Cilicia Nascimento
PhD Student in the University of São Paulo, in Brazil
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I have been working with Group B Streptococcus for four years. I majored in Biomedical Sciences and I have a master's degree in sciences, obtained in 2019. In the same year I started my PhD. I truly believe in the power of spreading science.
Group B Strep and Lactobacillus: another chapter develops.
The vaginal microbiome is a complex environment that consists of many microorganisms, some commensal, others symbiotic and some pathogens. The main genus that constitutes the vaginal microbiota is Lactobacillus sp, which contribute to vaginal health in several ways, including maintaining a low pH (3.5-4.5) through the production of lactic, producing bacteriocins, biosurfactants and H2O2, inhibiting the growth of pathogenic bacteria and competing for adhesion to the vaginal epithelia. The most common species is Lactobacillus crispatus. One of the most important pathogens that can commensally inhabit the vaginal microbiome is Group B Streptococcus (GBS). Streptococcus agalactiae, or GBS, is the major cause of newborn sepsis worldwide. In this project we explore the ability of L. crispatus (LC), one of the most abundant Lactobacilli of the vaginal microbiota, to inhibit GBS growth or stunt its capacity to colonize the vaginal epithelia. We obtained six GBS strains from vaginal swabs of pregnant women, LC strains were acquired commercially. GBS strains were characterized according to capsular serotype, virulence factors, resistance to antibiotics, Restriction Fragment Length Polymorphism (RFLP) and Multi-Locus Sequence Types (MLST). We also built an 8h-growth-curve for each GBS strain. The interaction between GBS and LC was evaluated with co-culture assays, where both growth and biofilm formation were measured. GBS and LC interactions when in human cell culture (HeLa) was also observed. Our results showed that LC can interfere with GBS growth, biofilm formation and other mechanisms. However, that effect depends on GBS strain, regardless of capsular serotypes.
Can garlic be used to treat Group B Strep infection? And what happens to Lactobacilli?
Garlic is a common ingredient in most countries’ cuisines, it also has health properties that encourage its consumption. However, many women in Brazil use garlic as an antimicrobial agent, inserting cloves into the vaginal canal and leaving it overnight. This practice is common among women who want to have their labor outside a hospital, which is impossible with a positive GBS test. A great number of women report that the garlic technique is effective, and the GBS tests turn negative. In Brazil, this method is increasing in popularity, even being recommended by doctors and other health professionals. So, the goal of this study is to verify the true effect of garlic on GBS growth and adhesion to vaginal cells, in addition we want to determine the effect of garlic on Lactobacilli commonly found in the vaginal microbiota, Lactobacillus crispatus and Lactobacillus gasseri. Thus, inferring what is the influence of garlic in the vaginal environment. GBS was obtained from healthy women and the strain used was previously characterized and belongs to the serotype Ia; we obtained commercially available Lactobacilli. GBS and Lactobacilli were incubated together and separately, in the presence or absence of garlic, for 4 hours, in liquid media. After that, a fraction of the content was spread across specific GBS and lactobacilli media, then colonies were counted. Results showed that garlic inhibits GBS growth significantly, while lactobacilli growth remained unaffected. When cultured together, garlic inhibited GBS growth, and did not interfere with L. crispatus or L. gasseri growth. Our results show that garlic can be used to inhibit GBS growth, not affecting other microorganisms. Our future research will explore the effect of garlic on GBS and lactobacilli along with HeLa cells.
What is happening between Group B Strep and Lactobacillus?
Group B Streptococcus (GBS) is a common vaginal pathogen, but its interaction with Lactobacillus is controverse. Past studies show no correlation between a decrease of Lactobacillus in the vaginal microbiota and the prevalence of GBS infection in vivo; some in vitro studies show that Lactobacillus gasseri (LG) and Lactbacillus crispatus (LC) can inhibit GBS adhesion to vaginal epithelial cells, but not all studies find the same results. The goal of this study is to evaluate the influence of LC and LG on GBS. In our study, GBS was obtained from healthy pregnant women, we used serotypes Ia, II, III and V. LC and LG were obtained commercially. The first experiment consisted of incubating the microorganisms together in liquid media, afterwards GBS colonies were counted in specific agar. We performed two assays using hela cells: competition and exclusion. Competition assay was performed incubating GBS and LC or LG with HeLa cells in 12-well plates containing coverslips, and exclusion assay consisted in incubating LG or LG with HeLa cells overnight, then GBS was added and incubated again. Coverslips were stained, and the results were observed in the microscope. In the assays involving just the microorganisms, no significant difference was observed on GBS growth. But we found differences in growth within serotypes. In the competition assay, LG and LC increased Serotype III adherence. In the exclusion assay LC inhibited adherence of serotypes Ia, II and III, but increased serotype V; LG inhibited only serotype III and V, but not serotypes Ia and II. We saw that GBS serotypes behave differently even when submitted to the same conditions. The influence that LC and LG have on GBS is different, but results do not show if LC or LG can be used to treat or prevent GBS infection.
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Cilicia Nascimento
PhD Student in the University of São Paulo, in Brazil
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