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Review Article

Prevalence of Group B Streptococcus in Pregnant Women in Iran

A Systematic Review and Meta-analysis

Emaneini, Mohammad PhD*; Jabalameli, Fereshteh PhD*; van Leeuwen, Willem B. PhD†; Beigverdi, Reza PhD*

Author Information

From the *Department of Microbiology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; and †Faculty of Science & Technology, University of Applied Sciences, Leiden, the Netherlands.

Accepted for publication July 19, 2017.

The authors have no conflicts of interest to disclose.

Supported by Tehran University of Medical Sciences and Health Services. Study grant no. 91-04-30-18746.

Address for correspondence: Reza Beigverdi, PhD, Department of Microbiology, School of Medicine, Tehran University of Medical Sciences, 100 Poursina St., Keshavarz Blvd., Tehran, Iran. E-mail: [email protected].

The Pediatric Infectious Disease Journal: February 2018 - Volume 37 - Issue 2 - p 186-190
doi: 10.1097/INF.0000000000001713
  • Free

Abstract

Group B Streptococcus (GBS or S. agalactiae) is a major cause of life-threatening infections in susceptible hosts such as newborn infants, pregnant women and adults with underlying diseases such as diabetes mellitus, cancer and heart disease.1,2 In United States, approximately 10–30% of pregnant women are colonized by GBS in the vagina and rectum.3–5 Recto-vaginal colonization of the mother at the time of birth is the primary risk factor for invasive disease in newborns.3,6 Neonatal infections are divided into early-onset disease and late-onset disease based on infants’ age and disease manifestation.1,3,6 Early-onset disease is acquired through vertical transmission from a colonized mother, occurring in 0–6 days of life, whereas late-onset disease can result from horizontal sources and occurring in 7–90 days of life.6 Sepsis (80–85%) and pneumonia (10%) were the most common manifestation of early-onset disease, whereas meningitis (7%) was the most common manifestation of late-onset disease, and 46–50% of infants who survived GBS meningitis have moderate to severe neurologic impairment.2,6–8 GBS has also been associated with adverse pregnancy outcomes such as low birth weight, preterm delivery, preterm premature rupture membranes and still birth.9,10 The most important virulence factor of GBS is the polysaccharide capsule, which protects it from phagocytosis, and currently, 10 different serotypes have been identified.11,12 Globally, serotype III alone accounts for approximately 50% of neonatal disease.13,14 There are several reports from different areas of Iran on the prevalence of GBS among pregnant women,15–20 but most of these studies have reported local information, and no systematic study has been performed. The purpose of this study was to determine the prevalence of GBS colonization rates among Iranian pregnant women using a systematic review and met analysis according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement.

MATERIALS AND METHODS

Search Strategies

We searched different electronic databases (Pubmed, Embase, Web of Science and Iranian database) to find studies that reported incidence of GBS colonization in pregnant women in Iran. Searches were restricted to articles published between January 2000 and September 2016, and language restrictions were applied to English and Persian. The following search terms were used: “Streptococcus agalactiae” or “S. agalactiae” or “group B streptococcus” or “GBS” and “colonization” and “pregnant women” in combination with Iran. Cross-sectional or cohort studies that reported the prevalence of GBS among pregnant women were considered. The titles and abstracts were initially screened by the 2 independent reviewers for possible inclusion. Eligible articles were selected based on title, abstracts and full-text publication. Studies with the following characteristics were included: a standard method had to be used to detect GBS in pregnant women (specimen collection from lower vagina and rectum using the same swab or 2 different swabs) and processing for GBS identification performed according to the Centers for Disease Control and Prevention (CDC) guidelines using selective media,3 culture at 35–37 weeks’ gestation, detection of GBS-specific gene (dltS) by molecular methods (polymerase chain reaction or real-time polymerase chain reaction),21 studies that reported sample size and the number of women colonized with GBS. Studies were excluded if they had one or more of the following criteria: studies using nonstandard methods (cervical, perianal, perirectal or perineal specimens), duplicate and overlapping studies, studies published in languages other than English or Persian, studies other than maternal colonization, studies that did not report GBS prevalence, nonhuman studies, review articles, congress abstracts, meta-analyses or systematic reviews, as well as articles available only in abstract form.

Data Extraction and Definitions

The following details were extracted from each study: the first author’s name, year of publication, year of study, study setting, number of cases investigated, method of studies, isolate source, sample size and prevalence of GBS in pregnant women. Two reviewers independently extracted all data from included studies, and results were reviewed by a third reviewer. Inconsistencies between the reviewers were resolved by general consensus. Study quality was assessed independently by 2 reviewers using a checklist which was provided by the Joanna Briggs Institute.22

Statistical Analysis

Meta-analysis was performed by Comprehensive Meta-Analysis (Biostat V2.2) software. We reported the amount of residual heterogeneity by using t2 statistic and Q statistic to test the heterogeneity between the inquiries. To assess any possible publication bias, Begg rank correlation and Egger-weighted regression methods in combination with a funnel plot were used (P < 0.05 was considered indicative of statistically significant publication bias).

RESULTS

Overall, 250 studies were identified. Of these, 150 articles remained after duplicates were removed. By screening the titles and abstracts, 87 studies were excluded because they were not relevant. Of the remaining 63 articles, only 25 studies were included in this meta-analysis. The study selection process and reasons for exclusion are shown in Figure 1, and the main characteristics of the selected studies are described in Table 1. Based on the 25 selected articles, the pooled prevalence of GBS colonization was 9.8% (95% confidence interval, 7.9–12) in pregnant women. Heterogeneities between studies (I2 = 87.4; P < 0.001) were found, so the random effect model was used for meta-analysis. Details of the meta-analysis for the subgroup are summarized in Table 2. Some evidence for publication bias was observed (Fig. 2); however, as it is shown in Table 2, the results of Begg rank correlation (P = 0.1) and Egger weighted regression test (P = 0.1) did not show bias in this study (culture positive cases). Asymmetric shape of funnel plots (Fig. 3) shows some evidence of publication bias among evaluated papers.

T1
TABLE 1.:
Characteristics of Studies Included in the Meta-analysis
T2
TABLE 2.:
Meta-analysis of Prevalence of GBS Among Pregnant Women in Iran
F1
FIGURE 1.:
Summary of the literature search and study selection.
F2
FIGURE 2.:
Forest plot of prevalence of GBS among pregnant women in culture positive cases. (The squares represent the point estimates of individual studies with their 95% confidence intervals, and the size of the square represents the weight given to each study in the meta-analysis. The diamond represents the overall result and 95% confidence interval of the random effect meta-analysis. Vertical line indicates null value. CI, confidence interval.
F3
FIGURE 3.:
Funnel plot of prevalence of GBS among pregnant women in culture-positive cases (funnel asymmetry suggest bias in meta-analysis).

DISCUSSION

To our knowledge, this is the first comprehensive systematic review and meta-analysis to assess the prevalence of GBS colonization among Iranian pregnant women. Based on the meta-analysis results, the pooled prevalence of GBS in pregnant women was 9.8% (95% confidence interval, 7.9–12). In United Arab Emirates (UAE), Amin et al43 showed that the prevalence of GBS in pregnant UAE women was 10.1%. In Turkey, Alp et al44 reported that the prevalence of GBS among Turkish pregnant women was 9.8%. In Italy, Savoia et al45 reported that the prevalence of GBS among Italian pregnant women was 18%. In Lebanon, Seoud et al46 showed that prevalence of GBS colonization rate among Lebanese pregnant women was 17.7%. In Zimbabwe, 60.3% of pregnant women were colonized with GBS.47 Kwatra et al6 reported that the estimated mean prevalence of GBS colonization among pregnant women was 6.8–26.7% in different countries. The prevalence of GBS in the current study is similar to that identified in Taiwan (11.2%), India and Pakistan (12%), but it is lower than that reported in the United States (26%).48 Differences in colonization rates might be related to the race, age, parity, sexual activity, geographic region, pregnancy week, culture sites, laboratory techniques, smoking and education.44,46,49 Furthermore, body mass index and occupation have been associated with GBS colonization in pregnancy.49 Obesity (body mass index ≥30) and access to prenatal care are the risk factors related to GBS colonization in pregnancy.49,50 According to the Centers for Disease Control and Prevention guidelines (2010), all pregnant women should be screened for GBS with vaginal and rectal cultures between 35 and 37 weeks’ gestation and should receive intrapartum antibiotic prophylaxis with penicillin or ampicillin for culture-positive women.3 If GBS colonization status is unknown, antibiotic prophylaxis is recommended for pregnant women with one or more risk factors, including prolonged membrane rupture, intrapartum temperature 38°C and preterm labor.3 Many developed countries have published various guidelines for GBS in pregnancy,51 while in developing countries such as Iran, there is no guidelines for GBS prevention. There are limited data available on the serotypes associated with maternal colonization in Iran. Mansouri16 reported that serotypes III (41.8%), Ib (25.45%) and II (14.5%) were the predominant types among pregnant women in southeast of Iran (Kerman). In northwest of Iran (Tabriz), serotypes V (19.5%) and Ia (17.6%) were the most common type in the pregnant women.39 In the other region of Iran (Kashan), serotypes III (32.1%) and V (24.1%) were the most common type in the pregnant women.42 In another study from Iran (Tehran), serotype III was predominant (65.8%) in the pregnant women.11 Unfortunately, there are no data about which serotypes and clone (clonal complexes) are responsible for invasive diseases in neonates in Iran. One study showed that the clonal complex 19 was the common colonizing clone in neonates in the neonatal intensive care unit of Imam Khomeini hospital.8 Overall, the rate of invasive GBS disease is low (0.02 per 1000 live births) among neonates in Asia.52 Maternal antibodies have an important role in protection of neonates against GBS disease.53 If a licensed vaccine was available, immunity to neonatal GBS disease could be achieved through maternal vaccination.3,53 The present review had several limitations. First, the studies could not fully indicate the prevalence of GBS among pregnant women in Iran because the magnitude of GBS colonization were not yet determined in different areas of the country. Second, only published articles were considered in the present meta-analysis; hence, as in any other meta-analysis, the potential for publication bias should be considered. Third, heterogeneity due to variation between effect sizes of each study was observed among the included studies. In conclusion, there are no preventive strategies for GBS disease in Iran, and it is time that national guidelines for prevention of neonatal GBS has been established in Iran, and these guidelines must be provided guidance for obstetricians, midwives and neonatologists on the prevention of GBS infections.

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                                    Keywords:

                                    group B Streptococcus; pregnant women; recto-vaginal colonization; Iran; systematic review

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