KSA-1, a naturally occurring Ambler class A extended spectrum β-lactamase from the enterobacterial species Kosakonia sacchari.

Background: Several bacterial species belonging to the Gammaproteobacteria possess intrinsic class A β-lactamase genes that may represent a source of further dissemination and acquisition to other Gram-negative species. Here we characterised KSA-1 class A β-lactamase, the gene of which was identified within the chromosome of an environmental Enterobacterales species, namely Kosakonia sacchari, which was also recently identified as the progenitor of an MCR-like colistin-resistance determinant.

Methods: In silico analysis using the GenBank database identified a class A β-lactamase gene within the chromosome of K.

NDM-35-Producing ST167 Highly Resistant to β-Lactams Including Cefiderocol.

A multidrug-resistant (carbapenems, aztreonam + avibactam, and cefiderocol) ST167 Escherichia coli clinical isolate recovered from a patient hospitalized in Switzerland produced NDM-35 showing ca. 10-fold increased hydrolytic activity toward cefiderocol compared to NDM-1. The isolate co-produced a CMY-type β-lactamase, exhibited a four amino-acid insertion in PBP3, and possessed a truncated iron transporter CirA protein.

Co-resistance to ceftazidime-avibactam and cefiderocol in clinical isolates producing KPC variants.

Cefiderocol (FDC) and ceftazidime-avibactam (CZA) are among the latest generation of commercialized antibiotics against carbapenem-resistant Gram negatives. However, emergence of CZA resistance is being increasingly reported, involving different KPC variants in Enterobacterales. By analyzing two CZA-resistant KPC-3 clinical variants, KPC-41 and KPC-50, we showed that KPC-41, and to a lesser extent KPC-50, may also have an impact on susceptibility to FDC leading to a cross-resistance.