Yersinia Background

Yersinia enterocolitica

Yersiniosis is an infection caused most often by eating raw or undercooked pork contaminated with Yersinia enterocolitica bacteria. CDC estimates Y. enterocolitica causes almost 117,000 illnesses, 640 hospitalizations, and 35 deaths in the United States every year. Children are infected more often than adults, and the infection is more common in the winter. Pigs are the major animal reservoir for the few strains of Y. enterocolitica that cause human illness, but rodents, rabbits, sheep, cattle, horses, dogs, and cats also can carry strains that cause human illness.

Most people become infected by eating contaminated food, especially raw or undercooked pork, or through contact with a person who has prepared a pork product, such as chitlins. For example, babies and infants can be infected if their caretakers handle contaminated food and then do not wash their hands properly before handling the child or the child’s toys, bottles, or pacifiers. People occasionally become infected after drinking contaminated milk or untreated water, or after contact with infected animals or their feces. On rare occasions, people become infected through person-to-person contact. For example, caretakers can become infected if they do not wash their hands properly after changing the diaper of a child with yersiniosis. Even more rarely, people may become infected through contaminated blood during a transfusion.

The symptoms of yersiniosis depend on the age of the person infected. Infection occurs most often in young children. Common symptoms in children are fever, abdominal pain, and diarrhea, which is often bloody. Symptoms typically develop 4 to 7 days after exposure and may last 1 to 3 weeks or longer. In older children and adults, right-sided abdominal pain and fever may be the predominant symptoms and may be confused with appendicitis. Complications are rare, and may include skin rash, joint pains, or spread of bacteria to the bloodstream.

Most symptoms go away completely. However, some people may experience joint pain, called reactive arthritis, most commonly in the knees, ankles, or wrists. These joint pains usually develop about 1 month after yersiniosis illness begins and generally go away after 1 to 6 months. A skin rash, may also occur, called “erythema nodosum,” on the legs and torso. The rash is more common in women and usually goes away within a month (CDC).

Yersinia pestis

Rodents are the main reservoirs of Yersinia pestis, known as the cause of the “Black Death”, an outbreak of plague which caused 50 million deaths in 14th-century Europe (WHO, 2022). Pneumonic plague can be fatal within 18 hours of the disease’s onset, highlighting the critical need for rapid diagnosis and the introduction of appropriate antibiotics (Africa CDC, 2020).

Currently, there is no FDA-approved vaccine against the plague for human use, but ongoing research addresses Yersinia pestis as a re-emerging threat (Feng et al., 2020). The infection rate of plague has increased significantly since the 1990s. Moreover, antibiotic-resistant strains of Yersinia pestis have been reported, and the bacteria have been engineered as a potential biological weapon (Lei & Kumar, 2022). 

Y. pestis produces F1 as the bacterium transfers from the flea vector to the human or rodent host, forming a capsule-like structure made of Caf1 protein subunits sticking to the bacterial cell surface. The F1 capsular polymer is unique to Y. pestis and can elicit a rapid, effective immune response in mice (Levy et al., 2018). V antigen is also considered a vaccine candidate, and the combination of both in F1/V vaccine has recently shown promising results in the first human trial (Hamzabegovic et al., 2020). 

References

• CDC. Yersinia enterocolitica (Yersiniosis) factsheet.

• Fields, K.A. et al. (1999) ‘Virulence role of V antigen of            yersinia pestis            at the bacterial surface’, Infection and Immunity, 67(10), pp. 5395–5408. doi:10.1128/iai.67.10.5395-5408.1999.  

• Gahlot, D.K., Ifill, G. and MacIntyre, S. (2021) ‘Optimised heterologous expression and functional analysis of the yersinia pestis F1-capsular antigen regulator CAF1R’, International Journal of Molecular Sciences, 22(18), p. 9805. doi:10.3390/ijms22189805 

• Hamzabegovic, F. et al. (2020) ‘Flagellin adjuvanted F1/V subunit plague vaccine induces T cell and functional antibody responses with unique gene signatures’, npj Vaccines, 5(1). doi:10.1038/s41541-020-0156-y.  

• Levy, Y. et al. (2018) ‘Targeting of the yersinia pestis F1 capsular antigen by innate-like B1B cells mediates a rapid protective response against bubonic plague’, npj Vaccines, 3(1). doi:10.1038/s41541-018-0087-z.  

• Leary, S.E. et al. (1995) ‘Active immunization with recombinant V antigen from yersinia pestis protects mice against plague’, Infection and Immunity, 63(8), pp. 2854–2858. doi:10.1128/iai.63.8.2854-2858.1995.