PLASMID DNA PROFILES OF ACINETOBACTER-BAUMANNII - CLINICAL-APPLICATION IN A COMPLEX ENDEMIC SETTING

OBJECTIVE: To study the epidemiological, microbiological, and clinical features of infections due to Acinetobacter baumannii in a complex en demic situation over an 18-month period and to determine the clinical usefulness of plasmid DNA analysis of A baumannii in epidemiological i nvestigations. DESIGN: Review of medical and laboratory records. Antib iotic resistance patterns, biotyping, and plasmid profile analysis wer e used to characterize clinical and environmental isolates. Pulsed-fie ld gel electrophoresis (PFGE) of chromosomal DNA was performed to veri fy results obtained with the other typing methods. SETTING: Four diffe rent intensive care units of an 800-bed tertiary care center in Cologn e, Germany. RESULTS: 240 patients were colonized or infected with A ba umannii during the study period. No seasonal variations were observed. The majority of isolates (53%) were recovered from the respiratory tr act. Major infections occurred in 61 patients; these included 48 bacte remias and eight pulmonary infections. Five different epidemic strains were identified: one each was A baumannii biotype 2 and 6, and three were biotype 9. A baumannii biotype 9 accounted for the vast majority of isolates (88%), which were clustered into three epidemic strains de monstrating distinct plasmid profiles. Two of these were considered ge netically related as shown by PFGE. Epidemic strains were multidrug re sistant, being uniformly susceptible to imipenem only. An epidemiologi cal investigation failed to identify any point source of infection. Ba rrier precautions and improved handwashing was instituted in three of the four units and significantly reduced the incidence of colonization and infection in these units. Attack rates remained unchanged, howeve r, in the burns unit where control measures were not implemented. CONC LUSIONS: Acinetobacter strains representing multiple biotypes and plas mid types were present in this endemic setting. Multidrug resistance i n A baumannii is an important concern. Plasmid DNA analysis proved to be useful in epidemiological typing of A baumannii strains and may ser ve as a complementary typing system to traditional epidemiological met hods.