Molecular investigation of carbapenem and colistin resistance mechanisms in klebsiella pneumoniae isolates

Aim: Carbapenem Resistant Klebsiella pneumoniae (CRKp) infections are worrying health problems due to decreasing treatment options. Enzyme-mediated mechanisms are most frequently caused by carbapenem resistance in clinical isolates. Colistin is considered one of the last resort treatments for infections caused by CRKp. The aim of this study is to investigate the carbapenemase (OXA-23, OXA-24, OXA-48, OXA-51, OXA-55, OXA-58, KPC, NDM-1, VIM, IMP) and mcr-1 genes of the CRKps isolates. Material and Method: A total of 33 CRKp isolates isolated from patient blood samples from the Dicle University Medical Faculty Hospital, ICUs between February 2020 and June 2020, were included in the study. Antibiotic susceptibility tests were performed by BD Phoenix 100 (BD, U.S.A.). Carbapenem resistance of isolates was determined phenotypically by Disk Diffusion Test (DDT), colistin susceptibility by Broth Microdilution (BMD) method. The presence of carbapenemase encoding genes including all CRKp isolates, blaOXA-23, blaOXA-24, blaOXA-48, blaOXA-51, blaOXA-55, blaOXA-58, blaKPC, blaNDM-1, blaVIM, blaIMP were investigated by multiplex PCR. CRKp isolates were tested for mcr-1 gene by PCR. Results: All CRKp isolates studied with DDT (100%) were resistant to ertapenem; 9 (27.27%) resistant to imipenem and 23 (69.7%) were resistant to meropenem. 20 (60.61%) of the isolates were found resistant to colistin. blaOXA-48 was found in 75.76% (n = 25) of isolates, blaNDM-1 in 6.06% (n = 2) and blaOXA-24 in 3.03% (n = 1). Both blaOXA-48 and blaNDM-1 genes were detected in two (6.06%) isolates and mcr-1 gene in 16 (48.48%) isolates. Conclusion: The very high rate of isolates carrying mcr-1 genes necessitates monitoring of colistin resistance by molecular epidemiological methods. The resistance mechanisms of CRKp should be investigated, monitored by molecular epidemiological methods. Each hospital should compare the automated system and the BMD method and determine the false susceptibility rates for their colistin susceptibility results. Key Words: Klebsiella pneumoniae, carbapenemase, blaOXA-48, mcr-1, multiplex PCR, broth microdilution.