Antimicrobial resistance: complexities and difficulties of determination

摘要

The prudent use of antimicrobials in aquaculture requires that these agents be used only when the evidence suggests that they will benefit the health of the treated animals. Thus, prudence can be achieved only when good quality clinical diagnoses aremade and when the decisions to treat are based on sound assessments of the susceptibility of the target bacterium. This paper discusses the issues of clinical diagnosis but concentrates on the protocols and interpretive criteria that are necessary for the determination of bacterial susceptibility. It suggests that there are compelling reasons why there should be international harmonization of the susceptibility testing protocols being used and argues that this harmonization should center on the currentClinical and Laboratory Standards Institutes guidelines M42-A and M49-A. The issue of interpretive criteria for the data generated by in vitro susceptibility testing is more complex, less resolved, and the extent of interlaboratory variation presents possibly insurmountable difficulties for international harmonization. This paper argues that, at least in the short and medium term, laboratory-specific wild-type cut-off values, estimated using normalized resistance interpretation (NRI), would provide thebest way forward. The special situation of susceptibility testing in laboratories with small throughputs is discussed. It is suggested that the Single Plate Internal Control (SPIC) protocol deserves serious consideration as a method of resolving the problems faced by these laboratories.