July is dedicated to making citizens more aware of Group B Strep (GBS) disease. And to keep up with the latest trends, GBS awareness even has its own ribbon logo – a trio of pink, white and blue ribbons.
Group A versus Group B Strep
While nearly everyone is aware of strep throat, not everyone may be aware of the various types of strep bacteria and how they are differentiated. Group A Streptococcus (Streptococcus pyogenes) infections are responsible for causing strep throat, scarlet fever, rheumatic fever, glomerulonephritis, and necrotizing fasciitis, as well as impetigo and toxic shock syndrome. Group B Streptococcus (Streptococcus agalactiae) bacteria can live harmlessly in the gastrointestinal and genital tracts; however, it can also be dangerous when it infects newborns or the bloodstream, leading to bacteremia and sepsis, bone and joint infections, meningitis, and pneumonia.
GBS Infections in Infants
In the United States, GBS is the most common cause of neonatal sepsis, meningitis, and other infections; therefore, it is often screened in pregnant women during the third trimester. Since it colonizes in the lower GI tract and vaginal canal, it can ascend toward the cervix, move into the uterus and affect gestational tissues. GBS infection can then invade the amniotic sac and cause chorioamnionitis, or inflammation of the placenta, which can induce preterm delivery and stillbirth. GBS can also invade fetal organs and cause tissue damage, inflammation, and injury.
Prophylactic antibiotic use during pregnancy is a common practice for the prevention of transferring GBS to the newborn during labor and delivery. According to randomized clinical trials, this method of prevention is effective but carries other negative health effects. For example, it is well known that antibiotic therapy disrupts the maternal microbiome and subsequently, the infant’s microbiome. In fact, perinatal antibiotic exposure not only prevents the development of a healthy microbiome and weakens the infant’s adaptive immune system, increasing susceptibility to infections, but also has been shown to make the infant’s microbiome more susceptible to colonization by various Streptococcus species. In a recent (2019) systematic review of 502 stool samples from 272 infants whose mothers used prophylactic antibiotics for GBS, infants “had a lower bacterial diversity, a lower relative abundance of Actinobacteria, especially Bifidobacteriaceae, and a larger relative abundance of Proteobacteria in their intestinal microbiota” compared to infants not exposed to antibiotic therapy. So although prophylactic antibiotic use may prevent dangerous outcomes from GBS, it also creates susceptibility to other forms of Streptococcus.
GBS infection can be prevented by various immune responses in the vaginal and intestinal epithelia and mucosa. Vigorous action by neutrophils, mast cells, macrophages, and T cells is vital for preventing GBS colonization and infection. A healthy immune response is dependent upon a robust microbiome in both the GI and genital tracts.
GBS and Probiotics
Clinical studies have found that probiotic Lactobacillus species can help prevent GBS colonization and adherence to epithelial cells. Another probiotic strain, Streptococcus salivarius, potentially possesses antimicrobial activity against GBS. In vitro studies using samples of vaginal microbiota of 30 non-pregnant and 24 pregnant women analyzed several Lactobacillus isolates and found that Lactobacillus salivarius strains effectively eradicated GBS. In fact, when 57 GBS-positive pregnant women consumed approximately 9 log10 cfu of L. salivarius between gestational week 26 and 38, 72 and 68 percent were GBS-negative in their rectal and vaginal tracts, respectively. In a randomized controlled trial of 99 pregnant women who were between 35 and 37 gestational weeks and GBS-positive, oral administration of probiotic capsules containing L. rhamnosus and L. reuteri resulted in a negative GBS culture upon delivery in 42 percent of the women receiving probiotic therapy.
GBS is not only a common, yet highly dangerous infection among pregnant women, but it can also affect immunocompromised adults. In either case, probiotic therapy is not only a strong preventative against GBS, but according to clinical studies, it may also be an effective therapy for active infections.