Kate Johnson

September 12, 2014

WASHINGTON, DC — A rapid test to detect pathogens and antimicrobial resistance can lead to more judicious use of antibiotics compared to standard testing, but the key to the benefit is real-time antimicrobial checks and balances, a new study shows.

"An antimicrobial stewardship team that reviews rapid test results and antimicrobial orders and provides feedback to providers can help clinicians understand and act upon rapid molecular test results," investigator Ritu Banerjee, MD, from the Mayo Clinic in Rochester, Minnesota, told Medscape Medical News.

The results of the study were presented here at the Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC).

"Current blood culture diagnostics require several days for bacterial identification and susceptibility testing, during which time patients may be receiving inactive antibiotics or unnecessarily broad-spectrum antibiotics, both of which contribute to poor outcomes," Dr. Banerjee explained. "Rapid detection of bloodstream organisms and their drug resistance can enable earlier initiation of effective therapy or more rapid antibiotic de-escalation."

The study used the FilmArray Blood Culture ID Panel, a US Food and Drug Administration–approved molecular rapid diagnostic tool that can identify 24 different bacteria and fungi and common antimicrobial-resistance genes within 1 hour of organism growth in a blood culture bottle.

This is the first randomized controlled study to evaluate what difference they make in patient care. Dr. Robin Patel

A total of 617 patients with a new positive blood culture were randomly assigned to receive either standard culture and antimicrobial susceptibility testing (control: n = 207), infectious disease panel testing with templated comments (INT1: n =198), or testing with real-time antimicrobial stewardship (INT2; n = 212).

The study found that time to pathogen identification was significantly shorter in both testing groups (1.4 hours) than in the control group (23.6 hours; P < .001).

However, time to antimicrobial de-escalation or escalation was significantly shorter only in the antimicrobial stewardship group (27.2 and 15.9 hours, respectively; P < .001 and P = .04) and similar between the control (40.4 and 36.5 hours) and INT1 (45 and 24 hours) groups.

Patient outcomes, such as mortality, length of stay, cure, Clostridium difficile infection, or colonization with multidrug-resistant organisms within 30 days after enrollment, did not differ between the groups.

"Rapid molecular test panels such as this for determining which organisms are present in blood culture bottles have recently become available, and work well, but are quite costly," said ICAAC program committee vice-chair Robin Patel, MD, who is also from the Mayo Clinic but was not involved in the research. "This is the first randomized controlled study to evaluate what difference they make in patient care."

The study underscores the fact that technological advances alone are not enough to combat antibiotic overuse and resistance, said Dr. Patel.

"Technology is moving very fast and that is great, but it is moving ahead faster than clinical awareness," she told Medscape Medical News. "In order to change clinical practice, we need to understand how best to use new technology. In this study, antimicrobial stewardship meant that an infectious diseases physician or pharmacist provided guidance as to how to change patient management based on the results of the new technology."

Thomas File, MD, chair of the Infectious Diseases Division at Summa Health System in Akron, Ohio, agrees.

"Without antimicrobial stewardship to appropriately interpret diagnostic results in light of the clinical response, there may be little change in behavior of practitioners," he said. "The message is that an effective antimicrobial stewardship program or similar support and intervention process is the best approach for utilization of new diagnostic testing methods and for ultimate benefit of our patients."

This study was supported in part by the National Institute of Allergy and Infectious Diseases of the National Institutes of Health under award number UM1AI104681; kits and instrumentation were provided by BioFire Diagnostics. Dr. Banerjee and Dr. File have disclosed no relevant financial relationships. Dr. Patel is a consultant for Thermo Fisher, St. Jude, and Curetis. She does instrument evaluations for Bruker, bioMérieux, Abbott, Nanosphere, BioFire, Siemens, and BD. She received grant or research support from Astellas, Tornier, Pocared, Pradama, Pfizer, 3M, BioFire, Curetis, and nanoMR. She has patents with Bordetella pertussis, parapertussis polymerase chain reaction, method and apparatus for device sonication, and anti-biofilm substance. She receives royalties from Up-to-Date and an editor's stipend from the Journal of Clinical Microbiology.

54th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC): Abstract D-910. Presented September 7, 2014.


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