The diabetic wound microenvironment drives emergence and maintenance of CovRS variants in group B Streptococcus

Diabetic wounds are often infected with microbes, which perpetuate inflammation, and stall wound healing. The bacterium Group B Streptococcus (GBS) is frequently isolated from diabetic wounds; however, little is known about how GBS adapts to survive in this niche. Previously, we found that GBS acquires stable mutations in the major two-component system CovRS during murine diabetic wound infection that result in increased pigmentation. Here, we further characterize these pigmented variants and determine the consequences on GBS survival. Using a murine model of wound infection, we find that covRS mutants arise specifically in diabetic hosts and are selected for across multiple GBS backgrounds. Whole genome sequencing of pigmented isolates revealed mutations in both covR and covS, with most isolates having a single nucleotide insertion or deletion in the covR promoter region. Phenotypic analysis of murine-acquired mutants reveals enhanced traits associated with virulence, including increased hemolytic activity, host cell cytotoxicity, and elevated nuclease activity. While our previous and current study indicated that engineered covR deletion mutants do not exhibit increased survival in the diabetic wound, we observe that a pigmented isolate survived better than wild-type during co-infection with Enterococcus faecalis, another frequently isolated wound pathogen. Finally, we find that depletion of neutrophils reduces the frequency of covRS mutant variants that arise in the population. Our work highlights the emergence of covRS mutations in GBS, and the consequences of these variations are associated with enhanced virulence and competitive fitness, underscoring the importance of these regulatory changes in the context of diabetic wounds.