ASSESSMENT OF BACTERIAL CROSS-TRANSMISSION AS A CAUSE OF INFECTIONS IN PATIENTS IN INTENSIVE-CARE UNITS

The prevalence of possible cross-transmission of selected bacteria (Es cherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Pseudomon as aeruginosa, Staphylococcus aureus, and enterococci) among infected patients was evaluated in five intensive care units (ICUs) over 6 mont hs. A total of 284 isolates from clinical specimens were typed by plas mid profile analysis (E. coli, K. pneumoniae, and E. cloacae), restric tion endonuclease analysis of plasmid DNA (S. aureus), and/or pulse-fi eld gel electrophoresis of chromosomal DNA (P. aeruginosa, enterococci , S. aureus, and other bacteria without plasmid DNA). By typing criter ia, only 13% of the 177 isolates obtained after >2 days in an ICU were classified as possibly cross-transmitted. Many patients whose culture s yielded bacteria of an identical type may have been the sources rath er than the recipients of these organisms. Episodes of possible cross- transmission were scattered among all ICUs, usually affected only two patients, and were associated with most bacterial species. These data suggest that endemic bacterial cross-transmission in ICUs is relativel y infrequent and that cross-transmitted bacteria are not common causes of endemic ICU-related nosocomial infections.