Rectal colonization by group B Streptococcus as a predictor of vaginal colonization

doi:10.1016/j.ajog.2009.02.011

American Journal of Obstetrics and Gynecology

Volume 201, Issue 1, July 2009, Pages 76.e1-76.e7

https://doi.org/10.1016/j.ajog.2009.02.011 Get rights and content

Objective

The purpose of this article was to describe rectal colonization by group B Streptococcus (GBS) and its role in the prediction of vaginal colonization.

Study Design

In this prospective cohort of 1248 nonpregnant women, vaginal and rectal swabs for GBS culture were obtained at enrollment and at three 4-month intervals. Generalized estimating equations were used to identify factors that are associated with colonization.

Results

Eight hundred fourteen (65%) women had GBS colonization sometime during the observation period. Rectal GBS colonization was the strongest predictor of vaginal colonization (adjusted odds ratio, 14.3; 95% CI, 11.9-17.1). Recent sexual intercourse, vaginal colonization with yeast, and a vaginal Nugent score ≥ 4 were also independent determinants of vaginal GBS colonization. Antimicrobial use decreased vaginal GBS colonization only among women who had no rectal colonization.

Conclusion

GBS in the gastrointestinal tract is a risk factor for vaginal GBS. Sexual activity and abnormal vaginal microflora are independent determinants of vaginal GBS colonization.

Section snippets

Materials and Methods

Nonpregnant women between the ages of 18 and 30 years, who were able to provide written informed consent and were willing to return for scheduled follow-up visits, were recruited from 3 clinics in Pittsburgh, PA: University of Pittsburgh Student Health Clinic, Allegheny County Health Department Clinic, and Family Health Council Clinic of Aliquippa. Exclusion criteria included current vaginal bleeding, current use of systemic antimicrobials active against GBS (penicillins, cephalosporins, or

Results

Of the 1248 women who were enrolled, 764 women (61%) were white; 434 women (35%) were black, and 50 women (4%) were Hispanic, Asian, American Indian/Alaskan Native, or multiethnic, based on self-report. The median age was 21 years; 878 women (70%) had > 12 years of education, and 1157 women (93%) were sexually active. From 4010 completed visits, 1333 rectal samples (33%) were positive for GBS. The unadjusted and adjusted associations of demographic and behavioral characteristics with rectal GBS

Comment

The present study that included > 4000 visits for 1248 women confirms previous studies that have documented an increased prevalence of colonization by GBS among black women10, 14, 15, 16, 17 and has documented that the increased rate of GBS in black women is attributable to an enhanced rate of rectal, rather than vaginal, colonization. Black women are more likely to harbor GBS in their gastrointestinal tract, which, in turn increases their likelihood of becoming vaginally colonized and

Acknowledgments

We acknowledge the support and cooperation of the staffs of the Family Health Council Clinic of Aliquippa, the Allegheny Health Department Clinic, and the University of Pittsburgh Student Health Clinic during this study.

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Colonization of Streptococcus agalactiae among pregnant patients in Trinidad and Tobago
2022, IJID Regions
To assess colonization of Streptococcus agalactiae [group B streptococcus (GBS)], and delineate capsular serotype distribution and antibiotic susceptibility profiles among pregnant women in Trinidad and Tobago.
Vaginal swabs were collected from 248 pregnant women attending antenatal clinics in northern Trinidad, and processed using standard microbiological laboratory tests to confirm GBS. Polymerase chain reaction detected atr and cps serotype genes. Antimicrobial susceptibility tests were performed using the Kirby–Bauer method, and SPSS Version 25 was used for statistical analysis. Prevalence ratio measured the risk, and P≤0.05 was considered to indicate significance.
The GBS carriage rate was 29% (72/248, 95% confidence interval 23.3–34.8), and carriage was significantly associated with variables including gestational diabetes (P=0.042), age 25–35 years (P=0.006), multiparity (P=0.035) and marital status (P=0.006). The most common serotype was type II [47.2% (34/72)], and serotypes V, VI, VII and VIII were not encountered. GBS showed high resistance to amoxicillin-clavulanic acid (37.5%), erythromycin (30.6%), trimethoprim-sulphamethoxazole (58.3%) and tetracycline (97.2%).
GBS colonization among pregnant women and resistance to commonly used antibiotics are high in Trinidad and Tobago. A population-based study is required to obtain accurate figures in order to improve maternal healthcare services.
Probiotic interventions to reduce antepartum Group B streptococcus colonization: A systematic review and meta-analysis
2022, Midwifery
Citation Excerpt :
The gastrointestinal (GI) tract is the source for vaginal GBS colonisation in women (American College of Obstetrics and Gynaecology, ACOG, 2019; Picard and Bergeron, 2004). Prenatal GBS colonisation is generally asymptomatic (Armistead et al., 2019; Marziali et al., 2019), and may be transient or persistent (ACOG, 2019; Armistead et al., 2019; Marziali et al., 2019; Meyn et al., 2009; Picard and Bergeron, 2004). ( Brzychczy-Włoch et al., 2014) conducted a descriptive study with a sample of 42 healthy adult pregnant women without signs of clinical genitourinary infection.
To systematically review and meta-analyse studies of the efficacy of probiotics to reduce antenatal Group B Streptococcus (GBS) colonisation.
Antenatal participants with known positive GBS colonisation or unknown GBS status.
Probiotic interventions containing species of Lactobacillus or Streptococcus.
Systematic review and meta-analysis.
The systematic review included 10 studies. Five articles contained in vitro studies of probiotic interventions to determine antagonistic activity against GBS. Six clinical trials of probiotics to reduce antenatal GBS were systematically reviewed and meta-analysed. The meta-analysis revealed that the use of an antenatal probiotic decreased the probability of a positive GBS result by 44% (OR = 0.56, 95% CI = 8.7%, 194.1%, p = 0.02) (n = 709). However, only one clinical trial of 10 had a low risk of bias.
The probiotic interventions subjected to in vitro testing showed antagonistic activity against GBS through the mechanisms of acidification, immune modulation, and adhesion. The findings of the meta-analysis of the clinical trials revealed that probiotics are a moderately effective intervention to reduce antenatal GBS colonisation. More well-controlled trials with diverse participants and with better elucidation of variables influencing GBS colonisation rates are needed.
Probiotic interventions appear to be a safe and effective primary prevention strategy for antenatal GBS colonisation. Application of this low-risk intervention needs more study but may reduce the need for intrapartum antibiotic prophylaxis in countries or regions where antenatal GBS screening is used. Midwives can be instrumental in conducting and supporting larger well-controlled clinical trials.
Lactobacillus rhamnosus reduces the cytotoxic effects of group B streptococcus on HeLa cells
2021, Microbial Pathogenesis
Group B Streptococcus (GBS) is an opportunistic pathogen found in the vaginal tract and is a leading cause of preterm birth and neonatal illness. Aside from GBS, the vaginal tract is predominantly colonized by commensal Lactobacillus species that are thought to protect the vaginal tract from pathogens, including GBS. Studies that examined if, and how Lactobacilli modulate GBS pathogenicity remain limited. This study sought to investigate the potential protective role of Lactobacillus rhamnosus against GBS, using an in vitro model system. Immunofluorescence microscopy and Scanning Electron Microscopy (SEM) captured images of infected HeLa cells and were analyzed using the image analysis program ImageJ. Results indicate that GBS causes HeLa cell detachment unless L. rhamnosus is present. SEM images show that GBS reduces length and number of microvilli on HeLa cell surface, as well as size of secreted vesicles. L. rhamnosus partially inhibits GBS-dependent microvilli and vesicle disruption. GBS also disrupts HeLa cell F-actin fibers unless L. rhamnosus is present. These results reveal effects of GBS infection on the host cell cytoskeleton and implies a protective role of L. rhamnosus against GBS colonization.
Gardnerella vaginalis promotes group B Streptococcus vaginal colonization, enabling ascending uteroplacental infection in pregnant mice
2021, American Journal of Obstetrics and Gynecology
Citation Excerpt :
A Lactobacillus-dominated vaginal microbiome is regarded as beneficial and is believed to ward off colonization by potential pathogens such as GBS. Although results vary, some clinical findings have suggested that GBS colonization is more likely in women with a polymicrobial, “dysbiotic” vaginal microbiota or those with decreased Lactobacillus (Supplemental Table 1).3,21–24 In addition, there is a notable parallel in the epidemiology of GBS colonization and the composition of the vaginal microbiota.
Group B Streptococcus is a common vaginal bacterium and the leading cause of invasive fetoplacental infections. Group B Streptococcus in the vagina can invade through the cervix to cause ascending uteroplacental infections or can be transmitted to the neonate during vaginal delivery. Some studies have found that women with a “dysbiotic” polymicrobial or Lactobacillus-depleted vaginal microbiota are more likely to harbor group B Streptococcus. Gardnerella vaginalis is often the most abundant bacteria in the vaginas of women with dysbiosis, while being detected at lower levels in most other women, and has been linked with several adverse pregnancy outcomes. Mouse models of group B Streptococcus and Gardnerella vaginalis colonization have been reported but, to the best of our knowledge, the two have not been studied together. The overarching idea driving this study is that certain members of the dysbiotic vaginal microbiota, such as Gardnerella vaginalis, may directly contribute to the increased rate of group B Streptococcus vaginal colonization observed in women with vaginal dysbiosis.
We used a mouse model to test the hypothesis that vaginal exposure to Gardnerella vaginalis may facilitate colonization and/or invasive infection of the upper reproductive tract by group B Streptococcus during pregnancy.
Timed-pregnant mice were generated using an allogeneic mating strategy with BALB/c males and C57Bl/6 females. Dams were vaginally inoculated at gestational day 14 with group B Streptococcus alone (using a 10-fold lower dose than previously reported models) or coinoculated with group B Streptococcus and Gardnerella vaginalis. Bacterial titers were enumerated in vaginal, uterine horn, and placental tissues at gestational day 17. The presence (Fisher exact tests) and levels (Mann-Whitney U tests) of bacterial titers were compared between mono- and coinoculated dams in each compartment. Relative risks were calculated for outcomes that occurred in both groups. Tissue samples were also examined for evidence of pathophysiology.
Inoculation of pregnant mice with 10⁷ group B Streptococcus alone did not result in vaginal colonization or ascending infection. In contrast, coinoculation of group B Streptococcus with Gardnerella vaginalis in pregnant mice resulted in a 10-fold higher risk of group B Streptococcus vaginal colonization (relative risk, 10.31; 95% confidence interval, 2.710–59.04; P=.0006 [Fisher exact test]). Ascending group B Streptococcus infection of the uterus and placenta occurred in approximately 40% of coinoculated animals, whereas none of those receiving group B Streptococcus alone developed uterine or placental infections. Immunofluorescence microscopy revealed group B Streptococcus in both the maternal and fetal sides of the placenta. Histologic inflammation and increased proinflammatory cytokines were evident in the setting of group B Streptococcus placental infection. Interestingly, placentas from dams exposed to group B Streptococcus and Gardnerella vaginalis, but without recoverable vaginal or placental bacteria, displayed distinct histopathologic features and cytokine signatures.
These data suggest that Gardnerella vaginalis vaginal exposure can promote group B Streptococcus vaginal colonization, resulting in a greater likelihood of invasive perinatal group B Streptococcus infections. These findings suggest that future clinical studies should examine whether the presence of Gardnerella vaginalis is a risk factor for group B Streptococcus vaginal colonization in women. Because Gardnerella vaginalis can also be present in women without bacterial vaginosis, these findings may be relevant both inside and outside of the context of vaginal dysbiosis.
Association between obesity and bacterial vaginosis as assessed by Nugent score
2019, American Journal of Obstetrics and Gynecology
Bacterial vaginosis is 1 of the most common vaginal conditions in the United States. Recent studies have suggested that obese women have an abnormal microbiota reminiscent of bacterial vaginosis; however, few studies have investigated the prevalence of bacterial vaginosis in overweight and obese populations. Moreover, despite the increased prevalence of obesity and bacterial vaginosis in black women, it is not known whether racial disparities exist in the relationship between obesity and bacterial vaginosis.
The objective of this study was to examine the relationship between body mass index and bacterial vaginosis as determined by Nugent score and to determine the influence of race in this context.
We performed a cross-sectional study using patient data and vaginal smears from 5918 participants of the Contraceptive CHOICE Project. Gram-stained vaginal smears were scored with the Nugent method and categorized as bacterial vaginosis–negative (Nugent score, 0–3), bacterial vaginosis–intermediate (Nugent score, 4–6), or bacterial vaginosis–positive (Nugent score, 7–10). Body mass index was determined with Centers for Disease Control and Prevention guidelines, and obese individuals were categorized as class I, II, or III obese based on National Institutes of Health and World Health Organization body mass index parameters. Linear regression was used to model mean differences in Nugent scores; Poisson regression with robust error variance was used to model prevalence of bacterial vaginosis.
In our cohort, 50.7% of participants were black; 41.5% were white, and 5.1% were of Hispanic ethnicity; the average age of 25.3 years old. Overall, 28.1% of participants were bacterial vaginosis–positive. Bacterial vaginosis was prevalent in 21.3% of lean, 30.4% of overweight, and 34.5% of obese women (P<.001). The distribution of bacterial vaginosis–intermediate individuals was similar across all body mass index categories. Compared with the scores of lean women, Nugent scores were highest among overweight and obese class I women (adjusted mean difference: overweight women, 0.33 [95% confidence interval, 0.14–0.51] and obese women, 0.51 [95% confidence interval, 0.29–0.72]). Consistent with this, overweight and obese women had a higher frequency of bacterial vaginosis compared with lean women, even after adjustment for variables that included race. Among white women, the prevalence of bacterial vaginosis was higher for overweight and class I and class II/III obese white women compared with lean white women, which is a phenomenon not observed among black women and suggests an effect modification.
Overweight and obese women have higher Nugent scores and a greater occurrence of bacterial vaginosis compared with lean women. Black women have a greater prevalence of bacterial vaginosis independent of their body mass index compared with white women.
Identification and characterization of NanH2 and NanH3, enzymes responsible for sialidase activity in the vaginal bacterium Gardnerella vaginalis
2019, Journal of Biological Chemistry
Gardnerella vaginalis is abundant in bacterial vaginosis (BV), a condition associated with adverse reproductive health. Sialidase activity is a diagnostic feature of BV and is produced by a subset of G. vaginalis strains. Although its genetic basis has not been formally identified, sialidase activity is presumed to derive from the sialidase A gene, named here nanH1. In this study, BLAST searches predicted two additional G. vaginalis sialidases, NanH2 and NanH3. When expressed in Escherichia coli, NanH2 and NanH3 both displayed broad abilities to cleave sialic acids from α2-3- and α2-6-linked N- and O-linked sialoglycans, including relevant mucosal substrates. In contrast, recombinant NanH1 had limited activity against synthetic and mucosal substrates under the conditions tested. Recombinant NanH2 was much more effective than NanH3 in cleaving sialic acids bearing a 9-O-acetyl ester. Similarly, G. vaginalis strains encoding NanH2 cleaved and foraged significantly more Neu5,9Ac₂ than strains encoding only NanH3. Among a collection of 34 G. vaginalis isolates, nanH2, nanH3, or both were present in all 15 sialidase-positive strains but absent from all 19 sialidase-negative isolates, including 16 strains that were nanH1-positive. We conclude that NanH2 and NanH3 are the primary sources of sialidase activity in G. vaginalis and that these two enzymes can account for the previously described substrate breadth cleaved by sialidases in human vaginal specimens of women with BV. Finally, PCRs of nanH2 or nanH3 from human vaginal specimens had 81% sensitivity and 78% specificity in distinguishing between Lactobacillus dominance and BV, as determined by Nugent scoring.

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: This research was supported by contract N01-AI-75326 from the National Institute of Allergy and Infectious Diseases of the National Institutes of Health and by Grant M01-RR000056 from the National Center for Research Resources of the National Institutes of Health and the General Clinical Research Centers.

: Reprints not available from the authors.

: Cite this article as: Meyn LA, Krohn MA, Hillier SL. Rectal colonization by group B Streptococcus as a predictor of vaginal colonization. Am J Obstet Gynecol 2009;201:76.e1-7.

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ResearchBasic science: GynecologyRectal colonization by group B Streptococcus as a predictor of vaginal colonization

Objective

Study Design

Results

Conclusion

Section snippets

Materials and Methods

Results

Comment

Acknowledgments

J Pediatr

Obstet Gynecol

Am J Obstet Gynecol

Ann Epidemiol

Obstet Gynecol

J Pediatr

Am J Obstet Gynecol

Streptococcus agalactiae (group B Streptococcus)

Rectal colonization with group B Streptococcus: relation to vaginal colonization of pregnant women

J Infect Dis

Selective intrapartum chemoprophylaxis of neonatal group B streptococcal early-onset disease: II, predictive value of prenatal cultures

J Infect Dis

Anorectal and vaginal carriage of group B streptococci during pregnancy

J Infect Dis

Group B streptococcal colonization in prepubertal children

Pediatrics

Determinants of co-colonization with group B Streptococcus among heterosexual college couples

Epidemiology

Sexual transmission and reinfection of group B streptococci between spouses

J Obstet Gynaecol Res

Prevalence of group B Streptococcus colonization and potential for transmission by casual contact in healthy young men and women

Clin Infect Dis

Association of sexual activity with colonization and vaginal acquisition of group B Streptococcus in nonpregnant women

Am J Epidemiol

Research
Basic science: Gynecology
Rectal colonization by group B Streptococcus as a predictor of vaginal colonization