Retrospective analysis of multidrug-resistant Acinetobacter baumannii strains isolated during a 4-year period in a university hospital

OBJECTIVE. To describe the epidemiology of Acinetobacter baumannii infection during 2000-2003 and to determine whether the multidrug-resistant strains were already present in our Toulouse hospital before the 2003 French national outbreak. DESIGN. Descriptive molecular and clinical epidemiologic study of A. baumannii isolates using a combination of antibiotyping and pulsed-field gel electrophoresis ( PFGE). SETTING. A 1,000-bed university hospital in Toulouse, France. METHODS. All clinical samples that had tested positive for A. baumannii between January 1, 2000, and December 31, 2003, were collected. Multidrug-resistant isolates of A. baumannii were then submitted to PFGE, and clinical characteristics of the source patients were noted. RESULTS. A total of 1,277 A. baumannii samples were identified, 791 of which had not been previously identified; 148 were positive for multidrug-resistant strains. These strains were more likely to have been isolated in the intensive care unit ( ICU) than were susceptible strains (; relative hazard, 3.77). The positive clinical samples were of various types ( eg, nonprotected respiratory samples [ 43%] P < .001 and blood [ 5%]), but no difference in type of source was seen between resistant and susceptible strains. A simultaneous analysis of pulsotypes and antibiotypes proved that the outbreak in the ICU in 2003 could be linked to an initially endemic clone that had been isolated in 2001. Furthermore, a second clone responsible for an extended-spectrum beta-lactamase phenotype was sporadically present in our institution. Although the strains isolated in the burn unit were also genetically related one to another, the specific responsible clone only appeared in 2003. CONCLUSION. Several multidrug-resistant clones can coexist endemically for several years and can be detected during an outbreak by close survey of epidemic sources.