The following is the summary of ‘Clinical outcome of wild-type AmpC-producing Enterobacterales infection in critically ill patients treated with β-lactams: a prospective multicenter study” published in the November 2022 issue of Intensive Care by Mounier, et al.

Antibiotics belonging to the β-lactam family are typically employed for treating wild-type AmpC-producing Enterobacterales (wtAE). But they could backfire or end up picking out mutants that produce too much AmpC. The purpose of this study was to evaluate potential causes of -lactam therapy failure in wtAE infections. Researchers prospectively enrolled all patients in 4 university Intensive care units ( ICUs)  who were treated with definitive-lactams for wtAE infection from September 2017 through December 2020. 

Lack of antimicrobial response leading to mortality or the need to switch to a broader-spectrum antibiotic was considered a clinical failure. The clinical failure occurred in 29.4% of the included 177 patients. Ventilator-associated pneumonia (VAP) was the most common wtAE infection (69.5%), while Enterobacter cloacae were the most common species (42.4%). In terms of final antibiotic treatment, 42.9% and 27.7% of patients received cefepime and cefotaxime, respectively. About 5.6% of patients were found to have an overproduction of AmpC, which was linked to clinical failure (P=0.004). Clinical failure was independently linked with VAP (P<0.001, OR 11.58 [95% CI 3.11-43.02]) and K. aerogenes (P=0.030, OR 3.76 [95% CI 1.13-12.46]) in multivariate analysis.

In contrast, the use of cefotaxime as definitive treatment was found to be negatively linked with the likelihood of clinical failure (P=0.022, OR 0.25 [95% CI 0.08-0.82]). Cefotaxime revealed a 20% risk reduction of clinical failure (95% CI 5-35%, P=0.007) regardless of infection site, SOFA score on the day of wtAE infection, or bacterial species after inverse probability weighting. The site of infection and the causative microorganism is linked to clinical failure in treating wtAE infections. The use of cefotaxime also protects against clinical failure due to wtAE infection.