Piperacillin-tazobactam ‘major’ mortality factor in E. lenta infections

Infection with the bacilli Eggerthella lenta has a high rate of mortality, and a commonly prescribed regimen for treating it was an independent risk factor for death in patients, according to researchers.

The association raises concerns over the appropriate breaking points for that regimen — piperacillin-tazobactam (TZP) — they wrote in Clinical Infectious Diseases.

“E. lenta infections were associated with high morbidity and mortality, especially for non-[bloodstream infections (BSIs)],” researcher Alejandra Ugarte-Torres, MD, of the Alberta Health Services Division of Infectious Diseases at the University of Calgary, and colleagues wrote. “The duration of antibiotics, ICU admission and mortality was largely similar between our study and previous reported series ... These findings highlight the clinical importance of E. lenta-associated infections and suggest that mismanagement could be associated with increased costs and poor patient outcomes.”

E. lenta is an anaerobic, gram-positive bacilli that is associated with polymicrobial, intra-abdominal infections. Although the species has been known since the 1930s, scientists have only recently discovered that it is “an important cause of anaerobic BSIs associated with high mortality,” the researchers noted.

The researchers conducted a retrospective cohort study to assess the impact of TZP’s relatively high minimal inhibitory concentrations (MICs) for E. lenta. They assessed data from patients treated by Alberta Health Services in the Calgary area between January 2009 and December 2015.

They identified 107 cases of E. lenta infection among adult patients, 95 of which were BSIs. Common comorbidities among the patients included diabetes (22%) and hematologic or solid organ malignancy (22%). The median patient age was 66 years.

E. lenta was part of a polymicrobial infection in 40% of cases. Of the E. lenta infections, 72.9% came from gastrointestinal sources.

Ninety-eight patients received antimicrobials. Of these, 45.3% received TZP alone, and 11.3% received TZP in addition to another agent. The TZP MIC50 for E. lenta isolates was 32 µg/mL, and the MIC90 was 64 µg/mL.

The 30-day mortality rate for E. lenta was 20.6%, and the 1-year mortality rate was 28.9%. For BSI alone, the 30-day mortality rate was 23.2%. Mortality was independently associated with empiric TZP monotherapy (OR = 4.4; 95% CI, 1.2-16), as well as ICU stay (OR = 6.2; 95% CI, 1.4-27.3). The researchers said the high MICs could account for TZP treatment being a major risk factor for mortality.

“Larger prospective studies are needed to confirm our results and to determine appropriate antibiotic management, along with review and agreement of global breakpoints that correlate with clinical outcomes,” they wrote. “More readily available identification methods such as [matrix-assisted laser desorption ionization time-of-flight, or MALDI-TOF], and increasingly complex patients due to an aging population, will likely make diagnosis of E. lenta infections more common and the distinctions between anaerobic susceptibility patterns more relevant in the future.” – by Joe Green

Disclosures: The authors report no relevant financial disclosures.