Just reflecting on some recent Listeria spp. recalls in the media. I've worked in chilled foods for a lot of my career and faced into several Listeria spp. issues in plants.
I thought I could share some of my learnings here and then people can chip in with more things that they've learned.
Barrier control for high care and high risk areas
Firstly, barrier control for me. I always approach it with a "how do I know it's working?" mindset. From a cultural perspective (are people actually compliant) to a physical standards point of view (how well are barriers sealed between high care / high risk and low risk?)
In one plant I was working in, once the sh-- hit the fan, the barrier risk assessment was something I reviewed, in practice, with a team.
What looked simple on paper was anything but. We really started to get our heads around what was happening and why. Also what happened when things were out of the ordinary. So for example, if a machine needed repair, we found the engineers (with the best of intentions) were taking that machine out of high risk and repairing it in the workshop. Why? Because they'd had the risks of metal contaminants drummed into them and so wanted to minimise that risk. Little did they know they were then carrying Listeria back into high risk. Despite a decent surface level clean, we'd often find the wheels of machines which had left high risk were then almost impossible to decontaminate (almost, I have another top tip on that though.)
In other places I've seen changing room benches which are open underneath and so when the floor is cleaned on the "low risk" outdoor shoes side, it washes into high care... 
But because that normally happened at about 2am, nobody considered the risk.
I've got many more but I'd be really interested to hear yours!
