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Genetic Basis and Functional Consequences of Differential Expression of the CmeABC Efflux Pump in Campylobacter jejuni Isolates.

ABSTRACT: The CmeABC multidrug efflux transporter of Campylobacter jejuni plays a key role in antimicrobial resistance and is suppressed by CmeR, a transcriptional regulator of the TetR family. Overexpression of CmeABC has been observed in laboratory-generated mutants, but it is unknown if this phenotype occurs naturally in C. jejuni isolates and if it has any functional consequences. To answer these questions, expression of cmeABC in natural isolates obtained from broiler chickens, turkeys and humans was examined, and the genetic mechanisms and role of cmeABC differential expression in antimicrobial resistance was determined. Among the 64 C. jejuni isolates examined in this study, 43 and 21 were phenotypically identified as overexpression (OEL) and wild-type expression (WEL) levels. Representative mutations of the cmeABC promoter and/or CmeR-coding sequence were analyzed using electrophoretic mobility shift assays and transcriptional fusion assays. Reduced CmeR binding to the mutated cmeABC promoter sequences or decreased CmeR levels increased cmeABC expression. Several examined amino acid substitutions in CmeR did not affect its binding to the cmeABC promoter, but a mutation that led to C-terminal truncation of CmeR abolished its DNA-binding activity. Interestingly, some OEL isolates harbored no mutations in known regulatory elements, suggesting that cmeABC is also regulated by unidentified mechanisms. Overexpression of cmeABC did not affect the susceptibility of C. jejuni to most tested antimicrobials except for chloramphenicol, but promoted the emergence of ciprofloxacin-resistant mutants under antibiotic selection. These results link CmeABC overexpression in natural C. jejuni isolates to various mutations and indicate that this phenotypic change promotes the emergence of antibiotic-resistant mutants under selection pressure. Thus, differential expression of CmeABC may facilitate Campylobacter adaptation to antibiotic treatments.

SUBMITTER: Grinnage-Pulley T

PROVIDER: S-EPMC4488513 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Genetic Basis and Functional Consequences of Differential Expression of the CmeABC Efflux Pump in Campylobacter jejuni Isolates.

Grinnage-Pulley Tara T Zhang Qijing Q

PloS one 20150701 7

The CmeABC multidrug efflux transporter of Campylobacter jejuni plays a key role in antimicrobial resistance and is suppressed by CmeR, a transcriptional regulator of the TetR family. Overexpression of CmeABC has been observed in laboratory-generated mutants, but it is unknown if this phenotype occurs naturally in C. jejuni isolates and if it has any functional consequences. To answer these questions, expression of cmeABC in natural isolates obtained from broiler chickens, turkeys and humans was ...[more]

PMID: 26132196

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Project description:Campylobacter jejuni is a foodborne pathogen that is recognized as the leading cause of human bacterial gastroenteritis. The widespread use of antibiotics in medicine and in animal husbandry has led to an increased incidence of antibiotic resistance in Campylobacter In addition to a role in multidrug resistance (MDR), the Campylobacter CmeABC resistance-nodulation-division (RND)-type efflux pump may be involved in virulence. As a vehicle for pathogenic microorganisms, the protozoan Acanthamoeba is a good model for investigations of bacterial survival in the environment and the molecular mechanisms of pathogenicity. The interaction between C. jejuni 81-176 and Acanthamoeba polyphaga was investigated in this study by using a modified gentamicin protection assay. In addition, a possible role for the CmeABC MDR pump in this interaction was explored. Here we report that this MDR pump is beneficial for the intracellular survival and multiplication of C. jejuni in A. polyphaga but is dispensable for biofilm formation and motility.IMPORTANCE The endosymbiotic relationship between amoebae and microbial pathogens may contribute to persistence and spreading of the latter in the environment, which has significant implications for human health. In this study, we found that Campylobacter jejuni was able to survive and to multiply inside Acanthamoeba polyphaga; since these microorganisms can coexist in the same environment (e.g., on poultry farms), the latter may increase the risk of infection with Campylobacter Our data suggest that, in addition to its role in antibiotic resistance, the CmeABC MDR efflux pump plays a role in bacterial survival within amoebae. Furthermore, we demonstrated synergistic effects of the CmeABC MDR efflux pump and TetO on bacterial resistance to tetracycline. Due to its role in both the antibiotic resistance and the virulence of C. jejuni, the CmeABC MDR efflux pump could be considered a good target for the development of antibacterial drugs against this pathogen.

Project description:Objectives: The aim of the study was to characterize (-)-Î±-Pinene, which is one of the chemical constituents of Alpinia katsumadai seed essential oil responsible for its resistance modulatory activity in Campylobacter jejuni. Methods: Broth microdilution method was used to evaluate the antimicrobial and resistance modulatory potential of (-)-Î±-Pinene and ethidium bromide accumulation assay to determine its efflux-inhibitory activity in subinhibitory concentration. The target efflux system was identified using knock-out mutants in several efflux related genes. Furthermore, the influence of subinhibitory concentration of (-)-Î±-Pinene on C. jejuni NCTC 11168 was investigated using microarray technology in order to elucidate the adaptive mechanism of bacteria to treatment with this phytochemical. Knock-out mutants of key adaptation genes were constructed and their role in adaptation to several stress factors, including (-)-Î±-Pinene, different osmolites and pH, was investigated using Biolog phenotypical microarrays and CFU counts. Results: (-)-Î±-Pinene was confirmed as highly efficient Campylobacter jejuni resistance modulator, due to its efflux inhibitory activity, which was significantly higher compared to reference inhibitors CCCP and reserpine. The CmeABC along with newly characterized CmeI (Cj1687) was confirmed as its main target efflux system. The transcriptional analysis indicated that the heat shock regulators HspR and HrcA are the main transcription regulators involved in adaptation to (-)-Î±-Pinene treatment. Conclusions: (-)-Î±-Pinene is a novel CmeABC and CmeI efflux inhibitor, which evokes the heat shock response in Campylobacter jejuni. Influence of (-)-Î±-Pinene on gene expression in C. jejuni NCTC 11168 was determined by expressional analysis and qRT-PCR. Exponential phase culture was adjusted to OD600=0.2 in MHB using spectrophotometer (Smart Spec, Bio-Rad, Hercules, CA, USA). Five ml of culture was treated with 62.5 mg/L of (-)-alpha-pinene dissolved in DMSO. Only DMSO (0.048 %) was added to untreated samples. Cultures were treated for 2 h, incubated microaerobically shaking (160 rpm) at 42Â°C. Experiments were carried out in 4 biological replicates. RNA Protect Bacteria reagent (Qiagen, Maryland, USA) was added to the culture and total RNA was isolated using RNeasy mini kit (Qiagen) and treated with AmbionÂ® Turbo DNA-freeTM kit (Invitrogen, USA). Microarrays with 4751 probes targeting 1756 genes specific for Campylobacter jejuni subsp. jejuni NCTC 11168 (Mycroarray, Biodiscovery-LLC, MI, USA) were used for gene expression analysis. The cDNA was synthesized with random hexamers, SuperScriptTM III Reverse Transcriptase and amynoallyl dUTP (all supplied by Invitrogen, USA) and labeled with monofunctional NHS-ester dye Amersham C3 or Cy5 (GE Healthcare, Buckinghamshire, UK). Concentration of cDNA and labeling efficiency was determined spectrophotometrically with NanoDrop 1000. Four biological replicates were hybridized to four microarrays according to manufacturerâs protocol, incubated for 24 hours at 42â°C and scanned at 532-nm (Cy3) and 635-nm (Cy5) wavelengths using GenePix 4100A (Molecular Devices, Sunnyvale, CA) following the manufacturer's protocol. Fluorescence intensities of each spot were extracted using GenePix Pro 7.0 (Molecular Devices).

Dataset Information

Genetic Basis and Functional Consequences of Differential Expression of the CmeABC Efflux Pump in Campylobacter jejuni Isolates.

Publications

Genetic Basis and Functional Consequences of Differential Expression of the CmeABC Efflux Pump in Campylobacter jejuni Isolates.

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