Yersinia enterocolitica and Yersinia pseudotuberculosis are bacteria known to cause foodborne gastroenteritis in humans. The pathogen can cause diarrhoea and pain that may be mistaken for appendicitis. More invasive illness occasionally occurs, and post-infection arthritis may occur in a small proportion of cases.
Not all Y. enterocolitica strains can cause human illness. Six biotypes can be differentiated using biochemical tests, and this forms a useful investigative tool for determining pathogenicity. Pathogenic biotypes are 1B, 2, 3, 4 and 5. Foodborne yersiniosis can be avoided by following standard food safety and hygiene advice.
Growth and Control
Note: Isolation of Y. enterocolitica is notoriously difficult; no single method is suitable for all serotypes. Y. enterocolitica is thought to compete poorly with spoilage organisms.
Temperature: Optimum 25 – 37°C. Range -1.3 – 42°C
pH: Optimum 7.2. Minimum 4.2 – 4.8 depending on temperature and acidulant. Maximum 9.6-10.
Atmosphere: Facultative anaerobe. 100% N2 and CO2/N2 gas mixes inhibitory (more so at refrigeration temperatures).
Water Activity: Minimum 0.96 aw. Growth in 5% salt, not in 7% salt.
Temperature: Pasteurisation effective. D55°C = ~ 2 min, D60°C = ~ 0.5 min, D65°C = ~ 2 sec.
pH: Below pH min, bactericidal activity order is: Acetic acid >lactic acid > citric acid > sulphuric acid.
Water Activity: 0.945 aw (7% NaCl) was bactericidal on all of 4 strains tested, when incubated at 3°C but at 25°C both bactericidal and bacteriostatic effects were observed. At 9% NaCl and 25°C, all 4 strains were killed.
Preservatives: Growth is retarded by potassium sorbate up to 5,000 ppm at pH 6.5 in a dose-dependent manner. At pH 5.5 concentrations above 1,000 ppm virtually eliminate growth or cause inactivation depending on dose. Sodium nitrite at a concentration of 150 ppm retarded growth on bologna.
Disinfectants / Sanitisers
Treatments with ozone (1.4 and 1.9 ppm) and with ozonated water (1 min exposure) reduce pathogen loading.
Incubation: Approximately 7 days, range 1-11 days.
Symptoms: Usually manifests as a self limiting gastrointestinal infection. Symptoms generally last 2-3 days but duration may extend to 3 weeks. More serious illness occurs less commonly. Common symptoms include diarrhoea (watery / mucoid in young children), enterocolitis, pseudoappendicitis syndrome in 5 yrs – adolescents, particularly with more virulent strains. Caused by acute inflammation of the terminal ileum or mesenteric lymph nodes in right lower quadrant, with little or no diarrhoea. Pharyngitis. Post infection autoimmune sequelae.
Less common: septicaemia, visceral abscesses, skin infections, pneumonia, endocarditis, osteomyelitis, peritonitis, meningitis and eye infections.
Dose: Insufficient data are available to ascertain dose response.
At Risk Groups: Highest notification rates for <5 age group, followed by >60 age group, more common in males than females. Immunosuppression, blood disorders, malnutrition, chronic renal failure, cirrhosis, alcoholism, diabetes mellitus and acute/chronic iron overload states.
Long Term Effects: Enterocolitis may persist for several months. Acute inflammatory, arthritic syndromes may develop 7-21 days after infection. Other symptoms, e.g. urethritis and skin lesions, can occur in adults.
Treatment: Antibiotics do not reduce severity or duration of gastrointestinal illness, but are of use in more serious manifestations of the disease.
Reservoirs / Sources
Infections are zoonotic, those sub-types that occur in humans also occur in domestic animals.
Human: Person-to-person transmission can occur.
Animal: Isolated from mammals, birds, frogs, flies, fleas, crabs and oysters. Associated with pigs, especially the tongue and tonsil area. Pigs are the only animal from which Y. enterocolitica biotype 4 and serotype O:3 are frequently isolated and this is the group commonly associated with human illness. Serotype O:3 is common in pigs globally and may also be carried by companion animals.
Food: Foodborne transmission is the primary route for infection and may be associated with pork, beef, lamb and poultry and has also been isolated from fruit, vegetables, tofu, pastries, sandwiches and pasteurised milk.
Environment: Terrestrial and freshwater ecosystems harbour the pathogen, including soils, vegetation, lakes, rivers, wells and streams. Extended survival periods at low temperatures.
Plague and Pestilence
Pasteurised milk: Vermont, USA, 1995; 10 cases, 3 hospitalised, 1 appendectomy. Control measure failure: likely post pasteurisation contamination.
Pork chops and pork brawn: Norway, 2006; 11 cases, 4 hospitalised, 2 died. Control measure failure: Unidentified.
Chitterlings (boiled pig intestine): Chicago, USA, 2002. 9 cases. 6 hospitalisations. Control measure failure: Probably poor handling practices in the home.
Ingestion of raw or undercooked pork is considered to be a major risk factor. Yersiniosis has been associated with consumption of pork products (including intestines), sausages, eating raw food or food cooked rare, and the consumption of untreated water.