Zombie thread!
I've got too much experience for this.
What is the best practice for cleaning a floor with listeria? Normally I would clean from the swab site to a 12 foot circle branched out. Would it be better to clean the entire rooms floor or just the effected area, and use cluster swabbing or branch out swabbing to see if there is a directional path for the listeria?
Why would you not clean your floors regularly assuming Listeria is there? Why only clean once the swab has been found? So no, I wouldn't just clean the affected area. I would clean all.
Swabs will not pick up all presence of Listeria so while starburst / circle swabbing can sometimes tell you interesting things, it cannot prove absence. So please stop chasing it round your floors with swabs. Deal with it now!
My recommendation for cleaning effectively for Listeria would be:
Remove all food contact equipment as much as you can.
Remove gross debris. Brush and shovel etc. Remove waste from drains and replace drain grids.
Apply detergent, ideally as a foam which clings to the surface (talk to your manufacturer for advice on foamers and set up). During the contact time I WOULD scrub despite advice above. Yes you will get minor splashing but no scrubbing = biofilms. YOU MUST SCRUB! You will not break down the soil without it.
The scrubbing time must allow 20-30 minutes contact minimum.
Then rinse with low pressure water. A tote bin with a tap on it can be helpful for this. Do not use high pressure from a hose due to aerosols. If you do use a hose make sure the water is just running out with zero pressure.
Squeegie water to drain.
Now change PPE and use specific brushes and equipment (we always used brown) to clean the drain, bung and trap. Soak in detergent etc, scrubbing. Do not obviously do this in a sink. Use a bucket only used for drains. Rinse. Replace. (Biofilms often happen in drain traps because of people not cleaning drains as a specific activity.)
Change PPE (ideally all disposable and non.)
If you have cleaned equipment in the area this is the time to disinfect everything (it's belt and braces too in case there was any splashing on your floors.)
If you REALLY have a problem, disinfect with hypochlorite first. If it's been a problem on your machines, then disinfect on them too.
Wait, c. 15 minutes then rinse, low pressure water etc.
Then apply disinfectant again (you don't have to disinfect twice but trust me, this is GMO's method for getting on top of Listeria, if you have a problem, it's worth it.) Depending on the country, you might or might not be able to use Quats and leave them on. If you can, use them, they're superb against Listeria. Even if you're in the EU or UK, I'd be tempted to use them on the floor and use biguanides or similar on food contact. Then if your process, legislation permits, leave them on.
A small word on application of disinfectants. There are some plants that use the "bucket and chuck it" technique. Don't. Most ends up straight to drain. Use a tote bin for the hypo with slow release to the floors then a specific disinfectant sprayer for your equipment and floor with your quat or biguanide.
Steam does have it's place but not on floors. You never get the temperatures you need. I would use the Maple Leaf foods technique on steam bagging though for equipment.