By James Peacock

The CDC announced on November 9, 2016 that they were ending their investigation into the Salmonella outbreak linked to shell eggs. There were a total of 8 cases of illness linked to the outbreak, which was first discovered in early October. There were only 3 states affected by the outbreak, including Illinois with 1 reported case, Kansas with 1 reported case, and Missouri, which reported 6 case of Salmonella poisoning. Two out of the eight people sickened, or 25 percent, needed to be hospitalized because of their illnesses. There were no deaths reported in connection to this outbreak. People sickened in the outbreak had illness onset dates between April 23 to August 24, 2016, but a majority of the cases began in August 2016. Persons sickened in the outbreak ranged in age from 1 to 85 years old, with a median age of 44.

At the onset of the investigation, the CDC conducted interviews with 7 of the 8 people sickened in the outbreak. The interviews revealed that as many as 6 people ate shell eggs in the week prior to their illness. There were reports of both homes and restaurants being the place for eating these shell eggs. The CDC was then able to perform a traceback investigation based on the restaurants that people reported waiting at. It was found that those restaurants were purchasing their shell eggs from Good Earth Egg Company in Bonne Terre, Missouri. Federal, state, and local health officials then took samples from both ill people and the shelled eggs in question. These samples were tested through two processes, Whole Genome Sequencing (WGS) and Pulsed Field Gel Electrophoresis (PFGE). These processes break apart and separate the DNA found in a sample. The process of PFGE results in a ladder-like set of DNA that can be called the “DNA fingerprint” of the pathogen. DNA with matching fingerprints are more than likely from the same source, making the identification and classification of foodborne illnesses easier. Through WGS, investigators can look at and classify the full sequence of DNA within an organism. Because of the way that DNA works, even strains of the same bacteria will have different WGS results. This further allows health investigators to tie together illnesses.

The PFGE and WGS performed for the Salmonella Oranienburg involved in this outbreak revealed that not only were there other illnesses caused by this outbreak, but also that the strain of bacteria responsible for this outbreak has been seen before. More specifically, the Salmonella Oranienburg involved in this outbreak was first seen in a Salmonella outbreak from 2015. That outbreak was also caused by Good Earth Egg Company. The 2015 outbreak was much larger, as it sickened 52 people across 6 states. The outbreak triggered a recall for many egg products in January 2016.

There was also a recall associated with the 2016 outbreak. On October 3, 2016, Good Earth Egg Company issued a recall for a variety of egg products that may be contaminated with Salmonella bacteria. Different arrangements of eggs, including 6 count cartons, 10 count cartons, 12 count cartons, 18 count cartons, 15 dozen cases, and 30 dozen cases. Not all eggs have been recalled, though, and those cartons affected by the recall can be identified with the best by dates on or prior to 10/8/16. Recalled products are also marked with the code 252. These products were distributed to Dierbergs, Shop n’ Save, Straubs, Midtowne Market, and Price Chopper locations throughout the states of Missouri and Illinois.

Salmonella infections are one of the most common forms of foodborne illness. Health Officials first tracked Salmonella in 1962, but they first detected Salmonella long before this time. Dr. Salmon first discovered the bacteria and its effects more than 125 years ago. There are many different strains of Salmonella bacteria, but all will cause illness in humans. The 32 different serotypes, or strains, of Salmonella bacteria help investigators pinpoint potential outbreaks, as well as their sources. When the number of infections reported increases rapidly and suddenly, it is an indicator to health officials that an outbreak is taking place. Health officials can then investigate the outbreak, usually by taking samples and by conducting interviews. There is sometimes a correlation between interview answers, which can help investigators locate a source. In this outbreak, investigators discovered that 17 of those sickened in the outbreak ate sprouts before their illness began. Although interviews can help locate potential sources, the best way for health officials to learn more about an outbreak is through the testing of samples. When medical providers retrieve samples from ill people or from the environment, the samples undergo testing to learn more about them. This type of testing reveals is the bacteria’s DNA fingerprint. This fingerprint, a solution of the process of pulsed field gel electrophoresis, is unique to the bacteria and strain involved in the outbreak. The DNA fingerprint is then uploaded to the PulseNet system. The PulseNet system is a database of DNA fingerprints maintained by the CDC. If a saved sample matches another sample, there may be a connection between the two. When multiple samples match through the PulseNet system, it is another clue to investigators about the origin and size of the outbreak.

The Centers for Disease Control and Prevention estimates that Salmonella bacteria infects about 1.2 million people each year in the United States. This leads to the hospitalization of about 19,000 people each year. There are an estimated 450 deaths caused by Salmonella infections. A case of Salmonella poisoning will generally produce symptoms within 12 and 72 hours after infection. Usually, Salmonella infections will produce symptoms including vomiting, fever, abdominal cramping, and nausea. While a Salmonella infection may subside on its own within a week, the infection may worsen or cause severe dehydration. This may make hospitalization necessary. Those with certain risk factors, including the elderly, children, and those with suppressed immune systems may be at an increased risk of developing a serious Salmonella infection. If you or a loved one begin to show the symptoms of Salmonella poisoning, contact a medical professional. Early diagnosis of Salmonella infection and treatment could greatly reduce the likelihood of future problems. As always, cooking eggs to at least 160 degrees Fahrenheit is a great idea to help kill harmful bacteria.

 

Sources:

http://www.fda.gov/safety/recalls/ucm523727.htm

https://www.cdc.gov/salmonella/index.html

https://www.cdc.gov/salmonella/oranienburg-10-16/map.html

https://www.cdc.gov/salmonella/oranienburg-10-16/epi.html

https://www.cdc.gov/salmonella/oranienburg-10-16/index.html