Saturday, January 21, 2012

Meet the Clostridiums

I'm copying this from a post I made to the blog for my Disease Ecology class but in terms of microbial biodiversity it's not a bad idea to take a closer look at one particular group of microbes. Clostridium is a group of low-GC gram-positive bacteria. There are only about 100 species but several of importance to humans.

The worst is Clostridium perfringens, the causative agent of gas gangrene - a major cause of death in World War 1, the US Civil War and many wars prior to the invention of antibiotics. Near the top of the list for 'ways not to die' although sadly many soldiers did.

You might also have heard of Clostridium botulinum, or at least of the disease it causes - botulism. Botulism is a paralytic food poisoning that is fortunately rare. The bacteria grow on food and cause harm in people as we digest a toxin produced by the bacteria. The neurotoxin is one of the most powerful toxins known to man, a single microgram is lethal. It is also used (in minute doses!) in the cosmetic treatment known as Botox.

Clostridium tetani is the causative agent of tetanus. The symptoms, muscle spasms and difficulty swallowing are caused by a neurotoxin produced by the bacteria. Infection generally occurs through wound contamination, and often involves a cut or deep puncture wound. Infection can be prevented by immunization, and this is often successful even if given after the wound occurs. Which is why it's a good idea to get a tetanus shot after a deep cut or puncture wound. If you wait to see if an infection develops it is too late for immunization to be much use.

The final member of our bad boys is Clostridium difficile. C. difficile, or just C. diff. is the latest, greatest threat in nosocomial infections and there have been numerous outbreaks lately. Try a google news search on Clostridium difficile to see where the latest outbreak is. C. diff is an interesting bacteria because it is found as a natural part of the gut flora in a small fraction of people, usually with no problems. But if the usual gut flora is eradicated with broad spectrum antibiotics C.diff can greatly increase in numbers and release toxins that cause severe diarrhoea and death in some cases. Some new strains appear to be producing much more toxin. Hospitals are very good places to find people taking broad spectrum antibiotics and, apparently, are good at spreading C.diff around as well.

On the positive side, non-pathogenic strains of Clostridium may help in the treatment of diseases such as cancer. Some strains of Clostridium can selectively target cancer cells and Clostridium could be used to deliver therapeutic proteins to tumours

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