Prevalence of antibiotic resistance among clinical isolates of Streptococcus agalactiae isolated from vaginal secretions in Bulgaria over a seven-year period.

Medical Review (Med. pregled), 2025, 61(3), 23-28.

V. Boyanov, A. Alexandrova, A. Muhtarova, R. Gergova

Department of Medical Microbiology, Medical Faculty, Medical University of Sofia

Abstract.
Background: It is essential to examine the antibiotic susceptibility of bacterial pathogens that lead to complications during pregnancy and pose risks to the health and life of newborns. An example of microorganism responsible for invasive infections and serious neonatal illnesses is Streptococcus agalactiae (group B streptococci, GBS).
The aim of the present study was to examine the antibiotics susceptibility of GBS, isolated from vaginal secretions over a period of seven years.
Materials and methods: GBS strains (n = 298), isolated from pregnant and non-pregnant patients, were examined for susceptibility to antibiotics. The minimum inhibitory concentration, the phenotype distribution and the frequency of resistance genes using PCR were determined.
Results: All tested strains were susceptible to penicillin and van¬comycin. The resistance to macrolides, lincosamides and tetracyclines was 57.7%, 21.8%, and 89.9%, respectively. The phenotype distribution was: cMLSb – 47.7%, iMLSb – 29.1%, M-type – 22.7%, L-type – 0.6%. Genes associated with resist¬ance to macrolides and lincosamides were ermB (49.4%), ermA/TR (29.1%), mefA (28.5%), msrD (15.7%), ermC (14.5%), IsaC (11.6%), mefE (7.0%), InuB (5.8%), IsaE (5.2%). Two genes – tetM (88.8%) and tetO (13.4%), determined tetracycline non-susceptibility. There was no statistical significance between the distribution of antimicrobial resistance in pregnant and non-pregnant patients (p > 0.05).
Conclusion: The analysis of antibiotic resistance is crucial for reducing the uncontrolled use of antibiotics and highlighting the need for new and improved antibiotic molecules to be introduced into clinical practice.

Key words: Streptococcus agalactiae, antibiotic resistance, pregnancy

Address for correspondence: Prof. Rayna Gergova, MD, е-mail: ; ORCID: Васил Боянов М https://orcid.org/0000-0002-0429-9252; Александра Александрова: https://orcid.org/0000-0001-5944-961X; Адиле Мухтарова: https://orcid.org/0000-0001-9111-991X; Райна Гергова: https://orcid.org/0000-0003-3605-6447