Group B streptococcal carriage, antimicrobial susceptibility, and virulence related genes among pregnant women in Alexandria, Egypt

Abstract

Background and aim: Group B Streptococcus (GBS) has emerged as a leading cause of illness and death among neonates. The study was conducted to estimate the prevalence of recto-vaginal carriage of GBS among pregnant women at 35–37 weeks, gestation, to describe GBS antimicrobial susceptibility profile and to investigate selected virulence genes by PCR.

Subjects and methods: Two-hundred pregnant women at 35–37 weeks of gestation attending antenatal clinic at Al-Shatby University Hospital were enrolled in the study. Both vaginal and rectal swabs were collected from each subject. Swabs were inoculated onto CHROMagar^TM StrepB and sheep blood agar plates. All GBS isolates were subjected to antimicrobial susceptibility testing using disc diffusion. Disc approximation test was performed to detect erythromycin resistance phenotype (MLSB). GBS virulence genes scpB, bac, bca, and rib were identified by PCR.

Results: Among the 200 pregnant women, 53 (26.5%) were identified as GBS carriers. All carriers had vaginal colonization (100%), four (7.5%) had combined recto-vaginal colonization. None of the carriers had rectal colonization alone. All isolates (100%) were susceptible to penicillin, ampicillin, ceftriaxone, cefotaxime, cefepime, vancomycin, and linezolid. On the other hand, 43.4%, 28.3%, 22.6%, and 15% of isolates were resistant to levofloxacin, azithromycin, erythromycin, and clindamycin respectively. Out of 12 erythromycin resistant isolates, six isolates had constitutive while two had inducible MLSB resistance. scpB was identified in 100%, rib in 79.2%, and bac in 35.8% of GBS isolates. None of the isolates possessed the bca gene.

Conclusion: Introduction of GBS screening in Egyptian pregnant women is recommended. Penicillin or ampicillin is still the antibiotic of choice for intrapartum prophylaxis.

Keywords:  Group B streptococci, Rib gene, Penicillin susceptibility, Vaginal carriage