Arcobacter Internalization in Fresh Produce: An Emerging Food Safety Issue under Extreme Weather Events

Introduction: The Arcobacter is an emerging waterborne and foodborne enteric pathogen. Arcobacter internalization is an important issue in raw vegetable consumption because washing and chlorination usually cannot remove the internalized pathogens effectively. 

Purpose: The objectives of this study were to 1) determine the extent of Arcobacter internalization into plants through roots or leaves; and 2) investigate the impact of extreme weather events, drought and heavy rains, caused by climate change. 

Methods:  A. butzleri was selected since it is a serious hazard to human health. Iceberg and romaine lettuce were cultivated, underwent three conditions (optimal, drought, storm) and contaminated with 10⁷, 10⁸ and 10⁹ colony forming unit (CFU)/g soil. 

Results: Results show that A. butzleri were internalized via entering the leaf surfaces and roots under all the weather conditions. Under the optimal condition (25–30 °C, 50–60% of relative humidity), a dose-dependency was observed. Under extreme conditions (drought and storm), the internalization level was higher than the lettuce grown at the optimal condition. Especially, under drought, the internalization level increased by 11 times and 20 times compared to the optimally irrigated group when the soil was contaminated with 8 and 9 log CFU/g soil, respectively. 

Significance: In summary, A. butzleri accumulate inside the lettuce from the contaminated soils and stay in the edible parts. The internalization levels were different depending on the location (leaf, root). The extreme weather conditions (drought or storm) can increase the level of internalization of A. butzleri.