Antibiotic resistance and penicillin tolerance in ano-vaginal group B streptococci

We sought to determine the prevalence of group B streptococcus (GBS) colonisation and to characterise antibiotic resistance patterns.

Vaginal and ano-rectal cultures were evaluated for GBS colonisation, and antibiotic susceptibility profiles were determined to 15 antibiotics according to the guidelines of the National Committee for Clinical Laboratory Standards.

Our GBS prevalence was 30%. All isolates were sensitive to amoxicillin/clavulanic acid, ampicillin, ampicillin/sulbactam, cefotaxime, ceftriaxone, cefuroxime-sodium, imipenem, linezolid, penicillin G and vancomycin. Thirty-two percent of the isolates were resistant to azithromycin, 21% to clindamycin, 25% to erythromycin and 23% to tetracycline.

The relatively high rates of resistance to four of the 15 antibiotics tested confirm that for women allergic to penicillin and colonised with GBS, antibiotic sensitivities should be determined. We noticed increasing resistance to clindamycin over a 7-year period. Ongoing surveillance of local antibiotic resistance patterns at the institutional level is important in determining optimal prophylaxis as resistance patterns differ between institutions and are increasing.