SURVIVAL OF ACINETOBACTER-BAUMANNII ON DRY SURFACES - COMPARISON OF OUTBREAK AND SPORADIC ISOLATES

Acinetobacter spp. are important nosocomial pathogens reported with in creasing frequency in outbreaks of cross-infection during the past 2 d ecades. The majority of such outbreaks are caused by Acinetobacter bau mannii. To investigate whether desiccation tolerance may be involved i n the ability of certain strains of A. baumannii to cause hospital out breaks, a blind study was carried out with 39 epidemiologically well-c haracterized clinical isolates of A. baumannii for which survival time s were determined under simulated hospital conditions. The survival ti mes on glass coverslips of 22 strains isolated from eight well-defined hospital outbreaks in a German metropolitan area were compared with t he survival times of 17 sporadic strains not involved in outbreaks but rather isolated from inpatients in the same geographic area. All spor adic isolates have been shown by pulsed-field gel electrophoresis to r epresent different strain types. There was no statistically significan t difference between the survival times of sporadic strains of A. baum annii and outbreak strains (27.2 versus 26.5 days, respectively; P les s than or equal to 0.44) by the Wilcoxon-Mann-Whitney test. All invest igated A. baumannii strains, irrespective of their areas of endemicity or epidemic occurrence, have the ability to survive for a long time o n dry surfaces. Antimicrobial susceptibility testing showed that A. ba umannii outbreak strains were significantly more resistant to various broad-spectrum antimicrobial agents than sporadic strains. Both desicc ation tolerance and multidrug resistance may contribute to their maint enance in the hospital setting and may explain in part their propensit y to cause prolonged outbreaks of nosocomial infection.