Survival of Campylobacter and Salmonella in transport medium

The detection of food born pathogens in the field can be complicated, especially for Campylobacter, which is sensitive to drying and high oxygen concentrations. Besides, time for transport of the samples to the laboratory may take several hours to days. Swabs tubes are on the market, consisting of a dry swab with a specific gel medium which facilitates survival of micro-organisms during transport. In this study, the performance of transport swabs was tested with Campylobacter and Salmonella in pure cultures and artificially contaminated fecal samples of chickens and bats. Appropriate dilutions of C. jejuni, C. lari and S. livingstone were sampled (100 µl) with Transystem Amies medium (Copan Diagnostics Inc., 108.USE) transport swabs to reach inoculation levels of 105, 102, 10 and 1 CFU per transport tube. For fecal samples, similar dilutions of the pathogens were added to 10% fecal matter of chickens and bats. The tubes were examined within one hour and 1,2,3 and 7 days after storage at 7°C. Campylobacter was isolated using Bolton Broth, Preston Broth and CCDA; Salmonella was cultured on BPW, MSRV and BGA/XLD. The pathogens were simply recovered from pure culture samples, up to 7 days of storage at inoculation levels as low as 10-102 CFU/tube. Similar results were obtained with fecal matter samples except for chicken feces: due to large amounts of contaminating flora, Campylobacter could only be isolated until 3 days of storage at low contamination levels of 10 CFU/tube whereas levels normally present in contaminated chickens (=105/g), were readily detected. In conclusion, the tested transport swabs perform well and Campylobacter and Salmonella are easily isolated both in pure cultures and in fecal matter, at levels normally present in fecal samples even after 7 days of storage at 7°C.