[In vitro activity of ceftazidime- avibactam and ceftolozane- tazobactam against clinical isolates of enterobacteriaceae and <i>pseudomonas æruginosa</i>: results from a trauma center and burn unit in tunisia].

Antibiotic resistance is an escalating public health challenge, particularly among Enterobacteriaceae and <i>Pseudomonas aeruginosa</i>. In this study conducted at a burn center in Tunisia, we collected 307 non-redundant strains of Enterobacteriaceae from predominantly hospitalized patients, with a majority in the burn intensive care unit (59%), the primary identified species being <i>Klebsiella pneumoniae</i> (34.8%). We evaluated the efficacy of two antibiotics, ceftazidime-avibactam (CZA) and ceftolozane-tazobactam (CT). The results revealed that the overall resistance to CZA was 11.7%, while to CT it was 25.7%. CZA proved to be the second most sensitive molecule among all tested antibiotics, following fosfomycin. Among strains resistant to third-generation cephalosporins, 73.3% were sensitive to CZA, and 41.5% to CT. Out of seventy-nine CT-resistant strains, eight were ESBL producers, twenty-two were high-level cephalosporinases, thirty-three carried <i>blaNDM</i>, twelve carried <i>blaOXA48</i>, and four carried both <i>blaNDM</i> and <i>blaOXA-48</i>. Indeed, <i>blaNDM</i> were the most prevalent carbapenemases. For <i>Pseudomonas aeruginosa</i> strains (n=161), resistance to CZA was 42.2%, and to CT it was 47.8%. These antibiotics ranked as the second and third most active beta-lactams after aztreonam. Among the 71 strains of CZA and carbapenem-resistant P. aeruginosa, 54.1% produced VIM2. Resistance to enterobacteriaceae against CZA and CT is relatively high in our study. However, CZA remains a salvage therapy for infections caused by carbapenem-resistant organisms, and its use should be considered only after documentation and in the absence of other alternatives among β-lactams. For <i>P. aeruginosa</i>, CZA currently represents the most active β-lactam against CAZ-R strains and the second most active molecule overall, including those producing carbapenemases.