Capsular serotype and antibiotic resistance of group B streptococci isolated from pregnant women in Ardabil, Iran

Group B Streptococci (GBS) is a major cause of neonatal and maternal infections. The aim of this study was to determine the serotype distribution and antibiotic resistance profile of GBS strains isolated from pregnant women in Ardabil. Antibiotic resistance of 56 GBS isolates was investigated using E-test strips and disk-diffusion method. Serotyping was performed using capsular antiserum. The results of MIC tests showed all isolates were susceptible to ampicillin, vancomycin and penicillin. One isolate (1.7%) showed reduced susceptibility pattern to penicillin (MIC; 0.25 µg/ml). There were 3 (5.3%) isolates semi-sensitive (0.25-1 µg/ml) to erythromycin (2; 0.5 µg/ml and 1; 0.38 µg/ml) and 2 (3.5%) isolates to clindamycin (1; 0.5 µg/ml, 1; 0.38 µg/ml). Additionally, 2 (3.5%) isolates were resistant to clindamycin (1; 16 µg/ml, 1; 2 µg/ml). According to the disk diffusion test, 47 (83.9%), 8 (14.2%) and 7 (12.5%) isolates were resistant to Co-trimoxazole, ciprofloxacin and ceftriaxone respectively. Serotypes V (19.6%), II (12.5%) and IV (12.5%) were the most frequent followed by serotypes III (10.7%) and VI (10.7%), Ib (8.9%), Ia (7/1%), VII (5/3%) and VIII (5/3%); 7.1% of strains were nontypeable. In this study, most isolates were sensitive to common antibiotics, but increased resistance to other antibiotics indicates the importance of monitoring of antibiotic resistance in group B streptococci over time.