Distribution of Capsular Serotypes in Group B Streptococci Clinical Isolates based on Genotyping

Group B Streptococci (GBS) or Streptococcus agalactiae is one of the most common causes of sepsis and meningitis in neonates and of invasive diseases in pregnant women. It can also cause infectious disease among adults with underlying medical conditions like immunocompromised individuals. Polysaccharide capsule is an important virulence factor. Nine GBS serotypes (Ia, Ib, II to VIII) based on capsular polysaccharide antigens have been described. Distribution of capsular serotypes varies over time and by geographic location. The aim of this study was to detect the capsular serotype distribution in GBS clinical isolates based on genotyping of cps-gene cluster and to determine the predominant serotypes of GBS. In this cross sectional study a total of 50 GBS strains were isolated from various clinical sources including: urine, vagina, semen and urethral secretions. GBS was identified by Gram stain, catalase test, CAMP test and also resistance to 0.04 U Bacitracin and SXT disks. DNA was extracted from all the isolates using the wizard SV Genomic DNA Purification system, Promega, USA. The capsular serotype of the isolates was assigned by using a specific-two Multiplex PCR assay. For statistical analysis, Chi-square method was used. SPSS V.13 was also used. In the 50 GBS isolates, the predominant serotypes were III with 25 isolates (50%) and serotype V with 8 isolates (16%). Seven isolates (14%) belonged to serotype Ia and 7 isolates (14%) belonged to serotype II, respectively. Serotypes Ib, IV, VI, VII and VIII were not found and 3 strains were classified as nontypeable. Based on the results of this study, serotypes III and V were the predominant serotypes in GBS clinical isolates.