Influence of Listeria innocua on the attachment of Listeria monocytogenes to stainless steel and aluminum surfaces

- Listeria innocua outgrew Listeria monocytogenes in co-culture conditions.
- L. innocua decreased attachment of L. monocytogenes on surfaces.
- No difference was noted between attachment to stainless steel or aluminum.

Listeria monocytogenes is an important foodborne pathogen that may be transmitted from the food-processing environment to food; however, the ecology and interaction of this organism with microbial residents on surfaces within the food industry is not well understood. The current study was undertaken to investigate the influence of Listeria innocua on the growth and attachment of L. monocytogenes to stainless steel or aluminum surfaces at 23 °C. When grown in broth as a mixed culture, L. innocua reached a higher cell count at 24 h than did L. monocytogenes. Attachment was evaluated by placing an aliquot containing 103 CFU/ml of L. innocua and 103 CFU/ml of L. monocytogenes on the coupons and by quantifying attached cells after 24 and 72 h. Attachment of L. monocytogenes was decreased by the presence of L. innocua. When compared to L. monocytogenes alone, there was a significant reduction of attachment of L. monocytogenes at 24 and 72 h on stainless steel and 72 h on aluminum surface when L. innocua was added at the same time. L. innocua exhibited an effect on the attachment of L. monocytogenes, increasing our knowledge of the behavior of L. monocytogenes in the presence of another Listeria species.