ABSTRACT
Streptococcus agalactiae--group B streptococci (GBS)--is a main cause of severe neonatal infections with a high mortality rate. The detection of pregnant GBS carriers (5-35
) allows intrapartum administration of antibiotic prophylaxis to these women and prevents perinatal infection. We studied the prevalence of GBS in 259 patients between 28 and 37 weeks gestation from April 2000 to March 2002. The anorectum (AR) and vaginal introitus swabs (VI) were cultured in selective Todd-Hewitt broth containing colistin (10 micrograms/ml) and nalidixic acid (15 micrograms/ml) while vaginal swabs (VFS) were cultured following conventional methods. A total of 47 strains of EGB were isolated from 259 patients (18.15
). The prevalence in different samples were: 5.40
in AR and 17.76
in VI + AR (reference method). The isolates were tested against penicillin, ceftriaxone, erythromycin, clindamycin, vancomycin, gentamicin and streptomycin to determine the minimum inhibitory concentration. The resistance phenotypes of erythromycin-resistant GBS were determined by the double-disk test. All strains were susceptible to penicillin, ceftriaxone and vancomycin, only one strain was erythromycin and clindamycin resistant by IMLSB mechanism. None of the isolated strains had a high resistant level to aminoglycosides. The sensitivity of cultures increased when selective broths were used as the primary detection method.