title: Mechanisms of intrinsic resistance and acquired susceptibility of Pseudomonas aeruginosa isolated from cystic fibrosis patients to temocillin, a revived antibiotic.
abstract: The β-lactam antibiotic temocillin (6-α-methoxy-ticarcillin) shows stability to most extended spectrum β-lactamases, but is considered inactive against Pseudomonas aeruginosa. Mutations in the MexAB-OprM efflux system, naturally occurring in cystic fibrosis (CF) isolates, have been previously shown to reverse this intrinsic resistance. In the present study, we measured temocillin activity in a large collection (n = 333) of P. aeruginosa CF isolates. 29% of the isolates had MICs ≤ 16 mg/L (proposed clinical breakpoint for temocillin). Mutations were observed in mexA or mexB in isolates for which temocillin MIC was ≤512 mg/L (nucleotide insertions or deletions, premature termination, tandem repeat, nonstop, and missense mutations). A correlation was observed between temocillin MICs and efflux rate of N-phenyl-1-naphthylamine (MexAB-OprM fluorescent substrate) and extracellular exopolysaccharide abundance (contributing to a mucoid phenotype). OpdK or OpdF anion-specific porins expression decreased temocillin MIC by ~1 two-fold dilution only. Contrarily to the common assumption that temocillin is inactive on P. aeruginosa, we show here clinically-exploitable MICs on a non-negligible proportion of CF isolates, explained by a wide diversity of mutations in mexA and/or mexB. In a broader context, this work contributes to increase our understanding of MexAB-OprM functionality and help delineating how antibiotics interact with MexA and MexB.
authors.affiliation: Pharmacologie cellulaire et moléculaire, Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium.
authors.forename: Hussein
authors.initials: H
authors.lastname: Chalhoub
authors.affiliation: Life Sciences, School of Engineering and Science, Jacobs University, Bremen, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Pletzer
authors.affiliation: Life Sciences, School of Engineering and Science, Jacobs University, Bremen, Germany.
authors.forename: Helge
authors.initials: H
authors.lastname: Weingart
authors.affiliation: Life Sciences, School of Engineering and Science, Jacobs University, Bremen, Germany.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Braun
authors.affiliation: CF &Airways Microbiology Research Group, Queen's University Belfast, Belfast, UK.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Tunney
authors.affiliation: CF &Airways Microbiology Research Group, Queen's University Belfast, Belfast, UK.
authors.forename: J Stuart
authors.initials: JS
authors.lastname: Elborn
authors.affiliation: Laboratoire de microbiologie, Cliniques Universitaires Saint-Luc, Université catholique de Louvain, Brussels, Belgium.
authors.forename: Hector
authors.initials: H
authors.lastname: Rodriguez-Villalobos
authors.affiliation: Laboratoire de bactériologie, Hôpital Jean Minjoz, Besançon, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Plésiat
authors.affiliation: University Hospital Münster, Münster, Germany.
authors.forename: Barbara C
authors.initials: BC
authors.lastname: Kahl
authors.affiliation: Laboratoire de microbiologie, Hôpital Erasme, Université libre de Bruxelles, Brussels, Belgium.
authors.forename: Olivier
authors.initials: O
authors.lastname: Denis
authors.affiliation: Life Sciences, School of Engineering and Science, Jacobs University, Bremen, Germany.
authors.forename: Mathias
authors.initials: M
authors.lastname: Winterhalter
authors.affiliation: Pharmacologie cellulaire et moléculaire, Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Tulkens
authors.affiliation: Pharmacologie cellulaire et moléculaire, Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium.
authors.forename: Françoise
authors.initials: F
authors.lastname: Van Bambeke
mesh_terms: D015057:1-Naphthylamine / Q000031:analogs & derivatives / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001692:Biological Transport; D000073537:Biological Variation, Population; D003550:Cystic Fibrosis / Q000150:complications*; D004252:DNA Mutational Analysis; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics; D008826:Microbial Sensitivity Tests; D009154:Mutation; D010406:Penicillins / Q000494:pharmacology*; D011135:Polysaccharides, Bacterial / Q000378:metabolism; D018272:Porins / Q000037:antagonists & inhibitors; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000302:isolation & purification*
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D026901:Membrane Transport Proteins; C118598:MexA protein, Pseudomonas aeruginosa; C118597:MexB protein, Pseudomonas aeruginosa; D010406:Penicillins; D011135:Polysaccharides, Bacterial; D018272:Porins; C031367:temocillin; C005444:N-phenyl-1-naphthylamine; D015057:1-Naphthylamine