Carbapenem-resistant Klebsiella pneumoniae: Risk Factors for Isolation Among Hospitalized Patients

**Background:** Carbapenem-resistant *Klebsiella pneumoniae* (CRKP) is an important healthcare-associated pathogen. This study aimed to identify factors associated with CRKP isolation among hospitalized patients, describe molecular epidemiology, and mortality associated with CRKP isolation. **Methods:** We performed a case-control study at two university-affiliated teaching hospitals. We included 150 patients (30 cases and 120 controls). Each patient with CRKP, a case-patient, was matched with four controls by admission facility, admission date, age, and sex. Controls, patients without CRKP, were randomly selected from a computerized list of inpatients whose admission date was the same as that of the case, within 48 hours of the date of the initial positive culture. We calculated the risk of in-hospital death as the number of deaths divided by the number of cases and evaluated the risk of mortality associated with the site of positive culture. Molecular epidemiology investigation using comparison of restricted DNA patterns of CRKP by pulsed-field gel electrophoresis (PFGE) was conducted. **Results:** A greater proportion of cases than controls had undergone an invasive procedure, including use of a central vein catheter, or mechanical nutrition by tube feeding. Pre-admission treatment within two months with the following antibiotic classes was associated with CRKP isolation: carbapenems, fluoroquinolones, anti-pseudomonal penicillins, and cephalosporins. The molecular analysis indicated that over 90% of isolates shared similar PFGE patterns. CRKP isolation was associated with significantly higher in-hospital mortality in comparison to controls. Positive cultures from sites other than urine were associated with substantially higher mortality than was a positive urine culture (RR= 4.0). **Conclusions:** The use of multiple broad-spectrum antibiotics, multiple comorbid conditions and poor performance status are important risk factors for developing CRKP in a hospitalized population.