Does stomach acid kill all bacteria that you eat?

[ForMyThunder]

Does stomach acid kill all bacteria that you eat? If it does, then how do we get food poisoning?

 

[bobze]

Does stomach acid kill all bacteria that you eat? If it does, then how do we get food poisoning?

No it doesn't kill them all. Some bacteria are more resistant to changes pH than others, some have ion pumps for dealing with changes in pH, others can form spore coats very resistant to changes in pH, others still can make toxins that survive the trip through the stomach (S. aureus for example). Ones that can survive the trip through the stomach, get a much more comfortable pH in the beginning of the small intestine, where they can start to proliferate.

Whether or not you get food poisoning depends on a number of factors. You have bacteria that normally live throughout the GI and part of their benefit is to out-compete any potential pathogens that may try and grow there. Taking broad-spectrum antibiotics for too long, or taking antibiotics when they are not needed can kill off these friendly bacteria and make room for the not so friendly types that maybe slower growing (like C. difficile).

If that pathogen can get through the stomach and if it can get a foothold it can potentially make you sick. How it does that is again, very diverse. Some organisms actually invade your intestinal epithelium (like enterohemorrhagic E. coli) , others make toxins which disrupt your epithelium (like diphtheria and cholera), etc

 

[Ken Natton]

If I might add something bobze… Another point that I think would aid your understanding ForMyThunder is that relationships between organisms can also evolve. That is, relationships that essentially begin as parasitic can become symbiotic. Initially, there is an evolutionary arms race where the host species develops a resistance to the parasite, and the parasite develops a response to that resistance. This process may be iterated many times before a peaceful symbiosis results. So there are types of bacteria that today we would regard as ‘friendly’ that in the past might have made our ancestors very sick. Am I correct in my understanding bobze, that even within the classification ‘E-coli’ there are some strains with which we have a symbiotic relationship and others that can make us very sick indeed?

 

[SW VandeCarr]

In the case of staphylococcal food poisoning, bacterial toxins rather than the bacterium itself causes the symptoms. A case in point is in re-freezing uncooked fish or poultry that has fully thawed. If the meat is subsequently re-thawed, cooked and eaten, there is a risk of this type of food poisoning even if the meat is well cooked because the toxins are not always degraded at cooking temperatures.

Salmonella (non typhoid) food poisoning, on the other hand, occurs because the bacterium is acid resistant as bobze described. This is probably the most common source of food poisoning in the North America and Western Europe.

http://www.merckmanuals.com/home/sec09/ch122/ch122c.html

 

[bobze]

In the case of staphylococcal food poisoning, bacterial toxins rather than the bacterium itself causes the symptoms. A case in point is in re-freezing uncooked fish or poultry that has fully thawed. If the meat is subsequently re-thawed, cooked and eaten, there is a risk of this type of food poisoning even if the meat is well cooked because the toxins are not always degraded at cooking temperatures.

Salmonella (non typhoid) food poisoning, on the other hand, occurs because the bacterium is acid resistant as bobze described. This is probably the most common source of food poisoning in the North America and Western Europe.

http://www.merckmanuals.com/home/sec09/ch122/ch122c.html

That was the S. aureus for example By the way, I've dabbled with that before, worst 24 hours of my life! I also knew a grad student who worked with staph toxins and (like the discover) accidentally dossed himself with some. That stuff is really potent.

 

[Andy Resnick]

Does stomach acid kill all bacteria that you eat? If it does, then how do we get food poisoning?

Some bacteria must survive passage through the digestive tract; that's how our gut gets populated with flora.

http://www.textbookofbacteriology.net/normalflora.html