I am not in the (Enoki) mushroom business, but Listeria is an pathogen who thrives well in many different environments. Including soil, packaging lines, fridge temperatures. And thus also especially well cutting/packaging facilities.
Pre-packaged vegetables are always susceptible to Listeria Monocytogenes. Because the raw vegetables can be contaminated with Listeria Monocytogenes. By cutting/packaging the Listeria Monocytogenes can infect the production line. And the infected line can in return infect all products produced on it. There is also no additional kill step in raw vegetables which can eliminate the problem. Thus causing a recall in some cases.
Most large production facilities will implement positive release, in which they will analyse all products on Listeria Monocytogenes before releasing it into the market.
So perhaps it is not just a (enoki) mushroom problem, but a pre-packaged food problem.