Listeria contamination of food

Listeria monocytogenes remains the leading cause of microbiological food recalls in Australia. Identifying the exact source of contamination is often challenging and, in many cases, cannot be conclusively proven. High-risk zones in food processing environments typically begin with drains and floors, which are common reservoirs for Listeria. Cross-contamination from these areas is frequently suspected, even though the precise mechanism of transfer to the product can be difficult to determine.

Equipment that is in contact with, or positioned close to, the floor also presents a significant contamination risk. This includes trolley wheels, pallets, tank footings, and other low-level processing equipment.

Any damage, pitting, or rust on equipment compromises cleanability, creating niches where pathogenic microorganisms can survive and proliferate. Effective cleaning is critical for minimising cross-contamination; all surfaces must be well-maintained, free from defects, and fully accessible. Cleaning and sanitising procedures must be performed correctly and consistently.

Finally, operator awareness is essential. Understanding Listeria and other harmful microorganisms—such as their potential harbourage sites and routes of cross-contamination—is a vital component of any robust Listeria control and management program within a food processing facility.