bioRxiv2021
SynopsisO_ST_ABSBackgroundC_ST_ABSWe previously reported the presence of mutations in gdpP among Staphylococcus aureus strains that were obtained by serial passaging in {beta}-lactam drugs. gdpP codes for a phosphodiesterase that cleaves cyclic-di-AMP (CDA), a newly discovered second messenger. ObjectivesWe sought to identify the role of gdpP in {beta}-lactam resistance of S. aureus. MethodsCDA concentrations in bacterial cytosol were measured through mass-spectrometric analysis. gdpP deletion mutagenesis and their complemented strains were created in clinically relevant S. aureus strains to characterize its function. ResultsgdpP associated mutations among passaged strains were identified to cause loss of phosphodiesterase function, leading to increased CDA accumulation in the bacterial cytosol. Deletion of gdpP led to an enhanced ability of the bacteria to withstand a {beta}-lactam challenge (two to three log increase in bacterial colony forming units) by promoting tolerance without enhancing MICs of {beta}-lactam antibiotics. Our results demonstrate that increased drug tolerance due to loss of GdpP function can provide a selective advantage in acquisition of high-level {beta}-lactam resistance and could lead to {beta}-lactam treatment failure of S. aureus infections. ConclusionsLoss of GdpP function increases tolerance to {beta}-lactams that can lead to its therapy failure and can permit {beta}-lactam resistance to occur more readily.