Detection of genital colonization of group B streptococci during late pregnancy.
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.


CONCLUSIONS
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.
El-Kersh
Talat A
TA
Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, King Khalid University, King Saud University, Riyadh, Kingdom of Saudi Arabia.
Al-Nuaim
Lulu A
LA
Kharfy
Turky A
TA
Al-Shammary
Fahd J
FJ
Al-Saleh
Saad S
SS
Al-Zamel
Faten A
FA
D000293:Adolescent; D000328:Adult; D002353:Carrier State / Q000453:epidemiology / Q000382:microbiology*; D015169:Colony Count, Microbial; D005260:Female; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D018445:Infectious Disease Transmission, Vertical / Q000517:prevention & control*; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis*; D011256:Pregnancy Outcome; D011263:Pregnancy Trimester, Third; D011336:Probability; D012307:Risk Factors; D012529:Saudi Arabia / Q000453:epidemiology; D012680:Sensitivity and Specificity; D013290:Streptococcal Infections / Q000175:diagnosis* / Q000453:epidemiology / Q000635:transmission*; D013292:Streptococcus agalactiae / Q000302:isolation & purification*; D014626:Vaginal Smears