672. Report of a Multi-species Outbreak of VIM-producing Carbapenem-resistant Organisms in a Burn Unit and Subsequent Experience Using Novel β-lactam Antibiotics for Treatment

Abstract

Background. The incidence of carbapenem-resistant organisms (CROs) has increased over the past 3 decades. Carbapenem-resistance due to metallo-β-lactamases (MBLs) such as the Verona integron-encoded metallo-β-lactamase (VIM) are particularly problematic due to the limited treatment options. We describe a multi-species outbreak of VIM-producing CROs (VIM CROs) in a tertiary care hospital along with our experience using novel β-lactam antibiotics for treatment. Methods. We performed a retrospective chart review after a cluster of patients in the burn unit of a tertiary care hospital were found to have infections with VIM CROs. Electronic medical records for all patients with a VIM CRO isolated between November 2021 and March 2022 were reviewed. Data regarding patient characteristics, antimicrobial use, culture results, antimicrobial susceptibility testing, and clinical outcomes were recorded for each patient. Results. 8 patients were found to have VIM-mediated CRO burn wound infections, 5 of whom were also bacteremic with a VIM CRO. A VIM gene was identified in 5 different species (Pseudomonas aeruginosa and 4 Enterobacterales). None of the patients received carbapenems prior to isolation of a CRO. Among the 5 patients treated with cefiderocol, 2 had cefiderocol-resistant VIM CROs isolated 10-20 days after starting cefiderocol. 3 patients received the combination of ceftazidime/avibactam and aztreonam, and all had subsequent clearing of their CRO infection on follow-up cultures taken from the same site. Only one of the 8 patients died within 30 days of initial CRO isolation, after developing a subsequent fungal infection. The median Pitt bacteremia score at the time of initial CRO isolation was 1 (range 0-4) in the 7 patients who survived versus a score of 6 in the patient who died. Conclusion. MBLs such as VIM have the potential for multi-species spread throughout hospital units even in the absence of carbapenem selection pressure. Although over 60% of the patients in this study had bacteremia and cefiderocolresistance developed in 40% of the patients treated with cefiderocol, mortality was fortunately low in this group. While newer β-lactam antibiotics remain an exciting addition to our armamentarium, we must remain diligent in monitoring for rapid development of resistance.