INACTIVATION OF MYCOBACTERIOPHAGE D29 USING FERROUS AMMONIUM-SULFATE AS A TOOL FOR THE DETECTION OF VIABLE MYCOBACTERIUM-SMEGMATIS AND MYCOBACTERIUM-TUBERCULOSIS

There is still an urgent requirement for more sensitive, cost-effectiv e methods for detection and susceptibility testing of mycobacteria in clinical samples. We have been investigating a simple bacteriophage-ba sed system which could be used for both purposes. As this depends upon the detection of phages which have successfully infected cells, a key step is the efficient removal or inactivation of phages remaining fre e in the culture medium. We demonstrate here the use of ferrous ammoni um sulphate as an effective agent for the inactivation of mycobacterio phage D29 without impairing phage replication in previously infected h ost bacteria. Using this property, we report the detection of viable M ycobacterium smegmatis, M. bovis BCG and M. tuberculosis using simple low-cost technology. The method is highly sensitive, since it is able to detect 10 colony-forming units of M. smegmatis. It is also rapid, w ith the detection of M. tuberculosis in sputum specimens within 48 h.