Our human body is colonized by thousands of different bacterial species. Likewise, our surrounding environment (air we breathe, water we drink, and food we eat) is inhabited by bacteria, many of which are incapable of inducing disease and some of which are capable of producing life-threatening disease. Disease can result from the poisonous effects of bacterial toxins or when bacteria inhabit generally sterile body sites.
The relationship between many bacteria and their diseases is not simple. Most bacteria do not cause a single, well-defined disease; however there are certainly ones that do (e.g. Treponema pallidum, syphilis; poliovirus, polio; Plasmodium species, malaria). It is more common for a particular bacterium to produce many manifestations of disease (e.g., Staphylococcus aureus – endocarditis, pneumonia, wound infections, food poisoning) or for many bacteria to produce the same disease. Depending on the virulence of the bacteria, the site of exposure and the human’s ability to respond to the bacteria, the manifestations of disease can range from mild symptoms to organ failure and death.
To improve the human body’s ability to prevent infection, the immune system can be augmented through vaccination. Infections can also be controlled with a variety of chemotherapeutic drugs. Unfortunately, with many microbes developing resistance to event the most potent antibiotics, the battle for control between microbe and host continues.
Reference:
Murray P, Rosenthal K & Pfaller M (2005) Medical Microbiology, 5th ed, Pennsylvania: Elsevier.