Evaluation of cleaning and disinfection strategies to control Escherichia coli aggregates and biofilms in swine transportation

Abstract

Livestock transport trailers can act as important vehicle of microbial persistence. After transport, trailer surfaces may retain fecal material and moisture, which can reduce the effectiveness of cleaning and disinfection. Escherichia coli can survive under these conditions and persist as aggregates or biofilm microbial communities, making disinfection more difficult to achieve. Innovative and effective cleaning and disinfection strategies are therefore needed to reduce microbial persistence and limit the risk of cross-contamination in live-haul environments. The objective of this research was to evaluate cleaning and disinfection strategies to control E. coli aggregates and biofilms associated with swine transport environments and to evaluate a selected treatment under field conditions. Two complementary studies were conducted. In the first study, E. coli TVS 353 was used to form aggregated cells and biofilms on aluminum coupons. Coupons were subjected to one of three mechanical cleaning procedures, scraping, vacuuming, or air, followed by disinfection treatments: 3% hydrogen peroxide (30 s), 400 ppm quaternary ammonium compounds (1 min), 400 ppm sodium hypochlorite (1 min), steam (100 °C, 30 s), carbon dioxide (30 s), and chlorine dioxide gas (500 ppm, 10 min). Treatments were evaluated at 30, 18, and 10 °C to represent seasonal transport conditions. Treatment efficacy was influenced by cleaning methods, disinfection treatment, temperature, and bacterial cell state (P < 0.05). Aggregated cells were more susceptible than biofilm cells (P < 0.001). The greatest reductions for aggregated cells ranged from 4.50 to 5.06 log CFU/cm², while the greatest reductions for biofilm cells ranged from 3.78 to 3.87 log CFU/cm². In the second study, 3% hydrogen peroxide applied for 30 s after pressure washing was evaluated in a naturally contaminated swine trailer. Aerobic counts were measured before cleaning, after pressure washing, and after hydrogen peroxide application. Aerobic counts were affected by intervention step (P < 0.001), surface type (P < 0.001), and their interaction (P = 0.004). Hydrogen peroxide produced additional significant reductions of 1.36 to 1.80 log CFU/cm² across trailer sections and 1.13 to 1.95 log CFU/cm² across surfaces after pressure washing. Total reductions from initial counts to after hydrogen peroxide application ranged from 1.67 to 2.52 log CFU/cm² across trailer sections and were 1.76 and 2.27 log CFU/cm² on the floor and wall. However, counts were higher on the floor than on the wall initially and after hydrogen peroxide application. Overall, the laboratory study identified treatment combinations that reduced E. coli aggregates and biofilms, while the field study showed that hydrogen peroxide further reduced aerobic counts after pressure washing, although its effect varied by surface type. These findings emphasize that C&D performance depends on microbial cell state, cleaning method, disinfectant, temperature, and surface characteristics.