High Prevalence of Capsular Type I and Resistance to Multiple Antibiotics Among Streptococcus agalactiae Isolated from Pregnant Women

Abstract

Background and purpose: Emergence of multidrug resistance (MDR) among Streptococcus agalactiae isolated from pregnant women and the presence of polysaccharide capsules in these strains play a significant role in pathogenicity. Therefore, the aim of this study was to investigate the prevalence of antibiotic resistance, multidrug resistance, and Ia and Ib capsular types in these strains. Materials and methods: Vaginal samples were transferred to Todd-Hewitt Broth medium. After 24 hours, they were inoculated on the blood agar medium, and then the bacteria were identified using standard methods. The antibiotic resistance pattern of the isolates was determined by the disk agar diffusion method. Then, the bacterial DNA was extracted and the capsular genes were identified using PCR method. Results: The prevalence of colonization in pregnant women was 23.25%. Tetracycline with 94.33% resistance rate was the least effective drug, while 78.3%, 81.13% and 83.01% of the isolates were non-susceptible to ofloxacin, erythromycin and quinupristin-dalfopristin, respectively. Also, 78.3% of the isolates were sensitive to penicillin. Meanwhile, 94 (88.7%) isolates were MDR, while 20 (18.86%) isolates and 32 (30.18%) isolates had the Ia and Ib capsular types, respectively. Conclusion: Penicillin is a suitable drug for prophylaxis in high-risk pregnant women in this region. The high prevalence of MDR strains indicates the lack of proper management of antibiotics. In addition, the high prevalence of capsular types Ib and Ia, especially in MDR strains, shows the importance of these serotypes for designing capsular vaccines.

Keywords

• streptococcus agalactiae
• multidrug resistance
• capsular type
• pregnant women