Antibiotic susceptibility testing

The purpose of this procedure is to determine the susceptibility of a bacterial strain to an antimicrobial agent. The procedure is conceived as an “all-in” procedure for antibiotic susceptibility testing of bacterial isolates recovered from blood cultures as part of ITM projects in low- and middle income countries, in particular those included in the study “Surveillance of antimicrobial resistance among consecutive blood culture isolates in tropical settings”. This procedure provides a full overview but the panels of antibiotics to be tested for patient care should be selected in the specific sites according to local guidelines .

The procedure combines disk-diffusion methods and gradient methods (referred to as “E-test” or “MIC-test”); bacteria, antibiotic combinations, methods and interpretative data are based on both EUCAST and CLSI guidance documents. Antibiotics are grouped according to the CLSI “A-B-C-U-O-Inv” categories (see explanation below) and focus on those products present on the World Health Organization List of Essential Medicines. Where relevant, we have added data (interpretative criteria and doses of antibiotics) for other infectious foci such as meningitis and urinary tract infections. We have not included rare fastidious organisms such as Haemophilus (para)influenzae and Campylobacter. The procedure is unique in the way that it combines both CLSI and EUCAST methods, where applicable we have explicitly referred to specific methods and interpretations. In a few cases, we have slightly adapted or extended the interpretation by either EUCAST or CLSI, in these cases we have explicitly referred to the source documents.

The EUCAST guidance on “Clinical breakpoints and dosing of antibiotics” can be found here.

The CLSI M100 “Performance Standards for Antimicrobial Susceptibility Testing” (and also M23, M27M44S and M60) can be found here.