Outbreak of aztreonam–avibactam-resistant NDM-5-producing Escherichia coli isolates in a hospital of Paris

The emergence of aztreonam–avibactam resistance among NDM-producing Escherichia coli represents a major therapeutic and infection control concern. Four cases of aztreonam–avibactam-resistant (AZAR) NDM-producing E. coli , recovered from three blood cultures and one rectal surveillance culture in a hospital of Paris, prompted an investigation based on whole-genome sequencing. The three isolates responsible for bloodstream infection, which were clonally related, belonged to the ST405 and produced NDM-5, DHA-1, CTX-M-15, and TEM-1 β-lactamases. They also had a penicillin-binding protein 3 (PBP3) modified by the insertion of four amino acids (YRIK). On the other hand, the isolate recovered from the rectal swab belonged to another sequence type (ST2083). It produced NDM-5, CMY-42, and TEM-1 β-lactamases and had an altered PBP3 by the insertion of four other residues (YRIN). Epidemiological investigation identified endoscopic retrograde cholangiopancreatography as a potential risk factor, leading to the detection of three additional patients infected with the ST405 clone after exposure to the same duodenoscope. The outcome of the bloodstream infections was favorable except for one patient. In total, seven patients infected or colonized by AZAR NDM-5-producing E. coli were identified over a 5-month period in 2025, six with duodenoscope exposure.