Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/5/2003
Publication Date: 10/3/2003
Citation: Line, J.E. 2003. Development of a selective broth medium for the detection of injured Campylobacter jejuni by capacitance monitoring. Journal of Food Protection. 67:901-907. Interpretive Summary: Campylobacters are foodborne pathogens of primary importance. To improve food safety, the need exists for rapid, automatable methods for detecting viable campylobacters in foods. Traditional enumeration of campylobacters involves time consuming procedures requiring up to 72 h for analysis and special microaerobic conditions. Conductimetric instruments monitor microbial metabolism inside a growth medium by the measurement of significant changes in electrical activity and may provide results in a timely manner. We developed a simple, more rapid method and broth media for Campylobacter detection using conductimetric methods without providing modified atmospheric conditions for growth. Using stressed pure cultures, Campylobacter growth was repeatably detected at very low inoculum levels (about one cell per well). There was a direct linear relationship between detection times (DT) and the initial inoculum level: suggesting that a standard curve could be plotted enabling the use of DT to more rapidly predict campylobacter populations in a sample than traditional methods. This information will be useful to food safety researchers and technicians in industry, academia and government. The poultry industry may be especially interested as further studies are ongoing to adapt this method specifically for the rapid detection of Campylobacter spp. from poultry products.
Technical Abstract: The purpose of these studies was to develop a conductimetric method for the rapid detection of Campylobacter spp. Numerous basal media components were analyzed to develop a growth- enhancing broth media for detection of freeze-injured Campylobacter cells using a conductimetric system. The final media was comprised of a modified Campy-Line agar from which the agar and TTC were removed and the amino acid, L-arginine was added. Pure isolates of Campylobacter spp. (frozen and thawed to produce stressed cells) were utilized to test the detection methodology. Monitoring of significant changes in the capacitance signal was found suitable for detection of Campylobacter proliferation. Using stressed pure cultures, Campylobacter growth was repeatably detected at very low inoculum levels (about one cell per well). There was a direct linear relationship between detection times (DT) and the initial inoculum level. For example, using a single strain, the mean DT (n=20) at the 10 cfu/ml inoculum level was 28.6 h with 100% of the inoculated wells detecting. The mean DTs at the 100, 1000, and 10000 cfu/ml inoculum levels were 24.9 h, 21.4 h, and 17.0 h, respectively. Further studies are ongoing to adapt this method for the rapid detection of Campylobacter spp. from poultry products.