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| The Emergence of Antibiotic-Resistant Bacteria |
Today we face a growing medical crisis: the emergence of bacteria resistant to multiple antibiotics. Strains of at least three potentially fatal bacterial species are now resistant to all the drugs available for treatment. Enterococcus faecalis is generally a benign intestinal bacterium. In the elderly and individuals with compromised immune systems, however, it can be deadly if it gets in the wrong location. E. faecalis can infect heart valves and other organs, causing a deadly systemic disease. Strains of Pseudomonas aeruginosa (which causes skin infections and deadly septicemia) and Mycobacterium tuberculosis (the causative agent of tuberculosis) also evade available drugs. Death rates for tuberculosis have begun to rise, in part because of the evolution of these new strains.
The wide use, and misuse, of antibiotics has encouraged new strains of pathogens to develop. For example, the widespread use of cephalosporin antibiotics has led to drug-resistant E. faecalis. The use of Vancomycin (a drug of last resort) has contributed to the development of VRE (vancomycin-resistant Enterococcus), which defies treatment. Antibiotic-resistant bacteria are generally not more potent and do not generate a more severe disease state; they are, however, more difficult to treat. Resistant bacteria proliferate when a population of microbes containing both susceptible and resistant bacteria are exposed to an antibiotic within the host: susceptible bacteria succumb and resistant bacteria proliferate.
Public health officials urge people to complete the full course of antibiotic treatment. Why? Bacterial susceptibility to an antibiotic is often dose-dependent; an individual bacterium that is only somewhat resistant may survive at low drug concentrations. There will be selection for such more-resistant bacteria and these will eventually predominate the bacterial population. Thus, the failure of patients to complete a full course of treatment, or the use of less than therapeutic doses of antibiotic, can lead to resistant strains. The full course of treatment should be sufficient to wipe out all the pathogenic bacteria.
An additional cause of the rise of antibiotic resistance is the use of antibiotics in animal feed. Humans may be exposed to such as bacteria by handling intestinal contents of the animals, as when butchering or preparing meats. Moreover, bacteria from livestock can get into our water systems.