RESUMO
We investigated the application of liquid chromatography-tandem mass spectrometry (LC-MS/MS) for pan-drug-resistant Acinetobacter baumannii (PDR-AB) with carbapenem resistance. Eight strains were randomly selected from 84 clinical isolates of PDR-AB strains obtained by the Kirby-Bauer and agar dilution methods. An efflux pump inhibition test was used to screen for the efflux pump phenotype. An ethylenediaminetetraacetic acid (EDTA) synergy test was used to screen for the ß-lactamase phenotype, and a three-dimensional test was used to detect extended spectrum ß-lactamase (ESBL) and ampicillin C, KPC, and carbapenemase. ESBL genes were amplified by polymerase chain reaction and sequenced. Outer membrane proteins were extracted from a sensitive strain and the PDR-AB strains by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and subjected to LC-MS/MS. Peptide mass fingerprinting data were retrieved, and proteins with differential expression were identified. Results of the efflux pump inhibition tests showed that the minimum inhibitory concentrations for meropenem were decreased in 4 of the 8 strains by at least 25% of the original value. The results of the EDTA synergy test were negative, and the modified Hodge's tests were positive for all strains. PCR and sequencing confirmed that seven, five, and all eight of the PDR-AB strains contained blaOXA-23, blaTEM-1, and KPC-2, respectively. OXA-23 and CsuC proteins were differentially expressed between the drug-resistant and -sensitive strains. Production of blaOXA-23 enzyme and pilus molecular chaperone to guide synthesis of CsuC protein may be involved in the resistance of A. baumannii to carbapenems. LC-MS/ MS provides a quick and easy method for carbapenemase detection.
Assuntos
Proteínas de Bactérias/isolamento & purificação , Cromatografia Líquida/métodos , Espectrometria de Massas em Tandem/métodos , beta-Lactamases/isolamento & purificação , Acinetobacter baumannii/química , Acinetobacter baumannii/efeitos dos fármacos , Proteínas de Bactérias/química , Farmacorresistência Bacteriana/genética , Humanos , beta-Lactamases/químicaRESUMO
We explored the mechanism of the development from sensitivity to resistance to carbapenem in Pseudomonas aeruginosa. Two P. aeruginosa strains were collected during treatment with carbapenem. Strain homology was investigated using pulsed-field gel electrophoresis. Porin oprD2 expression was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The minimum inhibitory concentrations (MICs) of imipenem and meropenem with or without MC207110 were determined using the agar dilution method. The expression level of efflux pump mRNA was tested using real-time polymerase chain reaction. Metallo-lactamases (MBLs) were screened using the EDTA-disk synergy test. Genes encoding MBLs were amplified and then analyzed by DNA sequencing. The two treated strains belonged to the same pulsed-field gel electrophoresis type. The SDS-PAGE profile of the P. aeruginosa strains revealed that the 46-kDa membrane protein OprD2 of IMP(R)MEM(R) type strains was lost, whereas OprD2 of 1 IMP(S)MEM(S) strain was normal. With or without MC207110 treatment, the MIC of carbapenem-resistant P. aeruginosa decreased by 4-fold, while the MIC of carbapenem-sensitive P. aeruginosa did not. Compared with the carbapenem-sensitive strain, MexX mRNA expression in the carbapenem-resistant strain increased by 102.5-fold, while the mRNA expression of other efflux pumps did not markedly increase. Neither carbapenem-resistant nor carbapenem-sensitive P. aeruginosa produced MBL. The mechanism of development from sensitivity to resistance of P. aeruginosa to carbapenem during carbapenem treatment is due to porin oprD2 loss and an increased expression level of MexXY-OprM.