to identifying probiotic traits. Finally we offer a perspective on classification of lactobacilli into new genera in a scheme that will make attributing probiotic properties to clades, taxa, and species more logical and more robust.

Draft Genome Sequence of Lactobacillus johnsonii Strain 16, Isolated from Mice

Here, we report the genome sequence of Lactobacillus johnsonii, a member of the gut lactobacilli. This draft genome of L. johnsonii strain 16 isolated from C57BL/6J mice enables the identification of bacterial genes responsible for host-specific gut persistence.

Study of the catabolism of thyme phenols combining in vitro fermentation and human intervention

The gut metabolism of four thyme phenolics (monoterpenes thymol and carvacrol, rosmarinic acid, and eriodictyol) was evaluated in vitro. After the in vitro transformations of the individual phenols had been studied, the presence of their microbial metabolites was investigated in human feces collected before and after a sustained intake (3 weeks) of 25 mL/day of a thyme phenol-enriched olive oil. Results of in vitro fermentation showed low degradation of thymol and carvacrol. By contrast, large catabolism was noted when rosmarinic acid and eriodictyol were fermented, yielding hydroxyphenylpropionic acid as the main metabolite. In accordance with these results, after the in vivo intervention with thyme phenol-enriched olive oil, an increase in the concentration of hydroxyphenylpropionic and phenylpropionic acids was observed in human feces, confirming the effective in vivo microbial degradation of rosmarinic acid and eriodictyol. Carvacrol was detected in fecal samples at trace levels, suggesting that monoterpenes are well absorbed in the upper part of the gastrointestinal tract.

Gene expression of lactobacilli in murine forestomach biofilms

Lactobacilli populate the gastro-intestinal tract of vertebrates, and are used in food fermentations and as probiotics. Lactobacilli are also major constituents of stable biofilms in the forestomach of rodents. In order to investigate the lifestyle of these biofilm lactobacilli in C57BL/6 mice, we applied metatranscriptomics to analyse gene expression (assessed by mRNA) and community composition (assessed by rRNA). Lactobacillales were the major biofilm inhabitants (62–82% of rRNA reads), followed by Clostridiales (8–31% of rRNA reads). To identify mRNA transcripts specific for the forestomach, we compared forestomach and hindgut metatranscriptomes. Gene expression of the biofilm microbiota was characterized by high abundance of transcripts related to glucose and maltose utilization, peptide degradation, and amino acid transport, indicating their major catabolic and anabolic pathways. The microbiota transcribed genes encoding pathways enhancing oxidative stress (glutathione synthesis) and acid tolerance. Various pathways, including metabolite formation (urea degradation, arginine pathway, γ-aminobutyrate) and cell wall modification (DltA, cyclopropane-fatty-acyl-phospholipid synthase), contributed to acid tolerance, as judged from the transcript profile. In addition, the biofilm microbiota expressed numerous genes encoding extracellular proteins involved in adhesion and/or biofilm formation (e.g. MucBP, glycosyl hydrolase families 68 and 70). This study shed light on the lifestyle and specific adaptations of lactobacilli in the murine forestomach that might also be relevant for lactobacilli biofilms in other vertebrates, including humans.

Microbiota of the chicken gastrointestinal tract: influence on health, productivity and disease

Recent advances in the technology available for culture-independent methods for identification and enumeration of environmental bacteria have invigorated interest in the study of the role of chicken intestinal microbiota in health and productivity. Chickens harbour unique and diverse bacterial communities that include human and animal pathogens. Increasing public concern about the use of antibiotics in the poultry industry has influenced the ways in which poultry producers are working towards improving birds' intestinal health. Effective means of antibiotic-independent pathogen control through competitive exclusion and promotion of good protective microbiota are being actively investigated. With the realisation that just about any change in environment influences the highly responsive microbial communities and with the abandonment of the notion that we can isolate and investigate a single species of interest outside of the community, came a flood of studies that have attempted to profile the intestinal microbiota of chickens under numerous conditions. This review aims to address the main issues in investigating chicken microbiota and to summarise the data acquired to date.

Active and secreted IgA-coated bacterial fractions from the human gut reveal an under-represented microbiota core

Host-associated microbiota varies in distribution depending on the body area inhabited. Gut microbes are known to interact with the human immune system, maintaining gut homoeostasis. Thus, we studied whether secreted-IgA (S-IgA) coat specific microbial taxa without inducing strong immune responses. To do so, we fractionated gut microbiota by flow cytometry. We found that active and S-IgA-coated bacterial fractions were characterized by a higher diversity than those observed in raw faecal suspensions. A long-tail effect was observed in family distribution, revealing that rare bacteria represent up to 20% of total diversity. While Firmicutes was the most abundant phylum, the majority of its sequences were not assigned at the genus level. Finally, the single-cell-based approach enabled us to focus on active and S-IgA-coated bacteria. Thus, we revealed a microbiota core common to the healthy volunteers participating in the study. Interestingly, this core was composed mainly of low frequency taxa (e.g. Sphingomonadaceae).

Timely approaches to identify probiotic species of the genus Lactobacillus

Over the past decades the use of probiotics in food has increased largely due to the manufacturer’s interest in placing “healthy” food on the market based on the consumer’s ambitions to live healthy. Due to this trend, health benefits of products containing probiotic strains such as lactobacilli are promoted and probiotic strains have been established in many different products with their numbers increasing steadily. Probiotics are used as starter cultures in dairy products such as cheese or yoghurts and in addition they are also utilized in non-dairy products such as fermented vegetables, fermented meat and pharmaceuticals, thereby, covering a large variety of products.

To assure quality management, several pheno-, physico- and genotyping methods have been established to unambiguously identify probiotic lactobacilli. These methods are often specific enough to identify the probiotic strains at genus and species levels. However, the probiotic ability is often strain dependent and it is impossible to distinguish strains by basic microbiological methods.

Therefore, this review aims to critically summarize and evaluate conventional identification methods for the genus Lactobacillus, complemented by techniques that are currently being developed.

Biodiversity of Enterococcus faecalis based on genomic typing

Enterococcus faecalis is a common inhabitant of the gastrointestinal tracts of different animals and is also found in other environments, such as plants, soil, food and water. The diverse nature of E. faecalis, which includes pathogenic, commensal and probiotic strains, calls for the development of tools for accurate discrimination and characterization at the strain level. Here we studied the genetic relationships among 106 E. faecalis strains isolated from diverse origins and possessing different degrees of virulence. Strain typing was conducted using a set of selected simple-sequence repeat (SSR) loci combined with multilocus sequence typing (MLST) analysis, which discriminated among the strains and separated them into three main clusters. While pathogenic and commensal isolates were dispersed along the dendrogram, probiotic and cheese-originated strains were highly associated with one specific cluster (cluster 1). The strain panel was further characterized by testing the occurrence of two virulence determinants (esp gene and β-hemolysis). The two determinants showed low abundance among probiotic and cheese-originated strains within cluster 1 when compared to non-cluster 1 cheese-originated strains, indicating a possible association of cluster 1 with non-virulent strains. Our results further emphasize the importance and challenge of precise characterization of E. faecalis strains from various sources.