Yersinia

Yersinia enterocolitica, Yersinia pseudotuberculosis

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Changed on: 31.10.2019
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Yersinia are facultative, anaerobic (can grow without oxygen), pleomorphic, Gram-negative (coloured red in the so-called Gram staining), rod-shaped bacteria of the family Enterobacteraceae. The psychrophile (= liking cold) pathogens can be isolated at temperatures between 4 °C and 42 °C. Animals are considered the main reservoir of the bacteria, which are commonly found in moderate climates.

The genus Yersinia includes 14 species -- of which enteropathogenic Yersinia (Y. enterocolitica and Y. pseudotuberculosis) are obligate pathogens important from a human medicine perspective.

Plague

Yersinia pestis, the causative agent of plague, is a Gram-negative, rod-shaped bacterium found around the globe. The pathogen is responsible for the great Plague epidemics to which almost 30 % of the European population fell victim in the 13th century alone. Plague outbreaks were described in the Democratic Republic of Congo, Kenya, Madagascar, India, Vietnam, China, Malawi, Namibia, Myanmar, Zambia and several other countries in recent years.

Plague is primarily a zoonotic disease, transferred from animals (fleas) to humans. However, in the case of the mostly terminal pneumonic plague, the pathogen can be transmitted from human to human.

Bubonic Plague and Pneumonic Plague

Plague ends mostly terminally when not treated, while survivors gain life-long immunity from further infection. The most prominent form is bubonic plague, the symptoms of which are fever and painful, dark-coloured swellings of the lymph nodes in the neck, armpit and groin areas.  In a good 20 % of cases, the infection takes on a septic and fatal form, which can also affect the lungs. In cases of pneumonic plague, the disease can be transmitted between humans. The disease is likely to end fatally despite the correct therapy, owing to its very short incubation period of just a few hours.

The survival of the patient depends on a rapid diagnosis, which makes molecularbiological methods that can deliver a diagnosis within hours so important upon the suspicion of an infection, in addition to isolating the culture, which can take several days. The mortality rate from pneumonic plague is far above 50 %, even with the right therapy. Other forms of plague can be treated well with antibiotics, provided the treatment is begun in time.

Laboratory workers, who are exposed to the risk of infection, are recommended to have prophylactic inoculations. Tourists should avoid travelling to regions where plague outbreaks have been reported recently, although the infection risk is usually low. Using insect repellents to protect yourself against fleas is recommended in endemic regions.

Yersinia are facultative, anaerobic (can grow without oxygen), pleomorphic, Gram-negative (coloured red in the so-called Gram staining), rod-shaped bacteria of the family Enterobacteraceae. The psychrophile (= liking cold) pathogens can be isolated at temperatures between 4 °C and 42 °C. Animals are considered the main reservoir of the bacteria, which are commonly found in moderate climates.

The genus Yersinia includes 14 species -- of which enteropathogenic Yersinia (Y. enterocolitica and Y. pseudotuberculosis) are obligate pathogens important from a human medicine perspective.

Plague

Yersinia pestis, the causative agent of plague, is a Gram-negative, rod-shaped bacterium found around the globe. The pathogen is responsible for the great Plague epidemics to which almost 30 % of the European population fell victim in the 13th century alone. Plague outbreaks were described in the Democratic Republic of Congo, Kenya, Madagascar, India, Vietnam, China, Malawi, Namibia, Myanmar, Zambia and several other countries in recent years.

Plague is primarily a zoonotic disease, transferred from animals (fleas) to humans. However, in the case of the mostly terminal pneumonic plague, the pathogen can be transmitted from human to human.

Bubonic Plague and Pneumonic Plague

Plague ends mostly terminally when not treated, while survivors gain life-long immunity from further infection. The most prominent form is bubonic plague, the symptoms of which are fever and painful, dark-coloured swellings of the lymph nodes in the neck, armpit and groin areas.  In a good 20 % of cases, the infection takes on a septic and fatal form, which can also affect the lungs. In cases of pneumonic plague, the disease can be transmitted between humans. The disease is likely to end fatally despite the correct therapy, owing to its very short incubation period of just a few hours.

The survival of the patient depends on a rapid diagnosis, which makes molecularbiological methods that can deliver a diagnosis within hours so important upon the suspicion of an infection, in addition to isolating the culture, which can take several days. The mortality rate from pneumonic plague is far above 50 %, even with the right therapy. Other forms of plague can be treated well with antibiotics, provided the treatment is begun in time.

Laboratory workers, who are exposed to the risk of infection, are recommended to have prophylactic inoculations. Tourists should avoid travelling to regions where plague outbreaks have been reported recently, although the infection risk is usually low. Using insect repellents to protect yourself against fleas is recommended in endemic regions.

Transmission

Infection occurs via the faecal-oral route by eating or drinking contaminated food and water. Given the fact that the bacteria can also proliferate at 4 °C (e.g. refrigerator), it is important to prepare meat dishes appropriately (heat through). Direct transmission via infectious animals and humans is rare. Additionally, contaminated blood from a blood bank can also be a cause of infection.

 

Symptoms

The infections caused – so-called Yersinioses – display a wide spectrum of symptoms.
In babies and infants, it is mainly a self-limited, acute gastroenteritis including vomiting, watery to bloody diarrhoea and fever. The infection may last one to two weeks.

Infections in school children and teenagers often progress as mesenteric lymphadenitis (inflammation of the mesenteric lymph nodes in the abdomen) with abdominal pain. The clinical symptoms can be similar to that of appendicitis (“pseudoappendicitis”).

There are various clinical symptoms in adults, such as influenza-like infections including pharyngitis (“sore throat”), myalgia (muscle pain) and fever, or ileocolitis (inflammation of the large and small intestine), including the mesentric lymph nodes (“pseudocrohn“).

Yersinioses can be associated with accompanying and long-term effects: reactive arthritis, erythema nodosum (acute inflammation of the subcutaneous adipose tissue), arthralgia (pain in the joints) or myalgia (muscle pain). Y. enterocolitica tends to result in gastroenteric symptoms, Y. pseudotuberculosis more in pseudoappendicitis.

The disease is predominantly diagnosed using stool samples. In addition, blood, body liquids, puncture fluids, lymph node aspirate, peritoneal fluid can be used.

Therapy

Infections are usually self-limited and the symptomatic treatment focuses on replacing lost liquids and electrolytes in most cases. Antibiotics are used in severe cases.


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