Suzanne Bialek-Davenet1, Jean-Philippe Lavigne2, Kathleen Guyot3, Noémie Mayer4, Régis Tournebize5, Sylvain Brisse6, Véronique Leflon-Guibout4, Marie-Hélène Nicolas-Chanoine7. 1. Service de Microbiologie, Hôpital Beaujon, AP-HP, Clichy, France Institut Pasteur, Microbial Evolutionary Genomics, Paris, France CNRS, UMR3525, Paris, France. 2. INSERM U1047, Université Montpellier 1, UFR de Médecine, Nîmes, France Laboratoire de Bactériologie, CHU Caremeau, Nîmes, France. 3. Service de Microbiologie, Hôpital Beaujon, AP-HP, Clichy, France Faculté de Médecine Paris Diderot, Paris, France. 4. Service de Microbiologie, Hôpital Beaujon, AP-HP, Clichy, France. 5. Institut Pasteur, Pathogénie Microbienne Moléculaire, Paris, France INSERM U786, Paris, France. 6. Institut Pasteur, Microbial Evolutionary Genomics, Paris, France CNRS, UMR3525, Paris, France. 7. Service de Microbiologie, Hôpital Beaujon, AP-HP, Clichy, France Faculté de Médecine Paris Diderot, Paris, France INSERM UMR 1149, Université Paris 7, Paris, France mhn.chanoine@bjn.aphp.fr.
Abstract
OBJECTIVES: In Klebsiella pneumoniae, overexpression of the AcrAB efflux pump and the more recently described OqxAB efflux pump has been linked to an antibiotic cross-resistance phenotype, but the mechanisms of regulation are largely unknown. Moreover, while AcrAB has been shown to participate in K. pneumoniae virulence, the contribution of OqxAB has not yet been assessed. METHODS: In the present study we investigated a K. pneumoniae clinical isolate (KPBj1 E+), displaying cross-resistance to quinolones, chloramphenicol and cefoxitin, and its phenotypic revertant (KPBj1 Rev, susceptible to antibiotics) by using whole-genome sequencing, RT-PCR, complementation and a Caenorhabditis elegans virulence model. RESULTS: We detected a point mutation in the oqxR repressor gene of KPBj1 E+, which overexpressed genes rarA, encoding a transcriptional regulator, and oqxB, but not acrB. Complementation with wild-type oqxR restored antibiotic susceptibility and normalized rarA and oqxB expression levels. Whole-genome sequencing showed that KPBj1 Rev had lost the entire rarA-oqxABR locus, situated close to an integration hot spot of phage P4. This large deletion seemed responsible for the significantly lower virulence potential of strain KPBj1 Rev compared with KPBj1 E+. Moreover, we found that KPBj1 E+ ΔacrB was significantly less virulent than its parental strain. CONCLUSIONS: This work demonstrates the role of the overexpression of efflux pump OqxAB, due to a mutation in gene oqxR, in the antibiotic resistance phenotype of a clinical isolate, and suggests that the presence of AcrAB, associated with overexpression of OqxAB, is required for high virulence potential.
OBJECTIVES: In Klebsiella pneumoniae, overexpression of the AcrAB efflux pump and the more recently described OqxAB efflux pump has been linked to an antibiotic cross-resistance phenotype, but the mechanisms of regulation are largely unknown. Moreover, while AcrAB has been shown to participate in K. pneumoniae virulence, the contribution of OqxAB has not yet been assessed. METHODS: In the present study we investigated a K. pneumoniae clinical isolate (KPBj1 E+), displaying cross-resistance to quinolones, chloramphenicol and cefoxitin, and its phenotypic revertant (KPBj1 Rev, susceptible to antibiotics) by using whole-genome sequencing, RT-PCR, complementation and a Caenorhabditis elegans virulence model. RESULTS: We detected a point mutation in the oqxR repressor gene of KPBj1 E+, which overexpressed genes rarA, encoding a transcriptional regulator, and oqxB, but not acrB. Complementation with wild-type oqxR restored antibiotic susceptibility and normalized rarA and oqxB expression levels. Whole-genome sequencing showed that KPBj1 Rev had lost the entire rarA-oqxABR locus, situated close to an integration hot spot of phage P4. This large deletion seemed responsible for the significantly lower virulence potential of strain KPBj1 Rev compared with KPBj1 E+. Moreover, we found that KPBj1 E+ ΔacrB was significantly less virulent than its parental strain. CONCLUSIONS: This work demonstrates the role of the overexpression of efflux pump OqxAB, due to a mutation in gene oqxR, in the antibiotic resistance phenotype of a clinical isolate, and suggests that the presence of AcrAB, associated with overexpression of OqxAB, is required for high virulence potential.
Authors: R Trastoy; T Manso; L Fernández-García; L Blasco; A Ambroa; M L Pérez Del Molino; G Bou; R García-Contreras; T K Wood; M Tomás Journal: Clin Microbiol Rev Date: 2018-08-01 Impact factor: 26.132