Wednesday, March 12, 2008

There's Bacteriophage in my Bologna

Listeria is a bacterial contaminant of food and while infection is rare, it has a higher mortality rate than Salmonella. Infection may be rare, but the bacteria itself isn't and it can grow at low temperatures, meaning even when refrigerated Listeria can multiply on contaminated food. Of particular concern are foods that aren't cooked or reheated before eating - like the bologna or deli-sliced ham on your sandwich at lunch. Two recent scares at New Zealand hospitals have lead to quarantine of certain ready-to-eat foods after positive Listeria tests as a precautionary measure.

But if Listeria is everywhere and it persists under normal food storage conditions, why aren't infections more common? Well, for one thing, companies do their utmost to eliminate bacterial growth niches in their processing plants - especially after a "kill" step (eg. cooking) - by sanitary design (eliminating nooks and crannies that are difficult to clean) and proper cleaning, followed by other quality control testing. In 2006 (old news, I know), the FDA approved another tool for use in an anti-Listeria arsenal: bacteriophage.

Bacteriophage are bacteriolytic viruses and have a history of use as an antibiotic in the Soviet Union and Eastern Europe. Bacteriophage is the bane of some food making (and other) processes - those based on bacterial fermentation, such as yogurt production. For Listeria management it was approved and recognized as a safe food additive by the FDA in August, 2006. The phage used is a mix of 6 different forms used to target different Listeria strains and to minimize development of resistance. The phages themselves are grown in Listeria and purified before being applied just prior to packaging. The FDA has a FAQ about the bacteriophage additive. (Unfortunately I couldn't find any information about phage use in Canadian food manufacturing, or if there was an uproar in the US when the decision was made) This decision opened the door for other phage uses in the food industry, such as controlling E. coli or Salmonella in a similar way. The designation as 'safe' may also help resurrect the idea of using bacteriophages as antibiotics, particularly to combat emerging superbugs (MRSA).

So there you have it - that turkey sandwich you had for lunch may be a turkey and phage sandwich, so keep it away from your probiotic yogurt.


3 comments:

monado said...

Thanks! Food safety in particular and microbiology in general seem to be neglected topics in the blogosphere.

Epicanis said...

(Is it just me, or does "blogger.com" seem to have an awful lot of trouble with posted comments? FOURTH try...)

"keep it away from your probiotic yogurt."

No worries - like other viruses, Listeria-infecting phage should have no effect whatsoever on the Lactobacillus, Streptococcus, Leuconostoc, Lactococcus, etc. bacteria used for yogurt, though each yogurt species does have its own viruses to worry about, especially in the concentrated environment of an industrial microbiology production setup.

Interestingly, this doesn't seem to be an issue for yeast at all[1]. Something to do with all the yeast sex that goes on, evidently[2].

(Monado posted:)"Food safety in particular and microbiology in general seem to be neglected topics in the blogosphere."

I agree so much that it's mostly what I blog about (so I hope everyone will forgive me for promoting my blog in this comment...)

[1]Yeast Herpes!

[2]Hot "a" on "α" action

[2] http://www.bigroom.org

kamel said...

No worries - like other viruses, Listeria-infecting phage should have no effect whatsoever on the Lactobacillus

Yeah, I know. It was an attempt at humour, but good point. Nice blog, BTW.

Modano, glad you enjoyed the post.