Teh Gross: Pork farms

Um, let's see. There's this article that I recently read in Rolling Stone about American swine farms. Here's an excerpt:

Taken together, the immobility, poisonous air and terror of confinement badly damage the pigs' immune systems. They become susceptible to infection, and in such dense quarters microbes or parasites or fungi, once established in one pig, will rush spritelike through the whole population. Accordingly, factory pigs are infused with a huge range of antibiotics and vaccines, and are doused with insecticides. Without these compounds -- oxytetracycline, draxxin, ceftiofur, tiamulin -- diseases would likely kill them. Thus factory-farm pigs remain in a state of dying until they're slaughtered. When a pig nearly ready to be slaughtered grows ill, workers sometimes shoot it up with as many drugs as necessary to get it to the slaughterhouse under its own power. As long as the pig remains ambulatory, it can be legally killed and sold as meat.

Yeah. Totally gross.

Of the four antibiotics mentioned in the article, only oxytetracycline is used in human medicine to prevent/treat bacterial infections. This drug is produced by a soil bacterium (Streptomyces rimosus) and was first isolated in 1953. Tetracyclines are broad-spectrum (work against a wide variety of bacteria) and do their thing (inhibiting the growth of bacteria) by reversibly binding to ribosomes (protein manufacturing centres found within cells) and inhibiting the production of bacterial proteins. Oxytetracycline is particularly awesome because it is used to treat bacterial infections affecting honey bee larvae.

Draxxin is actually a trade name for a drug called tulathromycin, which belongs to a new subclass of macrolide antibiotics (the best known drug of this class is erythromycin, mechanism of action is inhibition of protein synthesis) and is used primarily to prevent/treat SRD and BRD (swine/bovine respiratory disease, a broad term encompassing fun things like pneumonia). Apparently an entire treatment course can be administered by a single subcutaneous (under the skin) injection.

Ceftiofur is a broad-spectrum cephalosporin, meaning that it acts in a similar manner as penicillin, inhibiting the construction of an important component of the cell walls of bacteria called peptidoglycan. Ceftiofur, like tulathromycin, is administered solely by injection (intramuscular, or into a large muscle, in this case) and is mostly used to treat respiratory disease in cows and pigs.

Tiamulin is a broad-spectrum pleuromutilin that is is injectible (intramuscular), slows bacterial growth by inhibiting protein synthesis, and is particularly good at inhibiting the growth of bacteria belonging to the genera Brachyspira and Mycoplasma. Mycoplasma are nifty because they don't have a cell wall, a thing most other bacteria are in possession of.

A trend worth noting: most (and possibly all) of these antibiotics are broad-spectrum and administered by injection. Which makes sense, since you want to be able to prevent/treat as many types of bacterial infections as possible and have a relatively convenient method of doing so. The problem with this approach is that it selects for the survival of numerous strains of bacteria that are resistant to the drugs being used. Ick.

http://en.wikipedia.org/wiki/Oxytetracycline