CA-MRSA: Some groups more at risk - and many patients recolonize within months

October 1, 2007

Although community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is growing in numbers in North America, screening patients for MRSA is not cost-effective, as many patients will recolonize with MRSA in as little as three months. Given concerns about antimicrobial resistance, physicians should be selective about their use of antibiotic therapies to manage CA-MRSA.

Edmonton, Alberta - It is not cost effective or useful to screen patients for methicillin-resistant Staphylococcus aureus (MRSA), because of the sheer numbers who are infected and the rate of recolonization, one dermatologist says.

"How will you identify and treat this population?" Dr. Searles asks. "More than half of that population will be recolonized (with MRSA) in three months."

International community

Increasingly, cities in North America are being affected by CA-MRSA. Cities like Atlanta are a hotbed for CA-MRSA, Dr. Searles tells Dermatology Times, adding that CA-MRSA infection among individuals without healthcare-associated risk factors was first recognized about a decade ago in North America.

Dr. Searles predicts that the lines between healthcare-associated MRSA and community-acquired MRSA will blur in the future. For the moment, prevention is an area of controversy in terms of CA-MRSA.

"Should we be screening patients and who should be screened?" Dr. Searles inquires. "If you do identify the patients, what do we do? Do we have them sequestered and hope that they go away?"

Preventive measures to stop the spread of CA-MRSA include immunization to prevent transmission from person to person, Dr. Searles says.

"Patients who tend to have CA-MRSA are less healthy and have had trauma to the skin," Dr. Searles says. "Individuals in jail and intravenous drug users represent high-risk groups."

In hospital settings, some patients are more prone to developing infection because of MRSA. This subset includes patients undergoing cardiac or orthopedic surgery, patients who are immunosuppressed, those who have chronic antibiotic exposure and patients who have been exposed to central catheters, Dr. Searles notes.

A horse of a different color

CA-MRSA is regarded as responsible for conditions such as necrotizing pneumonia, severe sepsis and necrotizing fasciitis.

CA-MRSA differs from healthcare-associated MRSA in that it is usually pan-susceptible to non-beta-lactam antimicrobials.

Research published in peer-reviewed journals has supported the concept that Panton-Valentine leukocidin (PVL) genes are responsible for the increased virulence of CA-MRSA. Other research has indicated that CA-MRSA isolates are distinct strains emerging de novo from CA-methicillin-susceptible isolates instead of healthcare-associated MRSA isolates that have escaped from the hospital setting.

In addition, data have demonstrated that the relationship among various patient isolates strengthens the assumption that CA-MRSA infections may be caused by isolates closely related to methicillin-susceptible Staphylococcus aureus.

One of the most common sites where MRSA is carried is through the nasal passage. Patients whose MRSA is colonized, but who remain asymptomatic, should not undergo antibiotic therapy, Dr. Searles says.

When faced with a patient who has an abscess, a dermatologist can perform surgical drainage if the abscess has developed from a harder serous inflammation to a softer pus stage, Dr. Searles explains.

"If there is an abscess, you can let it drain spontaneously," Dr. Searles says. "It always heals on its own without using antibiotics. Incision and drainage alone are sufficient to heal."