Home Random Page


CATEGORIES:

BiologyChemistryConstructionCultureEcologyEconomyElectronicsFinanceGeographyHistoryInformaticsLawMathematicsMechanicsMedicineOtherPedagogyPhilosophyPhysicsPolicyPsychologySociologySportTourism






Laboratory Diagnostics of Cholera

What is cholera? Acute particularly dangerous antroponoses quarantine disease caused by Vibrio cholerae serogroups O1 and O139, which is characterized as the spread of epidemics, profuse watery diarrhea, vomiting, dehydration, severe intoxication, the fecal-oral mechanism of transmission and high fatality.
Taxonomic position of cholera germs. Family Vibrionaceae Genus Vibrio Type V. cholerae serogroup O1, serotype Ogáva (AB), Inába (AU), Hikodzhúma (FAA), biovar: classic - V. cholerae cholerae and El Tor - V. cholerae eltor serogroup V. cholerae O139 (Bengál).
Clinical signs of cholera. Tenesmus, vomiting, diarrhea (patient per day is losing up to 30 liters of liquid); feces in the form of "rice-water" (colorless, odorless heavy feces containing mucus and epithelial cells), dehydration, renal failure, aphonia, thickening of the blood, anoxia, cardiac insufficiency, hypothermia (cholera algid). Characteristic sign of dehydration is “Hippocratic face”: sunken eyes, pointed facial features, sharp protruding cheekbones. Also characteristic convulsions, the patient loses consciousness, the high mortality.
Features of immunity in cholera. It is humoral-cellular, the intense, short-lived, antitoxic, antimicrobial. Cross-immunity is absent. Post-vaccination immunity continues 6-8 months.
Morphological and staining properties of the causative agents of cholera. Short slightly curved or straight gram-negative rods are medium in size (1,5-4 × 0,2-0,4 mm), forming clusters in the form “flocks of fishes”, mobile (monotrixous). The spore and capsule are not forming.
Type of respiration V.cholerae. Aerobic, facultative anaerobic.
What is biovar of the bacteria? It is a type of bacteria, which differ in certain biological and biochemical characteristics.
What is antigenic structure of V. cholera? O and H antigens. The structure of O-antigen serogroups distinguished 139. The causative agent of cholera belongs to serogroup O1 and O139 (Bengal); vibrios other serogroups are not agents of NAG-vibrio cholera. Antigens O1 serogroup are A-, B-, C-subunits: AB - serovar Ogawa, AU - serovar Inaba, ABC - serovar Hikodzhúma; R-shape - lose the O-antigen, the M-shape - change the structure of O-antigen. H-antigen - the total for the genus Vibrio.
What is cholera NAG-nonagglutinating) vibrios? Vibrio cholera pathogen with similar morphological, cultural and biochemical characteristics, vibrio not-serogroup O1 (not agglutinated O1-serum), cause acute intestinal infection.
What is virulence factors V. cholera? The biological action of virulence factors. Exotoxins: choleragen, LT, ST, SLT; endotoxin; adhesiones provides adgesion to the glycocalyx of the epithelium of the mucous membrane of the small intestine; fibrinolysin and hyaluronidase - aggression, enzymes, enzymes mucynase and neuraminidase (increases the binding of cholera exotoxin from epithelium of the small intestine).
What are effects of choleragen V. cholera? It consists A and B subunits in monosial gangliozid interacts with the receptor and forms a hydrophobic intramembrane channel for the penetration of subunit A in the epithelium of the small intestine and provides the antigenic specificity of the toxin. Subunit A activates intracellular adenylate cyclase, a rise of cAMP content and the excretion of electrolyte solution from the intestine. Buffer fluid of the small intestine leads to profuse diarrhea.
What are effects of endotoxin of the V. cholera? It stimulates the synthesis of prostaglandins, causing the smooth muscles of the small intestine, inhibition of phagocytosis, a common cause intoxication, tenesmus, and diarrhea, lower blood pressure, infectious and toxic effects.
What is the source of infection the pathogen of cholera? The source of infection is patient and carier. The patient selects from 100 mln to 1 billion vibrios in 1ml of excreta. The reservoir of infection is also water.
What is resistance of the cholera causative agents? It sensitives to heat (at 56 º C killed after 30 minutes at 100 º C - instantly), the action of direct sunlight, under the action of disinfectants dies after 5-15 minutes, sensitive to acids. In stagnant water containing organic substances, it is viable for 2-3 weeks. It persists for 2-3 days in fresh faeces and 5 days in milk. Vibrio biovar El Tor is more resistant in the environment.
What are ways of transmission of V. cholera? Principal ways are through the water, milk, vegetables, fruits, often - food or water. All epidemics and pandemics of cholera have water in nature. A role played by flies.
What is distribution of vibrios in nature? The agent is able to multiply in the presence of organic substances in fresh and seawater by t> 12°C, growing in aquatic organisms (molluscs, crustaceans, fish, frogs).
What is material taken from the contact persons with cholera? It is faeces after using of the laxatives (25-30g of magnesium sulphate). They take the upper part of faeces.
What are methods of diagnosis of cholera? Bacteriological Method of rapid diagnosis (RIF, the reaction of immobilization of vibrios, PCR) Microscopic Serological (for a retrospective diagnosis) - ELISA, IFT, PHAT (definition of anti-cholera Ig titers and antitoxin).
What is the purpose of PCR using? 1 /. It is rapid identification of the small number of cholera in the test material. 2 /. Identify forms of V. cholerae, is not cultivated on nutrient media.
What are stages and duration of the identification of the causative agent of cholera? Determine the ratio of bacteria to the genus Vibrio.  
What is a natural protective mechanism in the penetration of cholera? It is the normal acidity of gastric juice. Infecting dose is 1 million vibrios.
What is preparation for nonspecific prevention of cholera? It is preparation of the tetracycline series.
What is application of cholera bacteriophages? It is using for diagnosis and prevention of cholera (contact persons).

Date: 2016-01-14; view: 826


<== previous page | next page ==>
LABORATORY DIAGNOSIS OF CHOLERA | Laboratory Diagnostics of the pseudotuberulosis and intestinal yersiniosis
doclecture.net - lectures - 2014-2024 year. Copyright infringement or personal data (0.006 sec.)