False susceptibility to cefotetan reported by MicroScan for DHA-type AmpC β-lactamase-producing Klebsiella pneumoniae

Abstract

This study evaluated the accuracy of cefotetan susceptibility determination using the MicroScan WalkAway system for AmpC-producing Klebsiella pneumoniae. In total, 57 K. pneumoniae isolates that showed a D-shape flattening in a double-disk synergy test were studied. Cefotetan MICs were determined by the agar dilution method. The bla(DHA) gene was detected in all 57 isolates, one of which co-harboured bla(CMY-1). According to the MicroScan system, 28 isolates were susceptible, 18 were intermediately-resistant, and 11 were resistant to cefotetan. Compared with the agar dilution method, very major, minor and major error rates were 28.1% (16/57), 47.4% (27/57) and 1.8% (1/57), respectively.

Genetic and Phenotypic Characterization of Multidrug-Resistant Klebsiella pneumoniae from Liver Abscess

“…In our collection, LAKp strains showed higher susceptible to cefotetan than these antibiotics. Of note, inducible DHA-type enzymes in K. pneumoniae could cause false sensitivity in vitro , thus requiring further confirmation by broth microdilution ( 18 ). Fortunately, the 18 MDR LAKp strains in this study remained 100% sensitive to the “last resort” antimicrobials, including tigecycline, meropenem-vaborbactam and ceftazidime-avibactam, suggesting that these drugs were reliable choices for the treatment of liver abscess caused by K. pneumoniae .…”