Antibiotic resistance and virulence of enterococci isolates from healthy humans in Tunisia

The healthy human gut can take it all: vancomycin-variable, linezolid-resistant strains and specific bacteriocin-species interplay in Enterococcus spp

Enterococcus spp. are opportunistic human pathogens colonizing the human gut and a significant reservoir for the continuous adaptation of hospital clones. However, studies on the features of enterococci species co-colonizing healthy individuals are scarce. We investigated the prevalence, antibiotic resistance, and bacteriocin profiles of Enterococcus species in fecal samples from healthy adults in Portugal using culture-based methods, WGS, and bacteriocin inhibition assays. Results were compared with data from a 2001 study in the same region. Enterococcus spp. (n = 315; 24% MDR) were recovered from all volunteers. Enterococcus lactis was the prevalent species (75%), followed by Enterococcus faecalis (65%) and Enterococcus faecium (47%). E. lactis prevalence increased 2.5-fold since 2001. Linezolid resistance genes (optrA/poxtA) were detected in E. faecium and Enterococcus thailandicus isolates, while a vancomycin-variable E. faecium was also identified. Virulence and plasmid profiles were diverse across species, with evidence of exchange of virulence markers and plasmid replicons between E. faecium and E. lactis. Bacteriocin gene repertoires were extensive and species-specific. Higher numbers of bacteriocin genes were associated with stronger inhibition profiles, and 25% of E. faecium and E. lactis isolates were capable of inhibiting relevant VRE clones. This study unveils the co-occurrence and ecological dynamics of Enterococcus species in the healthy human gut, reinforcing its role as a reservoir for key antibiotic resistance genes and potentially pathogenic strains. The shift toward E. lactis prevalence and the detection of linezolid resistance genes in healthy individuals underscore the need for ongoing surveillance of the gut microbiome to guide public health strategies and antibiotic stewardship efforts.IMPORTANCEThis study highlights the role of Enterococcus species in the healthy human gut, revealing important insights into their prevalence and antibiotic resistance. It emphasizes that the human gut serves as a significant reservoir for antibiotic-resistant strains and shows a notable increase and prevalence of Enterococcus lactis, which has been underappreciated due to identification challenges. The research also underscores the bacteriocins' role in microbial competition, where commensal strains inhibit clinical VRE, potentially aiding the restoration of the gut microbiota, after antibiotic treatment. The findings accentuate the need for ongoing surveillance to track changes in gut bacteria, especially with the emergence of resistance genes to last resort antibiotics. Such monitoring is crucial for shaping public health strategies and managing the growing threat of antibiotic-resistant infections. Profiling bacteriocins at the species and strain level can identify ecological adaptation factors and inform strategies to target high-risk clones.

Identification of drug-resistant phenotypes and resistance genes in Enterococcus faecalis isolates from animal feces originating in Xinjiang, People’s Republic of China

This study examined the presence and the antibiotic resistance patterns of Enterococcus faecalis isolated from the feces of 285 animals. Polymerase chain reaction tests verified the presence of E. faecalis from 49 pigs, 20 cows, 174 sheep, 17 horses, 21 chickens, and four dung beetles. Bacterial strains from different animals showed differences in susceptibility and resistance to the tested antimicrobials. The isolates exhibited resistance to ampicillin (6.32%), ciprofloxacin (40.00%), nitrofurantoin (1.40%), erythromycin (54.04%), streptomycin (82.11%), tetracycline (45.26%), amoxicillin (64.91%), penicillin (92.28%), and vancomycin (0.35%). The resistant strains also possessed varying complements of resistance genes including tem (77.89%), tetM (33.68%), gyrA (37.54%), parC (34.74%), aph(3′)-III (22.46%), aac(6′)/aph2″ (10.88%), and ant(6′)-I (8.42%). Genes for vancomycin resistance (vanB and vanC) and erythromycin resistance (mefA) were not detected. These results indicate high levels of antibiotic resistance among the isolates, although no positive correlation was observed between resistance genes and antibiotic resistance spectrum.

Genetic relatedness of the Enterococcus faecalis isolates in stool and urine samples of patients with community-acquired urinary tract infection

Background

Community-acquired urinary tract infection (CA-UTI) could be caused by endogenous or exogenous routes. To show this relationship, we investigated molecular fingerprints and genotypes of paired Enterococcus faecalis isolated from the urine of symptomatic patients and their fecal samples.

Results

Out of the studied patients, 63 pairs of E. faecalis isolates were obtained simultaneously from their urine and feces samples. All the strains were sensitive to vancomycin, linezolid, nitrofurantoin, and daptomycin (MIC value: ≤ 4 µg/ml), while resistance to tetracycline (urine: 88.9%; stool: 76.2%) and minocycline (urine: 87.3%, stool: 71.4%) was detected in most of them. The most common detected virulence genes were included efbA, ace, and gelE. RAPD-PCR and PFGE analyses showed the same patterns of molecular fingerprints between paired of the isolates in 26.9% and 15.8% of the patients, respectively.

Conclusions

Similarity of E. faecalis strains between the urine and feces samples confirmed the occurrence of endogenous infection via contamination with colonized bacteria in the intestinal tract. Carriage of a complete virulence genotype in the responsible strains was statistically in correlation with endogenous UTI, which shows their possible involvement in pathogenicity of uropathogenic E. faecalis strains.

Antimicrobial resistance and virulence profile of enterococci isolated from poultry and cattle sources in Nigeria

This study investigated the occurrence, antimicrobial resistance and virulence of Enterococcus from poultry and cattle farms. Three hundred and ninety samples: cloacal/rectal swabs (n = 260) and manure (n = 130] were processed for recovery of Enterococcus species. Standard bacteriological methods were used to isolate, identify and characterize Enterococcus species for antimicrobial susceptibility and expression of virulence traits. Detection of antibiotic resistance and virulence genes was carried out by polymerase chain reaction. Enterococcus was recovered from 167 (42.8%) of the 390 samples tested with a predominance of Enterococcus faecium (27.7%). Other species detected were Enterococcus gallinarum, Enterococcus faecalis, Enterococcus hirae, Enterococcus raffinosus, Enterococcus avium, Enterococcus casseliflavus, Enterococcus mundtii and Enterococcus durans. All the isolates tested were susceptible to vancomycin, but resistance to tetracycline, erythromycin, ampicillin and gentamicin was also observed among 61.0, 61.0, 45.1 and 32.7% of the isolates, respectively. Sixty (53.1%) of the isolates were multidrug resistant presenting as 24 different resistance patterns with resistance to gentamicin-erythromycin-streptomycin-tetracycline (CN-ERY-STR-TET) being the most common (n = 11) pattern. In addition to expression of virulence traits (haemolysin, gelatinase, biofilm production), antibiotic resistance (tetK, tetL, tetM, tetO and ermB) and virulence (asa1, gelE, cylA) genes were detected among the isolates. Also, in vitro transfer of resistance determinants was observed among 75% of the isolates tested. Our data revealed poultry, cattle and manure in this area are hosts to varying Enterococcus species harbouring virulence and resistance determinants that can be transferred to other organisms and also are important for causing nosocomial infection.