Inspectors from the U.S. Food and Drug Administration recently found Listeria monocytogenes in an onion processing facility in Washington state where some wholesale vegetable products, recalled in April, may be linked to several illnesses. The Oregon Potato Co., doing business as Freeze Pack, was told in a July 15 warning letter from FDA’s Seattle District Office that, following a March inspection of its processing plant in Pasco, WA, a number of environmental swabs taken there tested positive for the pathogen. FDA’s laboratory analysis of samples collected March 8 and 9 confirmed that 19 out 106 environmental swabs tested positive for Listeria monocytogenes. The warning letter noted that seven positive environmental swabs were collected from direct food contact surfaces in the plant’s processing and packaging rooms during the production of individually quick frozen (IQF) diced onions. Those direct food contact surface areas included:
- The chiller water and the interior north wall of the water chiller. Water from this chiller is not treated and is recirculated back to the blancher/chiller and used directly on blanched diced onions as a coolant;
- A white nylon strip in the tunnel discharge chute between the IQF freezer and the finished product packaging room. Blanched, finished onions are conveyed and come into direct contact with the nylon strip; and,
- The metal arm on the chain conveyor belt between the IQF freezer and packaging room where blanched, finished product is conveyed directly on this conveying system and comes into contact with the metal arm.
The remaining 12 positive environmental swabs were collected from locations in the plant’s processing room and the packaging room in areas adjacent to food contact surfaces and non-direct food contact surfaces, FDA stated. The 19 environmental samples were also analyzed using whole genome sequencing (WGS), which FDA noted can establish direct links between clinical isolates from sick people and food or environmental sources. The analysis found links between the isolates from the production plant and sick people, the agency stated. “The WGS phylogenetic analysis establishes that there are at least two different strains of L. monocytogenes present in the facility, with one strain containing 17 isolates and the second strain containing two isolates,” FDA stated. “Specifically, the WGS analysis of the strain with 17 isolates showed that the isolates are identical to each other. WGS analysis of the strain with two isolates showed that the isolates are identical to eight cases of human illness dating back to 2013, and to six isolates from finished products. These finished products included onions, with two isolates in 2014, and green beans with three isolates in 2015, tested by a third party laboratory, and a single isolate from white sweet corn collected and tested by the state of Ohio in 2016. Additional investigation established that at least six individuals were hospitalized as a result of related L. monocytogenes associated illness,” according to the warning letter. Violations of Current Good Manufacturing Practice (CGMP) regulations were also observed at the facility, FDA told the company. These problems included accumulated food debris and grime on some food contact surfaces, insufficient measures to keep drip or condensate from contaminating food or food contact surfaces or food packaging materials, and inadequate ventilation or control equipment to minimize vapors — including steam — from contaminating food items. Oregon Potato Co. contacted FDA after receiving the warning letter and detailed corrective actions it was taking. The company also ceased production in order to clean and sanitize all surfaces in the facility, FDA noted, and submitted environmental testing samples taken alongside those taken by the agency, which were negative for Listeria. However, FDA responded that it was unable to evaluate the adequacy of the measures to be taken without further information and that there was no timeline submitted for completion or for resuming operations. As for the negative Listeria results the company submitted, FDA questioned the firm’s sample testing. “Given that FDA’s sampling revealed 19 environmental swabs that tested positive for L. monocytogenes, we are concerned with the adequacy of your sampling program. Your response included the general protocol reference guide for the method utilized by your laboratory. However, your firm did not provide detailed documents on the actual laboratory method that was performed to provide a comprehensive review of this issue,” the warning letter stated. The letter also mentioned the company’s recalled frozen vegetables:
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