Carbapenem-Resistant Klebsiella pneumoniae Outbreak in an Israeli Hospital

Chris Berrie, MA, MPhil, PhD

April 04, 2007

April 4, 2007 (Munich, Germany) — Despite the implementation of important infection control measures, an outbreak of carbapenem-resistant Klebsiella pneumoniae (CRKP) has emerged as an important pathogen in an Israeli university hospital.

Khetah Hussein, MD, internist and resident in infectious diseases in the Infectious Diseases Unit, University Hospital, Rambam Health Care Campus, in Haifa, Israel, presented this case-control study here at the joint 17th European Congress of Clinical Microbiology and Infectious Diseases and 25th International Congress on Chemotherapy.

Over the past 10 years, a progressive increase in CRKP has been seen worldwide, and as Dr. Hussein told Medscape, "At the start of 2006, we discovered that we were at the beginning of an outbreak of carbapenem-resistant Klebsiella pneumoniae," and the outbreak has now spread to "all of the hospitals in Israel now," he said.

In April 2006, four possible index cases were identified. Three of these were hospitalized on 2 orthopaedic wards, and the other had been admitted with a wound infection due to CRKP after renal transplantation outside Israel. All of the isolates were found to be susceptible to colistin and gentamycin but resistant to all of the other antibiotics tested.

For this study, the patients in the hospital who were infected or colonized with CRKP after January 2006 were defined as the cases. Controls were drawn from patients in the hospital who were infected or colonized with a carbapenem-sensitive strain of K pneumoniae on the same day as each case. Only those patients with nosocomial isolates were included in the study, and their epidemiological and clinical data were extracted from their medical records.

In October 2006, by which time the outbreak had spread to 16 wards, a total of 867 patients with K pneumoniae had been identified; of these, 48 (5.5%) had CRKP. With the cases showing a mean age of 55.4 years (median, 57 years), there was a trend toward older patients in the control group (n = 48), with a mean age of 63.6 years (median, 70.5 years), although this did not reach statistical significance ( P = .09).

A comparison of the comorbidities across the patients in the study, which included diabetes, lung disease, malignancy, trauma, and burns, showed no significant difference between the cases and controls.

The initial analysis for risk factors for CRKP in this hospital indicated that CRKP acquisition was significantly more likely in those who were admitted to the general intensive care unit (ICU) ( P < .001); had central venous catheterization ( P = .007), had mechanical ventilation ( P = .008), had a longer length of stay before K pneumoniae isolation ( P < .001), or received imipenem and vancomycin treatment ( P < .0001).

In the multivariate analysis, 3 factors were seen to remain significantly associated with acquisition of CRKP: admission to the ICU (odds ratio [OR], 3.5; 95% confidence interval [CI], 1.3 - 9.5; P = .01), length of stay longer than 7 days (OR, 3.2; 95% CI, 1.0 - 11.0; P = .05), and previous treatment with vancomycin (OR, 5.1; 95% CI, 1.5 - 17.9; P = .01).

When questioned about the significance of previous vancomycin treatment, Dr. Hussein said, "It was something that was very surprising for us.... It may be an indicator of the treatment with a lot of antibiotics, and so may be an indicator of the severity of the situation.... We can't find any cross-resistance between vancomycin and carbapenem."

Molecular characterization was carried out on15 of the isolates using pulse-field gel electrophoresis. This indicated that these isolates were genetically related and that they were different from 2 other CRKP isolates previously identified in that hospital.

The study received no commercial support and the authors report no relevant financial relationships.

Joint 17th European Congress of Clinical Microbiology and Infectious Diseases, and 25th International Congress of Chemotherapy: Abstract P1704. Presented April 2, 2007.

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