Contents
Jersinioses are acute and possibly chronic infectious diseases caused by small Gram-negative rods Yersinia enterocolitica and Y. pseudotuberculosis, belonging to the Enterobacteriaceae family. They cause serious epidemics or sporadic diseases in humans. Y. enterocolitica is the most common cause of enterocolitis, while Y. pseudotuberculosis infections are most common in the form of adenitis mesenterica.
Jersinioza — epidemiology
Characteristics of Y. enterocolitica
Y. enterocolitica is widespread in the environment and its reservoirs are water and soil. This microorganism is found in the digestive tract of many animal species: mammals (rodents, farm animals – especially pigs, dogs, cats, wild animals) and birds. It is excreted in the feces into the environment. The animals get sick, but they can also be asymptomatic vectors. Y. enterocolitica is sometimes isolated from both sick and healthy animals, and from products of animal origin (meat – especially pork), fish and crustaceans. Often contamination with yersiniosis concerns dairy products (milk, ice cream). The ability of Y. enterocolitica to grow at 4 ° C means that meat stored in cold stores can be a source of infection.
Infections with yersiniosis occur in different parts of the world. In Northern Europe (more often in Scandinavia) Y. enterocolitica is recognized as the cause of diarrhea and abdominal pain. Infections in Europe are mainly caused by serotypes 03 and 09, and increasingly 08. In the USA, serotype 08 is more common, but food poisoning has been reported, also caused by serotypes 03 and 09. Most cases of yersiniosis are found in the fall or winter, more often they concern children rather than adults.
In Poland, in the years 2004-2009, an increase in the number of cases of intestinal yersiniosis was recorded. Diseases caused by Yersinia bacilli are classified according to the current case definition for intestinal and parenteral yersiniosis. In 2009, 326 cases of yersiniosis were registered (incidence 0,85), including 288 cases of intestinal yersiniosis and 38 cases of parenteral yersiniosis. These numbers are significantly higher than the median for the years 2004-2008, which was respectively – the number of cases of 140 and the incidence – 0,37 (probably due to better diagnostics). The diagnoses concern mainly more severe and prolonged diseases. The disease caused by serotype 08 predominates. Testing for Y. enterocolitica infection should be included in the routine diagnosis in cases of diarrhea and abdominal pain.
Characteristics of Y. pseudotuberculosis
Y. pseudotuberculosis causes rodentiosis in humans and pseudotuberculosis in animals. Infections with this bacilli in humans are less common than those caused by Y. enterocolitica, but it is also very widespread in the environment and resistant to physical agents. Y. pseudotuberculosis can survive outside the host organism in water, soil and plants. The main reservoir and source of human infection are primarily rodents, which may be asymptomatic carriers of this pathogen (this also applies to rodents kept at home as companion animals and laboratory animals – rabbits, guinea pigs). Breeding birds on farms and various species of animals in the zoo can also be infected. Y. pseudotuberculosis can cause sepsis in rodents and birds. Sick animals or vectors excrete the sticks into the environment with their faeces. Sometimes the source of the infection may be a sick person with symptoms of diarrhea. Also, the transmission of Y. pseudotuberculosis via insects such as fleas and lice is not excluded.
Jersiniosis in humans caused by infection with this bacillus occurs all over the world. They are more common in Northern Europe. Children are most often sick – especially of the male sex. Most cases of disease occur in winter. They can take the form of sporadic or family diseases, less often in the form of epidemics.
The infection with Yersinia sp. Most often occurs through the ingestion – by eating products of animal origin contaminated with microorganisms:
- meat,
- milk and its products,
- fish,
- fertilized vegetables,
- drinking contaminated water.
Y. enterocolitica was isolated from well waters and clear lakes in Canada. Surfaces and objects contaminated with these sticks in slaughterhouses, cold stores and food processing plants may be a source of worker contamination. Less frequently, Yersinia sp. Infection may occur through direct contact with a sick animal or an animal – asymptomatic carrier. Y. enterocolitica nana infections by blood transfusion that have been stored for more than 3 weeks at 4 ° C have also been described. The number of sticks that can cause contamination is 10 (8) -10 (9) sticks / ml.
Jersiniosis – causes
Y. enterocolitica and Y. pseudotuberculosis belong to the genus Yersinia, of the Enterobacteriaceae family. They are gram-negative, mesophilic, non-spore-forming, non-enveloped, aerobic or conditionally anaerobic rods. On semi-liquid substrates, they show movement at 18-22 ° C, and are stationary at 37 ° C. The genus Yersinia includes 12 species:
- Y. pestis,
- Y. enterocolitica,
- Y. pseudotuberculosis,
- Y. intermediate,
- Y. frederiksenii,
- Y. kristensenii,
- Y. ruckeri,
- Y. philomiragia,
- Y. aldovae,
- Y. rohdei,
- Y. mollaretti,
- Y. bercovieri.
Apart from the first three species, their relationship to human disease is not well understood.
Y. enterocolitica and Y. pseudotuberculosis grow on conventional media and form colonies at 37 ° C after 48-72 hours. Slow growth does not allow them to be detected by routine tests. At room temperature, they form S forms on the media, and at 37 ° C – rough R colonies. On agar with 5% ram blood, they can cause alpha-hemolysis.
The virulence factors of Y. enterocolitica and Y. pse – in dotuberculosis are determined by genes. Belong to them:
- serum resistance, which is resistance to the bactericidal action of human serum, complement-dependent, two proteins with high molecular weight regulating iron levels,
- Invasin resistance, which determines the attachment of VLA to intestinal cells, which promotes tissue invasion.
The virulence factors of Y. enterocolitica and Y. pseudotuberculosis also include those encoded in the virulence plasmid (pYV). These are protein V antigen, W protein antigen, Yop1 protein (Yop, Yersinia outer protein), Yop2b, Yop3, Yop4a proteins. The proteins Yop20, Yop30, Yop84 are present only in Y. enterocolitica. The strains of Y. enterocolitica and Y. pseudotuberculosis contain the somatic O and ciliary antigen H.
Based on the structure of the somatic O antigen, a number of serological groups have been distinguished. Yersinia sticks are sensitive to commonly used disinfectants and heating. They multiply at room temperature but can also grow at 4 ° C. This poses a risk to human health due to the viability of these microorganisms in cold stores and food storage.
Pathogenesis of yersiniozy
After entering the gastrointestinal tract, Y. enterocolitica synthesizes urease, which breaks down urea into CO2 and ammonia. This causes alkalization of the immediate environment of the sticks and their resistance to the low pH of the stomach and the initial section of the small intestine. Both sticks produce the virulence-determining antigens and the Yop-antigens that facilitate adhesion and infection of the intestinal mucosa cells. VW antigens found in Yersinia pathogenic strains allow microorganisms to survive intracellularly.
Y. enterocolitica and Y. pseudotuberculosis produce endotoxin. Y. enterocolitica also produces a low molecular weight, warm enterotoxin responsible for food poisoning. STa toxin (heart-stable enterotoxin), produced by Y. enterocolitica, binds to cells of the mucosa of the small intestine through a receptor on the cell membrane of enterocytes C (guanylate cyclase – GC-C), causing the secretory effect of enterotoxin.
Some strains of enteropathogenic Y. pseudotuberculosis produce LT enterotoxin. As a result of its action, excessive secretion of mucus occurs by the cells of the crypts of the small intestine and the absorption of water and electrolytes from its lumen by the villi cells of the intestine is inhibited. This process is the result of an inflammatory reaction in the intestinal mucosa and is responsible for diarrhea in the course of the disease.
Y. enterocolitica and Y. pseudotuberculosis in the small intestine colonize cells of the intestinal mucosa, M cells of Peyer’s patches and macrophages. Transmission of Yersinia sp. Via the bloodstream may cause abscesses in various organs (liver, spleen, less frequently kidneys) or sepsis. Patients infected with Y. enterocolitica with the HLA-B27 histocompatibility antigen may develop reactive aseptic polyarthritis (polyarthritis aseptica).
Treatment of yersiniosis
Jersiniosis of a mild nature (food poisoning, enteritis) usually requires conservative treatment, which is based on sufficient hydration of the patient to prevent dehydration and disturbances in the water and electrolyte balance. For this purpose, it is recommended to take glucose-electrolyte fluids. In addition, a proper diet is important in treatment, especially easily digestible with a lot of groats. Meals should be frequent but small. In the course of high body temperature, the patient should be given antipyretic and anti-inflammatory preparations. In severe cases of yersiniosis, antibiotic therapy is indicated, although the disease usually resolves spontaneously after a few days of proper diet and anti-symptomatic treatment.
Jersiniosis and complications
Although yersiniosis is mild and self-limiting in most patients, there are situations in which complications arise. Then the following may occur:
- erythema nodosum,
- joint swelling and pain
- rash,
- bacteremia,
- sepsis,
- abscess of the liver or spleen.
Source: J. Cianciara, J. Juszczyk, Infectious and parasitic diseases; Czelej Publishing House