Rapid drug susceptibility testing of mycobacteria by culture on a highly porous ceramic support.

BACKGROUND Phenotypic, culture-based methods for drug susceptibility testing (DST) of Mycobacterium tuberculosis are relatively simple and may be particularly appropriate for resource-limited settings where tuberculosis (TB) is most prevalent. However, these methods can be slow and generate significant amounts of infectious waste. Low-cost digital imaging and a unique porous ceramic support for cell culture (Anopore) may offer opportunities to improve this situation. OBJECTIVE To test a rapid DST method based on fluorescence microscopy of mycobacteria grown for a few generations on Anopore. DESIGN Mycobacteria were cultured with and without drugs, and the resulting microcolonies were heat-killed and stained with the fluorogenic dye Syto16. Microscopy, image-capture with a charge-coupled device camera and digital processing were used to quantify the inhibition of growth by drugs. Rapid DST for rifampicin and isoniazid was performed for clinical isolates. RESULTS Mycobacteria could be cultured, killed, stained and imaged on Anopore. For DST, the Anopore method gave an accurate result in 3 days. CONCLUSION This is an unprecedented speed for culture-based DST for this group of organisms and results in minimal infectious waste (<20,000 colony forming units). Analysis of mycobacteria by fluorescence and electron microscopy on Anopore also opens up research possibilities.