2014 Outbreak of Listeria Infections Linked to Wholesome Soy Products, Inc. Sprouts

The U.S. Food and Drug Administration (FDA) isolated Listeria monocytogenes from mung bean sprouts and sprout irrigation water samples obtained during a routine assignment on August 13, 2014, at Wholesome Soy Products, Inc. Based on this finding, FDA conducted an inspection of the facility from August 12, 2014, through September 3, 2014, and isolated Listeria monocytogenes from 25 environmental swabs obtained during the inspection. FDA also issued a report with 12 inspectional observations, citing the firm for numerous unsanitary conditions and poor equipment maintenance.

On August 28, 2014, Wholesome Soy Products, Inc. agreed to conduct a voluntary recall of mung bean sprouts and notified customers by telephone. Wholesome Soy Products, Inc. ceased production of sprouts on August 28, 2014, and resumed production on September 15, 2014 after Listeria monocytogenes was not identified in the finished product. From October 7, 2014, to October 31, 2014, FDA re-inspected the facility and identified Listeria monocytogenes in nine environmental swabs. FDA investigators issued another report to the firm, noting 12 inspectional observations involving unsanitary conditions and poor equipment maintenance. Nine of these observations had persisted from the previous inspection.

On October 14, 2014, Wholesome Soy Products, Inc. ceased production of all products except mung bean and soy bean sprouts. On November 7, 2014, Wholesome Soy Products, Inc. verbally agreed to close their facility and to cease production and distribution of sprouts. The facility is no longer in production. Sprouts produced by Wholesome Soy Products Inc. are likely no longer available for purchase or consumption given the 5-day shelf life reported by the facility.

FDA performed pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS) on the isolates from mung bean sprouts and environmental samples from Wholesome Soy Products, Inc. to further characterize the Listeria isolates. Compared with PFGE, WGS provides a clearer distinction of genetic differences among Listeria isolates, and strains that are highly related by WGS are more likely to have a common source.

Public health investigators used PFGE and WGS to identify cases of illness that were caused by highly related strains and therefore possibly related to products made at Wholesome Soy Products, Inc. This included data from PulseNet, the national subtyping network of public health and food regulatory agency laboratories that are coordinated by CDC. 

Whole-genome sequences of Listeria strains isolated from five ill people were found to be highly related to sequences of the Listeria strain isolated from mung bean sprouts produced by Wholesome Soy Products, Inc. These ill people have been reported from two states: Illinois (4) and Michigan (1).  They became ill from June through August 2014. All five people were hospitalized, and two deaths were reported. Two of the five people were interviewed, and both reported consuming bean sprouts in the month before becoming ill.

The high degree of genetic similarity between isolates from ill people and from mung bean sprouts and environmental samples collected at Wholesome Soy Products, Inc. shows that the food was contaminated with a strain of Listeria monocytogenes that can cause serious illness. Although limited information is available about the specific sprout products that the ill people consumed, the whole genome sequencing findings, together with the sprout consumption history of two patients and inspection findings at the firm, suggest that these illnesses could be related to products from Wholesome Soy Products, Inc.

This investigation is closed. However, Listeria is still an important cause of human illness in the United States. More information about Listeria and steps people can take to reduce their risk of infection can be found on the CDC Listeria Web Page.

Investigation

The U.S. Food and Drug Administration (FDA) isolated Listeria monocytogenes from mung bean sprouts and sprout irrigation water samples obtained during a routine assignment on August 13, 2014, at Wholesome Soy Products, Inc. Based on this finding, FDA conducted an inspection of the facility from August 12, 2014, through September 3, 2014, and isolated Listeria monocytogenes from 25 environmental swabs obtained during the inspection. FDA also issued a report with 12 inspectional observations, citing the firm for numerous unsanitary conditions and poor equipment maintenance.

On August 28, 2014, Wholesome Soy Products, Inc. agreed to conduct a voluntary recall of mung bean sprouts and notified customers by telephone. Wholesome Soy Products, Inc. ceased production of sprouts on August 28, 2014, and resumed production on September 15, 2014 after Listeria monocytogenes was not identified in finished product. From October 7, 2014, to October 31, 2014, FDA re-inspected the facility and identified Listeria monocytogenes in nine environmental swabs. FDA investigators issued another report to the firm, noting 12 inspectional observations involving unsanitary conditions and poor equipment maintenance. Nine of these observations had persisted from the previous inspection.

On October 14, 2014, Wholesome Soy Products, Inc. ceased production of all products except mung bean and soy bean sprouts. On November 7, 2014, Wholesome Soy Products, Inc. verbally agreed to close their facility, cease production and distribution of sprouts, and recall sprouts that are already on the market. FDA continues to work with the company to ensure that they do not produce sprouts until FDA has ensured that this strain of Listeria is sufficiently controlled. Illinois Department of Public Health (IDPH) is working to embargo all product at Wholesome Soy Products, Inc. and the other wholesalers that presently have product. In addition, IDPH has asked local health departments to contact facilities in their jurisdictions that have received the product to have the facilities either hold the product or destroy per the CDC recommendations.

FDA performed pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS) on the isolates from mung bean sprouts and environmental samples from Wholesome Soy Products, Inc. to further characterize the Listeria isolates. Compared with PFGE, WGS provides a clearer distinction of genetic differences among Listeria isolates (strains that are highly related by WGS are more likely to have a common source).

Public health investigators used PFGE and WGS to identify cases of illness that were caused by highly related strains and therefore possibly related to products made at Wholesome Soy Products, Inc. This included data from PulseNet, the national subtyping network of state and local public health laboratories, CDC, and federal food regulatory laboratories that perform molecular surveillance of foodborne infections. 

Whole-genome sequences of Listeria strains isolated from five ill people were found to be highly related to sequences of the Listeria strain isolated from mung bean sprouts produced by Wholesome Soy Products, Inc. These ill people have been reported from two states: Illinois (4) and Michigan (1).  They became ill from June through August 2014. All five people were hospitalized, and two deaths were reported. Two of the five people were interviewed, and both reported consuming bean sprouts in the month before becoming ill.

The high degree of genetic similarity between isolates from ill people and from mung bean sprouts and environmental samples collected at Wholesome Soy Products, Inc. shows that the food was contaminated with a strain of Listeria monocytogenes that can cause serious illness. Although limited information is available about the specific sprout products that the ill people consumed, the whole genome sequencing findings, together with the sprout consumption history of two patients and inspection findings at the firm, suggest that these illnesses could be related to products from Wholesome Soy Products, Inc.

CDC, the states involved, and FDA continue to work closely on this ongoing investigation, and new information will be provided when available.