Methacillin-resistant Staphylococcus aureus
From RationalWiki
Methacillin-resistant Staph aureus (MRSA) is a variant of a common bacterium present on and in human beings. Other than its antibiotic resistance profile, it is no different from other variants of S. aureus.
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[edit] The organism
Staph aureus is a nasty little gram positive bacterium that is a common cause of human disease. It was first described by Scottish surgeon Alexander Ogston in the 19th century, after he observed the bacteria growing in pus from abscesses.
Previously treatable with many penicillin derivatives, such as methacillin, the population of Staph aureus is becoming increasingly resistant to these medications.
MRSA is contrasted to MSSA (methacillin-sensitive staph aureus) based on antibiotic susceptibility. It is further classified as either hospital-acquired (HA) or community-acquired (CA).
[edit] Disease
Most commonly, Staph aureus is responsible for cutaneous (skin) infections, such as cellulitis and abscess. It can also cause more serious diseases, such as endocarditis (infection of a heart valve), sepsis (blood infection), pneumonia, necrotizing fasciitis, and other life-threatening infections. It is particularly common in patients with foreign bodies in their blood vessels, such as hemodialysis patients and intravenous drug users.
[edit] Significance
MRSA is a classic example of evolution in action. Before the invention of penicillin in the middle of the 20th century, there could be no MRSA as there was no "M". Populations of MSSA and MRSA probably existed. As antibiotics came into widespread use, populations of SA were subjected to selective pressures, increasing the numbers of MRSA relative to MSSA.
Any setting in which people are close together, such as hospitals, nursing homes, high school locker rooms, or military barracks increase the chances of spreading staph.
Creationists have always had a hard time with antibiotic resistance. Sometimes the arguments are as simple as trying the old trick of differentiating microevolution from macroevolution, but more often they resort to intellectual acrobatics in attempting to explain it.
[edit] Hype
The press is full of reports about MRSA, especially in schools. The hype is both good and bad. Physicians have been warning patients for years about the misuse of antibiotics that leads to more MRSA infections. The hype is overblown, in that there is no epidemic of staph infections, and staph has not become more common or more deadly.
The potential for the above problems is increasing, however. As resistance patterns change, staph will likely become resistant to more antibiotics. It is conceivable that there will be a time when many staph infections are not curable.
