Prevalence, serotypes and antibiotic resistance patterns of Streptococcus agalactiae isolated from pregnant women in Khoy, Iran

Abstract Background Streptococcus agalactiae colonizes pregnant women and if transmitted to newborns during delivery, can lead to serious and fatal diseases such as sepsis, pneumonia, and meningitis. The aim of this study was to evaluate the frequency, serotypes, and antibiotic resistance patterns of Streptococcus agalactiae isolated from pregnant women’s vaginas. Methods In this cross-sectional study, 446 vaginal swab samples were collected from pregnant women. Suspected colonies were confirmed by conventional tests such as hemolytic activity, catalase, Gram staining, bile-esculin agar, CAMP, and hippurate hydrolysis. The antimicrobial susceptibility of Streptococcus agalactiae strains was determined via the Kirby-Bauer disk diffusion method. The presence of resistance genes (ermB, ermTR, mefA, and linB) was detected via Multiplex PCR method. The isolates were serotyped via the sequential multiplex-PCR method. Results A total of 42 strains were isolated from 446 vaginal swab samples. All the strains were sensitive to penicillin, ampicillin, and vancomycin, and 45.2% and 28.5% of the isolates were not susceptible to erythromycin or clindamycin, respectively. The ermTR, ermB, mefA, and linB genes were detected in 11(26.19%), 9(21.42%), 2 (4.76%), and 4 (9.52%) isolates, respectively. The most common serotype in this study was III (61.9%) followed by II (14.28%), Ia (11.9%), V (7.14%), and Ib (4.76%). Conclusions Serotype III is highly prevalent in Iran and due to its association with invasive diseases, screening of pregnant women and prophylactic treatment of carriers are necessary. The most important resistance mechanism for macrolides is the ermTR gene and the M phenotype.