Explain to me how food poisoning from tainted food works

Looking for an explanation of the mechanics of the process.

What happens exactly? Let’s say you have chicken with salmonella or egg salad that’s gone bad.

What exactly happens to the food that makes it dangerous? Is it the bacteria itself, the toxins made by the bacteria… what? What is your body doing in making you vomit and have explosive diarrhea? Is it trying to quasi-intelligently get rid of the bacteria and the toxins, or is this just some kind involuntary reaction?

Does it matter if you only eat a little bit as the toxic bacteria will replicate inside you and make you ill?

Is there some point where your immune system can deal with tainted food if you eat it often enough?

Do these bacteria gain some evolutionary benefit from being poisonous or is that beside the point for their life cycle?

There are two broad categories of food poisoning (although they overlap a bit too); infectious and toxic.

Infectious food poisoning occurs when you ingest a sufficient population of pathogens (such as salmonella) to overwhelm your body’s defences; they reproduce out of control and cause damage to tissues by a number of means, but mainly by secretion of toxic waste products. Eventually, your immune system catches up and wipes them out. Well, either that, or you die.

Toxic food poisoning occurs when you ingest food contaminated with sufficient levels of toxins to cause chemical poisoning of your body. These toxins may have been produced by pathogenic bacteria living in the food (and they may persist even if cooking kills or attenuates the live pathogens), or they could be chemical toxins from other sources such as cleaning materials (at least they lumped this in with toxic food poisoning on my food hygiene courses).

You won’t get ill from ingesting a single pathogenic bacterium; it takes a population of them to get past your defences (although I expect this is a statistcial curve where the likelihood of infection increases continuously with the size of the sample ingested).

No food is really aseptic either; there are probably low levels of food poisoning pathogens in just about everything - they are abundant in soil, dust, animal faeces, human hair and skin, etc, but again, they’re only a problem when you encounter them en masse.

Food poisoning normally occurs when food is improperly handled or stored; the pathogens (both the infectious ones and those that produce residual toxins) require food, moisture, time and warmth to do the damage.
The food they require consists usually of protein-rich items such as meat, dairy, fish, eggs.

So, a typical story would be:
Juices from a defrosting chicken are allowed to drip into a bowl of fresh cream on the shelf below (this is cross-contamination through improper storage); the pathogens present in the chicken will not be a problem, because that will be cooked before consumption, but the cream is whipped and plonked onto some cakes, which are then left unrefrigerated in a room for a couple of hours; by the time they are eaten, the pathogens have multiplied dramatically in the cream and are now present at levels sufficient to cause illness.

To attempt your last two questions; certainly individuals with compromised immune systems are at much greater risk of developing food poisoning and also at much greater risk of death from it, but I’m not sure if you can actually acquire specific immunity to, say, salmonella from regular, low-level exposure.

I can’t think of any specific advantage the pathogens enjoy as a result of making us ill - I suppose explosive diarrhoea and vomiting might help to distribute them a bit, but not in the same way that coughs and sneezes spread the common cold. For the most part, I think the toxins are just a byproduct of massive-scale reproduction and consumption of the infected foodstuff; bacteria shit, if you like.

Thanks! Very informative!

Botulism comes from the toxins. “Botox” is botulism toxin, which paralyzes muscles.

Don’t ever get campilobacter. I did. Shudder.

Oh, one thing that cannot be repeated enough on this topic (but I forgot to): Odour is not a reliable indicator of food safety (in fact neither is taste, texture or appearance); food can stink and be safe, and other food can smell completely normal and contain dangerous levels of pathogens and/or their toxins.
The processes that cause decay and odour do not necessarily progress in proportion to one another.

Worse is Ciguatera
The symptoms can last for months! :eek:

A lot of the toxins you get in food poisoning act as molecular water pumps. They get into your cells and start pumping water from your cells into your gut. Thus, diarrhea.

Also your gut’s self-defence mechanism when irritated is to dump as much fluid as possible in an attempt to eliminate the irritant.

Shigellosis is a particularly nasty diarrhoeal disease, usually caught from drinking water or eating food washed in water contaminated with one of the various Shigella spp, and it only takes a miniscule dose (~10 organisms) to cause the disease. The bacteria attach themselves to the cells lining the gut and destroy them, this results in bloody diarrhoea.

Shigella dysenteriae is a particularly nasty variant because in addition to causing bloody diarrhoea that all the other Shigella species cause through physically invading cells, it produces a toxin called shigatoxin. This toxin enters cells and inhibits protein synthesis causing further tissue damage.

I’ve got to disagree with you. Diarrhoea is an excellent method of spreading yourself about if you’re a bacteria. It’s no coincidence that places with poor sanitation are where most of the serious diarrhoeal diseases (cholera, shigellosis, amoebic dysentary etc) are most commonly encountered.

The faeco-oral route of infection is a pretty effective means of distributing yourself if you happen to be a bacterium, that’s why we wash our hands after using the loo.

Was early canned food a major source of botulism poisoning? i read that one theory about the demise of the 1845 Arctic franklin Expedition, was that the canned food they carried was contaminated with botulism. When cooked at high heat, botulism contaminated food can become safe to eat, but if only warmed, the food is deadly. How common is botulism poisoning today?

I was under the impression that cooking food contaminated with botulism only killed the organisms themselves, not the toxins that actually do you in?

I’d heard expeditions were lost because of lead poisoning instead.

Clostridium botulinum is exceedingly hard to kill as it forms spores which are quite heat resistant (will resist 100C for several hours, and moist heat of 120C for 30+ minutes, which is enough to kill most other microbes). The toxin, botulin, on the other hand is heat labile and will be broken down quite easily during the cooking process.

The problems arise when the canning process is done improperly, the spores contaminate the foodstuff, ‘germinate’ in the can and start producing botulin. You come along, eat straight from the can and then keel over.

You could poke around the CDC’s website to find exact numbers - cdc.gov, if you’re feeling that motivated. But the majority of botulism cases these days come from home canning that hasn’t been processed properly. The FDA requires canners to treat their food to a so-called “12-D” process. In other words, something that would kill 99.9999999999% of any botulism spores present. I’m sure occasional mistakes are made, but for the most part, canned food for sale is plenty safe.