Interference with lipoprotein maturation sensitizes methicillin-resistantStaphylococcus aureusto human group IIA secreted phospholipase A₂and daptomycin

AbstractMethicillin-resistantStaphylococcus aureus(MRSA) has been classified as a high priority pathogen by the World Health Organization underlining the high demand for new therapeutics to treat infections. Human group IIA secreted phospholipase A2(hGIIA) is among the most potent bactericidal proteins against Gram-positive bacteria, includingS. aureus. To determine hGIIA-resistance mechanisms of MRSA we screened the Nebraska Transposon Mutant Library using a sublethal concentration of recombinant hGIIA. We identified and confirmed the role oflspA, encoding the lipoprotein signal peptidase LspA, as a new hGIIA resistance gene in bothin vitroassays and an infection model in hGIIA-transgenic mice. Increased susceptibility of thelspAmutant was associated with faster and increased cell wall penetration of hGIIA. Moreover,lspAdeletion also increased susceptibility to daptomycin, a last-resort antibiotic to treat MRSA infections. Exposure of MRSA wild-type to the LspA-specific inhibitors globomycin and myxovirescin A1 induced alspAmutant phenotype with regard to hGIIA and daptomycin killing. Analysis of >26,000S. aureusgenomes showed that LspA is highly sequence-conserved, suggesting that LspA inhibition could be applied universally. The role of LspA in hGIIA resistance was not restricted to MRSA sinceStreptococcus mutansandEnterococcus faecaliswere also more hGIIA-susceptible afterlspAdeletion or LspA inhibition, respectively. Overall, our data suggest that pharmacological blocking of LspA may disarm Gram-positive pathogens, including MRSA, to enhance clearance by innate host defense molecules and clinically-applied antibiotics.