DNA microarray technologies offer a promising method for detection of antimicrobial resistance genes and point mutations in resistance-related sequences (rRNA, katG, gyrA) . Detection and identification of multiple tetracycline resistance genes by a glass-based DNA microarray were recently described . In this study, microarray probes for 17 tet genes, the b-lactamase blaTEM-1 gene, and a 16S-rDNA gene (E. coli) were generated and successfully applied to clinical isolates.
Recently, the application of the microarray-based single-base-mutation identification assay for detection of resistance against fluoroquinolones in clinical diagnostics has been demonstrated by identifying prevalent gyrA mutations in 30 clinical E.coli isolates . Moreover, oligonucleotide microarrays offer an attractive option for the identification and epidemiologic monitoring of TEM b-lactamases in the routine clinical diagnostic laboratory. Using these DNA arrays Grimm et al. describe the identification of the single nucleotide polymorphisms (SNPs) of 96% of the TEM b-lactamase variants known to date which are related to extended-spectrum beta-lactamase (ESBL) and/or inhibitor-resistant TEM (IRT) phenotype . High-density oligonucleotide arrays have also been applied to simultaneous species identification and detection of mutations that confer rifampicin and pyrazina-mide resistance in mycobacteria [54, 67]. Consequently, the DNA microarray strategy could be expanded to include parallel testing of various genes mediating drug resistance in M. tuberculosis. The design of such an array for the simultaneous testing of isoniazid, rifampicin, streptomycin, and fluoroquinolone susceptibilities is desirable, as this approach could provide an essential contribution to the rapid diagnosis of drug-resistant tuberculosis. In conclusion, the detection of antibiotic-resistance mutations shows that microarray technology is very promising and will probably soon be among the laboratory tools available to microbiologists. However, it should be emphasized that it is the functional expression rather than the presence of the antibiotic resistance gene that determines the success of antibiotic treatment.
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