Objective: The aim of the study was to determine the degree of colonization Streptococcus agalactiae (GBS--Group B Streptococcus) in women at 35.-37. weeks of pregnancy and to evaluate drug susceptibility of the isolated strains.

Methods: We analyzed the results of 1111 tests for GBS colonization performed between 2010-2013 in pregnant women (aged 16-40) from the West Pomeranian region. Swabs were taken from the vagina and the anus of the study subjects at 35.-37. weeks of pregnancy Materials were cultured on Granada Agar and in selective Todd-Hewitt broth, which was next cultured on Granada Agar The degree of GBS colonization was determined by the semi-quantitative method on solid media. The strains were tested for susceptibility to penicillin, erythromycin and clindamycin by disc diffusion method according to the EUCAST standards.

Results: Positive cultures for S. agalactiae were found in 22.5% of the pregnant women. The highest (25.4%) and the lowest (15.9%) rates of GBS colonization were observed in the age groups of 31-35 and 16-20 years, respectively Massive GBS colonization was detected in 68.4% of pregnant subjects, with the highest and the lowest rates in the age groups of 31-35 and 16-20 years, (75.3% and 50.0%, respectively). All isolated GBS strains were sensitive to penicillin. Macrolide, lincosamide and streptogramin B resistance (MLSB) was found in 28% of the isolates, resistance only to erythromycin (phenotype M) in 2% of the strains. There were no significant differences in the degree of GBS colonization and drug sensitivity of GBS strains versus the year of our examination.

Conclusions: Monitoring for GBS colonization in the last weeks of pregnancy seems to be necessary for effective prevention of S. agalactiae infections.