Determination of an Effective Sanitizing Procedure for Listeria innocua in Personal Protective Equipment Used in...

The presence of Listeria monocytogenes in the dairy environment remains a food safety challenge. The source of microbial contamination may include employees and their personal protective equipment (PPE). This study investigated the effectiveness of cleaning protocols (i.e., detergents and mechanical action) and three chemical sanitizers commonly employed at dairy facilities against Listeria innocua contamination on different types of gloves, aprons, and boots. Coupons made of PPE material were inoculated with a two-strain cocktail of L. innocua suspended in either Phosphate Buffered Saline (PBS) or skim milk to determine the potential effect of organic matter. In general, peroxyacetic acid (0.20% (v/v)) was more effective at reducing Listeria counts on aprons and gloves compared to chlorine and quaternary ammonium at 200 ppm. Depending on the type of sanitizer, Listeria reductions ranged from 1.95 to 4.72 and 1.52 to 4.60 log CFU/in² on aprons and gloves, respectively. In comparison, sanitizers achieved a 0.93-2.32 log CFU/in² reduction on boot soles, with no significant differences observed among sanitizers. PVC (vinyl) gloves achieved lower Listeria log reductions than nitrile and latex gloves. Sanitizers were less effective on boots with wider and deeper lugs than those with shallow lugs. The presence of organic matter significantly reduced the antimicrobial efficacy of all sanitizers (<1 log CFU/in² reduction). However, the inclusion of cleaning protocols with and without mechanical action achieved a ≥3 log CFU/in² reduction in the different types of PPE. This study highlights the importance of scrubbing as an essential step to reduce Listeria on PPE.