Virulence factors, antimicrobial susceptibility and molecular characterization of Streptococcus agalactiae isolated from pregnant women

Forty-one Streptococcus agalactiae isolates collected from pregnant women at 35–37 weeks of gestation were analysed for their capsular types, antimicrobial resistance determinants, distribution of virulence factors and genetic relatedness using PCR and multiplex PCR. Capsular type III was predominant (65.8%), followed by capsular type II (14.6%), Ib (7.3%), and V(4.9%). All isolates were susceptible to penicillin, vancomycin, linezolid and quinupristin-dalfopristin. Resistance to tetracycline, erythromycin and clindamycin were found in 97.6%, 24.4%, and 14.6% of isolates, respectively. The most common antimicrobial resistance gene was tetM found in 97.6% of the isolates followed by ermTR and ermB found in 12% and 7.3% of isolates, respectively. The most common virulence gene was hly (100%), followed by scpB (97.6%), bca (97.6%), rib (53.65%) and bac (4.9%). The insertion sequence IS1548 was found in 63.4% of isolates. By multi locus variable number of tandem repeat analysis (MLVA) typing, 30 different allelic profiles or MLVA types (MTs) were identified. The most frequent was the MT1 (5/41, 12.2%) and followed by MT2 (4/41, 9.75%). Our data revealed that population structure of these isolates is highly diverse and indicates different MLVA types.