title: The rising influx of multidrug-resistant gram-negative bacilli into a tertiary care hospital.
abstract: BACKGROUND
  The prevalence of multidrug resistance (MDR) among gram-negative bacilli is rapidly increasing. Quantification of the prevalence and the common antimicrobial coresistance patterns of MDR gram-negative bacilli (MDR-GNB) isolates recovered from patients at hospital admission, as well as identification of patients with a high risk of harboring MDR-GNB, would have important implications for patient care.
  
  
  METHODS
  Over a 6-year period, patients who harbored MDR-GNB (i.e., patients who had MDR-GNB isolates recovered from clinical cultures within the first 48 h after hospital admission) were identified. "MDR-GNB isolates" were defined as Pseudomonas aeruginosa, Escherichia coli, Enterobacter cloacae, and Klebsiella species isolates with resistance to at least 3 antimicrobial groups. A case-control study was performed to determine the independent risk factors for harboring MDR-GNB at hospital admission.
  
  
  RESULTS
  Between 1998 and 2003, the prevalence of MDR-GNB isolates recovered from patients at hospital admission increased significantly for all isolate species (P < .001), with the exception of P. aeruginosa (P = .09). Of 464 MDR-GNB isolates, 12%, 35%, and 53% of isolates were coresistant to 5, 4, and 3 antimicrobial groups, respectively. Multivariable analysis identified age > or = 65 years (odds ratio [OR], 2.8; 95% confidence interval [CI], 1.1-7.4; P < .04), prior exposure to antibiotics for > or = 14 days (OR, 8.7; 95% CI, 2.5 -30; P < .001), and prior residence in a long-term care facility (OR, 3.5; 95% CI, 1.3-9.4; P < .01) as independent risk factors for harboring MDR-GNB at hospital admission.
  
  
  CONCLUSIONS
  A substantial number of patients harbor MDR-GNB at hospital admission. Identification of common coresistance patterns among MDR-GNB isolates may assist in the selection of empirical antimicrobial therapy for patients with a high risk of harboring MDR-GNB.
authors.affiliation: Division of Infectious Diseases, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA. apopvic@bidmc.harvard.edu
authors.forename: Aurora E
authors.initials: AE
authors.lastname: Pop-Vicas
authors.forename: Erika M C
authors.initials: EM
authors.lastname: D'Agata
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000302:isolation & purification*; D016905:Gram-Negative Bacterial Infections / Q000453:epidemiology* / Q000382:microbiology*; D006761:Hospitals; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D015995:Prevalence; D012307:Risk Factors; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents