The Calgary Biofilm Device: New technology for rapid determination of antibiotic susceptibilities of bacterial biofilms

Determination of the MIG, based on the activities of antibiotics against pl anktonic bacteria, is the standard assay for antibiotic susceptibility test ing. Adherent bacterial populations (biofilms) present with an innate lack of antibiotic susceptibility not seen in the same bacteria grown as plankto nic populations, The Calgary Biofilm Device (CBD) is described as a new tec hnology for the rapid and reproducible assay of biofilm susceptibilities to antibiotics. The CBD produces 96 equivalent biofilms for the assay of anti biotic susceptibilities by the standard 96-well technology. Biofilm formati on was followed by quantitative microbiology and scanning electron microsco py, Susceptibility to a standard group of antibiotics was determined for Na tional Committee for Clinical Laboratory Standards (NCCLS) reference strain s: Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Stap hylococcus aureus ATCC 29213, Growth curves demonstrated that biofilms of a predetermined size could be formed on the CBD at specific time points and, furthermore, that no significant difference (P > 0.1) was seen between bio films formed on each of the 96 pegs. The antibiotic susceptibilities for pl anktonic populations obtained by the NCCLS method or from the CBD were simi lar. Minimal biofilm eradication concentrations, derived by using the CBD, demonstrated that for biofilms of the same organisms, 100 to 1,000 times th e concentration of a certain antibiotic were often required for the antibio tic to be effective, while other antibiotics were found to be effective at the MICs, The CBD offers a new technology for the rational selection of ant ibiotics effective against microbial biofilms and for the screening of new effective antibiotic compounds.