Sludge Watch ==> Salmonella survives better in stomach due to altered DNA

[Maureen Reilly]

Sludgewatch Admin:

Note that the researchers found that an anaerobic environment was a trigger 
for enhanced toxicity of this pathogen.

Anaerobic digestion - as in sewage treatment plants...

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Salmonella survives better in stomach due to altered DNA
30.jan.07
Netherlands Organization for Scientific Research


Since 1995 there has been a considerable increase in the number of 
infections with a specific type of Salmonella bacteria transmitted via food. 
This type, Salmonella serovar Typhimurium DT104, is resistant to at least 
five different antibiotics. Dutch researcher Armand Hermans found new 
genetic information in DNA of DT104 that might be involved in its survival 
and infection mechanism. This genetic information might also be involved in 
the increase in the number of infections caused by this pathogen.
By comparing the DNA of Salmonella serovar Typhimurium DT104 with the known 
DNA code of another Salmonella strain, Hermans found new DNA fragments in 
DT104. These pieces of DNA were found to contain genetic information that 
might play a role in the survival and infectiousness of this pathogen. The 
presence of such extra genetic characteristics can make the pathogen 
stronger and more infectious.
To examine how DT104 behaves to survive various "extreme" conditions, the 
switching on and off of 500 genetic characteristics was studied. This 
happened under different conditions such as in a hot, acid or oxygen-free 
environment. Almost all of the survival characteristics were found to be 
active under all conditions, whereas the pathogenic characteristics were 
only active under a few of the conditions. Therefore this pathogen always 
does everything it can to survive under all conditions, for example, during 
food conservation or in gastric acid. The pathogenic characteristics of 
DT104 on the other hand are only active in the intestines where the 
infection takes place.
Evolution of the pathogen
The DNA of the pathogen says something about how it survives and is 
transmitted. When a pathogen reproduces, the DNA can change a bit and this 
can lead to changes in the genetic characteristics. This can, for example, 
lead to antibiotic resistance but also heat or acid resistance. The 
pathogens with the best genetic characteristics can spread and survive 
better and are therefore more infectious: the evolution of a pathogen. 
Examining which genetic characteristics are present in an infectious 
Salmonella (in this case the DT104 type) can reveal how this pathogen has 
become stronger and caused more outbreaks. This information can also be used 
to make a less dangerous variant of this infectious Salmonella. Such a 
harmless variant can be used as a vaccine.
Salmonella serovar Typhimurium DT104 is an antibiotic-resistant pathogen 
that is transmitted via food and is considered to be dangerous for humans. 
In recent decades the number of infections with this variant has increased 
in many parts of the world. This research was funded by NWO and contributes 
to knowledge about the characteristics and behaviour of this dangerous 
Salmonella.