Rapid assessment of cleanliness of commercial hog transport trailers using ATP bioluminescence method

Abstract

Abstract. Animal transport vehicles have been identified as a significant risk factor for transmission of pig diseases (such as PED), thus serious effort has been exerted to ensure that commercial transport trailers are properly washed, disinfected and inspected prior to use. At present, confirmation of cleanliness of a newly-washed and disinfected trailer involves conducting a thorough visual inspection of the trailer, supplemented by microbiological testing in certain situations. The traditional microbiological culture method takes at least 2-3 days to obtain the results, which can cause significant down-time for trailer operations and can delay implementation of corrective actions. In this study, the feasibility of using adenosine triphosphate (ATP) bioluminescence method as a rapid tool for assessing hog trailer cleanliness was investigated. Eighteen (18) newly-cleaned commercial trailers were tested using both ATP bioluminescence and microbiological techniques. In each trailer, six (6) locations including floors, walls, ramps, partitions and trailer exterior surfaces were sampled by swabbing an area of 10 cm x 10 cm for testing microbial contamination level using an ATP bioluminescence meter. These were compared with samples taken from the same locations using standard microbiological techniques with MacConkey and R2A agar contact plates (O = 60 mm). From a total of more than 500 paired samples collected from all the sampled trailers, a significant correlation (r = 0.206; p=0.001) was found between ATP bioluminescence method and standard microbiological technique using R2A agar plates. Lower correlation (r = 0.154; p=0.002) was observed between ATP method and MacConkey agar plate counts. R2A detects a wider group of bacteria compared to MacConkey, while ATP bioluminescence detects ATP from both microbial and organic sources. Based on the cleanliness rating criteria established for microbiological tests, equivalent threshold values for ATP bioluminescence method were derived, with readings of less than 430 RLU per 100 cm2 as ‘Pass‘ while higher than 850 RLU per 100 cm2 as ‘Fail‘ or has high risk of disease propagation. These equivalent criteria would enable the use of ATP bioluminescence method for rapid assessment of surface cleanliness of transport trailers.