Oral Annual Conference of the Genetics Society of Australasia with the NZ Society for Biochemistry & Molecular Biology

Evolution of antibiotic resistance in Pseudomonas aeruginosa (736)

Iain L Lamont 1 , Sam L Taylor-Wardell 1 , Wayne M Patrick 1 , Lois W Martin 1
  1. University of Otago, Dunedin, OTAGO, New Zealand

Background/ Aims. Pseudomonas aeruginosa infects patients with a wide range of predisposing conditions. The bacterium intrinsically has low antibiotic resistance, but constant exposure to antibiotics results in resistant strains that are difficult or impossible to treat. Resistance arises through mutations that alter antibiotic target proteins or increase efflux of antibiotics from the bacterial cells. However understanding of the genetics underlying resistance is far from complete. The aim of this research was to carry out genome-wide analysis of resistance-causing mutations in order to more comprehensively determine the range of antibiotic resistance genes.

Methods. Mutants that were highly resistant to either meropenem or tobramycin, two widely used anti-Pseudomonas antibiotics with different protein targets, were selected in vitro. Whole genome sequencing was carried out to identify the associated mutations.

Results. Fifteen mutants with high resistance to meropenem and thirteen with high resistance to tobramycin were selected. Whole genome sequencing showed that each mutant contains multiple mutations. Many of these are in known antibiotic-resistance genes, validating our approach, but many are in genes not previously recognised as conferring antibiotic resistance. Seven of the meropenem-resistant mutants had large (>200 kb) deletions. The nature of the mutated genes suggests previously under-appreciated mechanisms of antibiotic resistance in P. aeruginosa. Bioinformatic analysis indicated that resistance alleles in the laboratory mutants are also commonly present in clinical isolates of P. aeruginosa.

Conclusions. Whole genome sequencing of in vitro-derived mutants provides a powerful tool for identifying genes that contribute to antibiotic resistance of P. aeruginosa.