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Rapid S. aureus diagnosis, direct ID response improve outcomes
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Rapid nucleic acid microarray testing, followed by a direct infectious disease specialist consultation, improves outcomes for patients with Staphylococcus aureus bacteremia, according to researchers.
The nucleic acid microarray (NAM) and direct consultation led to decreases in time to antimicrobial treatment and 30-day mortality, and included detection of MRSA, they wrote in Clinical Infectious Diseases.
“A major difference between this study and others is not the implementation of NAM but the response,” study researcher Joshua C. Eby, MD, an assistant professor of medicine in division of infectious diseases and international health at the University of Virginia School of Medicine, and colleagues wrote. “Whereas other studies include an antimicrobial stewardship program (ASP)-directed response to NAM, the intervention here included a bedside physician response, with involvement of ASP after the initial consultation. The new process was more efficient, with fewer steps from microbiologic data to bedside.”
The researchers tested their intervention in a retrospective study including 226 patients with at least one positive S. aureus test at the University of Virginia Medical Center between December 2012 and July 2015.
Of those patients, 106 were treated before and 120 were treated after the intervention. Both groups underwent initial Gram’s stains on cultures to detect bacteremia.
Of all isolates assessed in the study, 53.8% were MRSA and 46.2% were methicillin-susceptible S. aureus (MSSA).
Before the intervention, and for cultures with gram-positive cocci clusters, health care providers conducted the peptide nucleic acid (PNA)-FISH tests. The PNA-FISH test does not differentiate MSSA from MRSA.
In addition, the test was not performed on each culture at the time it showed cocci clusters but was instead batched twice a day on weekdays and once a day on weekends, the researchers said. When S. aureus was detected in a sample, an ASP pharmacist or physician would contact an inpatient management team and provide recommendations for antibiotics and an ID physician.
After the intervention, the response to culture tests was faster and more direct, the researchers said. Once gram-positive cocci were found in a sample, providers immediately conducted the intervention’s NAM test, which has a sensitivity of 98.6% and specificity of 94.3% in detecting methicillin resistance, they added.
NAM tests could be processed in 2 to 2.5 hours. Detection of S. aureus would prompt a page to an on-call ID fellow available at all hours. The ID fellow would make antibiotic recommendations and perform a bedside consultation, among other steps.
The researchers in part measured times from Gram’s stain test results to treatment with the institutionally preferred anti-staphylococcal (IPA) drug, depending on the type of S. aureus — MSSA or MRSA — and other circumstances.
They found that the mean time from stain results to IPA after the intervention was 10.6 hours, compared with 31.8 hours before (95% CI of difference, 31.4-11).
The researchers did not provide times from stain results to IPA for samples with MRSA. However, among those with MSSA, the mean time was 18.9 hours after the intervention, compared with 59.6 hours before the intervention (95% CI of difference, 58.0-23.5).
In addition, treatment before the intervention was associated with an increased risk for 30-day mortality (OR = 3.17; 95% CI, 1.27-7.93). The 30-day mortality rate among patients treated after the intervention was 8.3%, compared with 17.9% among those treated before the intervention.
The researchers also said ID physicians cooperated well with the implemented changes.
“ID physicians responded favorably to this intervention, integrating it into care and sustaining the process change,” they wrote. “The positive outcomes of the intervention and more efficient consults for S. aureus bacteremia further motivated physicians to sustain change. Non-ID physicians have accepted mandatory consults, with the few refusals occurring early during process change.” – by Joe Green
Disclosure: The researchers report no relevant financial disclosures.
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