Characterization of Two Novel AmpC Beta-Lactamases from the Emerging Opportunistic Pathogen, <i>Cedecea neteri</i>

• Main Authors: Stephen M. Sharkady (Author), Brandon Bailey (Author), Dorothea K. Thompson (Author)
• Format: Book
• Published: MDPI AG, 2023-01-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.

Summary

The genus <i>Cedecea</i> (family <i>Enterobacteriaceae</i>) causes a wide spectrum of acute infections in immunocompromised hosts, from pneumonia and bacteremia to oral ulcers and dialysis-related peritonitis. While <i>Cedecea</i> infections are reported infrequently in the literature, documented clinical cases of this emerging opportunistic human pathogen have occurred worldwide. <i>Cedecea neteri</i> has clinical significance and exhibits antimicrobial drug resistance. However, little is known about the molecular basis underlying the resistance phenotypes in <i>C. neteri</i>. We previously hypothesized that the open-reading frame <i>cnt10470</i> in the <i>C. neteri</i> SSMD04 genome encodes a chromosomal Ambler class C (AmpC) β-lactamase based on sequence homology. In this study, recombinant polyhistidine-tagged proteins were created by cloning the putative <i>ampC</i> genes from SSMD04 and <i>C. neteri</i> ATCC 33855 (a clinical isolate) into the pET-6xHN expression vector, overexpressing the proteins, and then purifying the recombinant AmpCs (rAmpCs) using immobilized metal affinity chromatography (Ni-NTA). The in vitro enzymatic analysis of the purified rAmpCs was performed to determine the <i>K_m</i> and <i>k_cat</i> for various β-lactam substrates. The rAmpCs are functional class C β-lactamases when assayed using the chromogenic β-lactamase substrate, nitrocefin. The presence of functional AmpCs in both <i>C. neteri</i> strains underscores the necessity of performing antibiotic susceptibility testing in the management of <i>C. neteri</i> infections.

Item Description

10.3390/antibiotics12020219
2079-6382