Food Poisoning Lawyer & Attorney : Marler Clark : Food Poison Blog

The outbreak investigation into the Listeria outbreak traced to the consumption of Whittier Farms milk products revealed contamination in several areas of the milk plant, according to reports from the Boston Herald and the Metro West Daily News. 

The Massachusetts Department of Public Health announced today:

More than 100 environmental and milk samples were taken from the processing plant as part of the investigation. A total of twelve milk samples and four environmental samples tested positive for varying strains of Listeria contamination (see summary below).

The findings do not pinpoint where the contamination of the milk occurred, but they do suggest that Listeria bacteria colonized somewhere in the processing plant and that the bacteria entered the milk products at some point during the production process. Records indicate that the plant’s equipment met federal standards for time, temperature and flow for effective pasteurization, however, pasteurization at the processing plant will be further examined.

The presence of Listeria in the physical plant of the facility is consistent with contamination occurring during post-pasteurizing processing and bottling. One theory under consideration by health officials is that cleaning activities at the plant may have unintentionally caused contamination of the processing equipment allowing bacteria to enter the finished milk products. Three of the four positive environmental tests for Listeria were collected from sections of the plant that are considered part of the post-pasteurization areas of the facility.

Listeria is the common name for the pathogenic or disease-causing bacterium known as Listeria monocytogenes. It is a foodborne illness that when ingested causes an infection known as listeriosis (Cossart & Bierne, 2001). Approximately 2,500 illnesses and 500 deaths are attributed to listeriosis in the United States annually (CDC, 2005).

Listeria is ubiquitous in the environment, and can be isolated from wild and domestic animals, birds, insects, soil, wastewater, and vegetation. The bacterium easily comes into contact with farm animals as it has been found to be present in grazing areas, stale water, and poorly prepared animal feed. In addition to being present in the environment, Listeria can live in the intestines of humans, animals and birds for long periods of time without causing infection. Because Listeria is present in nearly every environment - including in some food processing facilities - numerous opportunities for contamination exist during the food production process (Cossart & Bierne, 2001).

• Email This
• Print
• Comments
• Trackbacks
• Share Link

The Boston Globe reported today on the death of an 87-year-old man who passed away after suffering a Listeria infection he contracted from drinking milk supplied by the Whittier Farms Dairy.  Stephen Smith, the story's author, wrote about this most recent death and about the illness of a pregnant woman and her baby:

The 87-year-old man fell ill in November and died Thursday, said Donna Rheaume, spokeswoman for the state department of public health.

The number of people sickened by listeria bacteria also rose to five after health officials linked a 31-year-old woman's listeriosis, diagnosed in September, to products from the diary.

The infection was detected while the woman was in the hospital to deliver a baby, and "both mother and child are doing well," Rheaume said.

Elderly populations and pregnant women are the most vulnerable populations to Listeriosis, the illness caused by the ingestion of Listeria monocytogenes bacteria. 

Certain groups of individuals are at great risk for listeriosis. These are pregnant women (and their unborn children) and immunocompromised persons (e.g., transplant recipients). Among infants, listeriosis occurs when the infection is transmitted from the mother, either through the placenta or during the birthing process. These host factors, along with the amount of bacteria ingested and the virulence of the strain, determine the risk of disease.

Listeria can invade the body through a normal and intact gastrointestinal tract. Once in the body Listeria bacteria can travel through the blood stream, but are often found inside cells (they are "intracellular" pathogens). Listeria can co-opt the cell's machinery to its own advantage by manipulating the host cell genes, and then move directly from cell-to-cell, avoiding many of the host's defense mechanisms5. The bacteria also produce toxins that damages cells.

For unknown reasons, in immune-deficient hosts Listeria invades and grows best in the central nervous system, causing meningitis and/or encephalitis (brain infection). In pregnant women, the fetus is most heavily infected, leading to spontaneous abortion, stillbirths, or sepsis in infancy.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Public health officials in Massachusetts have confirmed that a listeriosis outbreak was caused by the consumption of milk purchased from Whittier Farms.  They used Pulsed Field Gel Electrophoresis (PFGE) to obtain the "genetic fingerprint" of the strain of Listeria that was isolated from case-patients and milk provided by the dairy for testing. 

PFGE is a technique used to separate the DNA of a bacterial isolate into its component parts. It operates by causing alternating electric fields to run the bacteria's DNA through a flat gel matrix of agarose, a polysaccharide obtained from agar. The pattern of bands of the DNA fragments — or “fingerprints” — in the gel after exposure to the electrical current is unique for each strain and sub-type of bacteria. By performing this procedure, scientists can identify hundreds of strains of Listeria, E. coli O157:H7, and and other pathogenic bacteria.

PFGE patterns of bacteria isolated from products can be compared and matched to PFGE patterns of bacteria isolated from people suffering illness after consuming contaminated products. When PFGE patterns of bacteria isolated from foods and human samples match, they, along with solid epidemiological work, provide proof that the contaminated product was the source of a person's illness.

The Boston Globe reported on the outbreak investigation today:

"The pattern is very unique," said Dr. Alfred DeMaria, the state's director of communicable disease control. "It means there's an outbreak here. There's no question there's an outbreak. And it implies that the dairy is the common source."

It is exceedingly rare, disease investigators said, to discover that cases of listeria are caused by germs with identical genetic profiles. Instead, each infection tends to be the result of a slightly different form of the bacterium.

In 19 other cases in 2007 in Massachusetts, each infection was caused by a germ with a distinctive fingerprint. Similarly, there were no genetic matches among 99 listeriosis cases in the previous five years.

That, specialists said, is why it was so telling that the samples from the dairy, the patient's refrigerator, and the four patients all matched.

According to the article, the investigation is now focusing on the packaging process as the potential source of contamination. 

More information on the outbreak investigation is available on the MDH website. 

• Email This
• Print
• Comments (1)
• Trackbacks
• Share Link