Major Article
Emergence of resistant Acinetobacter baumannii in critically ill patients within an acute care teaching hospital and a long-term acute care hospital

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Background

Acinetobacter baumannii is a gram-negative, coccobacillus found in water and is a significant nosocomial pathogen in hospitals. This report chronicles the appearance in June 2003 of a multidrug-resistant A baumannii (MDR-AB) strain, its dissemination, and interventions used to control it in an acute care hospital (ACH) and long-term acute care facility (LTAC).

Methods

Molecular typing using pulsed-field gel electrophoresis (PFGE) showed that 88 of 99 strains (89%) gave an identical banding designated as clone A. Eight additional isolates were variants of clone A, and 3 isolates were unrelated.

Results

A baumannii was isolated from 229 patients between January 2003 and December 2004. Of these patients, 151 (66%) were colonized/infected with MDR-AB. Most isolates were resistant to antibiotics except for imipenem and ampicillin/sulbactam. Isolates included 108 (72%) in the respiratory tract, 32 (21%) in wounds, 6 (4%) in blood, and 5 (3%) in urine. Most isolates were found in the LTAC (70 isolates), ICU step-down (27 isolates), and ICU (26 isolates).

Conclusion

This epidemiologic history illustrates (1) epidemic clonal spread, (2) target populations, (3) variable monthly prevalence, and (4) intervention outcomes. With intervention, the number of new isolates in the ACH decreased by dedicating an infection control professional to critical care, daily surveillance, isolation of positive MDR-AB patients, universal gloving, and routinely reporting results.

Section snippets

Organism identification

Using standard commercial identification systems, 229 AB isolates were identified in the clinical microbiology laboratory between March 2003 and December 2004. Of the 229 isolates, 151 (66%) were (MDR-AB).

Susceptibility testing

Initial susceptibility testing was performed by either disk diffusion or broth microdilution using a commercially prepared panel (DADE Microscan, West Sacramento, CA). Isolates were considered to be MDR-AB if they were sensitive to 3 or less antibiotics. A notable characteristic was that all

Results

Age and sex demographics show a total of 86 men ranging in age from 22 to 85 years and 65 women ranging in age from 34 to 84 years. Sources of isolates were respiratory tract, 108 (72%); wounds, 32 (21%); blood, 6 (4%); and urine, 5 (3%). An epidemiologic review of MDR-AB isolates revealed that 20% of the ventilator-associated pneumonias (VAPs) reported in 2003 and 22% of the VAPs in 2004 were associated with MDR-AB. A low percentage of bloodstream infections (BSIs) and surgical site infections

Discussion

To control the spread of this organism in the ACH, a 3-fold team approach was initiated. This approach included (1) the Microbiology Department's rapid preliminary identification and notification to the Infection Control Department, (2) the placement of all new patients with positive isolates into contact precaution,4 and (3) the notification of attending physicians of the increased occurrence of MDR-AB.

The original infection control precautions—isolation of patients into private rooms, contact

Conclusion

MDR-AB, in agreement with the experience of others,6 is primarily a respiratory organism, with the majority of the isolates found to be colonizers rather than causing disease. The organism is very resistant to most antibiotics, but we do not believe it to be highly pathogenic. The incidence of new cases was as high as 15 isolates in June of 2003 and as low as 3 isolates in each of the months of March, April, and June of 2004. The LTAC appears to have been an ongoing reservoir for

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Supported by MERCK and Co., Inc. with a research grant.

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