Salmonella and Campylobacter most frequent causes of infection - CDC

The 10 US sites of the Foodborne Diseases Active Surveillance Network (FoodNet) monitor cases of laboratory-diagnosed infections caused by nine pathogens transmitted through food.

The most frequent causes of infection in 2017 were Salmonella and Campylobacter, which is consistent with previous years.

Compared with 2014–16, the incidence of infections with Campylobacter, Listeria, non-O157 Shiga toxin-producing E. coli (STEC), Yersinia, Vibrio and Cyclospora increased.

Targeted control measures​

Compared with 2006–08, incidence of infections with Salmonella serotypes Typhimurium and Heidelberg decreased and serotypes Javiana, Infantis and Thompson increased.

Incidence of STEC O157 infections during 2017 also decreased compared with 2006-08.

“The declines in two Salmonella serotypes and STEC O157 infections provide supportive evidence that targeted control measures are effective. The marked increases in infections caused by some Salmonella serotypes provide an opportunity to investigate food and non-food sources of infection and to design specific interventions,” ​said the study.​

Laboratory-diagnosed bacterial infections are defined as isolation of bacteria from a clinical specimen by culture or detection by a culture-independent diagnostic test (CIDT). A CIDT-positive–only bacterial infection is a positive CIDT result without culture confirmation.

Bacterial infections diagnosed by CIDT increased 96% overall compared with those diagnosed during 2014–16.

“As use of CIDTs continues to increase, higher, more accurate incidence rates might be observed. However, without isolates, public health laboratories are unable to subtype pathogens, determine antimicrobial susceptibility, and detect outbreaks,” ​said the study.​

Highest incidence of infection for Campylobacter​

During 2017, FoodNet identified 24,484 cases of infection, 5,677 hospitalizations and 122 deaths.

Incidence of infection per 100,000 population was highest for Campylobacter (19.2) and Salmonella (16), followed by Shigella (4.3), STEC (4.2), Cryptosporidium (3.7), Yersinia (1), Vibrio (0.7), Listeria (0.3) and Cyclospora (0.3).

Compared with 2014–16, incidence was higher for Cyclospora (489% increase), Yersinia (166%), Vibrio (54%), STEC (28%), Listeria (26%) and Campylobacter (10%).

One reason Cyclospora appears to be increasing is that labs may be testing for it more often and identifying more infections.

Yersinia is difficult to culture but CIDTs are easier than traditional culture methods and becoming widely used to diagnose such infections.

Thomas Gremillion, director of Consumer Federation of America’s Food Policy Institute, said data shows more needs to be done to protect people from unsafe food.

“The steep increase in campylobacteriosis is particularly concerning. Campylobacter affects millions of people every year and often causes serious long-term health impacts," ​he said. ​

“The Salmonella data gives some cause for optimism, but it’s too early to tell whether it will be ​sustained. There is more to the story here than just a shift to culture independent diagnostic testing.​”

Source: MMWR Morb Mortal Wkly Rep 2018; 67:324-328​

“Preliminary Incidence and Trends of Infections with Pathogens Transmitted Commonly Through Food - Foodborne Diseases Active Surveillance Network, 10 US Sites, 2006-2017”​

Authors: Marder, MPH EP, Griffin PM, Cieslak PR, et al