Environmental Acidification Drives S. pyogenes Pilus Expression and Microcolony Formation on Epithelial Cells in a FCT-Dependent Manner

Group A Streptococcus (GAS, Streptococcus pyogenes) is a Gram-positive human pathogen responsible for a diverse variety of diseases, including pharyngitis, skin infections, invasive necrotizing fasciitis and autoimmune sequelae. We have recently shown that GAS cell adhesion and biofilm formation is associated with the presence of pili on the surface of these bacteria. GAS pilus proteins are encoded in the FCT (Fibronectin- Collagen-T antigen) genomic region, of which nine different variants have been identified so far. In the present study we undertook a global analysis of GAS isolates representing the majority of FCT-variants to investigate the effect of environmental growth conditions on their capacity to form multicellular communities. For FCT-types 2, 3, 5 and 6 and a subset of FCT-4 strains, we observed that acidification resulting from fermentative sugar metabolism leads to an increased ability of the bacteria to form biofilm on abiotic surfaces and microcolonies on epithelial cells. The higher biofilm forming capacity at low environmental pH was directly associated with an enhanced expression of the genes encoding the pilus components and of their transcription regulators. The data indicate that environmental pH affects the expression of most pilus types and thereby the formation of multicellular cell-adhering communities that assist the initial steps of GAS infection

The Group B Streptococcus-Secreted Protein CIP Interacts with C4, Preventing C3b Deposition via the Lectin and Classical Complement Pathways.

The group B Streptococcus (GBS) is a leading cause of neonatal invasive disease. GBS bacteria are surrounded by a thick capsular polysaccharide that is a potent inhibitor of complement deposition via the alternative pathway. Several of its surface molecules can however activate the classical and lectin complement pathways, rendering this species still vulnerable to phagocytic killing. In this study we have identified a novel secreted protein named complement interfering protein (CIP) that downregulates complement activation via the classical and lectin pathways, but not the alternative pathway. The CIP protein showed high affinity toward C4b and inhibited its interaction with C2, presumably preventing the formation of the C4bC2a convertase. Addition of recombinant CIP to GBS cip-negative bacteria resulted in decreased deposition of C3b on their surface and in diminished phagocytic killing in a whole-blood assay. Our data reveal a novel strategy exploited by GBS to counteract innate immunity and could be valuable for the development of anti-infective agents against this important pathogen

Hypoglycaemic effect of total alkaloids extracted from Sambucus wightiana Wall. ex Wight & Arn. in streptozotocin-nicotinamide induced diabetic rats

Diabetes mellitus is the most prevalent metabolic disease, and almost 1200 plants are reported with hypoglycaemic potential. Some of these plants are scientifically proven for the hypoglycaemic and antidiabetic effects. This study was designed to assess the hypoglycaemic effect of Sambucus wightiana Wall. ex Wight & Arn. extract in streptozotocin-nicotinamide induced diabetic Wistar Albino rats. An acute toxicity study was performed to establish the safe dose of total alkaloids extracted from S. wightiana (TASW). TASW was administered orally (50 mg, 100 mg, and 200 mg/kg body weight per day) to diabetic rats for 21 days. Fasting blood glucose level was determined, along with other associated parameters that may fluctuate in diabetes, consisting of the lipid profile, body weight, serum liver marker enzymes and Hb level. The test groups that were administered TASW at three different doses showed a marked reduction in hyperglycaemia when compared to the control group. Moreover, body weight and food intake improved among test group animals. Administration of TASW also reduced the levels of triglycerides, cholesterol and LDL while increasing HDL and Hb levels. Serum liver enzyme activity is generally increased in diabetes, and this was reduced after dosing with TASW. The findings of this study elucidate that the total alkaloids extracted from S. wightiana are not toxic at the tested doses, and present potential hypoglycaemic activity

The ancillary protein 1 of Streptococcus pyogenes FCT-1 pili mediates cell adhesion and biofilm formation through heterophilic as well as homophilic interactions

Summary: Gram-positive pili are known to play a role in bacterial adhesion to epithelial cells and in the formation of biofilm microbial communities. In the present study we undertook the functional characterization of the pilus ancillary protein 1 (AP1_M6) from Streptococcus pyogenes isolates expressing the FCT-1 pilus variant, known to be strong biofilm formers. Cell binding and biofilm formation assays using S. pyogenes in-frame deletion mutants, Lactococcus expressing heterologous FCT-1 pili and purified recombinant AP1_M6, indicated that this pilin is a strong cell adhesin that is also involved in bacterial biofilm formation. Moreover, we show that AP1_M6 establishes homophilic interactions that mediate inter-bacterial contact, possibly promoting bacterial colonization of target epithelial cells in the form of three-dimensional microcolonies. Finally, AP1_M6 knockout mutants were less virulent in mice, indicating that this protein is also implicated in GAS systemic infection