Researchers at the Mayo Clinic and elsewhere are racing to develop rapid-detection tests for Staphylococcus aureus, both to better tailor appropriate antibiotic prescribing and to halt the galloping spread of methicillin-resistant strains of the bacteria.
“There are many companies now developing rapid tests,” Betsy McCaughey, Ph.D., said in an interview.
Among the contenders are Innovative Biosensors Inc. in College Park, Md., which is using light-based technology developed at the Massachusetts Institute of Technology; Cepheid, a Sunnyvale, Calif.-based company about to introduce another genetic-based rapid test; and 3M, which has “waded deep into this territory,” said Dr. McCaughey, director of the New York City-based nonprofit Committee to Reduce Infection Deaths.
Progress has been keenest in identifying colonized patients prior to or during hospitalization to help reduce the spread of resistant bacteria.
At the University of Maryland Medical Center in Baltimore, for example, patients considered at risk for methicillin-resistant S. aureus (MRSA) can be screened in 2 hours with a polymerase chain reaction (PCR) DNA test developed by Becton, Dickinson & Co., rather than waiting 24–48 hours to get an answer by culturing for the bacteria.
All intensive care unit patients are being screened at admission, on a weekly basis, and on discharge so that infected patients can be identified and treated with appropriate isolation and contact precautions, said Richard Venezia, Ph.D., professor of pathology and director of clinical microbiology at the university.
“This is the first of a generation of tests that are going to be using 'within-the-tube' closed systems,” based on either DNA or immunology, that represent a major technological advance in the way risky bacteria are identified, Dr. Venezia said.
The tests do not require complex interpretation nor the level of training or sophisticated precautions against cross-contamination that were necessary with previous PCR procedures developed in research laboratories.
The new tests are currently confined to hospital or community laboratories, but Dr. Venezia said that they will almost certainly be available for bedside or community office practices within 5 years.
At the Mayo Clinic in Rochester, Minn., two swab-based PCR tests are being developed, one to signal the presence of S. aureus and the other to identify MRSA, Dr. Mark Pittelkow, professor of dermatology, said in an interview.
S. aureus is rapidly overcoming streptococcus as the bacteria of concern, Dr. Pittelkow said.
The Mayo tests, to be marketed by Roche Pharmaceuticals, use a specially designed swab that does not wick samples in the same way as a cotton-tipped swab. For now, it still requires laboratory technicians to transfer material from the applicator to a plate for analysis, but the technology is heading toward a self-contained swab similar to those used for rapid strep tests in physicians' offices.
The Becton, Dickinson & Co. test, available since early 2006, is approved only for detecting colonization, not to guide antibiotic choices in individual patients. It requires laboratories to make an initial investment of more than $20,000 for a real-time PCR cycler, plus $20-$30 for each test performed. The equipment, however, can be used to perform other cutting-edge tests for detection of influenza, respiratory syncytial virus, and vancomycin-resistant enterococci, Dr. Venezia said.
Rapid, practical, easy-to-perform tests for S. aureus will become even more necessary for hospitals, because the Centers for Medicare and Medicaid Services has proposed that Medicare diagnosis-related group reimbursements for nosocomial infections be stopped.
The advent of such restrictions on payments for hospital-acquired illnesses might lead some institutions to universally test patients on admission and throughout their stays. Treatment of an MRSA infection can run as much as $36,000, said Barbara Kalavik, director of worldwide public relations for Becton, Dickinson & Co.
Just who pays for the tests is still a matter of contention.
When a physician orders a test to pinpoint the best antibiotic to treat a patient, the cost can be charged to the patient or insurance. Who will bear the cost of screening hospital patients is less clear, Ms. Kalavik said.
“Most hospitals absorb the cost of these programs,” she said, but “starting Jan. 1, 2007, new CPT codes have been instituted that allow for hospitals to be reimbursed approximately $49 for screening outpatients” for MRSA.
Staphylococcus aureus is rapidly overcoming streptococcus as the bacteria of concern. DR. PITTELKOW