Microbial Safety and Sanitary Quality of Strawberry Primary Production in Belgium: Risk Factors for Salmonella and Shiga Toxin-Producing Escherichia coli Contamination

Abstract

ABSTRACTStrawberries are an important fruit in Belgium in both production and consumption, but little information is available about the presence ofSalmonellaand Shiga toxin-producingEscherichia coli(STEC) in these berries, the risk factors in agricultural production, and possible specific mitigation options. In 2012, a survey was undertaken of three soil and three soilless cultivation systems in Belgium. NoSalmonellaspp. were isolated. No STEC was detected in the strawberry samples (0 of 72), but STEC was detected by PCR in 11 of 78 irrigation water and 2 of 24 substrate samples. Culture isolates were obtained for 2 of 11 PCR-positive irrigation water samples and 2 of 2 substrate samples. Multivariable logistic regression analysis revealed elevated genericE. colinumbers (the odds ratio [OR] for a 1 log increase being 4.6) as the most important risk factor for STEC, together with the berry-picking season (elevated risk in summer). The presence of genericE. coliin the irrigation water (≥1 CFU per 100 ml) was mainly influenced by the type of irrigation water (collected rainfall water stored in ponds was more often contaminated than groundwater pumped from boreholes [OR = 5.8]) and the lack of prior treatment (untreated water versus water subjected to sand filtration prior to use [OR = 19.2]). The follow-up study in 2013 at one of the producer locations indicated cattle to be the most likely source of STEC contamination of the irrigation water.