AFAB

Keywords: Antimicrobial, disk diffusion, hybridization, microarray, oligonucleotide, PCR, resistance genes

Abstract:

We report the development of a microarray-based transcriptomic expression analysis method for the detection of 131 antimicrobial resistance genes in multidrug-resistant clinical (Enterococcus faecium, E. faecalis), aquaculture (Aeromonas veronii), poultry (Campylobacter jejuni, Staphylococcus aureus), and out break (Salmonella enterica serovar Typhimurium) strains.Unmodified oligonucleotide probes and 131 pair of primers for the genes conferring resistance to 22 different antimicrobials were used for transcriptomic array and PCR analysis. Detection of resistance genes by transcriptomic array and PCR methods correlated well with the susceptibility profiles of the isolates used in the study. However, some of the genes conferring resistance to ampicillin (amp), bleomycin (ble), lincomycin (linAn2, lmr, lmrA, lmrB, mgt), neomycin (neo, nptII, himaR), oleandomycin (oleB, oleC-orf4, oleC-orf5), penicillin (mecA), and rifampin (arr2) could not be detected by above methods. Co- or cross-resistance to these drugs and their extracellular transport due to the presence of 2 to 5 efflux pump genes (oleB, marA, tetA, tetB, vraD) is believed to confer resistance to the above antimicrobials. Moreover, the presence of resistance genes for bacitracin, chloramphenicol, erythromycin, kanamycin, streptomycin, and tetracycline in phenotypically sensitive isolates indicated either inactive versions of these genes or modulation of gene expression. Overall, the transcriptomic array method provided a valuable insight into the mechanism(s) of resistance, status of gene expression at transcription level, and detection of all the antimicrobial resistance genes among bacteria from different ecological sources.

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