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Updated: Aug 9, 2026
The MODS method for diagnosis of tuberculosis and multidrug resistant tuberculosis
Published on: August 11, 2008
The use of spiral plating and microscopic colony counting for the rapid quantitation of Mycobacterium
W L Smith1, K L McGarvey, J S Cullor
1Dairy Food Safety Laboratory, School of Veterinary Medicine, Veterinary Medicine and Teaching Research Center, University of California, Davis, CA 95616, USA. wlsmith@ucdavis.edu
Aims:
To evaluate a spiral plating and microscopic colony counting technique to hasten the quantitation of Mycobacterium paratuberculosis.
Methods And Results:
Broth and milk cultures of M. paratuberculosis were spirally plated onto Middlebrook agar plates and microscopically counted at 8 and 14 days of incubation. The same plates were recounted at 27-28 days of incubation when grossly visible colonies were present. The results were statistically compared with no difference in CFU ml-1 derived from the shorter vs longer incubation times. Other mycobacteria isolates were also plated and microscopically examined and found to be easily distinguishable from M. paratuberculosis.
Conclusions:
Microscopic quantitation of spirally plated M. paratuberculosis cultures can be achieved within 8-14 days of plate incubation and compare favourably to counts derived after prolonged incubations.
Significance And Impact Of The Study:
The technique could greatly hasten the quantitation of viable M. paratuberculosis.
