I was surprised today to find a recall of butter because of Listeria monocytogenes being found in it. Anyone who reads this blog, or has read The Safe Food Handbook, knows that these bacteria are quite common in processed foods, including in dairy products, and especially in cheeses. But offhand, I could not recall any instances of it being found in butter in the U.S.
Out of curiosity, I checked back on some of the recall data bases. As I suspected, there have been very few cases of butter being contaminated with anything in the U.S. I located three butter recalls in the last fifteen years - one in Illinois, one in California and one in Nevada. In two out of three of these instances it was the very common Norovirus which was involved. In one, it was Staphylococcus aureus bacteria (which usually gives you a much worse case of food poisoning than does Norovirus).
And in at least two of these cases, the contamination occurred in banquet or restaurant food, which would make you suspect food handlers or poor storage. In other words, they were localized outbreaks, probably not originating at the point where the butter was produced. However, I do know of a sizeable outbreak of Listeria monocytogenes bacteria in butter in the UK in 2003.
So never say "never" in food safety. As soon as you do, it will happen. Beware pregnant women, and anyone else who has a poor immune system. This bacterium can be deadly.
To your good health,