Group B streptococcus colonization in preterm labor and preterm premature rupture of membranes

Prevalence of maternal colonisation with group B streptococcus: a systematic review and meta-analysis

BACKGROUND

The most important risk factor for early-onset (babies younger than 7 days) invasive group B streptococcal disease is rectovaginal colonisation of the mother at delivery. We aimed to assess whether differences in colonisation drive regional differences in the incidence of early-onset invasive disease.

METHODS

We did a systematic review of maternal group B streptococcus colonisation studies by searching MEDLINE, Embase, Pascal Biomed, WHOLIS, and African Index Medicus databases for studies published between January, 1997, and March 31, 2015, that reported the prevalence of group B streptococcus colonisation in pregnant women. We also reviewed reference lists of selected studies and contacted experts to identify additional studies. Prospective studies in which swabs were collected from pregnant women according to US Centers for Disease Control and Prevention guidelines that used selective culture methods were included in the analyses. We calculated mean prevalence estimates (with 95% CIs) of maternal colonisation across studies, by WHO region. We assessed heterogeneity using the I(2) statistic and the Cochran Q test.

FINDINGS

221 full-text articles were assessed, of which 78 studies that included 73 791 pregnant women across 37 countries met prespecified inclusion criteria. The estimated mean prevalence of rectovaginal group B streptococcus colonisation was 17·9% (95% CI 16·2-19·7) overall and was highest in Africa (22·4, 18·1-26·7) followed by the Americas (19·7, 16·7-22·7) and Europe (19·0, 16·1-22·0). Studies from southeast Asia had the lowest estimated mean prevalence (11·1%, 95% CI 6·8-15·3). Significant heterogeneity was noted across and within regions (all p≤0·005). Differences in the timing of specimen collection in pregnancy, selective culture methods, and study sample size did not explain the heterogeneity.

INTERPRETATION

The country and regional heterogeneity in maternal group B streptococcus colonisation is unlikely to completely explain geographical variation in early-onset invasive disease incidence. The contribution of sociodemographic, clinical risk factor, and population differences in natural immunity need further investigation to understand these regional differences in group B streptococcus maternal colonisation and early-onset disease.

FUNDING

None.

A combined enrichment/polymerase chain reaction based method for the routine screening of Streptococcus agalactiae in pregnant women

Group B Streptococcus (GBS) is the most common cause of life-threatening infection in neonates. Guidelines from CDC recommend universal screening of pregnant women for rectovaginal GBS colonization. The objective of this study was to compare the performance of a combined enrichment/PCR based method targeting the atr gene in relation to culture using enrichment with selective broth medium (standard method) to identify the presence of GBS in pregnant women. Rectovaginal GBS samples from women at ≥36 weeks of pregnancy were obtained with a swab and analyzed by the two methods. A total of 89 samples were evaluated. The prevalence of positive results for GBS detection was considerable higher when assessed by the combined enrichment/PCR method than with the standard method (35.9% versus 22.5%, respectively). The results demonstrated that the use of selective enrichment broth followed by PCR targeting the atr gene is a highly sensitive, specific and accurate test for GBS screening in pregnant women, allowing the detection of the bacteria even in lightly colonized patients. This PCR methodology may provide a useful diagnostic tool for GBS detection and contributes for a more accurate and effective intrapartum antibiotic and lower newborn mortality and morbidity.

Microbiological characteristics and inflammatory cytokines associated with preterm labor

PURPOSE

To evaluate vaginal microflora and interleukin-1β (IL-β), interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-α) concentrations in the cervicovaginal fluid of a group of pregnant women in preterm labor when compared with a group of full-term pregnant women not yet in labor.

METHOD

Case-control study performed in a University tertiary referral maternity in Campinas, Brazil with 45 pregnant women in preterm labor and 45 full-term pregnant women not in labor. All patients underwent speculum examination for the collection of cervicovaginal fluid. Bacterial vaginosis (BV) was diagnosed according to the criteria of Amsel and Nugent. Culture was performed for group B streptococcus (GBS) and lactobacilli, and hybrid capture assay for screening for chlamydial and gonococcal infection. Cytokine concentrations were measured using ELISA technique. Statistical analysis was performed using χ(2), Fisher's exact, and crude and adjusted odds ratios. Significance level was defined at 5%. The main outcome measures were cervicovaginal cytokines in preterm labor.

RESULTS

IL-6 and IL-8 were significantly associated with preterm labor. The changes in vaginal microflora, as well as BV and GBS, were more frequent in women in preterm labor, although BV and GBS showed no statistical significance. The presence of Candida sp., absence of lactobacilli, positive screening for chlamydial and gonococcal infection and the presence of IL-1β and TNF-α were not associated with preterm labor.

CONCLUSIONS

IL-6 and IL-8 and the presence of any type of vaginal infection were the factors that were significantly associated with preterm labor.