Yersinia enterocolitica: Isolation from human clinical, animal samples and from food, molecular confirmation of pathogenicity and identification of the main O serotypes.
Yersinia enterocolitica is a Gram - negative bacteria of the family Enterobacteriaceae, genus Yersinia includes 17 species, although there are only three pathogenic Yersinia pestis (plague producer); Y. pseudotuberculosis (producer mesenteric adenitis box) and Yersinia enterocolitica. Among its microbiological characteristics we must be mentioned for its implications: be psicrófila, ie it can develop at 4 ° C and survive long periods at this temperature; tolerates a very wide range of pH between pH 4 and pH 10 (resists well alkalinity); It is mobile at temperatures between 4 ° C and 30 ° C, while still at 37 ° C. There are 6 biotypes (1A, 1B, 2, 3, 4 and 5) and over 70 serotypes O, established according to the antigenic variations in the cell wall lipopolysaccharide. Of these serotypes O, only some of them are related to pathogenicity (O3 and O9 in Europe, US and O5 O8 and O27 in Canada and Japan). Pathogenic biotypes (1B, 2, 3, 4 and 5; biotype strains 1A is considered generally non - pathogenic, but may have some pathogenicity factotres as ail, myfA and YSTA -see later-), they are for having a plasmid of 70 Kb, highly conserved, containing genes encoding virulence factors. 70 Kb plasmid, virulence plasmid, is present in all three species of Yersinia, although different names in each: pCD1 in Yersinia pestis (Calcium Dependence); PIB1 in Yersinia pseudotuberculosis; Yersinia enterocolitica in pYVe (Yersinia Virulence). This plasmid is found only in strains containing virulence genes (plasmid PYV: Yersinia Virulence plasmid or PLCR: Low Calcium Response Plasmid, by requiring calcium to develop at 37 ° C). This plasmid encodes the protein YadA (Yersinia Adhesin A), a type III secretion system consisting of several Ysc-Yop proteins (TTSS: Type Three Secretion System). This type III secretion system, helps resist phagocytosis altering human defense cells. There are six protein Yop (YopH, yopT, yopE, Yopa, YopJ and yopM), which are introduced by the system type III secretion into the cell and are responsible for phosphorylation alter the Cas and FAK proteins, (Yop H), that the activity of intracellular GTPases (Yop T, E, a), that the activation of NF-? (YopJ) factor is affected, and nuclear function (YopM) is changed. In addition, pathogenic strains possess chromosomal genes also encode pathogenicity factors. These chromosomal genes are ail gene (locus attachment invasion; locus fixing invasion), encoding a protein necessary for the outer membrane adhesion to mucosal cells; myfA gene (mucoid Yersinia fibrillae A), encoding fimbriae for adhesion; inv gene (invasin) encoding an outer membrane protein required by the bacterium to its translocation (pass) through the M cells of the epithelium of the ileum; YSTA genes, ystB or YSTC (Yersinia heat-Stable Enterotoxin A, B or C; thermostable enterotoxin Yersinia types A, B, or C), encoding the three types enterotoxin by increasing the concentration of cGMP (guanin- cyclic) monophosphate cause loss of fluid and electrolytes that cause of diarrhea; HPI gene (Hyghly Pathogenicity Island; island highly pathogenic), consisting of a group of genes encoding iron uptake systems, lacking this bacterium siderophores used by other bacteria. Besides these virulence factors, the structure and metabolism of the bacteria also influences pathogenicity: firstly has lipolpolisacáridos (LPS) in the outer membrane of the cell wall, which can trigger own inflammatory phenomena of endotoxins Gram - negative bacteria; It has a superoxide dismutase (SodA) that degrade hydrogen peroxide prevents death by mechanisms oxygen-dependent defense, and possesses potent urease, which allows alkalize the surrounding environment and thus avoid the adverse effect of gastric acid pH it passes through the stomach.
This bacteria is common in the intestines of several animal species: pigs, poultry, cattle, dogs, cats, even frogs. From them can contaminate land and water. It is considered a zoonosis and man becomes infected, generally, when handling meat products without proper hygienic measures, or when they eat dairy products or not heat - treated.
When it reaches the digestive tract it attaches to M cells ( "Microfold") that exist on the Peyer's patches of the ileum mucosa of the small intestine. These M cells are responsible for transferring microorganisms and particles from the gut lumen, to bring them into contact with antigen - presenting cells and immune cells that are found in the lamina propria of the mucosa and Peyer's patches. The infective dose is between 106 and 108 CFU, depending on the infecting strain and conditions of the host, being more susceptible children under 5 or 10 years, the elderly and individuals with reduced gastric acidity or defenses immune and those with the cellular phenotype HLA-B27 and B7.
Human infection by pathogenic strains, causes gastrointestinal syndromes of varying intensity, from mild diarrhea to mesenteric adenitis simulating appendicitis. Systemic involvement is rare, but described tables arthritis and erythema nodosum. There have been reports of sepsis related to erythrocyte transfusion contaminated with high mortality.
Because non - pathogenic strains of Y. enterocolitica can contaminate food, water, or clinical samples, it is important to distinguish pathogenic strains from which they are not. PCR amplification of ail gene can distinguish between them.
Gastrointestinal infection is usually self - limited so antimicrobial treatment is usually not necessary, unless it is extended, or the patient 's conditions make it advisable. Antimicrobial treatment can be performed with some of the following antimicrobials: aminoglycosides (gentamicin), third generation cephalosporins (cefotaxime), fluoroquinolones (ciprofloxacin), tetracyclines (doxycycline), sulfamethoxazole trimethoprim-.
For preventing the spread should be avoided during handling of meat products of poultry, pigs or cattle, avoiding raw or undercooked meats, ingestion of unpasteurized milk, hygiene measures when handling raw meats, wash hands to prevent transmission , cleaning kitchen surfaces, animal feces contaminated.
Diagnostic tests recommended
- Culture isolation, from clinical samples of human infections, especially in cases of gastroenteritis stools or blood in systemic infections, or from samples of animal products for the presence of Yersinia enterocolitica in them.
- Differentiation of pathogenic strains, through detection of the plasmid genes pathogenicity preferably ail chromosomal gene, by the ease with which crop is lost in 70 Kb plasmid.
- Determination of the most common serotypes (O 3, O 5, O: 8, OR 9, O: 5, 27) of interest in epidemiological studies to determine the distribution of serotypes. May miss the O antigen during cultivation, in which case the strain is "not typable".
Tests in IVAMI:
- Culture isolation, from human clinical specimens (feces, blood, ...), or samples from animals like meat or dairy products), and identification.
- Differentiation of pathogenic strains, for nonpathogenic, by detecting the ail gene (chromosome) or inv gene (plasmid), by PCR.
- Detection of the most common serotypes (O 3, O 5, O: 8, OR 9, O: 5, 27), by PCR amplification (Polymerase Chain Reaction) of the genes encoding the antigens O.
- Isolates cultured, to know if it is pathogenic or nonpathogenic strains.
- Clinical samples for isolation of Yersinia enterocolitica. (feces, blood, ...).
- Samples from animals, such as meat or dairy products, for culture isolation of Yersinia enterocolitica.
Preservation and shipment of sample:
· Refrigerated (preferred) for less than 2 days.
· Congelada: over 2 days.
· 48 to 72 hours maximum.
Cost of the test:
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