Perturbations of Phosphatidate Cytidylyltransferase (CdsA) Mediate Daptomycin Resistance in Streptococcus mitis/oralis by a Novel Mechanism.

is an important pathogen, causing life-threatening infections such as endocarditis and severe sepsis in immunocompromised patients. The β-lactam antibiotics are the usual therapy of choice for this organism, but their effectiveness is threatened by the frequent emergence of resistance. The lipopeptide daptomycin (DAP) has been suggested for therapy against such resistant strains due to its bactericidal activity and demonstrated efficacy against other Gram-positive pathogens. Unlike other bacteria, however, has the unique ability to rapidly develop stable, high-level resistance to DAP upon exposure to the drug both and Using isogenic DAP-susceptible and DAP-resistant strain pairs, we describe a mechanism of resistance to both DAP and cationic antimicrobial peptides that involves loss-of-function mutations in (encoding a phosphatidate cytidylyltransferase). CdsA catalyzes the synthesis of cytidine diphosphate-diacylglycerol, an essential phospholipid intermediate for the production of membrane phosphatidylglycerol and cardiolipin. DAP-resistant strains demonstrated a total disappearance of phosphatidylglycerol, cardiolipin, and anionic phospholipid microdomains from membranes. In addition, these strains exhibited cross-resistance to cationic antimicrobial peptides from human neutrophils (i.e., hNP-1). Interestingly, CdsA-mediated changes in phospholipid metabolism were associated with DAP hyperaccumulation in a small subset of the bacterial population, without any binding by the remaining larger population. Our results indicate that CdsA is the major mediator of high-level DAP resistance in and suggest a novel mechanism of bacterial survival against attack by antimicrobial peptides of both innate and exogenous origins.