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

Abstract

BACKGROUND/OBJECTIVES: <i>Acinetobacter baumannii</i> is a gram-negative, non-fermenting, coccobacillus found in water. This organism is commonly found in the hospital environment and has emerged as an important nosocomial pathogen especially in critical care settings. In June 2003, a significant increase in the number of multidrug-resistant <i>A. baumannii</i> (MDR-AB) isolates was recognized, primarily from critically ill patients located in an acute care hospital (ACH) and a long-term acute care (LTAC) facility contained within the same physical building. This report chronicles the initial appearance and dissemination of these MDR-AB strains. METHODS: <i>A. baumannii</i> was isolated from a total of 229 patients between January 2003 and December 2004. Of these 229 patients, 151(66%) were colonized/infected with MDR-AB. Most isolates were resistant to all antimicrobial agents tested except imipenem and ampicillian/sulbactam. Retrospective analysis of laboratory results found that MDR-AB were uncommon isolates in our hospital until May 2003. Between May 2003 and December 2004, 103/151 MDR-AB collected were studied using molecular-based methods. RESULTS: Sites of infection included: respiratory tract (108, or 72%), SSI (32, or 21%), blood (6, or 4%), and urine (5, or 3%). The index case appeared in March 2003, and the highest monthly occurrence of MDR-AB was in June 2003 (15 cases). The most frequent hospital ward locations were LTAC (70 isolates), ICU step-down (27 isolates), and ICU (26 isolates). Molecular typing using pulsed-field gel electrophoresis (PFGE) showed that 88/103 strains tested (85%) gave an identical banding pattern which was designated as clone A; 8 additional isolates were variants of clone A, and 7 isolates were unrelated to clone A. CONCLUSION: This epidemiologic history illustrates 1) epidemic clonal spread; 2) target patient populations in the critical care settings; 3) variable monthly prevalence; and 4) diminished prevalence with intervention. Infection control departments and laboratories must be vigilant in identifying MDR-AB. With intervention, the number of new isolates decreased in ACH, but not in LTAC. The interventions included dedicating an infection control professional to the critical care units in the ACH, daily surveillance, universal gloving in all affected units, and reporting results to the individual nursing units on a routine basis.