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CA-MRSA Facts

MRSA is a type of Staphylococcus aureus (S. aureus) bacterial infection that is resistant to some antibiotics called beta-lactam antibiotics, like penicillin and cephalosporin. CA-MRSA stands for “community-acquired methicillin resistant staphylococcus aureus.” The label “community-acquired” means that the infection was not contracted in the hospital or care facility setting that, but out in the community. The fact that MRSA is now out in the community means that the bacterium is extremely adaptive and a potential threat to people who are not hospitalized or in a group home.

CA-MRSA accounts for between 10 and 15 percent of MRSA cases, so it is still the minority. But this type of infection can affect otherwise healthy individuals living in the community, who may contract the infection through cuts or scrapes in the skin, at schools or daycare centers, or while playing sports. CA-MRSA can infect people of any age, but it is more common in the very young and the elderly. CA-MRSA is most common in locations where large numbers of people are exposed to one another, such as schools and gyms.

CA-MRSA usually occurs as a localized skin infection, causing redness, swelling, fever and abscess or boil formation, but the danger is that the infection can spread and cause more serious medical problems if it is left untreated. CA-MRSA can cause death if it spreads to the internal organs through the bloodstream.

Individuals who are sick, but not hospitalized, are more likely to contract CA-MRSA. This can happen with diseases such as HIV/AIDS, in which the immune system is deficient and makes a person more susceptible to contracting a host of opportunistic infectious diseases that healthy people can normally fight off. Studies indicate that HIV patients are about six times more likely to catch CA-MRSA than a healthy person.

CA-MRSA vs HA-MRSA

MRSA started out as a nosocomial (hospital-induced) infection, abbreviated HA-MRSA (hospital-acquired methicillin-resistant Staphylococcus aureus), but then started to spread outside of the hospital setting. Research has shown that CA-MRSA and HA-MRSA have different traits, even though they both have resistance to a certain type of antibiotic medication in common.

HA-MRSA tends to cause more complications, but it infects those who are already hospitalized because they are ill or have had surgery. HA-MRSA is more resistant to antibiotic treatment and has a higher mortality rate. CA-MRSA, on the other hand, is more virulent; this makes sense, as CA-MRSA can infect healthy individuals in the community. CA-MRSA has a lower mortality rate and is more treatable with antibiotics. The exception to this rule is that CA-MRSA tends to be more resistant to the antibiotic tetracycline than HA-MRSA. Certain complications, such as endocarditis or inflammation of the inner lining of the heart, are more common with CA-MRSA than HA-MRSA. CA-MRSA and HA-MRSA are both antibiotic-resistant Staphylocccus aureus infections, but they are different strains of the bacterium.

But why are CA-MRSA and HA-MRSA different, if they are both MRSA infections? The answer lies in the fact that CA-MRSA originated from an old strain of HA-MRSA that went through mutations and spread into the community. The current HA-MRSA bug that is going around has also changed from the original strain over time, but the bacteria have been evolving in completely different environments since the original split. This evolution results in differences between the strains in drug resistance, virulence factors and disease patterns.

Web Resources:

http://infectiousdiseases.about.com/od/diseasesbyname/a/CA-MRSA.htm

http://www.sciencedaily.com/releases/2010/03/100323161823.htm

http://www.rwjf.org/pr/product.jsp?id=27271

http://www.docguide.com/invasive-community-acquired-mrsa-differs-hospital-acquired-infections-presented-idsa