title: Polymyxin resistance of Pseudomonas aeruginosa phoQ mutants is dependent on additional two-component regulatory systems.
abstract: Pseudomonas aeruginosa can develop resistance to polymyxin as a consequence of mutations in the PhoPQ regulatory system, mediated by covalent lipid A modification. Transposon mutagenesis of a polymyxin-resistant phoQ mutant defined 41 novel loci required for resistance, including two regulatory systems, ColRS and CprRS. Deletion of the colRS genes, individually or in tandem, abrogated the polymyxin resistance of a ΔphoQ mutant, as did individual or tandem deletion of cprRS. Individual deletion of colR or colS in a ΔphoQ mutant also suppressed 4-amino-L-arabinose addition to lipid A, consistent with the known role of this modification in polymyxin resistance. Surprisingly, tandem deletion of colRS or cprRS in the ΔphoQ mutant or individual deletion of cprR or cprS failed to suppress 4-amino-L-arabinose addition to lipid A, indicating that this modification alone is not sufficient for PhoPQ-mediated polymyxin resistance in P. aeruginosa. Episomal expression of colRS or cprRS in tandem or of cprR individually complemented the Pm resistance phenotype in the ΔphoQ mutant, while episomal expression of colR, colS, or cprS individually did not. Highly polymyxin-resistant phoQ mutants of P. aeruginosa isolated from polymyxin-treated cystic fibrosis patients harbored mutant alleles of colRS and cprS; when expressed in a ΔphoQ background, these mutant alleles enhanced polymyxin resistance. These results define ColRS and CprRS as two-component systems regulating polymyxin resistance in P. aeruginosa, indicate that addition of 4-amino-L-arabinose to lipid A is not the only PhoPQ-regulated biochemical mechanism required for resistance, and demonstrate that colRS and cprS mutations can contribute to high-level clinical resistance.
authors: Department of Pediatrics, Massachusetts General Hospital, Boston, Massachusetts, USA.
authors: Alina D
authors: AD
authors: Gutu
authors: Nicole
authors: N
authors: Sgambati
authors: Pnina
authors: P
authors: Strasbourger
authors: Mark K
authors: MK
authors: Brannon
authors: Michael A
authors: MA
authors: Jacobs
authors: Eric
authors: E
authors: Haugen
authors: Rajinder K
authors: RK
authors: Kaul
authors: Helle Krogh
authors: HK
authors: Johansen
authors: Niels
authors: N
authors: Høiby
authors: Samuel M
authors: SM
authors: Moskowitz
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001089:Arabinose / Q000031:analogs & derivatives / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D003550:Cystic Fibrosis / Q000188:drug therapy / Q000382:microbiology; D004251:DNA Transposable Elements; D024881:Drug Resistance, Bacterial / Q000187:drug effects* / Q000235:genetics; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D005809:Genes, Regulator / Q000187:drug effects*; D005816:Genetic Complementation Test; D056426:Genetic Loci; D006801:Humans; D008050:Lipid A / Q000378:metabolism; D009154:Mutation; D010957:Plasmids; D011113:Polymyxins / Q000494:pharmacology*; D011552:Pseudomonas Infections / Q000188:drug therapy / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D008050:Lipid A; C079792:PhoQ protein, Bacteria; D011113:Polymyxins; D001089:Arabinose