Increase in Nosocomial S. aureus Infection Documented

September 26, 2007

CHICAGO -- The incidence and economic burden of hospital-acquired Staphylococcus aureus infections have increased significantly in recent years, investigators here have concluded.

CHICAGO, Sept. 26 -- The incidence and economic burden of hospital-acquired Staphylococcus aureus infections have increased significantly in recent years, investigators here have concluded.

From 1998 to 2003 the rate of nosocomial S. aureus infection increased by 7.1% to 11% annually across differ types of hospital stays, Gary Noskin, M.D., of Northwestern University, and colleagues, reported online ahead of the November issue of Clinical Infectious Diseases.

The largest cumulative overall increase in the S. aureus infection rate over the six years was 53.5% among patients hospitalized for invasive orthopedic stays.

The findings emerged from attempt to clarify current trends in nosocomial S. aureus infection by retrospectively reviewing data from the Agency for Healthcare Research and Quality Nationwide Inpatient Sample. With about seven million hospital stays annually, the Nationwide Inpatient Sample is the nation's largest all-payer inpatient database.

During the same 1998 to 2003 period the economic burden of S. aureus infection in hospitals increased from 9.2% to 17.9%, reaching an estimated .5 billion in 2003 for all inpatient stays. The findings reflect a pressing need to implement and adhere to CDC guidelines related to nosocomial infections, they asserted.

Despite the increased rate of infection, mortality attributable to S. aureus decreased during the follow-up period.

"The observed decrease in in-hospital mortality risk may be associated with the introduction of more stringent infection-control programs or with appropriate early treatment of [methicillin-resistant S. aureus] infections with vancomycin," the authors said. "There are very limited data on the impact of S. aureus infections on in-hospital mortality with which to compare our results."

The study and findings grew out of a background of growing concern about the increasing rate of MRSA infections. For example, a report from the National Nosocomial Infectious Surveillance System indicated that the rate of antimicrobial resistance among ICU patients with S. aureus infection increased by 40% in 1999 compared with 1994-1998.

A report from the Canadian Nosocomial Infection Surveillance Program indicated that the rate of MRSA infections increased more than 10-fold from 1995 to 2003 (0.46 cases/1,000 admissions versus 5.1 cases/1,000 admissions). Similar disquieting evidence has emerged from studies in Europe and most other regions of the world, the authors noted.

In the current study, the percentage of patients with S. aureus-related infection at discharge increased from 0.74% in 1998 to 1.0% in 2003, representing an annual increase of 7.1% (P=0.004 for trend). The incidence of S. aureus infection associated with surgical stays increased from 0.90% to 1.3%, a 7.9% annual change (P=0.001). The infection rate associated with invasive orthopedic stays increased from 1.2% to 1.8%, an annual rate of change of 9.3% (P