Direct serogrouping of group B streptococci from urogenital and gastric swabs with nitrous acid extraction and the Phadebact streptococcus test.

The micro-nitrous acid extraction-Phadebact coagglutination method was demonstrated to be a highly sensitive means to identify group B streptococci directly from cervical, uterine, and placental swab specimens, as well as from gastric and amniotic fluids. The swabs used for the standard culture method were used successfully for the direct extraction method. Accordingly, the direct swab extraction method yielded an identification of 92.0% of the group B streptococci identified by a standard culture procedure. Identification of the group B streptococci by the direct method was obtainable within 25 minutes of receipt of the clinical specimen in the laboratory. At this time, this highly rapid and sensitive method appears to be most applicable for the identification of group B streptococci from infants and colonized parturient women with associated risk factors before delivery, and therefore could provide a better opportunity for infant survival.