Selective versus non-selective culture medium for group B Streptococcus detection in pregnancies complicated by preterm labor or preterm-premature rupture of membranes

Department of Obstetrics and Gynecology, Medical School, Campinas State University, São Paulo State, Brazil.
Brazilian Journal of Infectious Diseases (Impact Factor: 1.3). 09/2006; 10(4):247-50. DOI: 10.1590/S1413-86702006000400006
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The objective of this study was to identify group B streptococcus (GBS) colonization rates and compare detection efficiency of selective versus non-selective culture media and anorectal versus vaginal cultures in women with preterm labor and preterm-premature rupture of membranes (PROM). A prospective cohort study of 203 women was performed. Two vaginal and two anorectal samples from each woman were collected using sterile swabs. Two swabs (one anorectal and one vaginal) were placed separately in Stuart transport media and cultured in blood-agar plates for 48 hours; the other two swabs were inoculated separately in Todd-Hewitt selective media for 24 hours and then subcultured in blood-agar plates. Final GBS identification was made by the CAMP test. A hundred thirty-two cultures out of 812 were positive. The maternal colonization rate was 27.6%. Colonization rates were 30% for preterm PROM and 25.2% for preterm labor. Todd-Hewitt selective medium detected 87.5% and non-selective medium 60.7% GBS-positive women. Vaginal samples and anorectal samples had the same detection rate of 80.3%. Anorectal selective cultures detected 75% of carriers; 39% of GBS-positive women were detected only in selective medium. A combined vaginal-anorectal selective culture is appropriate for GBS screening in this population, minimizing laboratory costs.

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    • "However, variable results have been reported using different media preparations while studying direct plating versus subculture from Lim broth. Some studies found comparable sensitivity of direct plating on a differential (Granada) medium compared with Lim broth enrichment (Gil et al., 1999; Votava et al., 2001), whereas other reports (De la Rosa et al., 1992; Rosa-Fraile et al., 1999) suggested that direct plating on chromogenic and or selective media was significantly less sensitive (Overman et al., 2002; Nomura et al., 2006). "
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    ABSTRACT: This study was undertaken to evaluate chromogenic medium and direct latex agglutination test (DLA) for detection of Group B Streptococcus (GBS) in the vaginal specimens of pregnant women, and to ascertain the prevalence of GBS in this population in Kuwait and Lebanon. Vaginal swabs, collected from women at 35-37 weeks, were cultured on 5% sheep blood agar (SBA), colistin nalidixic acid agar (CNA), Strept B Select chromogenic agar (SBS) as well as Lim enrichment broth in 168 cases in Lebanon while only SBA was used for 1391 samples in Kuwait. In addition, vaginal samples from 102 GBS-positive and 20 GBS-negative women near the time of delivery were collected in Kuwait for evaluation of DLA test. During the study period, the prevalence of GBS colonization was determined to be 20.7% (288/1391) in Kuwait while 18.4% of 168 pregnant women in Lebanon had vaginal cultures positive for GBS. By direct plating of vaginal swabs on the three media used, the isolation rates of GBS was 51.6%, 64.5%, and 77.4% on SBA, CNA, and SBS, respectively, which increased to 90.35, 93.1%, and 96.8%, respectively, following subculture of Lim broth after 18 h of incubation. The sensitivity of DLA test was found to be dependent on the density of GBS colonization, resulting in 100% sensitivity and 100% specificity for heavy (> 10(2) CFU/swab) and moderately heavy (50-100 CFU/swab) growth of GBS. However, for vaginal specimens yielding < 50 CFU/swab, the sensitivity, specificity, positive and negative predictive values of DLA were 100%, 55.5%, 63.6%, 100%, respectively. In conclusion, a chromogenic agar, such as, SBS and DLA test can be used for rapid detection of GBS in pregnant women. DLA test, in particular, can prove to be a useful tool for immediate detection of GBS in women near delivery so that intra-partum antibiotic prophylaxis can be initiated.
    Journal of Medical Microbiology 07/2014; 63(Pt_10). DOI:10.1099/jmm.0.066738-0 · 2.25 Impact Factor
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    • "The carriage rate found by us was higher when compared with the results described in Santa Catarina (21.6%) (Pogere et al., 2005), Ribeirão Preto (17.9%) (Zusman et al., 2006) and São Luis (20.4%) (Costa et al., 2008) (Fisher , s Exact Test, p = 0.0192, p = 0.005, p = 0.0143, respectively ). However, the present data were similar to those described by other authors in Brazil: Rio de Janeiro (26%) (Benchetrit et al., 1982) and Campinas (27.6%) (Nomura et al., 2006). Among the 39 GBS isolates studied, the serotypes III and V were the most prevalent and the most resistant to antibiotics in agreement with the results of other authors (Oliveira et al., 2005). "
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    ABSTRACT: GBS serotypes III and V were the most prevalent in pregnant women and exhibited resistance to tetracycline, clindamycin and sulfamethoxazole/trimethoprim. Serotype III showed high sialic acid content and PFGE analysis discerned 33 heterogeneous profiles. Phenotypic and genotypic characterization could be relevant to control GBS infections unaffected by intra-partum chemoprophylaxis.
    07/2013; 44(3):869-72. DOI:10.1590/S1517-83822013000300032
    • "The colonization rate in the third trimester of pregnancy was found to be 12.67%. Though this is low when compared to studies done in Europe and Brazil,[1516] these are much higher than the colonization rates obtained in Indian studies.[5] The isolation of GBS from the vaginal swabs depends on the methods used for isolation. "
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    ABSTRACT: Group B Streptococcus (GBS) is one of the most common causes of neonatal sepsis throughout the world. Reports of vaginal colonization of GBS in India are few and variable. A study was conducted on pregnant women in a tertiary care hospital to compare various methods for isolation of GBS, to study the prevalence of GBS in pregnant women in third trimester, and to determine risk factors for GBS colonization. Observational descriptive study. High vaginal swabs from 150 pregnant women in their third trimester were used to compare three methods for isolation of GBS viz. direct culture on 5% Sheep Blood agar, direct culture on selective Columbia Blood Agar and culture in LIM enrichment broth with subsequent culture on 5% Sheep Blood agar. A history of associated risk factors was also taken. Statistical analysis was performed by Chi-square test. Isolation was best from LIM enrichment broth with subsequent culture on 5% Sheep Blood Agar. Prevalence of GBS colonization by using culture method was 12.67%. Most frequently associated risk factor was intrapartum fever (42.11%). Standard Culture Method using LIM enrichment should be adopted as standard practice for isolation of GBS from vaginal swabs.
    Journal of laboratory physicians 03/2013; 5(1):42-5. DOI:10.4103/0974-2727.115938
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