| Summary: | Introduction: Multiple resistance to antibiotics is a problem in modern medicine and acceptable definitions are needed to describe it. The widely accepted method for this purpose is the Multiple Drug Resistance (MDR) definition and the older but less used Multiple Antibiotic Resistance (MAR) indexing system. The aim of this study was to analyze their ability for comparing multiple resistance results for the same Enterobacteriaceae members obtained using these two methods and to investigate whether there is a need to improve these definitions.
Materials and Methods: Antimicrobial resistance test results of 665 Escherichia coli and 292 Klebsiella spp. strains isolated in the Clinical Microbiology Laboratory of our hospital were evaluated retrospectively. Resistance results were grouped under antibiotic categories and classified as multiple, extensively, and pan-drug resistance groups according to the MDR definition. MAR indices were determined by dividing the number of resistant antibiotics in both microorganism isolates separately and collectively by the number of antibiotics for which susceptibility was tested. The results were divided into subgroups according to the origin of the patients and the clinical samples obtained and were evaluated according to their total results. Than the two resistance classification methods were compared.
Results: Among the E. coli and Klebsiella spp. strains analyzed in this study, 45.86% and 40.06% of the strains were classified as multidrug-resistant according to the MDR definition, respectively. However, when these strains were evaluated with the MAR index method, it was found that the resistance rates were (from most to least resistant) 1.65%, 6.46%, 10.97%, 7.36%, 6.61%, and 11.12% in E. coli and 5.13%, 7.87%, 8.56%, 3.79%, 4.10%, and 8.21% percent in Klebsiella spp. Similar results were observed in subgroup analysis.
Conclusion: Our study demonstrates that the MAR index method, which is used less frequently in medical research, yields more detailed results than the commonly used MDR method and provides more objective outcomes since it expresses resistance results numerically.
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