Death risk of MRSA bacteremia infection rises with age, nursing home link, organ impairment

January 12th, 2015

What predicts death for patients with Methicillin-resistant Staphylococcus aureus bacteremia (i.e., MSRA infection in the bloodstream as opposed to a skin and soft tissue sites)? Older age, residence in a nursing home and organ impairment are all independently associated with increased risk for death, according to a study published in the current issue of Emerging Infectious Diseases

In a secondary finding that suggests knowledge is power when it comes to infectious diseases, the researchers determined that consultation with an ID specialist was associated with lower risk for death. They examined 699 episodes of MRSA bacteremia involving 603 patients admitted to an academic medical center in New York City during 2002–2007. Data came from chart reviews, hospital databases, and recultured frozen MRSA specimens. Among the 699 episodes, 55 were caused by vancomycin–intermediate resistant S. aureus strains, 55 by heteroresistant vancomycin-intermediate S. aureus strains, and 589 by non–vancomycin-resistant strains. Overall, 190 (31.5%) patients died.

“Our findings can help clinicians estimate the risk that a patient with MRSA bacteremia will die,” the authors note. “For example, an elderly patient with liver cirrhosis and MRSA bacteremia who lived in a nursing home before hospital admission would have an extremely poor prognosis. Conversely, an otherwise healthy patient with diabetes mellitus might have a better prognosis that could be improved even more by consultation with an infectious disease specialist.”

Until now, the major focus on active MRSA infections has been on the organism and its susceptibility to the drug, the remind. Although decreased vancomycin susceptibility has resulted in prolonged bacteremia and treatment failure in several studies, these findings suggest that incorporating the context, the host, and the environment is similarly useful. The study underscores that after a diagnosis of MRSA bacteremia is made, it is crucial to determine patient risk factors -- not just the vancomycin MIC for the infecting strain.

“The consequences of MRSA bacteremia are clear—many patients will die or experience a decline from their baseline clinical condition,” the researchers conclude. “The adjusted risk difference enables clinicians to use a targeted approach, directed toward patients with the highest risk for death—i.e., the elderly, patients with liver cirrhosis, patients with renal insufficiency, and patients from nursing homes. These patients should be treated carefully and should possibly receive a consult from an infectious diseases specialist. What remains unclear is whether patients with increased risk for death should be treated with antimicrobial drugs other than vancomycin.”