The Determination of Carbapenem Resistance in Escherichia Coli and Klebsiella Pneumoniae Isolates Related to Nosocomial Infections and the Evaluation of Risk Factors

We aimed to investigate carbapenem resistance, resistance mechanisms, risk factors and epidemiological features of Escherichia coli and Klebsiella pneumoniae strains isolated from related infections in intensive care unit (ICU) patients. Carbapenemase activity was determined by MHT, MBL Etest and enzyme extraction methods. Presence of extended-spectrum b-lactamase (ESBL) and carbapenemaseencoding genes were investigated by PCR and sequencing. Clonal relationship of the strains was investigated by pulse field gel-electrophoresis. Acquired AmpC and Qnr were investigated by PCR. Throughout this study, 1,657 patients, and 11,483 hospitalization days were followed by active surveillance in the ICU of our 1,000-bed training hospital. Out of 108 of 196 patients, 130 E. coliand K. pneumoniae-related nosocomial infections were determined. Minimum inhibitory concentration (MIC) levels of ertapenem were ≥1 mg/l in 14 K. pneumoniae and 2 E. coli strains. The highest MIC level of carbapenem was found in K. pneumoniae and E. coli strains of ≥128 mg/l and 8 mg/l, respectively. In the carbapenem resistant strains, KPC and MBL activity were not found. On the other hand, 14 strains of K. pneumoniae and one strain of E. coli exhibited OXA-48 b-lactamase activity. Fiftyseven percent of K. pneumoniae isolates produced OXA-48 orginating from two clones and remaining isolates originated from different clones. Thus carbapenem resistance was determined as 22% and 3% in K. pneumoniae and E. coli strains, respectively. Invasive devices, duration of total parenteral nutrition, duration of hospitalization, presence of transfusions, ESBL and multiple drug resistance were found to be risk factors for carbapenem resistance.