title: Mechanisms of reduced susceptibility and genotypic prediction of antibiotic resistance in Prevotella isolated from cystic fibrosis (CF) and non-CF patients.
abstract: OBJECTIVE
  To investigate mechanisms of reduced susceptibility to commonly used antibiotics in Prevotella cultured from patients with cystic fibrosis (CF), patients with invasive infection and healthy control subjects and to determine whether genotype can be used to predict phenotypic resistance.
  
  
  METHODS
  The susceptibility of 157 Prevotella isolates to seven antibiotics was compared, with detection of resistance genes (cfxA-type gene, ermF and tetQ), mutations within the CfxA-type β-lactamase and expression of efflux pumps.
  
  
  RESULTS
  Prevotella isolates positive for a cfxA-type gene had higher MICs of amoxicillin and ceftazidime compared with isolates negative for this gene (P < 0.001). A mutation within the CfxA-type β-lactamase (Y239D) was associated with ceftazidime resistance (P = 0.011). The UK CF isolates were 5.3-fold, 2.7-fold and 5.7-fold more likely to harbour ermF compared with the US CF, UK invasive and UK healthy control isolates, respectively. Higher concentrations of azithromycin (P < 0.001) and clindamycin (P < 0.001) were also required to inhibit the growth of the ermF-positive isolates compared with ermF-negative isolates. Furthermore, tetQ-positive Prevotella isolates had higher MICs of tetracycline (P = 0.001) and doxycycline (P < 0.001) compared with tetQ-negative isolates. Prevotella spp. were also shown, for the first time, to express resistance nodulation division (RND)-type efflux pumps.
  
  
  CONCLUSIONS
  This study has demonstrated that Prevotella isolated from various sources harbour a common pool of resistance genes and possess RND-type efflux pumps, which may contribute to tetracycline resistance. The findings indicate that antibiotic resistance is common in Prevotella spp., but the genotypic traits investigated do not reflect phenotypic antibiotic resistance in every instance.
authors.affiliation: CF & Airways Microbiology Group, Queen's University Belfast, Belfast, UK School of Pharmacy, Queen's University Belfast, Belfast, UK l.sherrard@qub.ac.uk.
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Sherrard
authors.affiliation: CF & Airways Microbiology Group, Queen's University Belfast, Belfast, UK School of Pharmacy, Queen's University Belfast, Belfast, UK.
authors.forename: Bettina
authors.initials: B
authors.lastname: Schaible
authors.affiliation: CF & Airways Microbiology Group, Queen's University Belfast, Belfast, UK School of Pharmacy, Queen's University Belfast, Belfast, UK.
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Graham
authors.affiliation: CF & Airways Microbiology Group, Queen's University Belfast, Belfast, UK School of Pharmacy, Queen's University Belfast, Belfast, UK.
authors.forename: Stef J
authors.initials: SJ
authors.lastname: McGrath
authors.affiliation: CF & Airways Microbiology Group, Queen's University Belfast, Belfast, UK School of Pharmacy, Queen's University Belfast, Belfast, UK.
authors.forename: Leanne
authors.initials: L
authors.lastname: McIlreavey
authors.affiliation: Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Hatch
authors.affiliation: Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Wolfgang
authors.affiliation: Department of Pediatrics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Marianne S
authors.initials: MS
authors.lastname: Muhlebach
authors.affiliation: CF & Airways Microbiology Group, Queen's University Belfast, Belfast, UK School of Pharmacy, Queen's University Belfast, Belfast, UK.
authors.forename: Deirdre F
authors.initials: DF
authors.lastname: Gilpin
authors.affiliation: Centre for Infection & Immunity, School of Medicine, Dentistry & Biomedical Science, Queen's University Belfast, Belfast, UK.
authors.forename: Thamarai
authors.initials: T
authors.lastname: Schneiders
authors.affiliation: CF & Airways Microbiology Group, Queen's University Belfast, Belfast, UK Centre for Infection & Immunity, School of Medicine, Dentistry & Biomedical Science, Queen's University Belfast, Belfast, UK.
authors.forename: J Stuart
authors.initials: JS
authors.lastname: Elborn
authors.affiliation: CF & Airways Microbiology Group, Queen's University Belfast, Belfast, UK School of Pharmacy, Queen's University Belfast, Belfast, UK.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Tunney
mesh_terms: D019943:Amino Acid Substitution; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016866:Bacteroidaceae Infections / Q000382:microbiology; D016022:Case-Control Studies; D002442:Ceftazidime / Q000494:pharmacology; D018550:Cephalosporin Resistance / Q000235:genetics; D003550:Cystic Fibrosis / Q000382:microbiology*; D004352:Drug Resistance, Microbial / Q000235:genetics*; D005798:Genes, Bacterial; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D009154:Mutation; D018720:Prevotella / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D013752:Tetracycline / Q000494:pharmacology; D013753:Tetracycline Resistance / Q000235:genetics; D006113:United Kingdom; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D002442:Ceftazidime; D001618:beta-Lactamases; D013752:Tetracycline
keywords: efflux pumps; resistance genes; β-lactamases