Submitted to: Canadian Journal of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2009
Publication Date: 6/8/2009
Citation: Rothrock Jr, M.J., Cook, K.L., Bolster, C.H. 2009. Comparative quantification of Campylobacter jejuni from environmental samples using traditional and molecular biological techniques. Canadian Journal of Microbiology. 55: 633–641
Interpretive Summary: Campylobacter jejuni (C. jejuni) is one of the most common causes of gastroenteritis in the world. Given the potential risks to human, animal and environmental health the development and optimization of methods to quantify this important pathogen in environmental samples is essential. In this study, we compared two common techniques used for the detection and quantification of C. jejuni, selective plate counts and quantitative, real-time polymerase chain reaction (QRT-PCR). We found that QRT-PCR more accurately enumerated C. jejuni from a variety of environmental samples (water, leachate, soils), and was able to distinguish smaller differences in C. jejuni concentrations between samples as compared to selective plate count concentrations. Selective plate count concentrations tended to be 10-100 times lower than QRT-PCR concentrations. E. coli, a common indicator organism, did not exhibit this same difference between the two methods, with both selective plate counts and QRT-PCR yielding similar results from environmental samples. Additionally, E. coli was not found to be an effective indicator organism for C. jejuni from environmental samples. Overall, this work suggests that QRT-PCR is the more precise and accurate technique to detect and quantify C. jejuni from the environment and E. coli is not an effective indicator organism for C. jejuni from those environments.
Technical Abstract: Campylobacter jejuni (C. jejuni) is one of the most common causes of gastroenteritis in the world. Given the potential risks to human, animal and environmental health the development and optimization of methods to quantify this important pathogen in environmental samples is essential. Two of the most commonly used methods for quantifying C. jejuni are selective plate counting and quantitative real-time PCR (QRT-PCR). Unfortunately, the efficacy of using these techniques for environmental samples is dependant on the microbe of interest, and little comparative research has been performed to evaluate the accuracy of these methods for quantification of Campylobacter jejuni. In this study, the limit of detection and level of resolution obtained using these two methods was evaluated for C. jejuni and compared to that of the common indicator organism Escherichia coli (E.coli). The use of selective plate count media for quantification of C. jejuni resulted in a 0.7-1.2 log underestimation of cell concentrations, as compared to QRT-PCR in both water and column leachate samples, while E. coli concentrations were found to be similar using either technique. For C. jejuni, only the QRT-PCR assay accurately measured two-fold changes in cell concentrations in water samples, while concentrations of E. coli were accurately measured regardless of method. Based on these data, QRT-PCR assays were found to be more accurate than selective plate counts for quantification of C.jejuni from environmental samples.