Research-based assessment of antibiotic resistance of β hemolytic group B streptococci

Abstract

Since the 1950s, β hemolytic streptococcus group B have constituted the major etiological factor of perinatal infections. GBS colonization of the genital tract among pregnant women is diagnosed between 35 and 37 weeks of gestation, and is associated with approximately 25% risk of neonatal early-onset infections (EOD). The infection is severe among 1-3% of the newborns, and usually results in sepsis or pneumonia. β-lactam antibiotics are drugs of choice to prevent vertical infection of group B streptococcus. In case of hypersensitivity to penicillin among pregnant women, second line drugs are macrolides and lincosamides. Objective: In light of numerous reports on the decreasing susceptibility of GBS, the aim of this study was to characterize the isolated strains of Streptococcus agalactiae in terms of their resistance to antibiotics. Material: The study included 395 pregnant women in the third trimester of pregnancy, hospitalized in the Department of Perinatology, and Department of Gynecology and Obstetrics, Medical University of Lodz, between 02.2010– 02.2012. Methods: Vagino–rectal swabs were collected from all pregnant women. We recovered 121 GBS positive isolates. Identification was based on the streptococcal agglutination test. Antimicrobial susceptibility was determined by disk diffusion method. Results: A positive result for GBS colonization was found among 89 patients, representing 22.5% of the studied population. Inducible MLSB resistance to erythromycin and clindamycin was 23.1% and 10.7% of the isolated strains, respectively. Constitutive MLSB resistance was detected in 14.9 % of the cases. Conclusions: The obtained results confirm that all GBS isolates are sensitive to β-lactam antibiotics and prove that phenotypes resistant to macrolides and clindamycin are becoming more widespread. This leads to the conclusion that regular supervision of drug sensitivity of Streptococcus agalactiae is necessary.