Laboratory Medicine and Nosocomial Infections: Doing Blood Cultures

Bloodstream infections acquired in hospitals cause significant morbidity and mortality. According to the Infectious Diseases Society of America, every year, 350,000 patients contract bloodstream infections in U.S. hospitals, causing more than 90,000 unnecessary deaths and significant costs to the health care system. Rapid and accurate identification, by the clinical laboratory, of the specific infecting pathogen is thus crucial to ensure early and appropriate therapy and save patient lives.

An easy-to-use and highly sensitive and specific fluorescence in situ hybridization (FISH) assay uses peptide nucleic acid (PNA) probes to target species specific ribosomal RNA (rRNA) in live bacteria and yeast. In May 2009, AdvanDx (Woburn, MA, USA) received U.S. Food and Drug Administration (FDA; Silver Springs, MD, USA) clearance for its EK/P. aeruginosa PNA FISH test for identifying Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa directly from positive blood cultures. Patients with bloodstream infections caused by these organisms spend an average of 5 to 24 days in the hospital, suffer mortality rates as high as 40%, and cost institutions on average US$40,000-$60,000 per case.

These statistics are due in part to the Gram-negative bacteria's increasing resistance to a multitude of antibiotic agents, especially in P. aeruginosa and increasingly in K. pneumoniae, which creates complex therapy decisions for clinicians.

AdvanDX's new test provides critical results 24-48 hours sooner than conventional methods, with test results available within hours, instead of days, for 95%-99% of all patients with bloodstream infections.

Studies show that providing a 24-hour early start on appropriate narrow-spectrum therapy for Gram-negative bloodstream infections should improve clinical outcomes, reduce antibiotic resistance rates, and reduce the incidence of adverse events.

Acinetobacter is building up resistance to the antibiotic imipenem, often used as a last resort to combat blood infections and pneumonia in hospitalized patients. The bacterium is usually only a problem in intensive-care units (ICUs)--but has also infected troops wounded in Iraq and Afghanistan.

Related Links:
AdvanDx
U.S. Food and Drug Administration