Functional characterization of TtgABC efflux pump of the RND family in the entomopathogenic bacterium Pseudomonas entomophila

Abstract

Pseudomonas entomophila is a recently characterized entomopathogenic bacterium that can infect and kill Drosophila melanogaster upon ingestion. Although it is an environmental strain, it exhibits intrinsic resistance towards several antibiotics, as demonstrated in the present study. The intrinsic antibiotic resistance of P. entomophila was tested for ampicillin, chloramphenicol, kanamycin, streptomycine, tetracycline, imipenem, and ethidium bromide. Minimum inhibitory concentrations (MICs) were 1000 μg/ml for ampicillin, 150 μg/ml for chloramphenicol, 100 μg/ml for streptomycin, and >2000 μg/ml for ethidium bromide. The MIC values for kanamycin, tetracycline, and imipenem were much lower (5, 4, and <1 μg/ml respectively). Genome mining of the P. entomophila genome identified genes belonging to the resistance-nodulation-division (RND) family which encode efflux pumps. The ttgABC operon encoding an RND-type efflux pump in the P. entomophila genome was disrupted and its implication in ampicillin, chloramphenicol, streptomycin and ethidium bormide resistance was confirmed. © 2015, Springer-Verlag Berlin Heidelberg and the University of Milan.