MRSA carriers have persistent infection risk

July 26, 2008

By Scott BalticFri Jul 25, 3:27 PM ET

People who harbor methicillin-resistant Staphylococcus aureus (MRSA) for more than 1 year still have a substantial risk of MRSA-related infection and death, according to a study published in the journal Clinical Infectious Diseases.

Patients with newly acquired MRSA have a significant risk of infection and death in the short-term, note Dr. Susan S. Huang of the University of California Irvine Medical Center and Dr. Rpak Detta of the Yale School of Public Health in New Haven, Connecticut.

MRSA is not only resistant to methicillin, an antibiotic that is able to kill may types of bacteria, it is also resistant to almost all antibiotics currently available. Patients are often infected with these bacteria during hospitalization and the elderly, very young children and people with weakened immune system are the most vulnerable.

Their current study focused on 281 patients who tested positive for MRSA between 2002 and 2005 and also tested positive for the bacteria at least one year earlier.

The average age of these MRSA-carriers was 62 years, and the average time since the first evidence of being MRSA-positive was 2.4 years. In addition, 35 patients (16 percent) were known to be MRSA-positive for four or more years.

Approximately half had MRSA infections with symptoms while the others tested positive for MRSA but had no symptoms when they entered the study.

Sixty-five patients (23 percent) developed a total of 96 additional, unrelated MRSA infections one year after being identified as carriers.

The risk of subsequent MRSA infection was significantly higher for subjects who had evidence of being MRSA carriers for one to two years (27 percent), compared with those who had evidence of being positive for two years or longer (16 percent).

Fourteen deaths were associated with MRSA infection.

Although the researchers caution that their results should not be generalized, they conclude that "MRSA carriers remain at considerable risk for subsequent MRSA infection, regardless of the time since the initial detection of MRSA carriage."

Huang told Reuters Health that they consider these results to be "fairly conclusive."

SOURCE: Clinical Infectious Diseases, July 15, 2008.