Petya Koycheva Hristova

Petya Koycheva Hristova


Research Focus & Metrics

Academic Career Length

1Year (2026-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
8 July 2026 in Microbiology Research
Verified
Journal Article
Open access
PDF file
MPMaria Ilieva Pandova
Maria Ilieva Pandova
РПРалица Николаева Петрова
Ралица Николаева Петрова
YKYoana Krasimirova Kizheva
Yoana Krasimirova Kizheva
SISergei Ivanov
Sergei Ivanov
PHPetya Koycheva Hristova
Petya Koycheva Hristova
Influent wastewater, characterized by a diverse bacterial composition of human and animal origin, is a suitable source for studying the spread of antibiotic resistance and virulence genes, particularly in Enterococcus faecalis and Enterococcus faecium. This study aimed to evaluate the potential of these two species as reservoirs and indicators of antibiotic resistance and virulence genes. Wastewater treatment plants near the three largest cities of Bulgaria (Sofia, Varna and Burgas) were selected for sampling. Influent wastewater samples were collected for a period of 3 months (February, March and May) and used in the analyses. Overall, 34 bacterial isolates (E. faecalis, n = 13 and E. faecium, n = 21) were isolated and identified by MALDI-ToF. Phenotypic and genotypic methods were used to evaluate their antibiotic resistance profiles (focusing on clinically relevant antibiotics) and virulence potential. High dissemination of phenotypic ampicillin and quinupristin-dalfoprisin resistance (97% of all tested strains and 81% of all E. faecium strains, respectively) was established. In March, the highest number of antibiotic-resistant profiles was observed, including the emergence of MDR strains, primarily among E. faecium strains. Molecular analyses revealed a dissemination of genes encoding resistance to aminoglycosides and β-lactam antibiotics. The most prevalent virulence genes were gelE and ace, found only in E. faecalis strains. All gelE-positive strains also exhibited phenotypic gelatinase activity. In this study, E. faecium shows greater antibiotic resistance potential, whereas E. faecalis exhibits increased virulence capacity. These exploratory findings support the usefulness of influent wastewater as a matrix for monitoring antibiotic-resistant and potentially virulent enterococcal isolates, while larger-scale and seasonally representative studies are needed to confirm temporal and geographic patterns.