A COMPARISON OF THE YIELD OF POSITIVE ANTENATAL GROUP-B STREPTOCOCCUSCULTURES WITH DIRECT INOCULATION IN SELECTIVE GROWTH-MEDIUM VERSUS PRIMARY INOCULATION IN TRANSPORT MEDIUM FOLLOWED BY DELAYED INOCULATION IN SELECTIVE GROWTH-MEDIUM
Hm. Silver et J. Struminsky, A COMPARISON OF THE YIELD OF POSITIVE ANTENATAL GROUP-B STREPTOCOCCUSCULTURES WITH DIRECT INOCULATION IN SELECTIVE GROWTH-MEDIUM VERSUS PRIMARY INOCULATION IN TRANSPORT MEDIUM FOLLOWED BY DELAYED INOCULATION IN SELECTIVE GROWTH-MEDIUM, American journal of obstetrics and gynecology, 175(1), 1996, pp. 155-157
OBJECTIVE: Our purpose was to compare the yield of positive group B St
reptococcus cultures with standard medium for transport of culture swa
bs compared with use of selective medium during transport. STUDY DESIG
N: Cultures of introitus, perineum, and rectum were obtained on prenat
al patients; one was placed in standard transport medium, and the othe
r directly in selective growth medium. Swabs in standard transport med
ium were plated for routine culture and then transferred to selective
growth medium, Todd-Hewitt broth, in the laboratory. RESULTS: A total
of 307 of 1222 (25.1%) patients had a positive result by any method. W
ith direct inoculation into selective growth medium at the time of sam
pling, 4.6% of positive cultures were missed. With delayed inoculation
into selective growth medium, 16.3% were missed (p < 0.001). Without
use of selective media (routine culture), 31.9% were missed (p < 0.001
). CONCLUSIONS: Use of standard transport medium with subsequent trans
fer into selective growth medium results in a significantly decreased
yield of positive group B Streptococcus cultures.