Dangerous bacteria

[MarkE]

It is known that some bacteria are dangerous ONLY when they're in the wrong place, f.i. E. Coli. Does anyone know some more examples?

[CharonY]

I do not know what you mean by that. Could you elaborate? Non-pathogenic E. coli strains such as K12 are harmless pretty much everywhere (except in huge concentrations). Or do you mean inside the body? In that case pretty much anything is bad news if for some reasons it reaches the brain, for example. But this is one major factor that distinguishes harmless and pathogenic bacteria. The former are unable to mount successful infections.

Edited January 16, 2015 by CharonY

[MarkE]

E. Coli's natural habitat inside the body is the lower intestine. That's his place, because outside it, he can be harmful. So it's not a harmful bacterium in defenition, only when it resides at the wrong place.

 

I meant if there are any examples of other bacteria, who's natural habitat is f.i. the liver, and outside it, it can be harmful. Does anyone know such an example?

[MarkE]

For instance, Prevotella, Sphingomonas, Streptococcus are bacteria that belong to our lungs. Bacteroides pneumosintes belong to our pharynx, Acinetobacter calcoaceticus and Acidaminococcus fermentans to our large intestines, Bacterionema matruchotii to our gingiva, Citrobacter freundii to our sputum, the list goes on and on. They are not dangerous in their own area, but my question is if some of them are, just like E. Coli, dangerous outside their own area, and instead, inside an other one.

Edited January 19, 2015 by MarkE

[CharonY]

E. Coli's natural habitat inside the body is the lower intestine. That's his place, because outside it, he can be harmful. So it's not a harmful bacterium in defenition, only when it resides at the wrong place.

 

I meant if there are any examples of other bacteria, who's natural habitat is f.i. the liver, and outside it, it can be harmful. Does anyone know such an example?

 

I have to expand your view on what is dangerous (let us say pathogenic) or not in this context, because that is the main aspect of your misunderstanding here). There are harmless E. coli and pathogenic ones. The reason some are pathogenic is not because they are suddenly invading parts of your body, but because they have the ability (typically genes associated with virulence) that allows them to do so. That includes secretion of toxins and/or invasion of host cells. For example, K12 cannot cause diseases by itself, whereas EHEC strains, which are also E. coli, can.

 

That aside, in immunocompromised patients, a lot of otherwise apathogenic bacteria can cause issues, but that is probably not what you are asking for.

 

In short, localization and associated disease are just a symptom, bacteria got there because they a) have the ability to do so (goes for all pathogenic strains) or b) the host is compromised in some way that allows passage of otherwise harmless bacteria.

 

As a general rule of thumb, all bacteria are harmful once they get into our body. Remember, lung, skin, gut are all physiologically outside and present a barrier to bacteria entering our blood stream.

[animodel123]

The bacteria listed below cover a range of diseases and levels of resistance. All of them present a threat to humans in some way or another. Some, like Tuberculosis for example, are already a huge challenge to overcome in their own right and will only become harder to control as their resistance to antibiotics grows.

Staphylococcus aureus (MRSA)

Burkholderia cepacia

Pseudomonas aeruginosa

Clostridium difficile

Klebsiella pneumoniae

Escherichia coli (E.coli)

Acinetobacter baumannii

Mycobacterium tuberculosis

Neisseria gonorrhoeae

Streptococcus pyogenes

[BabcockHall]

I am not a medical doctor. If one has a serious abdominal injury, my understanding is that presumably nonpathogenic strains of E. coli are released into areas that they ordinarily are not found and that this is dangerous. Offhand, I don't know of other similar examples, but it would not surprise me if they exist.

Edited March 25, 2015 by BabcockHall

[CharonY]

Significant amount of bacteria in your bloodstream, regardless of whether they are pathogenic or not is bad news. At minimum it will trigger widespread immune responses/inflammation (sepsis).