Resistance of ruminal microorganisms to supermethrin

The effect of the pyrethroid insecticide supermethrin on the growth and cyanogenic activity of 8 ruminal bacterial species (S bovis A0 24/85, S xylosus 310, E faecium 2, L plantarum, M elsdenii 4MJ, S ruminantium A17, B succinogenes 16J and B ruminicola 3/3) in pure culture was examined. Bacteria grown in 0.66 and 6.6 mg supermethrin/ml had similar growth rates and resistance to supermethrin. Production of cyanide from supermethrin occurred by all examined strains of ruminal bacteria, but the enzyme activity varied considerably with species and with the supermethrin concentrations.