PSEUDO-OUTBREAK OF LISTERIOSIS ELUCIDATED BY PULSED-FIELD GEL-ELECTROPHORESIS

Listeria monocytogenes was isolated from three patients hospitalized i n two departments of the same hospital over a two-week period, A nosoc omial outbreak of listeriosis was suspected, Patients presented with t enosynovitis, central venous catheter infection, and bacteremia. The f irst patient had a community-acquired infection, the second a nosocomi al infection, and the source of: the third patient's illness was uncer tain. Epidemiological investigations failed to identify a common sourc e of contamination within the hospital. The three strains were nontype able by phage typing, but SmaI macrorestriction analysis and pulsed-fi eld gel electrophoresis yielded three distinct profiles, Therefore, th e three cases seemed to represent a cluster of sporadic cases as oppos ed to an outbreak break of listeriosis, Rapid typing oi isolates is es sential in the early investigation of potential outbreaks of listerios is and may prevent the initiation of expensive and lime-consuming epid emiological investigations.