RapidIdentification ofMaterial Colonization withGroupB Streptococci byUseofFluorescent Antibody

Toidentify women colonized withgroup B streptococci during parturition, we usedpooled type-specific fluorescent antibody toexamine vaginal swabsenriched bypreincubation inselective brothmedium.Inpreliminary experiments, group B streptococcus strain III-Bell was reliably detectable withfluorescent antibody atconcentrations of-105colony-forming units per ml,achieved after 6h of incubation ofsmall inocula (18to26colony-forming units). Ofthevaginal swabs from924parturient women examined prospectively bybothfluorescent antibody andselective bacteriology techniques, groupB streptococci were isolated in154. Thesensitivity ofthefluorescent antibody technique increased withincreasing incubation timeandranged from49%(3to6h)to81%(7to12h)to83%(13to 18h)to93%(>18h).Colonized mothers identified within 6hbythefluorescent antibody technique hadhigher ratesofvertical transmission totheir newborn infants (61%)thancolonized mothers whosefluorescent antibody examinations were negative within this timeinterval (32%; P = 0.027). However, because ofthe timing oftheir admissions, none ofthecolonized mothers ofthefourinfants who developed early-onset groupB streptococcal sepsis were identified withfluorescentantibody until after delivery. Although itssensitivity approaches selective culture methodsafter 6 h ofincubation, fluorescent antibody examination of vaginal swabsdoesnotappear tooffer a practical approach toidentifying colonized parturient women forintrapartum antibiotic prophylaxis ofgroup B streptococcal infection.