A bioluminescent strain of avian pathogenic Escherichia coli (APEC) was developed.
In vitro correlations were found between luminescence and number of bacteria.
Ex vivo luminescence was correlated with the number of bacteria in tissues of chickens.
Bioluminescent labelling was useful for differentiation and identification of the infecting APEC strain.
The luminescent strain can be used to monitor colibacillosis and treatment effects.