Detection of genital colonization of group B streptococci during late pregnancy

Authors

• Talat A. El-Kersh, Professor of Microbiology, CLS Department, College of Applied Medical Sciences, King Saud University, PO Box 10219, Riyadh, Kingdom of Saudi Arabia. Tel. +966 (1) 4355142. Fax. +966 (1) 4355883.
• Lulu A. Al-Nuaim, Department of Obstetric and Gynecology, King Khalid University Hospital, King Saud University, PO Box 10219, Riyadh, Kingdom of Saudi Arabia.
• Turky A. Kharfy, Department of Obstetric and Gynecology, King Khalid University Hospital, King Saud University, PO Box 10219, Riyadh, Kingdom of Saudi Arabia.
• Fahd J. Al-Shammary, Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, King Khalid University Hospital, King Saud University, PO Box 10219, Riyadh, Kingdom of Saudi Arabia.
• Saad S. Al-Saleh, Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, King Khalid University Hospital, King Saud University, P O Box 10219, Riyadh, Kingdom of Saudi Arabia.
• Faten A. Al-Zamel, Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, King Khalid University Hospital, King Saud University, PO Box 10219, Riyadh, Kingdom of Saudi Arabia.

Abstract

OBJECTIVE: To detect group B streptococcal carrier state of Saudi females during 3rd trimester of pregnancy and to assess type of specimens and the techniques used for the organism detection. METHODS: A total of 867 consecutive vaginal and rectal swabs were obtained from 217 pregnant women at >28 weeks of gestation and their follow up testing from King Khalid University Hospital, Riyadh, Kingdom of Saudi Arabia. Swab-specimens were cultured comparatively on Islam and Edwards blood agar plates, and into selective Lim broth. Enrichment Lim broth cultures (>12 hours) with and without positive modified coagglutination test were then subcultured on Islam and Edwards sheep blood agar plates. Presumptive colonies were then tested for group B streptococcus identity by convential biochemical reactions, serogrouping and serotyping. Collected neonatal swab-specimens (184) were also treated similarly. RESULTS: In comparison to Lim broth enrichment culture, the direct swab specimen culture on Edwards blood agar or Islam agar plates technique revealed 84% sensitivity and 100% specificity, whereas modified coagglutination test after selective Lim broth enrichment revealed 100% sensitivity and 96% specificity. Group B streptococcus was isolated in at least one of the specimens from the 217 patients in 66 cases. Of these 66 cases, group B streptococcus was isolated from both vaginal and rectal swabs in 33 (50%) cases and only from vaginal swabs in 22 (33%) and rectal swabs in 11 (17%) cases. Of the group B streptococcus positive cases, 10 (15%) cases had spontaneously lost their carriage, upon follow up testing, whereas out of the 151 negative cases, 4 (2.6%) cases became positive for group B streptococcus colonization upon follow up testing with an overall carriage rate of (60/217) 27.6%. Certain demographic factors were found to alter such rate of carriage. Additionally, 50% of group B streptococcal colonized mothers vertically transmitted the homologous serotypes of the organism to their newborns, but clinical infection was not recorded during the study period. CONCLUSION: Group B streptococci colonization rate among term Saudi pregnant women is relatively high (27.6%); and thereby constitutes a group of women whose infants are at great risk of early-onset invasive disease. The modified coagglutination test after growth amplification seems rapid and cost-effective to detect lightly or heavily group B streptococcal colonized women. Vaginal and rectal swab specimens at late pregnancy appeared necessary to accurately identify group B streptococcus maternal colonization.

Article Type

Research Article

First Page

56

Last Page

61

Recommended Citation

El-Kersh, Talat A.; Al-Nuaim, Lulu A.; Kharfy, Turky A.; Al-Shammary, Fahd J.; Al-Saleh, Saad S.; and Al-Zamel, Faten A. (2002) "Detection of genital colonization of group B streptococci during late pregnancy," Saudi Medical Journal: Vol. 23: Iss. 1, Article 11.
DOI: https://doi.org/10.15537/1658-3175.1590