The Phosphoenolpyruvate Phosphotransferase System in Group A Streptococcus Acts To Reduce Streptolysin S Activity and Lesion Severity during Soft Tissue Infection

Abstract

ABSTRACTObtaining essential nutrients, such as carbohydrates, is an important process for bacterial pathogens to successfully colonize host tissues. The phosphoenolpyruvate phosphotransferase system (PTS) is the primary mechanism by which bacteria transport sugars and sense the carbon state of the cell. The group A streptococcus (GAS) is a fastidious microorganism that has adapted to a variety of niches in the human body to elicit a wide array of diseases. A ΔptsImutant (enzyme I [EI] deficient) generated in three different strains of M1T1 GAS was unable to grow on multiple carbon sources (PTS and non-PTS). Complementation withptsIexpressed under its native promoter in single copy was able to rescue the growth defect of the mutant. In a mouse model of GAS soft tissue infection, all ΔptsImutants exhibited a significantly larger and more severe ulcerative lesion than mice infected with the wild type. Increased transcript levels ofsagAand streptolysin S (SLS) activity during exponential-phase growth was observed. We hypothesized that early onset of SLS activity would correlate with the severity of the lesions induced by the ΔptsImutant. In fact, infection of mice with a ΔptsI sagBdouble mutant resulted in a lesion comparable to that of either the wild type or asagBmutant alone. Therefore, a functional PTS is not required for subcutaneous skin infection in mice; however, it does play a role in coordinating virulence factor expression and disease progression.