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Multistate Outbreak of Listeriosis Linked to Crave Brothers Farmstead Cheeses (Final Update)

Posted September 24, 2013 1:00 PM ET

This outbreak appears to be over. Listeria monocytogenes infection (listeriosis) is an important cause of illness in the United States. More information about listeriosis, and steps people can take to reduce their risk of infection, can be found on the CDC Listeria Web Page.

At a Glance:

Highlights

Outbreak Summary  ⇑

Introduction

CDC collaborated with public health and regulatory officials in several states and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of Listeria monocytogenes infections (listeriosis). Joint investigation efforts indicated that Les Frères, Petit Frère, and Petit Frère with Truffles cheeses made by Crave Brothers Farmstead Cheese Company of Waterloo, Wisconsin was the likely source.

Public health investigators used DNA “fingerprints” of Listeria obtained through testing with pulsed-field gel electrophoresis, or PFGE, to identify cases of illness that may have been part of this outbreak. They used data from PulseNet, the national subtyping network of state and local public health laboratories and federal food regulatory laboratories that performs molecular surveillance of foodborne infections. The DNA fingerprint of the outbreak strain is typically associated with about 14 cases per year, even in the absence of a recognized outbreak. For this reason, whole genome sequencing, a highly discriminatory subtyping method, was also used to define the outbreak strain. Whole genome sequencing helped clarify which patients’ illnesses were related to the outbreak.

A total of six persons infected with the outbreak strain of Listeria monocytogenes were reported from five states. The number of ill people identified in each state was as follows: Illinois (1), Indiana (1), Minnesota (2), Ohio (1), and Texas (1). No new ill persons were reported since the last update on August 22, 2013.

Among persons for whom information was available, dates that illness was diagnosed ranged from May 20, 2013 to July 7, 2013. All six ill persons were hospitalized. Ill persons ranged in age from 30 years to 67 years, with a median age of 55 years, and 83% were female. One death was reported in Minnesota. In addition, one illness in a pregnant woman resulted in a miscarriage.

Investigation of the Outbreak

Epidemiologic, laboratory, and traceback investigations conducted by officials in local, state, and federal public health, agriculture, and regulatory agencies indicated that cheeses manufactured by Crave Brothers Farmstead Cheese Company was the likely source of this outbreak of listeriosis.

In interviews, ill persons answered questions about foods consumed and other exposures in the month before becoming ill. Information about specific cheeses consumed was available for five of the six ill persons. Of those, all five either definitely or probably ate Les Frères cheese made by Crave Brothers before getting sick.

On July 3, 2013, Crave Brothers Farmstead Cheese Company voluntarily recalled its Les Frères, Petit Frère, and Petit Frère with Truffles cheeses with make dates of July 1, 2013 or earlier due to possible Listeria monocytogenes contamination. The recalled cheeses were distributed nationwide through retail and food service outlets, as well as by mail orders.

Between July 2 and July 10, 2013, FDA conducted an inspection at the firm's processing facility in cooperation with the Wisconsin Department of Agriculture.  During that inspection, FDA collected a sample of Petit Frère with Truffles that was found to contain Listeria monocytogenes with the same DNA fingerprint as the outbreak strain. Laboratory tests conducted by the Minnesota Department of Agriculture on samples of Les Frères and Petit Frère with Truffles cheeses made by Crave Brothers from two retail stores also indicated the presence of Listeria monocytogenes with the same DNA fingerprint. 

As of September 24, 2013, the firm is not in production. FDA and the Wisconsin Department of Agriculture are working closely to review the firm's corrective actions before the firm is authorized to resume cheese production.

Progression of the Outbreak Investigation  ⇑

September 24, 2013

Final Case Count Update

A total of six persons infected with the outbreak strain of Listeria monocytogenes were reported from five states. The number of ill people identified in each state was as follows: Illinois (1), Indiana (1), Minnesota (2), Ohio (1), and Texas (1). No new ill persons were reported since the last update on August 22, 2013.

Among persons for whom information was available, dates that illness was diagnosed ranged from May 20, 2013 to July 7, 2013. All six ill persons were hospitalized. Ill persons ranged in age from 30 years to 67 years, with a median age of 55 years, and 83% were female. One death was reported in Minnesota. In addition, one illness in a pregnant woman resulted in a miscarriage.

August 22, 2013

Case Count Update

A total of six persons infected with the outbreak strain of Listeria monocytogenes have been reported from five states. Since the last update, one ill person has been reported from Texas.

Among persons for whom information is available, dates that illness was diagnosed range from May 20, 2013 to July 7, 2013. All six ill persons were hospitalized. Ill persons range in age from 30 years to 67 years, with a median age of 55 years, and 83% are female. One death was reported in Minnesota. In addition, one illness in a pregnant woman resulted in a miscarriage.

Clinical specimens that were collected after August 10, 2013 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 3 weeks.

Investigation Update

Information about specific cheeses consumed is available for five of the six ill persons. Of those, all five either definitely or probably ate Les Frères cheese made by Crave Brothers before getting sick.

Public health investigators used DNA "fingerprints" of Listeria bacteria obtained through diagnostic testing with pulsed-field gel electrophoresis (PFGE) to identify cases of illness that may be part of this outbreak (PulseNet). The DNA fingerprint of the outbreak strain is typically associated with about 14 cases per year, even in the absence of a recognized outbreak. For this reason, whole genome sequencing, a novel highly discriminatory subtyping method, is also being used to define the outbreak strain. Whole genome sequencing has helped clarify which patients’ illnesses are related to the outbreak.

Between July 2 and July 10, 2013, the FDA conducted an inspection at the firm’s processing facility in cooperation with the Wisconsin Department of Agriculture. During that inspection, the FDA collected a sample of Petit Frère with Truffles that was found to contain Listeria monocytogenes with the same DNA fingerprint as the outbreak strain.

The firm stopped production and the FDA and the Wisconsin Department of Agriculture are monitoring corrective action being made by the firm.

Initial Announcement

July 5, 2013

CDC is collaborating with public health and regulatory officials in several states and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of Listeria monocytogenes infections (listeriosis). The joint investigation indicates that Les Frères, Petit Frère, and Petit Frère with Truffles cheeses made by Crave Brothers Farmstead Cheese Company of Waterloo, Wisconsin is the likely source of this outbreak.

Public health investigators are using DNA “fingerprints” of Listeria obtained through testing with pulsed-field gel electrophoresis, or PFGE, to identify cases of illness that may be part of this outbreak. They are using data from PulseNet, the national subtyping network of state and local public health laboratories and federal food regulatory laboratories that performs molecular surveillance of foodborne infections.

A total of five persons infected with the outbreak strain of Listeria monocytogenes have been reported from four states. The number of ill people identified in each state is as follows: Illinois (1), Indiana (1), Minnesota (2), and Ohio (1).

Among persons for whom information is available, dates that illness was diagnosed range from May 20, 2013 to June 17, 2013. All five ill persons were hospitalized. Ill persons range in age from 31 years to 67 years, with a median age of 58 years, and 80% are female. One illness in a pregnant woman resulted in a miscarriage. One death was reported in Minnesota.

The outbreak can be visually described with a chart showing the number of persons who were diagnosed each day. This chart is called an epidemic curve or epi curve. Clinical specimens that were collected after June 22, 2013 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 3 weeks.

About 800 laboratory-confirmed cases of listeriosis are reported each year in the United States, and typically 3 or 4 outbreaks are identified and reported to CDC annually. Some foods that have been linked to outbreaks in recent years are Mexican-style soft cheeses, imported ricotta salata cheese, whole cantaloupe, raw sprouts, and precut celery. 

Investigation of the Outbreak

Epidemiologic, laboratory, and traceback investigations conducted by officials in local, state, and federal public health, agriculture, and regulatory agencies indicate that Les Frères, Petit Frère, and Petit Frère with Truffles cheeses manufactured by Crave Brothers Farmstead Cheese Company is the likely source of this outbreak of listeriosis.

In interviews, ill persons answered questions about foods consumed and other exposures in the month before becoming ill. All five ill persons reported consuming a soft cheese. Information about specific cheeses consumed is available for four of the ill persons. Of those, three either definitely or probably ate Les Frères cheese made by Crave Brothers before getting sick. Investigation of specific types of cheeses consumed by other ill persons is ongoing.

Laboratory tests conducted by the Minnesota Department of Agriculture on samples of Les Frères and Petit Frère with Truffles cheeses made by Crave Brothers from two retail stores indicate the presence of the outbreak strain of Listeria monocytogenes.  Further testing and confirmation of the results are pending.

On July 3, 2013, Crave Brothers Farmstead Cheese Company of Waterloo, Wisconsin voluntarily recalled its Les Frères, Petit Frère, and Petit Frère with Truffles cheeses with make dates of July 1, 2013 or earlier due to possible Listeria monocytogenes contamination. The recalled cheeses were distributed nationwide through retail and foodservice outlets as well as by mail orders.

The FDA is conducting an inspection at Crave Brothers’ processing facility in coordination with the Wisconsin Department of Agriculture. FDA is working closely with CDC, Crave Brothers, and public health authorities in states where illnesses occurred to determine the exact cause of contamination.

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