Contamination of raw poultry meat by airborne Listeria originating from a floor drain

Poultry processing plants can become colonized with Listeria monocytogenes, resulting in long-term residence in floor drains. Earlier work showed that water spray into a contaminated floor drain causes airborne dissemination of a nonvirulent surrogate, Listeria innocua. The objective of the current study was to determine the extent to which a hose spray can result in the transfer of L. innocua from an established floor drain biofilm to raw poultry meat. Model floor drains were inoculated and subjected to a 2-s water spray during which broiler breast fillets were left uncovered on a table 2.4 m away. Other fillets were indirectly exposed by placement on the table 10 min after the drain spray. The number of Listeria on each fillet was determined on the day of exposure and after 4 d of refrigerated storage. An average of approximately 18 Listeria cells was detected per air-exposed filet; about half that number was detected on indirectly exposed fillets. The number of Listeria did not change substantially during 4 d of cold storage. An inadvertent 2-s spray into a contaminated floor drain could result in transfer of low numbers of Listeria to raw meat on a work surface.