Evaluation of in vitro bactericidal activity of commercial disinfectants against Lawsonia intracellularis

Wattanaphansak S, Singer RS, Gebhart CJ

Objective: To evaluate the bactericidal activity of seven commercial disinfectants against Lawsonia intracellularis using a tissue culture system.

Materials and methods: Two L intracellularis isolates were tested for susceptibility to several classes of disinfectants, including iodine, a biguanide, phenol, an oxidizing agent, a quaternary ammonium compound (QAC), and the combinations of QACs with aldehydes (formaldehyde and glutaraldehyde). All disinfectants were diluted with simulated hard water by adding 400 or 1000 ppm of calcium carbonate (CaCO3) and 5% fetal bovine serum (FBS). The effects of disinfectant concentrations (0.5×, 1×, and 2× the recommended dose) and exposure times (10, 30, and 60 minutes) at each concentration were investigated.

Results: The susceptibilities of both L intracellularis isolates to the disinfectants were similar. When recommended doses of disinfectants were tested for 10 minutes at 400 ppm of CaCO3 and 5% FBS, both L intracellularis isolates were completely inactivated with QAC and the combinations of QAC with aldehydes. Inactivation was ≥ 99% with the oxidizing agent, 90% to 99% with the biguanide and phenol, and < 90% with iodine. At a CaCO3 concentration of 1000 ppm, the efficacies of combinations of QAC with glutaraldehyde were unchanged, while efficacies of the other disinfectants were reduced slightly.

Implications: These data provide an in vitro guide for disinfectant selection to control L intracellularis. The results suggest that QAC, the combinations of QACs with aldehydes, and oxidizing agents would perform well for inactivation of L intracellularis under field conditions.

Journal of Swine Health and Production 18:11-17