title: Epidemiology of an outbreak of antibiotic-resistant Klebsiella pneumoniae at a tertiary care medical center.
abstract: 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 beta-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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Division of Infectious Diseases, New York Medical College, Valhalla, NY, USA.
authors.forename: Alina
authors.initials: A
authors.lastname: Filozov
authors.forename: Paul
authors.initials: P
authors.lastname: Visintainer
authors.forename: Carol
authors.initials: C
authors.lastname: Carbonaro
authors.forename: Maria
authors.initials: M
authors.lastname: Aguero-Rosenfeld
authors.forename: Gary P
authors.initials: GP
authors.lastname: Wormser
authors.forename: Marisa A
authors.initials: MA
authors.lastname: Montecalvo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D015373:Bacterial Typing Techniques; D016022:Case-Control Studies; D002648:Child; D016000:Cluster Analysis; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D016172:DNA Fingerprinting; D004196:Disease Outbreaks; D024901:Drug Resistance, Multiple, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D005838:Genotype; D006761:Hospitals; D006801:Humans; D007710:Klebsiella Infections / Q000453:epidemiology* / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents