Activity of NXL104 in combination with beta-lactams against genetically characterized Escherichia coli and Klebsiella pneumoniae isolates producing class A extended-spectrum beta-lactamases and class C beta-lactamases.

The novel non-beta-lactam beta-lactamase inhibitor NXL104, in combination with cefepime, ceftazidime, ceftriaxone, amdinocillin, and meropenem, was tested against 190 extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae isolates, 94 AmpC-hyperproducing E. coli isolates, and 8 AmpC/ESBL-coexpressing E. coli isolates. NXL104 restored 100% susceptibility to the partner cephalosporins for all isolates tested. Amdinocillin and meropenem MICs were modestly improved (2 to 32 times lower) by NXL104. These results suggest that NXL104 may be useful in combination with beta-lactams for the treatment of infections caused by ESBL- and AmpC-producing Enterobacteriaceae.