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S almonella

S almonella. Gastroenteritis, typhoid fever, paratyphoid fever. Salmonellae. Over 2000 different antigenic types Originally classified into different species Now! Represent serotypes of a single species Salmonella enterica Various subspecies

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S almonella

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  1. Salmonella Gastroenteritis, typhoid fever,paratyphoid fever

  2. Salmonellae • Over 2000 different antigenic types • Originally classified into different species • Now! Represent serotypes of a single species Salmonella enterica • Various subspecies • Most mammals associated species are found in subspecies enterica • Example: S. enterica subspecies enterica serotype Enteritidis • Simply: S. Enteritidis

  3. Serotypes • Many are host-specific • Certain serotypes are major cause of food-borne infection • Most are benign and restricted • Some salmonellae cause life-threatening systemic infections (such as S. entericaserotypes Typhi and Paratyphi)

  4. Description and antigenic structure • Enterobacteriaceae • Somatic or “O” antigen (heat-stable LPS) • Flagella or “H” antigen (heat-labile PP) • “H” antigen has two phases (1 and 2) • “Vi” (virulence) antigen in serotype Typhi

  5. Kauffmann-White classification • Named salmonella as individual species • 30 groups based on “O” antigen • Subdivided into groups by “H” antigen • Example: S. typhi (9,12, [Vi]:d-)

  6. Host range and pathogenicity • Strains of S. entericaare widely distributed • Vertebrates GIT • Certain serotypes: flies and cockroaches • Asymptomatic to self-limiting gastro-enteritis

  7. Morbidity, mortality and economical loss • Cholerae-suis (pigs) • Dublin (cattle) • Gallinarum-pullorum (poultry) • Abortus-equi (horses) • Abortus-ovis (sheep) • Other serotypes (no host preference)

  8. Host adapted serotypes • Typhi, Paratyphi A, B and C • Primarily human pathogens • Only found in human • Occasionally, Paratyphi B isolated from cattle, pigs, poultry, exotic reptiles and other animals

  9. Pathogenicity • Enteric fever (typhoid and paratyphoid) • Typhi, Paratyphi A, B and C • Gastroenteritis and food poisoning • Typhimurium • Bacteraemia • Typhimurium • ParatyphiC • Asymptomatic carriers

  10. Enteric fever • Caused by serotypes Typhi, Paratyphi A, B and C • These Salmonellae are usually found only in human • Execrated in faeces and urine of patients and carriers • Typhi is mainly water-borne • Paratyphi is mainly food-borne

  11. Gall bladder Liver Spleen Bone marrow Kidney Primary bacteraemic phase (7-10 days of the incubation period) Second bacteraemia Second bacteraemia Blood stream Thoracic duct Mesenteric lymph nodes Fever and other sings Fever and other sings Lymph Penetration of ileal mucosa Intestine invasion inflammation and infiltration with mononuclear followed by necrosis and ulceration

  12. Other Salmonella infections • Bacteraemia • Abscesses • Arthritis • Inflammation of gall bladder • Osteitis • Neonatal meningitis (S. typhimurium)

  13. Laboratory diagnosis • Enteric fever: • Blood , urine and stool • Diarrheal diseases • Faeces and blood for culture • Bacteraemia • Blood for culture • Abscesses and arthritis • Pus for culture

  14. Specimen selection in enteric fever

  15. Isolation • Aerobic incubation at 37 ° C • Faeces • Selective media (XLD, DCA, MacConkey) • Enrichment media (SF broth) • Blood culture

  16. Morphology • Gram –ve motile rods • Non-sporing • Non-capsulated (except S. typhi)

  17. Biochemical test for identification of bacteria

  18. Serological diagnosis of enterica • Antigen tests • Detect S. typhi in faeces • Sensitive and specific • Detect the bacteria in the first week • Antibody test • When no culture or antigen test available • Needs careful interpretation • Has no value in case of food-poisoning

  19. Shigella Non-motile bacteria that conform with the definition of the family Enterobacteriaceae

  20. Classification of Shigellae • Based on antigenic structure and bioactivity • Group A: S. dysenteriae • 12 different serotypes • Group B: S. flexneri • 10 serotypes • Group C: S. boydii • 18 serotypes • Group D: S. sonnei • 1 serotype

  21. Shigella infections • Shigella cause bloody diarrhea (dysentery) and non-bloody diarrhea. • Often begins with watery diarrhea accompanied by fever and abdominal cramps. • May progress to classical dysentery with scant stools containing blood, mucus and pus. • May be asymptomatic infection particularly in case of S. sonneistrains. • Rarely case other infections

  22. Transmission • Infect only humans • Mostly person-to-person spread • Faecal-oral route through contaminated food and water • House flies • Only few organisms are required to cause infection

  23. Epidemiology of Shigellosis • The most virulent species is S. dysenteriae serotype 1(Sd 1) • 164.7 million case annually • 163.2 in developing countries • 1.1 million death • 61% of mortalities in children < 5 years

  24. Etiology • S. flexneri(60%) • S. sonnei(15%) • S. boydii(6%) • S. dysenteriae(6%)

  25. In USA • Annual reported cases = 20,000 • Estimated undetected cases= 400,000 • 20% due to international travel • Common cause S. sonneifollowed by S. flexneri

  26. S. dysenteriae Shigellosis • Inflammation and ulceration of intestine • Severe dysentery (Shiga toxin) • Dehydration and protein loss • Abdominal cramps • Rectal pain • Toxaemia • High fever • High WBCs with neutrophilia

  27. Causes of death • Circulatory collapse • Kidney failure

  28. Bacterial virulence • Enterotoxin • Mainly due to bacterial invasiveness

  29. Laboratory diagnosis • Fresh faeces with enrichment media like Gram Negative (GN) broth or Selenite broth. • Transport medium • pH alkaline • Culture in selective media • XLD, DCA and MacConkey

  30. Serological identification of Shigellae • Polyvalent O group antisera • for groups A,B,C, and D • Monovalent O antiserum • e.gmonovalentS. dysenteriae 1 for identification of Sd 1

  31. The end

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