Assessment of the Use of Gentian Violet and Malachite Green as Selective Agents in the Isolation of Brucella

The aim of the work is to evaluate ability of gentian violet and malachite green to inhibit 2 Brucella test strains and 8 strains of unwanted organisms and the influence of autoclaving on their activity. The study also aims to evaluate variability of inhibition in different batches of colorants and necessity in adjustment of their concentration.Materials and methods. The study included 3 imported lots of gentian violet and malachite green. Inhibitors were put into nutrient medium containing pancreatic hydrolysates of gelatin and fsh meal, yeast extract, sodium chloride, glucose, sodium pyrosulfate, and agar. The same medium without colorants was used as a control medium. Effect of the colorants was studied with the help of test strains of Brucella abortus 19 ВА, B. melitensis Rev I, Enterococcus faecium VKM B-602, Escherichia coli ATCC 25922, Proteus vulgaris HX 19 222, Pseudomonas aeruginosa 22/99, Serracia plymuthica 1, Shigella flexneri 1a 8516, Staphylococcus aureus ATCC 25923, Yersinia enterocolitica C-187.Results and discussion. We have determined biological parameters of nutrient media containing gentian violet (5,0; 2,5 1,25 mg/L) and malachite green (2.0; 1.0; 0.5 mg/L) when cultivating brucella. Gentian violet is able to inhibit Brucella greatly at concentration of 5 mg/L. S. aureus ATCC 25923 did not show any growth on the media containing malachite green or gential violet (5.0 and 2.5 mg/L). Malachite green inhibited the growth of enterococcus more actively than gentian violet. However, it inhibited swarming growth of Proteus less successfully than gentian violet. Other unwanted organisms were not sensitive to such concentrations of colorants at all. We have demonstrated the necessity to combine colorants with other selective agents, as well as advisability to put gentian violet into sterile media, while malachite green – into the media before its autoclaving. Adjustments to the concentration of gentian violet should be made when producing nutrient medium, as variations in inhibiting activity in different batches of this colorant were revealed