Abstract
Objective: Resistant gram-negative microorganisms, especially Klebsiella pneumoniae and Acinetobacter baumannii, cause life-threatening infections. Hence, it is critical to determine the antibiotic susceptibility of clinical isolates rapidly and accurately. Nowadays, carbapenem resistance is determined by phenotypic/genotypic methods. For phenotypic methods (disk diffusion, microdilution), differences in specificity and sensitivity can often occur. Since molecular methods such as polymerase chain reaction giving relatively more reliable results, are labor-intensive and costly, new fast, reliable and economical methods are needed.
Material and Method: The performance of chromogenic AST Fast ES/NF agar for the EUCAST standard disk diffusion method was investigated. Four K. pneumoniae and five A. baumannii isolates, which were determined to be carbapenem resistant by molecular method and automated system results, were included in the study.
Result and Discussion: The inhibition zone diameters were became measurable within 4-6 hours in AST Fast ES/NF and the susceptibility categories were interpreted according to the manufacturer's recommendations. The results of disk diffusion test performed with MHA, were largely consistent with the results obtained with the AST Fast ES/NF. Considering that the incubation period recommended by EUCAST in the standard disk diffusion test method is 16-20 hours and the sensitivity category is measured at the end of this period, it is thought that the chromogenic medium may provide a significant advantage.