Maternal colonization of group B streptococcus: prevalence, associated factors and antimicrobial resistance

Group B streptococcus (GBS, Streptococcus agalactiae) can be transferred during delivery to neonates from mothers who are colonized with GBS in the genital tract. GBS can cause sepsis and meningitis in newborns. This study was conducted to determine GBS colonization rates among pregnant women and the antibiotic sensitivity patterns.

Prospective descriptive study at the Maternity and Children Hospital, Makkah.

Vaginal swabs from 1328 pregnant women (>=35 weeks of gestation) attending antenatal clinic were cultured in Todd-Hewitt broth supplemented with gentamicin and nalidixic acid. After 36 hours of incubation, subculture was made onto sheep blood agar and incubated in 5% carbon dioxide for 18 to 24 hours. A Microscan Walk Away system was used for the identification and antibiotic susceptibility of GBS isolates. Each isolate was also tested for group B by using latex slide agglutination test. Information such as maternal age, gestational age and parity was collected using a predesigned questionnaire.

The study population ranged between ages 17-47 years. The GBS colonization in all age groups was found to be 13.4%. A higher colonization rate was seen in pregnant women > 40 years of age (27.4%). Women with gestational age > 42 weeks were colonized (25%) more frequently that women with a gestational age from 41-42 weeks (20.2%). An increased rate of colonization was found in women who delivered > 5 times and no colonization in women who delivered once. All GBS isolates were 100% sensitive to penicillin G, ampicillin and vancomycin. Erythromycin and clindamycin showed resistance-15.7% and 5.1%, respectively.

The high prevalence of GBS colonization in pregnant women demands for screening in women attending an antenatal clinic so that intrapartum antimicrobial prophylaxis can be offered to all women who are colonized with GBS, thus preventing its transfer to the newborn.