Macrolide-resistance, capsular genotyping and associated factors of group B Streptococci colonized pregnant women in Isfahan, Iran

Group B streptococcus (GBS) can cause severe and invasive infections in pregnant women, infants, and adults. This study aimed to investigate the risk factors of GBS colonization in pregnant women and determine the macrolide resistance and capsular type of isolates.

In a cross-sectional study, a total of 200 pregnant women were screened for GBS colonization by phenotypic methods. Antibiotic susceptibility pattern of colonizing isolates and ermB, ermTR, mefA/E genes were detected. Also, molecular capsular types of isolates were distinguished.

The overall prevalence of colonization of participates with GBS was 13.5%. Statistical analysis showed that there was no association between risk factors and colonization with GBS. The highest resistance was observed to erythromycin (44.4%) followed by clindamycin (29.6%), penicillin, ampicillin, and ceftriaxone (18.5%), levofloxacin (11.1%), and 29.6% isolates were multidrug-resistant. ermTR and mefA/E genes were detected in 37% and 11.1% isolates; respectively and the ermB gene was not detected. The most common capsular type was type Ib (44.4%) followed by type III (40.7%), type II (11.1), and type Ia (3.7%).

In the present study, the prevalence of GBS was in the medium range. Resistance to key antibiotic agents was relatively high. Also, capsular serotype Ib was the predominant serotype, which emphasizes the importance of monitoring the molecular typing of the GBS isolates regularly.