FoodNet 2015 Preliminary Data

Culture independent diagnostic tests (CIDTs) work by detecting the presence of a specific antigen or genetic sequence of a germ. CIDTs do not require labs to grow a culture for isolation and identification of living organisms (also known as culturing). Consequently, these tests can be conducted more rapidly and yield results far sooner than can be done through traditional culturing methods.

Unlike cultures, CIDTs do not provide the information needed to characterize organisms that cause infections—information that is needed to find outbreaks and monitor disease trends. Measures can be taken to address this problem. Laboratories can culture specimens after a CIDT is positive (called “reflex culturing”), and CIDT manufacturers can create new tests to provide information that is now available only from cultured specimens.

Learn more about use of CIDTs for diagnosis of enteric infections >

Testing for Cryptosporidium has always been done using CIDTs, which are easier to use than traditional culture methods. Thus, the increasing incidence of Cryptosporidium infections might be due, in part, to more laboratories testing for these infections and, consequently, more infections being recognized.

In addition, Cryptosporidium infections have been increasing since 2005, the same year when a new drug, nitazoxanide, was approved to treat these infections. This same pattern has been seen throughout the country. The availability of this new treatment may have triggered more doctors to test patients for cryptosporidiosis and thus may partially explain the steady increase in infections that are diagnosed and reported.

Learn how to protect yourself from Cryptosporidium infections >

Both groups of infections have similar symptoms, which often include severe stomach cramps, diarrhea (often bloody), and vomiting. Symptoms vary for each person and can range from mild diarrhea to hemorrhagic colitis to hemolytic uremic syndrome (HUS), a type of kidney failure. Here are some of the differences between O157 and non-O157:

• O157 is the most common type of STEC causing illness in the United States.
• Non-O157 STEC are a diverse group that includes all Shiga toxin-producing E. coli of serogroups other than O157. In the United States, most non-O157 strains isolated from humans belong to serogroups O26, O111, O103, O121, O45, and O145 (in order of frequency).
• Illnesses caused by STEC O157 are typically more severe than those caused by non-O157. For example, STEC O157 infections cause most cases of HUS.
• The most common sources of STEC O157 infection are beef and leafy vegetables. In contrast, a variety of foods have caused outbreaks of non-O157 STEC.

Learn how to protect yourself from E. coli infections >

CIDTs, which are easier to use than traditional culture methods, are becoming widely used to diagnose STEC infections. The increasing incidence of non-O157 STEC infections might be due, in part, to more laboratories testing for Shiga toxin and, consequently, more non-O157 STEC infections being recognized.

Salmonella infection is a complicated problem because Salmonella has many sources, the sources vary by the type of Salmonella.

Many sources can spread Salmonella to people. Most food animals and many wild animals carry Salmonella in their intestines without getting sick. Most often, Salmonella bacteria are spread to people through contaminated food, including meat, poultry, and eggs; raw produce contaminated with animal or human fecal matter; and processed foods made with contaminated ingredients. People can also get Salmonella infection by drinking contaminated water and by having contact with animals or the places they live.

There are many different types of Salmonella bacteria (called serotypes) and the sources vary by serotype. The six most common serotypes reported to FoodNet in 2015 were Enteritidis, Newport, Typhimurium, Javiana, I 4,[5],12:i:-, and Poona. Some types of Salmonella are found mainly in one source (e.g., Heidelberg in chicken) and some are found in many food and wild animals (e.g., Typhimurium).

The particular interventions that work for each type of Salmonella may vary. To reduce incidence, we need interventions that target the types of Salmonella that are increasing or staying level. Work to decrease the incidence of Salmonella infection is ongoing. Whole genome sequencing is helping us better figure out the sources of people's illnesses, and FoodNet continues to track illnesses so we can see if prevention measures are working.

Learn how to protect yourself from Salmonella infections >

Infections with S. Typhimurium have been decreasing for 20 years. The reasons are unclear. People get S. Typhimurium infection from a wide variety of food sources. Efforts by regulatory agencies and industry to make food safer might have contributed to the decrease in incidence. For example, the United States Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) has implemented many measures to decrease Salmonella contamination in beef and poultry. In addition, the poultry industry has increasingly used vaccines against Salmonella.