AmpC β-lactamases detected in Southeast Asian and .

OBJECTIVES

AmpC β-lactamases are neglected compared with ESBL as a cause of third-generation cephalosporin (3GC) resistance in Enterobacterales in low- and middle-income countries and the burden is unknown. The aim of this study was to investigate the presence of AmpC β-lactamase-producing and in clinical specimens from three clinical research laboratories in Southeast Asia.

METHODS

Stored clinical isolates of and resistant to ceftriaxone or ceftazidime or cefpodoxime and ESBL confirmation test negative were screened using MASTDISCS AmpC, ESBL and Carbapenemase Detection Set-D72C. Short-read WGS was performed to identify genes.

RESULTS

Of 126 isolates collected between 2010 and 2020, 31 (24.6%) and 16 (12.7%) were phenotypically AmpC and inducible AmpC positive by MASTDISCS testing, respectively. All inducible AmpC isolates were ceftriaxone susceptible and 97.7% of AmpC/inducible AmpC isolates tested against cefoxitin were resistant. Through WGS, 17 and eight different STs were detected for the AmpC/inducible AmpC and isolates, respectively. Twelve different β-lactamase resistance genes were detected, with most commonly in AmpC-positive isolates (20/31; 64.5%; 15 chromosomal, five plasmid). All inducible AmpC-positive isolates had the gene (seven chromosomal, nine plasmid).

CONCLUSIONS

Though uncommon, AmpC and inducible AmpC β-lactamases in and are an important cause of infection in Southeast Asia. With current testing methods, these infections may be going undetected, resulting in patients receiving suboptimal treatment.