An in vivo development of Pantoea agglomerans mutants (isolates PA2-4) with reduced ertapenem susceptibility from isolate PA1 was associated with an inadequate clinical response to ertapenem therapy. All the four isolates harbored the bla(ACT-9) AmpC beta-lactamase gene. However, a loss-of-function mutation in the ampD gene in PA2-4, but not PA1, led to derepressed ACT-9. The reduced ertapenem susceptibility caused by derepressed ACT-9 was confirmed with an ampD-knockout mutant of PA1.
Date:
2011-09
Relation:
Antimicrobial Agents and Chemotherapy. 2011 Sep;55(9):4440-4442.
