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Anaerobic culture results may not influence treatment regimens, patient outcomes
Few physicians change antibiotic regimens in response to the results of anaerobic cultures, according to the results of a retrospective chart review.
Researchers wrote that anaerobic cultures had “questionable utility” if most physicians ignored them.
“Clinicians routinely order aerobic and anaerobic cultures when obtaining specimens from body fluids, abscesses and deep wounds,” Tanaya Bhowmick, MD, assistant professor of medicine in the department of medicine, division of infectious diseases at Rutgers Robert Wood Johnson Medical School, New Brunswick, New Jersey, and colleagues wrote. “Once specimens are collected, clinicians choose their initial, empiric antimicrobial regimen based on the likely pathogens at the site of infection, often selecting a broad-spectrum drug, or combination of drugs, to cover both aerobic and anaerobic organisms. However, it is not clear that results translate into modifications. After extensive literature review, we found no prior studies addressing anaerobic cultures from specimens other than blood.”
Bhowmick and colleagues reviewed the charts of all patients with positive anaerobic cultures taken at Robert Wood Johnson Memorial Hospital in 2012, analyzing a total of 174 positive cultures from 154 patients. The samples included cultures from a variety of sources, except blood: wounds, drainage from abscesses, bone, pleural fluid, synovial fluid, ascetic fluid and spinal fluid. Intra-abdominal and pelvic sites were the most common source of anaerobic positive abscess cultures, the researchers reported, while anaerobes were least common in pleural fluid. The mean time for reporting the results of anaerobic cultures was 4.5 days. Bacteroides and Prevotella species made up most anaerobes in the cultures.
Thirty-nine (25%) patients were discharged before culture results could be reported, the researchers wrote. Of the 115 whose results were returned before discharge, however, physicians acknowledged the cultures in just 27% (n = 31) of cases. Physicians changed antibiotic treatments based on the results of the cultures for 15 of these patients, narrowing the antimicrobial spectrum in 14 cases. One hundred-fifteen (75%) patients received antimicrobials that included anaerobic coverage before culture results had been returned, and physicians changed treatment for one patient in the remaining 25%.
“Our study suggests that there is little utility of routine anaerobic tissue/body cultures, as clinical management does not change based on the results. This finding may have major implications for lab resource utilization and cost saving practices,” Bhowmick and colleagues wrote. “More studies are needed to evaluate whether results of anaerobic cultures from specimens other than blood impact patient outcomes (i.e. hospital length of stay, readmission rates and morbidity/mortality). If the findings are consistent with our results, we would question the utility of routinely performing anaerobic cultures on most non-blood specimens.” – by Andy Polhamus
Disclosure: The researchers report no relevant financial disclosures.