2022 Annual Meeting and Alumni Reunion
Category : Basic and Translational Research Candidate : Suelen Scarpa de Mello Poster #: B19
Blocking the Emergence of Resistance to Last Line Antibiotic , Daptomycin
Suelen Scarpa de Mello , Michael S . Gilmore
Purpose : Multidrug resistant Enterococcus faecium is a leading cause of postsurgical infections of the eye and other anatomical sites . Daptomycin ( DAP ) is a last-line drug for treating vancomycin-resistant E . faecium infections but is compromised by the emergence of resistant mutants during protracted therapy . We discovered that defects in the gene encoding a glycosyltransferase involved in biosynthesis of the cell wall component , lipoteichoic acid , render E . faecium hypersusceptible to DAP . Our work has focused on determining the role of this gene in cell wall biosynthesis and determining whether it is dominant to mutations that otherwise are capable of conferring DAP resistance to the organism .
Methods : We first generated a deletion of the glycosyltransferase lafB gene , to generate a lafB-defective E . faecium strain incapable of reversion by back mutation . Minimum Inhibitory Concentration ( MIC ) assays were determined for daptomycin and other antibiotics . We next introduced mutated genes known to confer increased daptomycin resistance , specifically mutant forms of liaR and cls synthetase . Finally , we attempted to evolve daptomycin resistant derivatives of the lafB-deleted strain ( along with wild type controls ).
Results : The deletion was successfully constructed and as predicted was found to be hypersusceptible to daptomycin and select other antibiotics . Although mutations in liaR and cls synthetase genes led to an increase daptomycin resistance in a wild type E . faecium cell , they did not confer resistance to the lafB deleted mutant , supporting the prospect that lafB mutation is dominant to known daptomycin resistance mechanisms . Whereas from the evolved strains – as expected – strains exhibiting over 100-fold resistance to daptomycin were readily obtained when beginning with wild type E . faecium controls , little change in resistance was observed for the otherwise identical lafB-deleted strain .
Conclusions : These results support the notion that daptomycin resistant mutations will not emerge in an E . faecium strain in which the LafB glycosyltransferase is inhibited . We are now launching a small molecule screen for LafB inhibitors to identify compounds that sensitize E . faecium to daptomycin and prevent emergence of resistance .