Epidemiology of an outbreak of antibiotic-resistant Klebsiella pneumoniae at a tertiary care medical center
published online 08 June 2009.
Background
In 2004, a 650-bed, tertiary care medical center experienced an outbreak of multiple antibiotic-resistant Klebsiella pneumoniae (MR-KP) that included extended-spectrum β-lactamase (ESBL)-producing and non-ESBL-producing strains.
Methods
Characteristics associated with MR-KP were evaluated by case-control study with variables tested by conditional regression analyses. Pulsed-field gel electrophoresis (PFGE) was used to compare the molecular relatedness of isolates.
Results
In 2004, the incidence rate of MR-KP increased significantly compared with 2003 (relative risk [RR], 5.1; 95% confidence interval [CI]: 3.10-8.37) when only ESBL-producing K pneumoniae were present. The increase involved both ESBL-producing MR-KP and MR-KP in which ESBL production was not detected by the testing in use. Nineteen isolates were identical or closely related by PFGE. Characteristics associated with MR-KP were longer length of hospital stay (odds ratio [OR], 2.92; 95% CI: 1.17-7.30; P = .022), greater total antibiotic-days (OR, 2.81; 95% CI: 1.19-6.65; P = .018], and higher Acute Physiology and Chronic Health Evaluation (APACHE) II score (OR, 1.15; 95% CI: 1.06-1.25; P = .001). When the MR-KP cases were subdivided into ESBL-producing K pneumoniae and ESBL-negative K pneumoniae, while controlling for length of stay, total antibiotic-days was significantly associated with ESBL-producing K pneumoniae (OR, 3.8; 95% CI: 1.2-12.1; P = .02).
Conclusion
Compared with patients housed on the same unit at the same time, patients with MR-KP had a longer length of stay and greater antibiotic exposure. Patients with longer length of stay and greater total antibiotic exposure should be potential targets for stringent infection control measures.
aDivision of Infectious Diseases, New York Medical College, Valhalla, NY
bDepartment of Epidemiology and Biostatistics, School of Public Health, New York Medical College, Valhalla, NY
cDepartment of Pathology, New York Medical College, Valhalla, NY
Address correspondence to Marisa A. Montecalvo, MD, Division of Infectious Diseases, New York Medical College, Munger Pavilion room 245, Valhalla, NY 10595.
ABSTRACT