Genotypic Characterization of Virulence and Antibiotic–Heavy Metal Resistance in Enterococcus Strains from Vladivostok’s Water Bodies
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Background
Enterococcus species are Gram-positive, facultative anaerobic bacteria commonly found in soil, water, and the gastrointestinal tracts of humans and animals. Their ability to acquire antibiotic resistance has made them significant opportunistic pathogens in both clinical and environmental settings. The presence of antibiotic-resistant Enterococcus strains in aquatic environments reflects contamination from human activities and poses a potential risk of horizontal gene transfer to other bacterial species.
Aims
This study aims to assess the antibiotic and heavy metal resistance patterns of Enterococcus strains isolated from water bodies in Vladivostok and evaluate their potential environmental risks.
Study design
Experimental study.
Methods
Water samples were collected from the Vtoraya Rechka River and Zolotoy Rog Bay in Vladivostok. 30 enterococcus strains were identified by polymerase chain reaction (PCR) technique. The presence of antibiotic and heavy metal resistance genes was determined using specific primers.
Results
Genetic analysis of the isolated Enterococcus strains revealed that 23% of strains carried the tetL gene, 33% harbored the ermB gene, and the heavy metal resistance genes tcrB and cadA were detected in 40% and 27% of strains, respectively. Notably, the ermB and tcrB genes co-occurred in 13.3% of strains, while none of the tetL -positive strains exhibited simultaneous presence of ermB, tcrB , and cadA .
Conclusion
Enterococcus strains isolated from Vladivostok’s water bodies exhibit resistance to multiple antibiotics and heavy metals, with a notable co-occurrence of copper and antibiotic resistance genes. These findings contribute to understanding microbial contamination in aquatic environments and its public health implications, providing valuable insights for future research in clinical and environmental microbiology.
IMPORTANCE
The dissemination of antibiotic and heavy metal resistance genes in environmental reservoirs poses a serious public health threat, as these genes may be transferred to clinically relevant pathogens. Enterococcus species, widely present in aquatic ecosystems, serve as both reservoirs and indicators of such resistance. This study identifies patterns of co-occurrence among resistance genes and highlights a potential genetic linkage between macrolide ( ermB ) and copper ( tcrB ) resistance in environmental Enterococcus strains. Notably, none of the tetL -positive strains carried all three of ermB, tcrB , and cadA , suggesting a mutually exclusive distribution pattern and a potentially distinct mechanism of acquisition for tetL . These findings reveal novel gene distribution dynamics in environmental Enterococcus populations and underscore the importance of integrated surveillance of antimicrobial and metal resistance in human-impacted ecosystems.
