Modified Granada Agar Medium for the detection of group B Streptococcus carriage in pregnant women.
OBJECTIVE
To improve the detection rate of group B streptococci (GBS) in pregnant women, aiming at the prevention of early-onset septicemia in the newborn.


METHODS
The yield from culturing two sites, vaginal and anorectal, on a Modified Granada Medium (MGM) was compared with our standard approach of culturing a vaginal swab on blood agar (BA).


RESULTS
Samples were processed from 430 consecutive pregnant women. GBS was isolated from the vagina in 11.6% with BA, and in 13.7% with MGM. In 17.0% of anorectal samples, GBS was identified with MGM. The combination of both sites and media had a yield of 20.0%. MGM identified all but six (2%) of 310 GBS strains after aerobic incubation, with use of a cover slide, and missed only three strains (1%) after anaerobic incubation.


CONCLUSIONS
Separate culture of vaginal and anorectal samples using the same MGM agar plate resulted in an increase in detection rate for GBS of 76% as compared to BA alone. The technique is simple and results are available after overnight incubation. MGM was confirmed as a specific medium for the identification of GBS, with a sensitivity of 98-99%.
Claeys
G
G
Department of Microbiology, Ghent University, Ghent, Belgium. geert.claeys@rug.ac.be
Verschraegen
G
G
Temmerman
M
M
D001003:Anal Canal / Q000382:microbiology; D001431:Bacteriological Techniques; D002353:Carrier State / Q000382:microbiology*; D003470:Culture Media; D005260:Female; D006801:Humans; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000382:microbiology*; D012007:Rectum / Q000382:microbiology; D013290:Streptococcal Infections / Q000382:microbiology*; D013292:Streptococcus agalactiae / Q000302:isolation & purification*; D014621:Vagina / Q000382:microbiology
D003470:Culture Media