China - New PCR method to detect Campylobacter jejuni

A highly specific, fast and sensitive PCR based method to detect C. jejuni has been developed by researchers in China. Campylobacter jejuni is a species of curved, rod shaped bacteria, and is responsible for an estimated 14 per cent of diarrhoea worldwide. The possible sources of infection include unpasteurised milk, undercooked meat products, while the major source is poultry and poultry products. Current detection methods are time-consuming and laborious, hampered by the fact that the infective dose of C. jejuni is very small - as few as 500 cells are estimated to be enough to cause human illness. The new method, developed by Guangming Liu and colleagues at Shantou University, Xiamen University and the Inspection and Quarantine Bureau, involves isolation of the target pathogen by immunocapture using a polymerase chain reaction (PCR). Two species-specific gene sequences were identified that would allow detection by fluorescent PCR. Special sequences in the flaA gene and the hipO gene were reported to be specific to C. jejuni and were also anti-jamming, which means the sequences in C. jejuni can be detected even in a bacterial mixture. “When two pairs of primer/probe targeting hipO and flaA genes were applied, it was positive for all isolates of C jejuni,” wrote Liu in Food Control (vol. 17, pp.527-532). “The method permits direct detection of this bacterial pathogen without the need for enrichment and can be performed in approximately eight hours, thus making it more rapid than the other direct PCR methods or cultivation,” said Liu. The method also positively identified C. jejuni in the presence of 13 other bacteria, proving its high specificity. “We believe that the IMC-FPCR assay has potential as a surveillance method for the maintenance of food safety,” concluded the researchers. Food safety and early warning systems are a growing area of study. In April 2004 researchers from Barcelona, Spain, developed miniature sensors that could positively identify Salmonella DNA inside 4 hours.