Rapid quantification of coliforms in ready-to-eat foods using lateral-flow immunochromatographic assay

The degree of coliform contamination in pastries was estimated based on culturing times until positive results were obtained with the lateral-flow immunochromatographic assay (LFIA). Coliform generaCitrobacter, Cronobacter, Enterobacter, Klebsiella, Kluyvera, Pantoea, Raoultella, andSerratiawere detected in spoiled pastries, as established with next-generation sequencing. A lateral-flow test strip was constructed using antibodies recognizing the above genera. The culture times required for positive detection with LFIA were 0, 3, 6, and 9 hr at initial inoculation concentrations of 3.8, 2.8, 1.8, and 0.8 log(10)(cfu/ml), respectively. In pastries contaminated with >5.0, 3.0-5.0, 2.0-3.0 log(10)(cfu/g) coliform bacteria, samples became LFIA-positive from 3, 6, and 9 hr culture, respectively. LFIA showed negative for pastries with <2.0 log(10)(cfu/g) coliform contamination. The quantitative category of initial coliform content before culture was predictable with 87% accuracy. This novel method can be applied to monitor food safety of other ready-to-eat consumables.