Combined detection of foodborne pathogens in irrigation water in Jiangsu, China.

Abstract

Numerous foodborne disease outbreaks have been attributed to the consumption of fresh produce contaminated with foodborne pathogens. Contaminated irrigation water is a well-established source of bacterial and viral contamination during primary production and is frequently responsible for the contamination of fresh produce. However, efficient methods for the simultaneous detection of bacterial and viral pathogens present in irrigation water are still scarce. A new recombined method was developed to recover two foodborne viruses (human norovirus [huNoV, GI and GII] and rotavirus [RV]) and three pathogenic bacteria (Salmonella Enteritidis, Listeria monocytogenes, and Staphylococcus aureus) from irrigation water for strawberry production. The foodborne viruses and pathogenic bacteria were effectively recovered from spiked water using this method, even at low concentrations. The detection limits of the viruses (huNoV GII, huNoV GI, and RV) were 11, 4.5, and 16 genocopies/mL, while the detection limits of pathogenic bacteria (S. Enteritidis, L. monocytogenes, and S. aureus) were 7, 10, and 4 cells/mL. Using this method, the presence of foodborne pathogens in strawberry irrigation water samples collected from the Jiangsu province (China) was confirmed, with 61 % of samples testing positive for huNoV GII, 38.7 % for huNoV GI, 29.0 % for Salmonella spp., 16.1 % for L. monocytogenes, 9.7 % for S. aureus, and 3.2 % for RV or hepatitis A virus (HAV). HuNoV was also detected in strawberry samples, collected simultaneously from the same farm, when high huNoV detection frequencies and contamination levels were found in irrigation water samples, indicating that huNoV-contaminated irrigation water is a risk when used for strawberry production. This is the first report on the simultaneous detection of selected viral and bacterial pathogens from irrigation water in China, with the new method reported applicable for monitoring other relevant pathogens (e.g., coronavirus) in various water resources.