Comparison of group B streptococci colonization in vaginal and rectal specimens by culture method and polymerase chain reaction technique.

BACKGROUND

Streptococcus agalactiae (group B streptococci, GBS) is a colonizing microorganism in pregnant women and without causing symptoms. Colonization of GBS in the rectovaginal region in late of pregnancy is a risk factor for newborn diseases. GBS infection in newborn babies is acquired by the aspiration of infected amniotic fluid or vertical transmission during delivery through the birth canal. The aim of this study was determination of GBS prevalence among vaginal and anorectal specimens at gestation females by polymerase chain reaction (PCR) and culture-based methods.

METHODS

In this study, 137 rectal and vaginal swabs were separately collected from women with gestational age 35-37 weeks from July 2013 to March 2014 at the teaching hospital of Razi, Ahvaz, Iran. All samples were enrichment in selective culture media Todd-Hewitt broth for 24 hours and recognized by standard culture using blood agar, phenotypic tests, and amplification of the CFB gene.

RESULTS

Age range was 16-45 years (mean, 28.34 ± 0.7 years). Of rectal samples, 42 (30.7%) were positive based on culture method and 57 (41.6%) samples were positive by PCR. Of 137 vaginal samples, 38 (27.7%) were positive by culture and 60 (43.8%) samples were positive by PCR. The chance of colonization with GBS was increased in women with a history of urinary tract infection.

CONCLUSION

The frequency of GBS culture from rectal samples was higher than vaginal samples. However, the detection percentage of GBS using PCR from vaginal samples was higher than rectal samples. By contrast, the culture is a time-consuming method requiring at least 48 hours for GBS fully identification but PCR is a sensitive and rapid technique in detection of GBS, with the result was acquired during 3 hours.