Evaluation of a modified BACTEC method to study the activity of disinfectants against Mycobacterium tuberculosis.
METHODS
BACTEC radiometry could provide a useful tool for evaluating the effect of disinfectants on mycobacteria.


OBJECTIVE
The aim of this study was to improve the recovery of mycobacteria in the BACTEC system and thereby develop a new method for disinfectant testing with Mycobacterium tuberculosis.


METHODS
Protein was added to BACTEC 7H12B media. Growth and the recovery of M. tuberculosis after exposure to disinfectants was measured using viable counts and BACTEC radiometry.


RESULTS
Protein additives enhanced growth in 7H12B media. After serial dilution of inoculum, 7H12B plus 10% egg yolk recovered mycobacteria from a 10(-2) higher dilution than viable counts. After 5 min disinfection with 3% peroxygen compound (Virkon), 3% Virkon plus saline or 2% gluteraldehyde (Cidex) no mycobacteria were recovered using standard 7H12B. However, using 7H12B plus protein, growth was detected in all of these within 30 days. In contrast, viable counts detected growth with Cidex and Virkon after 5 min disinfection but not from Virkon in saline. Viable counts took 3-8 weeks to determine.


CONCLUSIONS
Using this modified BACTEC system for the evaluation of disinfectant action on mycobacteria provides advantages in speed, sensitivity and ease of use when compared with viable counts.
Cutler
R R
RR
Newham District Microbiology Laboratories, St Andrew's Hospital, London, UK.
Wilson
P
P
Clarke
F V
FV
D003470:Culture Media; D004202:Disinfectants; D005976:Glutaral; D008828:Microbiological Techniques; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000254:growth & development*; D010545:Peroxides; D011874:Radiometry; D013464:Sulfuric Acids
D003470:Culture Media; D004202:Disinfectants; D010545:Peroxides; D013464:Sulfuric Acids; C071517:monoperoxysulfate; D005976:Glutaral