Maternity patients and their newborn infants were cultured for group B streptococci (GBS) at Tampa General Hospital, Tampa, Fla., from September 1982 to May 1983. Culture swabs were placed into Lim Group B Strep Broth (GIBCO Laboratories, Madison, Wis.) and quantitated for GBS. A strong correlation was found between the numbers of GBS in the maternal vagina and the infant rectum. Infants symptomatic for early-onset GBS disease were delivered by mothers heavily colonized (:3 x 104 GBS per swab) at the vagina. Such mothers were identified as GBS carriers by slide coagglutination and latex agglutination after their broth cultures had been incubated for 5 h. These data indicate that maternity patients at high risk of delivering infants heavily colonized with GBS and potentially symptomatic for early-onset GBS disease can be rapidly and selectively identified.

Pregnant women admitted to Tampa General Hospital, Tampa, Fla., were cultured for group B streptococci (GBS). Culture swabs were placed into enriched, selective Todd-Hewitt medium and were quantitated for GBS. The broth cultures were tested by slide coagglutination before incubation and after 5 and 20 h of incubation. Fifty-four (27%) of the 201 maternity patients cultured were positive for GBS and were identified as such by slide coagglutination. A strong correlation was found between the magnitudes of colonization and the times required to identify the broth cultures as GBS positive. Cultures from mothers heavily colonized (mean concentrations of 3 x 104 GBS per culture swab or greater) were identified after 5 h or less of incubation. Mothers lightly colonized with GBS (mean concentrations of 2 x 102 GBS per culture swab) were identified only after their broth cultures had been incubated for 20 h.

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Strong multiple reactions often occur with the Phadebact Streptococcus test when the culture contains blood. These reactions interfere with the identification of the Lancefield groups of streptococci. Group B streptococci from the vagina of pregnant women are difficult to identify by slide coagglutination because of the frequent presence of blood on culture swabs. Elimination of these multiple reactions caused by blood would permit rapid identification of group B streptococci in pregnant women. Vaginal broth cultures were examined to determine the cause of multiple reactions with slide coagglutination and to eliminate them from the testing procedure. Of 245 maternal broth cultures, 135 (55%) yielded multiple reactions when tested by coagglutination. Such reactions were either eliminated or greatly diminished by heating the broth sample to 90 degrees C for 10 min. It was also found that globulins in the serum may be responsible for multiple reactions with blood. This heating protocol will permit vaginal broth cultures to be rapidly tested for group B streptococci by slide coagglutination.

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