Discerning strain-specific β-lactam drug resistance by clonal isolates of multi-drug resistant Pseudomonas aeruginosa using selected reaction monitoring

Abstract

The escalation of antimicrobial resistance poses a serious threat to global healthcare, and efficient assays for identifying precise antibiotic regimens are needed to increase antibiotic stewardship and fight multi-drug resistant infections. Numerous culture- and genetic-based methods are currently in use to generate antibiotic resistance profiles of clinically relevant pathogens. However, these methods are time consuming and lack the ability to discern key characteristics like rates of drug metabolism and concentrations of enzymes involved in antimicrobial resistance. Many pathogenic bacteria produce β-lactamases which covalently modify β-lactam antibiotics and the rise in extended spectrum β-lactamases is close to rendering an entire class of antibiotics ineffective. We investigated the use of selected reaction monitoring (SRM), a mass spectrometry technique, for differentiating β-lactam drug-resistant phenotypes in multi-drug resistant Pseudomonas aeruginosa (MRPA). Our ability to monitor precise drug concentrations and chemical modifications of antibiotic compounds using mass spectrometry has enabled us to detect strain-level differences in β-lactam resistant MRPA. Our results show that previously defined clonal populations of β-lactam-resistant MRPA differentially metabolize β-lactam antibiotics and contribute to varying degrees of β-lactam resistance in these pathogens. These phenotypic characteristics would not have been identified using either current genetic sequencing techniques alone or through culture-based diagnostics.