Monday May 21, 2012 Q&A

In which environment do tetanus bacteria proliferate?


1 Rusty old knives

2 The humus present in calcareous soils

3 The mammalian epidermis

Question related image
Answer: the humus present in calcareous soils. Contrary to popular belief, Clostridium tetani is not particularly fond of rusty environments. Actually, the tetanus vector bacteria can be found in large concentrations in humus, with a preference for calcareous soils. However, if you happen to cut your leg with an old plow when walking on a field, your doctor will most likely prescribe you to get a tetanus booster shot. Why so? It's all about probability. A rusty old blade and even more so a plow or a gardening tool have very likely been exposed to soil. In addition, the tetanus bacteria have the property of turning into an inactive but infinitely stronger form: the spore. When dormant, they can settle in the crevices of a rusty blade for several years. In other words, even though the bacillus is not particularly fond of rust, spores find an excellent storage medium in rusty crevices. Even if your old rusty opinel knife has not been used since the last mushroom harvest a few years before, it is still not safe. The vile bacilli await the right moment when conditions become favorable so that they are able to return to their active form and multiply again. For instance, when with a clumsy movement of the thumb you ‘test’ the edge of the blade. Small populations of Clostridium tetani can be found on the skin and in the intestines of herbivorous animals and humans. Unaware of it, and without going through much damage, we thus meet a mortal enemy every day. In France, where vaccination has reduced the number of reported cases by 50, it was fatal for 32% of the 41 people affected between 2005 and 2007, according to the National Institute of Public Health Surveillance. In developing countries, it takes about 500,000 lives a year.