Invasive MRSA rates dropped dramatically

Rates of health care-associated invasive methicillin-resistant Staphylococcus aureus (MRSA) declined substantially between 2005 and 2008, according to a CDC surveillance program.

Between 2005 and 2008, 21,503 invasive MRSA infections were reported to the CDC's Active Bacterial Core surveillance program. Of these, 17,508 were health care associated. In 2005, the incidence rate of hospital-onset invasive MRSA infections was 1.02 per 10,000 population. Over the next three years, that rate decreased by 9.4% per year. The incidence of health-care associated community-onset infections (which were defined as infections that could be linked to recent health care exposure but occurred in outpatients or patients recently admitted to the hospital) was 2.20 per 10,000. That rate declined by 5.7% per year during the study period.

The majority of the reported infections were MRSA bloodstream infections, and the greatest decreases were also seen in this subset (hospital-onset, −11.2%; community-onset, −6.6%). Decreased infection rates were also observed in the subset of patients who were on dialysis, comparable to the overall decreases. The results were published in the Aug. 11 Journal of the American Medical Association.

The study authors concluded that these significant declines in invasive MRSA infections (overall about 28% for hospital-onset and 17% for community-onset) could potentially be attributed to MRSA prevention practices in hospitals, and they noted that the results complement previous small studies that have found positive effects from infection prevention interventions. The greater decrease seen in the hospital compared with the community could also support this conclusion.

However, an accompanying editorial noted that the decreases pre-date many MRSA prevention efforts, and may instead be due to general infection control efforts, such as improved hand hygiene and central line management. In fact, the finding of widespread, continued decreases could have confounded the results of any before-after study that tested MRSA prevention efforts. The decreases could also be due to a natural biological trend rather than any intervention at all, the editorialists wrote. They called for more detailed and broader surveillance of MRSA and other similar pathogens to help establish explanations for this study's findings.