Antibiotic resistance, biofilm formation and virulence genes of Streptococcus agalactiae serotypes of Indian origin

Introduction: Streptococci are diverse group of gram-positive bacteria which causes serious life-threatening infections in developed as well as developing nations. Group B Streptococcus (GBS) or Streptococci agalactiae is one of the serologically distinct species of genus streptococcus which colonizes genitourinary and lower gastrointestinal tracts of female populations. GBS is a causative agent of various infections in new-born, non-pregnant adults and pregnant women. Understanding antibiotic resistance profiling will provide insight into the development of antibiotic prophylaxis against GBS infection. The aim of this study was to determine biofilm forming ability, presence of virulence genes and antibiotic susceptibility pattern of GBS clinical isolates. Methods: : Previously, identified 30 GBS isolates were used to check antibiotic susceptibility and resistance by Kirby-Bauer disk-diffusion method. All GBS isolates were subjected to biofilm detection using the Congo Red Agar (CRA) and Crystal Violet Assay (CVA). GBS isolates were subjected to PCR for the detection of various virulence genes involved in adhesion and invasion. Results: : Resistance towards penicillin was observed to be 26.6% (n=8 strains) as compared to other tested antibiotics which indicates the emergence of penicillin resistance among GBS isolates. Susceptibility for ofloxacin as 93.33% (n=28) was found to be highest, followed by azithromycin as it exhibited a 90% (n=27) susceptibility rate. Majority of the GBS isolates were found to be strong biofilm producers 70% (n=21) and 30% (n=9) were found to be moderate biofilm producers. Conclusions: : We demonstrated, GBS isolates exhibited resistance towards penicillin and a negative correlation between biofilm formation and penicillin was found. Further, we found, both strong and moderate biofilm producing isolates have most of the virulence genes at genetic level, however, strong biofilm formation phenotype was not significantly associated with the expression of any virulence gene.