Investigation of Listeria monocytogenes contamination pattern in local Chinese food market and the tracing of two clinical isolates by RAPD analysis Original Research Article

This study was undertaken to investigate the contamination pattern of Listeria monocytogenes in local Chinese food markets and to trace two clinical isolates. Random amplification polymorphic DNA (RAPD) was developed to track the source of L. monocytogenes in ready-to-eat (RTE) food products and from clinical origin. Three random primers, PB1, PB4 and HLWL74, were used to subtype all the L. monocytogenes strains isolated from RTE food products, fresh food products, environmental sewages in the markets and two clinical meningitis patients. It was shown that all the 49 isolates could be classified into 5, 4 and 4 types using these three random primers, PB1, PB4, and HLWL74, respectively. Twenty-seven composite profiles were identified by a combination of the three primers. The same composite profiles of L. monocytogenes could be found both in the fresh food products, environmental sewages and RTE food products, suggesting that the L. monocytogenes in the RTE food products may come from those in the fresh food products or sewage in the same market. The composite profiles of the two clinical isolates were the same as those of strains isolated from RTE food products, indicating that the disease might have resulted from the consumption of the RTE food products contaminated with L. monocytogenes. The results show that RAPD could be a powerful tool for the investigation of contamination pattern of L. monocytogenes in Chinese food markets and also for tracking the source of L. monocytogenes in clinical patients.