Mastitis: II. Evaluation of antimicrobial amines for use as teat dips

Recent proposals by the Food and Drug Administration to regulate teat dips as drugs have led to a search for safer teat dip ingredients. Primary, secondary, and tertiary alkyl amines (carbon-10 to -18 chain length) inhibit growth of mastitic bacteria (Streptococcus agalactiae, Streptococcus uberis, Staphylococcus aureus, Escherichi coli, Klebsiella pneumoniae) in a broth tube culture assay. Since carbon-13 compounds were active, a carbon-13 primary (tridecanamine hydrochloride), secondary methyl (N-methyltridecanamine), secondary ethyl (N-ethyltridecanamine), tertiary dimethyl amine (N, N-dimethyltridecanamine), and carbon-12 quaternary amine (N, N, -trimethyldodecaneammonium chloride) were tested for their ability to reduce experimentally applied populations of S. agalactiae or E. coli on the bovine teat surface. The five compounds were compared at concentrations of 100, 500, 1,000, 3,000, 7,000, and 10,000 ppm. Activity was greater against the gram-positive S. agalactiae than against the gram-negative E. coli. The tertiary amine was most active, producing a log reduction of 4 (reduction of bacterial number from 10(6) to 10(2)) at a concentration of 3,000 ppm in the teat dip. The relative order of effectiveness for the amines was: dimethyl tertiary greater than methyl secondary greater than ethyl secondary greater than primary = quaternary. The results suggest that these amines may be useful as potent, effective antibacterial agents for incorporation into teat dips.