Comparison of colistin broth disc elution, colistin agar test, broth microdilution methods and investigation of the MCR-1 gene in klebsiella pneumoniae, pseudomonas aeruginosa, acinetobacter baumannii strains

ABSTRACT COMPARISON OF COLISTIN BROTH DISC ELUTION, COLISTIN AGAR TEST, BROTH MICRODILUTION METHODS AND INVESTIGATION OF THE MCR-1 GENE IN KLEBSIELLA PNEUMONIAE, PSEUDOMONAS AERUGINOSA, ACINETOBACTER BAUMANNII STRAINS As an alternative to the broth microdilution (BMD) method, which is the reference method for colistin sensitivity determination, colistin broth disk elution (CBDE) and colistin agar test (CAT) methods have been developed. Our aim in this study is to compare BMD, CBDE and CAT methods to determine colistin sensitivity in Klebsiella pneumoniae (K. pneumoniae), Pseudomonas aeruginosa (P. aeruginosa), and Acinetobacter baumannii (A. baumannii) strains; To investigate the the mcr-1 (mobile colistin resistance) resistance gene in colistin resistant isolates by polymerase chain reaction (PCR) method. A total of 176 isolates, including 62 K. pneumoniae, 52 P. aeruginosa and 62 A. baumannii, were included in the study. BMD, CBDE and KAT methods were used to detect colistin sensitivity, and genetic material was isolated from any of the isolates found to be resistant to colistin and PCR was applied. When the data are evaluated, in K. pneumoniae; for the CBDE method, the categorical agreement (CA), essential agreement (EA), major error (ME) and very major error (VME) rates were 93.5%, 91.9%, 13.3% and 0%, respectively, while the CA and EA rates for the CAT method were 96%, VME was detected in 6.2% and ME was not observed. Compared to the reference method, the rates of CA, EA, ME and VME in P. aeruginosa were found to be within acceptable limits in both methods. Finally, in A. baumannii; for the CBDE method, CA 83.8%, EA 80.6%, ME 11.7% and VME 36.3% were found to be, while for the CAT method CA and EA were found to be 88%, ME 2% and VME 54%. The mcr-1 gene was not detected in 58 isolates found to be resistant to colistin by any method. While it is thought that CBDE and CAT methods can be used as an alternative to the BMD method for colistin sensitivity detection in K. pneumoniae and P. aeruginosa, it is thought that using these methods for A. baumannii will cause erroneous results.