Original Research

CHROMagarTM Strep B for detecting group B Streptococcus in pregnant women at 35th to 37th of gestation


Introduction: Group B Streptococcus (GBS) is one of the common causes of neonatal sepsis spreading from mothers to newborns. A common method to isolate and identify GBS is using Blood agar which delivers results in at least 48 hours. Although chromogenic culture media including CHROMagarTM StrepB, can develop colored colonies for detecting pathogenic bacteria easily, there has not been approached GBS isolation in Vietnam. This study was conducted to find out the GBS infection ratio in pregnant women at the 35th – 37th week of gestation. Furthermore, this research evaluates the efficacy of CHROMagarTM StrepB media and Blood agar in GBS detection as well.

Method: In a cross-sectional survey, a total of 258 pregnant women at 35th to 37th of gestation screened for GBS at Thuan Kieu General Clinic from 04/2021 to 12/2021 were recruited. Rectovaginal swabs from these patients were cultured on Blood agar and CHROMagarTM StrepB. We performed data analysis using SPSS ver 20, p<0.05 was statistically significant.

Result: Overall, out of 258 participants, 52 (20.16%) were GBS carriers. CHROMagarTM StrepB has significantly higher sensitivity than blood agar if spending a similar time (1.52 fold, p-value < 0.001), or event training a shortened time (18 hours and 48 hours), CHROMagarTM StrepB media is still more sensitive than blood agar (1.16 fold, p-value 0.044).

Conclusion: In this study, the GBS infection ratio in pregnant women at 35-37 weeks of gestation at Thuan Kieu General Clinic is 20.16%. Culturing vaginal-rectal specimens on CHROMagarTM StrepB medium is higher sensitivity and rapidly than blood agar for GBS detection. CHROMagarTM StrepB should be used to get more effective in identifying GBS carriers in near-term pregnant women. 

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