Mechanism and fitness costs of PR-39 resistance in Salmonella enterica serovar Typhimurium LT2.
PR-39 is a porcine antimicrobial peptide that kills bacteria with a mechanism that does not involve cell lysis. Here, we demonstrate that Salmonella enterica serovar Typhimurium can rapidly acquire mutations that reduce susceptibility to PR-39. Resistant mutants appeared at a rate of 0.4 x 10(-6) per cell per generation. These mutants were about four times more resistant than the wild type and showed a greatly reduced rate of killing. Genetic analysis revealed mutations in the putative transport protein SbmA as being responsible for the observed resistance. These sbmA mutants were as fit as the wild-type parental strain as measured by growth rates in culture medium and mice and by long-term survival in stationary phase. These results suggest that resistance to certain antimicrobial peptides can rapidly develop without an obvious fitness cost for the bacteria and that resistance development could become a threat to the efficacy of antimicrobial peptides if used in a clinical setting.
Department of Medical Biochemistry and Microbiology, Uppsala University, S-751 23 Uppsala, Sweden.
Maria
M
Pränting
Aurel
A
Negrea
Mikael
M
Rhen
Dan I
DI
Andersson
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D005260:Female; D005816:Genetic Complementation Test; D051379:Mice; D008807:Mice, Inbred BALB C; D008826:Microbial Sensitivity Tests; D008957:Models, Genetic; D016254:Mutagenesis, Insertional; D009154:Mutation; D012481:Salmonella Infections, Animal / Q000188:drug therapy / Q000382:microbiology; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000235:genetics; D017384:Sequence Deletion; D054804:Cathelicidins
D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D001426:Bacterial Proteins; C072212:PR 39; D054804:Cathelicidins