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ENTEROBACTERIACEAE

ENTEROBACTERIACEAE . SALMONELLA. INTRODUCTION. The genus salmonella consists of bacilli that parasitise the intestines of a large of vertebrate sp and infect human beings leading to enteric fever, gastroenteritis, septicemia .

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ENTEROBACTERIACEAE

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  1. ENTEROBACTERIACEAE SALMONELLA

  2. INTRODUCTION • The genus salmonella consists of bacilli that parasitise the intestines of a large of vertebrate sp and infect human beings leading to enteric fever, gastroenteritis, septicemia

  3. The most important member of genus is salmonella typhi the causative agent of typhoid fever. • 2000 serotypes or species.

  4. For practical purpose they may be divided into 2 groups: • The enteric fever group. • The food poisoning group.

  5. MORPHOLOGY • Gram-negative rods • Peritrichate flagella • Non capsulated • Non sporing • Fimbriated

  6. CULTURAL CHARACTERS • Aerobic and facultativelyanerobic NUTRIENT AGAR:-Large, circular low convex and smooth. MACCONKEY AGAR:-Nonlactose fermentor. WILSON & BLAIR BISMUTH SULPHITE MEDIUM:-jet black colonies with a metallic sheen are formed due to production of H2S.

  7. BLOOD AGAR

  8. Mac CONKEY AGAR

  9. WILSON BLAIR AGAR

  10. XYLOSE-LYSINE-DEOXYCHOLATE (XLD) AGAR

  11. BIOCHEMICAL REACTIONS • Ferment glucose, mannitol, maltose forming acid and gas. • Lactose ,sucrose and salicin are not fermented. • Indole-negative • MR-positive • VP-Negative • Citrate-positive • Urease-negative

  12. MR INDOLE VP CITRATE

  13. RESISTANCE • Killed at 55˚C in one hour. • Boiling or chlorination of water and pasteurisation of milk destroy the bacilli. • There are killed within 5 mins by mercuric chloride or 5 % phenol.

  14. ANTIGENIC STURCTURE • Three antigens are identified:- 1. Flagellar antigen H 2. Somatic antigen O 3. Surface antigen Vi

  15. H ANTIGEN • Heat labile protein • Strongly immunogenic • When mixed with antisera H suspensions agglutinate rapidly producing large, loose, fluffy clumps • Dual in nature

  16. O ANTIGEN • Phospholipid-protien-polysaccharide complex • Identical with endotoxin • Unaffected by boiling • When mixed with antisera O antigen suspensions form compact, chalky, granular clumps • Less immunogenic

  17. VI ANTIGEN • Heat labile • Many strains fails to agglutinate with the O antiserum, due to the presence of a surface polysaccharide antigen • Acts as a virulence factor by inhibiting phagocytosis • Poorly immunogenic

  18. ANTIGENIC VARIATIONS H-O VARIATIONS:- These variations is associated with the loss of flagella • When salmonella are grown on the agar containing phenol, flagella inhibited • Flagella reappears when the strain is sub cultured on the media without phenol

  19. INOCULATION CRAIGIE’S TUBE SUBCULTURE

  20. PHASE VARIATION:- • Phase1 antigen are either specific for a species or shared by a few species only so called as specific phase. Designated as a,b,c….z, z1 etc • Phase2 antigen are widely shared and hence also called as non specific or group phase. Designated as 1,2,…. • Stains that possess both phases are called diphasic

  21. V-W variations:- • V form • W form • VW form S-R variations :- The smooth to rough variation is associated with the change in the colony morphology and loss of O antigen

  22. CLASSFICATION & NOMENCLATURE- KAUFFMANN-WHITE SCHEME

  23. SALMONELLA GASTROENTERITIS:- Also called food poisoning group. Most common S typhimurium.Others S enteritidis, S haldar, S newportetc SALMONELLA SEPTICEMIA:- • S choleraesuis

  24. FOOD POISONING

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