Many pathogenic bacteria are easily grown on nutrient agar, a form of solid medium that supplies carbohydrates and proteins necessary for growth, along with copious amounts of water. A single bacterium will grow into a visible mound on the surface of the plate called a colony, which may be separated from other colonies or melded together into a "lawn". The size, color, shape and form of a colony is characteristic of the bacterial species, its specific genetic makeup (its strain), and the environment that supports its growth. Other ingredients are often added to the plate to aid in identification. Plates may contain substances that permit the growth of some bacteria and not others, or that change color in response to certain bacteria and not others. Bacteriological plates such as these are commonly used in the clinical identification of infectious bacterium. Microbial culture may also be used in the identification of viruses: the medium, in this case, being cells grown in culture that the virus can infect, and then alter or kill. In the case of viral identification, a region of dead cells results from viral growth, and is called a "plaque". Eukaryotic parasites may also be grown in culture as a means of identifying a particular agent.In the absence of suitable plate culture techniques, some microbes require culture within live animals. Bacteria such as Mycobacterium leprae and Treponema pallidum can be grown in animals, although serological and microscopic techniques make the use of live animals unnecessary.
Once larvae have broken through the skin,
they enter the bloodstream and are carried to the lungs (however, unlike ascarids, hookworms do not usually cause pneumonia). The larvae migrate from
the lungs up the windpipe to be swallowed and carried back down to the
intestine. If humans come into contact with larvae of the dog hookworm or the
cat hookworm, or of certain other hookworms that do not infect humans, the
larvae may penetrate the skin. Sometimes, the larvae are unable to complete their
migratory cycle in humans. Instead, the larvae migrate just below the skin
producing snake-like markings. This is referred to as a creeping eruption or
cutaneous larva migrans. Diagnosis
They commonly infect the skin, eyes, and viscera in humans. Ancylostoma brasiliensis causes cutaneous larva migrans. Toxocara causes visceral larva migrans. Prevention
Control of this parasite should be directed against reducing the level of
environmental contamination. Treatment of heavily infected individuals is one
way to reduce the source of contamination (one study has estimated that 60% of
the total worm burden resides in less than 10% of the population). Other
obvious methods are to improve access to sanitation, e.g. toilets, but also
convincing people to maintaining them in a clean, functional state, thereby making
them conducive to use. Treatment
The drug of choice for the treatment of hookworm disease is mebendazole which is effective against both species, and in addition, will remove the intestinal worm Ascaris also, if present. The drug is very efficient, requiring only a single dose and is inexpensive.