Oral Presentation Australian Institute of Medical Scientists National Scientific Meeting 2013

Gram Negative Resistance and Phenotype Testing (#8)

Peter B Ward 1
  1. Austin Health, Heidelberg, vic, Australia

ß-Lactam resistance has increased in many Gram-negative pathogens that cause serious community acquired and nosocomial infections, including Enterobacteriaceae, Acinetobacter spp., and Pseudomonas aeruginosa. Such multiresistant “superbugs” often carry multiple other resistances, they are more difficult to treat and lead to extended hospital stays, increased health care costs, and significantly higher mortality. Early introduction of laboratory informed or targeted therapy improves outcomes.

Resistance mechanisms to ß-Lactams including serene proteases (Extended Spectrum ß-Lactamases (Class A, plasmid mediated ampC (Class C), and OXA carbapenemases (Class D)) and the Metallo ß-Lactamases (Class D) transfer between genera. Accurately identifying the mechanism by phenotype such as cephalosporin MIC has proved problematic and has resulted in CLSI significantly changing breakpoint MICs for Enterobacteriaceae. Understanding how the enzymes work and the best current laboratory detection methods should help direct appropriate therapy early, especially I blood stream infections. Recent resistances of considerable concern in Australia include, MBLs, KPCs, ELBLs especially CTXM, OXA-48 and pampC. Many of these resistances are spreading rapidly throughout many areas of the world. Rapid methods are needed in all diagnostic Microbiology laboratories to help prevent establishment in our institutions. This session will summarise current options for detection of these resistances.