Supplementary Material for: agr-Dependent Interactions of Staphylococcus aureus USA300 with Human Polymorphonuclear Neutrophils

The emergence of serious infections due to community-associated methicillin-resistant <i>Staphylococcus aureus </i>(CA-MRSA) has fueled interest in the contributions of specific staphylococcal virulence factors to clinical disease. To assess the contributions of <i>agr</i>-dependent factors to the fate of organisms in polymorphonuclear neutrophils (PMN), we examined the consequences for organism and host cells of feeding PMN with wild-type CA-MRSA (LAC) or CA-MRSA (LAC <i>agr </i>KO) at different multiplicities of infection (MOIs). Phagocytosed organisms rapidly increased the transcription of RNAIII in a time- and MOI-dependent fashion; extracellular USA300 (LAC) did not increase RNAIII expression despite having the capacity to respond to autoinducing peptide-enriched culture medium. HOCl-mediated damage and intracellular survival were the same in the wild-type and USA300 (LAC <i>agr </i>KO). PMN lysis by ingested USA300 (LAC) was time- and MOI-dependent and, at MOIs >1, required α-hemolysin <i>(hla)</i> as USA300 (LAC <i>agr</i> KO) and USA300 (LAC <i>hla</i> KO) promoted PMN lysis only at high MOIs. Taken together, these data demonstrate activation of the <i>agr</i> operon in human PMN with the subsequent production of α-hemolysin and PMN lysis. The extent to which these events in the phagosomes of human PMN contribute to the increased morbidity and mortality of infections with USA300 (LAC) merits further study.