Environmental swabs collected last Oct. 19 inside a Grandview, WA cheese processing facility were positive for Listeria monocytogenes, according to the U.S. Food and Drug Administration (FDA). So were samples of cheese taken from the company’s retail shelves.

FDA confirmed the Listeria contamination at the Yakima Valley business in an April 1 warning letter to Jesus Rodriguez Banuelos, owner of the Del Bueno cheese-making plant.

The warning letter was made public Tuesday.

“FDA laboratory analyses of the environmental swabs found the presence of Listeria monocytogenes (L. monocytogenes), a human pathogen, in your facility,” causing the company’s cheese products to be be considered adulterated within the meaning of the Federal Food, Drug, and Cosmetic Act, the FDA warning letter says.

FDA said it also recovered L. monocytogenes from two finished product samples of Del Bueno’s Quesco Fresco Cheese collected on Nov. 1 from retail stores.

FDA’s Pacific Regional Laboratory-Northwest gave Del Bueno the analytical results for the retail samples on Nov. 10, 2010, and the Grandview cheese processor recalled its cheese on Nov. 17.  Del Bueno also had recalled its cheese in April 2010.

In its warning letter, FDA said the Washington State Department of Agriculture (WSDA) also found L. monocytogenes in finished product samples.


“Analysis using Pulsed Field Gel Electrophoresis (“PFGE”) showed that L. monocytogenes isolates obtained from the FDA environmental sample collected on October 19, 2010, and finished product samples collected on November 1, 2010, were indistinguishable by both a primary and secondary enzyme; the observed PFGE pattern was also indistinguishable with isolates from environmental and food samples collected by the WSDA in March 2010 and November 2010,” FDA said. 

“When a PFGE pattern of an isolate is indistinguishable from the pattern of another isolate from a common source, it is highly likely that two isolates are the same strain of L. monocytogenes. These PFGE results suggest that L. monocytogenes may have been transported throughout your facility and established niche areas,” it continued.

“The presence of a persistent strain of L. monocytogenes in your facility between March 2010 and November 2010 is significant in that it demonstrates that sanitation efforts were inadequate to remove this organism.

FDA urged the Grandview business to document how its cleaning and sanitation operations to deal with surfaces that have the potential to become a nice for Listeria. If the company does not promptly address the issues, FDA said it may take further action, which could include seizing products or enjoining the company from operating.

L. monocytogenes, as the letter states, is a pathogenic bacterium that can be found in soil, silage and other environmental sources and also in man-made environments such as food processing establishments. Without proper controls, it can proliferate and may contaminate food.  Any moist area, such as a cheese production area, can harbor L. monocytogenes, which can survive and even grow at refrigeration temperatures. 

Consuming Listeria-contaminated foods can lead to a severe, sometimes life-threatening illness called listeriosis, an atypical foodborne illness of major public health concern due to the severity of the disease, its high case-fatality rate, long incubation, and predilection for individuals with underlying conditions.