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J Antimicrob Chemother. 2014 Oct;69(10):2690-8. doi: 10.1093/jac/dku192. Epub 2014 Jun 10.

Mechanisms of reduced susceptibility and genotypic prediction of antibiotic resistance in Prevotella isolated from cystic fibrosis (CF) and non-CF patients.

Author information

1
CF & Airways Microbiology Group, Queen's University Belfast, Belfast, UK School of Pharmacy, Queen's University Belfast, Belfast, UK l.sherrard@qub.ac.uk.
2
CF & Airways Microbiology Group, Queen's University Belfast, Belfast, UK School of Pharmacy, Queen's University Belfast, Belfast, UK.
3
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.
4
Department of Pediatrics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
5
Centre for Infection & Immunity, School of Medicine, Dentistry & Biomedical Science, Queen's University Belfast, Belfast, UK.
6
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.

Abstract

OBJECTIVES:

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.

KEYWORDS:

efflux pumps; resistance genes; β-lactamases

PMID:
24917582
PMCID:
PMC4164140
DOI:
10.1093/jac/dku192
[Indexed for MEDLINE]
Free PMC Article

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