Endemic cross-infection in an acute medical ward.

Urine samples from patients on an acute medical ward were examined each week over a three-month period in order to detect endemic cross colonization or infection. The bed positions for each patient in the ward were recorded continuously and the patients cared for by each different nurse team noted. We found an outbreak of urinary colonization/infection with a strain of Klebsiella K8 in nine patients. Two groups of two patients probably suffered cross colonization/infection with different strains of Escherichia coli. These episodes were not detected by our routine laboratory ward liaison surveillance, but by the weekly samples and molecular typing methods applied to these relatively common strains. This survey demonstrates that cross colonization/infection may occur more widely than is normally detected. The implications of these findings to surveillance audit programmes are discussed.