Third-generation cephalosporins programmed restriction in the context of an outbreak of AmpC β-lactamase-producing gram-negative bacilli in critical units: a real-life experience

Abstract

Background: Programmed restriction (PR) of antimicrobials can selectively decrease the rate of infections by certain microorganisms. In this sense, AmpC β-lactamase-producing gram-negative bacilli (GNB-bla_AmpC) are selected for the overuse of third generation cephalosporins (3GC). These bacteria also acquire genes and co-produce other β-lactamases, such as Nueva Delhi ones (GNB-bla_NDM). Aim: To decrease the isolation rate of GNB-bla_AmpC and GNB-bla_NDM in cultures from ICU patients after a PR of 3GC. Methods: Quasi-experimental study, before (P₁= 12 months) and after (P₂= 12 months) a PR of 3GC in an adults´ hospital. The use of antibiotics was expressed as “percentage days of treatment (%DOT)” /100 beds occupied per day (100-BOD). The rates of GNB-bla_AmpC and GNB-bla_NDM were compared in blood cultures (BC), mini-bronchio alveolar lavages (mB) and urine cultures (UC) in the ICU. Results: In P₂, 3GC consumption was 2.5% DOT/100-COD. There was a decrease in GNB-bla_AmpC from BC (RR 0,48 [0,2-0,9] p<0,02) and mB (RR 0,52 [0,3-0,9] p<0,02), as well as of GNB-bla_NDM from BC (RR 8,1 [1,6-39,4] p<0,00).

Conclusions: PR of 3GC was linked to the reduction of GNB-bla_AmpC and GNB-bla_NDM in BC, as well as GNB-bla_AmpC in mB from ICU patients.