Incidence of virulence determinants among Streptococcus agalactiae isolated from pregnant women and association with their serotypes

Colonization of pregnant women by Streptococcus agalactiae (S. agalactiae) is the main reason for intrauterine infection or transmission during parturition. This study investigated the prevalence, antimicrobial susceptibility, serotypes, virulence traits of S. agalactiae in pregnant women across three hospitals in Dakahlia Governorate, Egypt. Isolates were identified by culturing onto Hichrome Sterp B selective medium, latex agglutination and biochemical tests. The antimicrobial susceptibility was determined by Kirby-Bauer disc diffusion method. Capsular serotypes were determined by latex agglutination test. Hemolysin production and biofilm formation were assessed quantitively. Virulence genes were detected by polymerase chain reaction (PCR). Among 290 samples, 31.7% were S. agalactiae. All isolates were sensitive to penicillin G, ampicillin, cefotaxime, and vancomycin, but notably resistant to tetracycline (83.6%), erythromycin (68.4%), and clindamycin (54.3%). Serotype III (26.08%) was most common. Strong biofilm was produced by 72.8% of isolates. High hemolytic activity was seen (80.4%). Prevalent virulence genes included fsbA (97.8%), fbsB (96.7%), and scpB (96.7%). rib and alp4 were frequent surface protein genes (60.8% and 57.6%, respectively). Serotypes were significantly correlated to clindamycin resistance, biofilm production (Ia, III, VI serotypes), hemolytic activity (serotype V), and several virulence genes and surface proteins. Our study found a high prevalence of S. agalactiae isolates in pregnant women with diverse resistance patterns, high virulence indicating potential for increased pathogenicity.