| Summary: | Intro: Streptococcus agalactiae (GBS) is a leading cause of neonatal morbidity and mortality. Hence knowledge of antibiotic sensitivity pattern is important in empirical therapy. Methods: A descriptive cross-sectional study was carried to determine antibiotic sensitivity of GBS among 175 pregnant women of >35 weeks of gestation attending antenatal clinics in four teaching hospitals in Western Province of Sri Lanka. Low vaginal and rectal swabs were collected separately, culture performed and GBS was identified by standard microbiological methods. Antibiotic sensitivity was determined by disk diffusion method and detection of minimum inhibitory concentration according to CLSI guidelines. DNA was extracted from culture isolates and resistance mechanisms were identified by PCR using ermB, ermTR, mefA and linB genes. Findings: GBS colonization in study sample was 25.7% (45/175) with detection rate of 22.9% and (40/175) and 2.9% (5/175) in vaginal and rectal samples respectively. All isolates were susceptible to penicillin with a MIC range of 0.03-0.12μg/ml. Seventeen (37.7%) were non-susceptible to erythromycin while 6 were intermediate and 11 were resistant. There were 15 (33.3%) non-susceptible isolates for clindamycin. with 5 intermediate and ten resistant isolates. Of them seven had inducible clindamycin resistance (iMLSB). Erythromycin and clindamycin MICs ranged 0.03–0.32 μg/ml and 0.06–0.32 μg/ml respectively. The ermB gene was detected in 7(15.5%) while two of these isolates did not show resistance to either drug phenotypically. The ermTR was found in 16 (35.6%) and one isolate did not show resistance phenotypically. Two iMLSB isolates harboured ermTR and ermB. The mefA gene was detected in two (4.4%) isolates. The linB gene was not detected in tested isolates. Conclusion: All isolates were sensitive to penicillin and the most prevalent resistance genotype was ermTR in study population.
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