COMPARISON OF AUTOMATIZED SYSTEM AND BROTH MICRODILUTION METHOD FOR DETERMINING COLISTIN RESISTANCE IN GRAM NEGATIVE BACTERIA
Project no. 296 · Status: Kapanmış · 2018
Summary
After its introduction in the 1940s, its use was restricted due to nephrotoxic and neurotoxic side effects. However, the increase in the incidence of multi-drug resistant bacteria and the difficulties of introducing new antibiotic molecules into use have brought colistin back into the spotlight. With the increase in its use, the incidence of colistin resistance in bacteria has also increased. Colistin resistance may occur chromosomally or may show interspecies spread via plasmids. Detection of colistin resistance before starting the treatment is crucial for both increasing effectiveness of the treatment and reducing unnecessary usage of antibiotics. In the determination of colistin resistance, the broth microdilution method was determined as the reference method by EUCAST and CLSI. However, in laboratories where the number of clinical samples is high, automated systems are generally used determine antibiotic susceptibility in order to use time and labor efficiently. In this study, it was aimed to determine and compare the colistin minimum inhibitory concentrations (MIC) of 91 Gram-negative bacteria isolated from patient samples in Ege University Medical Faculty Hospital Medical Microbiology Laboratory by automated system (bioMérieux Vitek 2) and broth microdilution method. In addition, the presence of plasmid-derived mcr-1 gene was investigated in colistin resistant isolates. The categorical agreement (CA) between the two methods was 94.5%, the essential agreement (EA) was 56.25%, the major error rate (ME) was 4.05%, and the very major error rate (VME) was 11.76%. The presence of the mcr-1 gene was investigated in 21 isolates that were found to be resistant to colistin by either of the two methods, but it was not found in any of the examined strains. Our results show that the Vitek 2 device does not meet the criteria to be used instead of the reference method in determining colistin susceptibility, and does not provide reliable results in determining colistin susceptibility. Although it was not encountered in the isolates investigated in our study, the fact that the mcr-1 gene was detected at low rates in clinical strains in Turkey reveals that the prevalence of this gene should be followed up at regular intervals.