Association of sexually-transmitted infection and African-American race with Streptococcus agalactiae colonization in pregnancy

Re-framing the importance of Group B Streptococcus as a gut-resident pathobiont

Streptococcus agalactiae (Group B Streptococcus, GBS) is a Gram-positive bacterial species that causes disease in humans across the lifespan. While antibiotics are used to mitigate GBS infections, it is evident that antibiotics disrupt human microbiomes (which can predispose people to other diseases later in life), and antibiotic resistance in GBS is on the rise. Taken together, these unintended negative impacts of antibiotics highlight the need for precision approaches for minimizing GBS disease. One possible approach involves selectively depleting GBS in its commensal niches before it can cause disease at other body sites or be transmitted to at-risk individuals. One understudied commensal niche of GBS is the adult gastrointestinal (GI) tract, which may predispose colonization at other body sites in individuals at risk for GBS disease. However, a better understanding of the host-, microbiome-, and GBS-determined variables that dictate GBS GI carriage is needed before precise GI decolonization approaches can be developed. In this review, we synthesize current knowledge of the diverse body sites occupied by GBS as a pathogen and as a commensal. We summarize key molecular factors GBS utilizes to colonize different host-associated niches to inform future efforts to study GBS in the GI tract. We also discuss other GI commensals that are pathogenic in other body sites to emphasize the broader utility of precise de-colonization approaches for mitigating infections by GBS and other bacterial pathogens. Finally, we highlight how GBS treatments could be improved with a more holistic understanding of GBS enabled by continued GI-focused study.

Prevalence of early neonatal sepsis and positive maternal culture for group B beta-hemolytic Streptococcus

OBJECTIVE

The aim of this study was to evaluate the prevalence of early neonatal sepsis in pregnant women with a positive culture for group B beta-hemolytic Streptococcus in a middle-income city in Southeastern Brazil.

METHODS

A retrospective cohort study was conducted, involving singleton low- and high-risk pregnancies in whom group B beta-hemolytic Streptococcus cultures were evaluated between 35 and 37 weeks of gestation using vaginal and anal swabs. A specific medium (Todd-Hewitt) was used for culturing. The pregnant women were divided into two groups based on positive (n==201) and negative (n==420) cultures for group B beta-hemolytic Streptococcus.

RESULTS

The maternal colonization rate by group B beta-hemolytic Streptococcus was 32.3%. The prevalence of early neonatal sepsis was 1.0% (2/201) among patients with a positive group B beta-hemolytic Streptococcus culture and 1.9% (8/420) among patients with a negative culture. Among the patients who underwent adequate prophylaxis, crystalline penicillin G was used in 51.9% (54/104), followed by cefazolin in 43.3% (45/104), ampicillin in 3.8% (4/104), and clindamycin in 1.0% (1/104). A model that included prematurity (p==0.001) proved to be an independent risk predictor of early neonatal sepsis [χ2 (1)==15.0, odds ratio: 16.9, 95% confidence interval: 4.7-61.6, p<0.001, Nagelkerke R2==0.157].

CONCLUSION

The prevalence of a positive culture for group B beta-hemolytic Streptococcus was high. However, the prevalence of early neonatal sepsis was low in pregnant women with both positive and negative group B beta-hemolytic Streptococcus cultures and in pregnant women with a positive culture who underwent both adequate and inadequate antibiotic prophylaxis. Prematurity proved to be an independent predictor of early neonatal sepsis, considering the entire study population.

Association between intracervical Foley balloon and clinical chorioamnionitis among patients with group B streptococcus colonization undergoing induction with standardized labor management

BACKGROUND

Intracervical Foley balloons are commonly used for cervical ripening, but there has been a historical concern regarding an increased risk of clinical chorioamnionitis with Foley balloon use in patients with group B streptococcus.

OBJECTIVE

This study aimed to determine whether intracervical Foley balloon use in patients with group B streptococcus is associated with an increased risk of clinical chorioamnionitis.

STUDY DESIGN

This was a secondary analysis of a randomized controlled trial Mechanical and Pharmacologic Methods of Labor Induction: A Randomized Controlled Trial that compared cervical ripening agents within a standardized labor protocol. Foley balloon (alone, with oxytocin, or with misoprostol) was compared with misoprostol only to evaluate the primary outcome of clinical chorioamnionitis, defined based on the American College of Obstetricians and Gynecologists guidelines. Patients with a term, singleton pregnancy with intact membranes and an unfavorable cervix (Bishop score of ≤6 and dilation ≤2 cm) and a known group B streptococcus status were included. The secondary outcomes included a composite postpartum maternal infectious outcome consisting of any occurrence of endometritis, wound infection, postpartum urinary tract infection, or maternal sepsis; additional secondary outcomes included neonatal outcomes. Binomial regression with robust error variance was used to evaluate whether group B streptococcus status modified the relationship between Foley balloon use and clinical chorioamnionitis and to adjust for confounders.

RESULTS

A total of 491 patients were enrolled in the original trial. Of these patients, 467 had a known group B streptococcus status and underwent cervical ripening: 182 (39.0%) had group B streptococcus, and 285 (61.0%) did not have group B streptococcus. Moreover, 73.0% of patients received a Foley balloon, and 27.0% of patients did not receive a Foley balloon. There was no difference in the demographic or clinical characteristics between groups. The overall rate of clinical chorioamnionitis was 12.2%, with no difference between those with and without a Foley balloon (12.6% vs 11.1%, respectively; P=.66). Group B streptococcus status did not modify the association between Foley balloon use and clinical chorioamnionitis (relative risk, 0.93; 95% confidence interval, 0.50-1.72). This remained unchanged after adjusting for gestational age (adjusted relative risk, 0.87; 95% confidence interval, 0.45-1.67). Furthermore, other maternal and neonatal outcomes were similar between groups.

CONCLUSION

In this secondary analysis of a large randomized trial using a standardized labor protocol, there was no increased risk of infectious morbidity with Foley balloon use in patients overall and in patients with group B streptococcus. Our findings support that a Foley balloon can be safely used for cervical ripening in patients with group B streptococcus colonization.

Polymicrobial Interactions Operative during Pathogen Transmission

Pathogen transmission is a key point not only for infection control and public health interventions but also for understanding the selective pressures in pathogen evolution. The “success” of a pathogen lies not in its ability to cause signs and symptoms of illness but in its ability to be shed from the initial hosts, survive between hosts, and then establish infection in a new host. Recent insights have shown the importance of the interaction between the pathogen and both the commensal microbiome and coinfecting pathogens on shedding, environmental survival, and acquisition of infection. Pathogens have evolved in the context of cooperation and competition with other microbes, and the roles of these cooperations and competitions in transmission can inform novel preventative and therapeutic strategies.