Streptococcus agalactiae in pregnant women: phenotypic and genotypic characters

OBJECTIVE: Streptococcus agalactiae (GBS) is considered a leading cause of neonatal sepsis. We evaluated the phenotypic and genotypic characters of 73 S. agalactiae strains isolated from different women at the 35-37 weeks of pregnancy. METHODS: Isolates were characterized by serotyping (direct agglutination) and by pulsed-field-gel-electrophoresis (PFGE). Resistance to antimicrobials (penicillin, macrolides, lincosamides, quinolones and tetracyclines) was assessed. RESULTS: All isolates were serologically typeable and ascribable to one of the six tested serotypes (Ia, Ib, II, III, IV, and V) and many strains of the same serotype were genetically heterogeneous. Strains belonging to serotypes III, V and Ia were the most prevalent and the most resistant to macrolides. CONCLUSIONS: This work reports GBS colonization rate (about 18%) and the prevalent capsular serotypes among pregnant women in Turin (Italy). Penicillin and erythromycin can be still considered the first and second choice drugs for prophylaxis and treatment of early-onset GBS infections in our district. The relevance of phenotypic and genotypic characterization of strains to monitor and control Streptococcus agalactiae infections is briefly discussed.