Systemic bacterilogy of samonella typhi slodeshare
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Salmonella basics Dr.T.V.Rao MD Dr.T.V.Rao MD 1
2. Salmonella • Causes Infections in Humans and vertebrates, • Enteric Fever ( Typhoid fever ) • Gastroenteritis • Septicemias, • Carrier state. Dr.T.V.Rao MD 2
3. Salmonella • A Very complex group • Contains more > 2,000 spp • Typed on the basis of Serotyping, and species typing • Divided into two groups 1 Enteric fever group 2 Food poisoning group – Septicemias. Dr.T.V.Rao MD 3
4. Enteric Fever Typhoid Fever • Caused by Salmonella typhi, and other Groups called as Paratyphi A, B, C • Salmonella typhi - Causes Typhoid • Salmonella Paratyphi A,B,C Causes Paratyphoid fevers. • Food Poison group • Spread from Animals – Humans • Causes Gastroenteritis – Septicemias, Localized Infection Dr.T.V.Rao MD 4
5. Typhoid Mary Most Dangerous Woman in America Dr.T.V.Rao MD 5
6. Morphology of Salmonella • Gram negative bacilli • 1-3 / 0.5 microns, • Motile by peritrichous flagella Dr.T.V.Rao MD 6
7. Bacteriology –Typhoid fever • The Genus Salmonella belong to Enterobacteriaceae • Facultative anaerobe • Gram negative bacilli • Distinguished from other bacteria by Biochemical and antigen structure Dr.T.V.Rao MD 7
8. Cultural Characters • Aerobic / Facultatively anaerobic • Grows on simple media – Nutrient agar, • Temp 15 – 41ºc / 37º c • Colonies appear as large 2 -3 mm, circular, low convex, • On MacConkey medium appear Colorless ( NLF ) Selective Medium - Wilson Blair Bismuth sulphide medium. Produce Jet black colonies H2 S produced by Salmonella typhi Dr.T.V.Rao MD 8
9. Enrichment Medium Liquid Medium • Selenite F medium • Tetrathionate broth • Above medium are used for isolation of Salmonella from contaminated specimens • Particularly stool specimens.. Dr.T.V.Rao MD 9
10. Identifying Enteric Organisms • Isolates which are Non lactose fermenting • Motile, Indole positive • Urease negative • Ferment Glucose,Mannitol,Maltose • Do not ferment Lactose, Sucrose • Typhoid bacilli are anaerogenic • Some of the Paratyphoid form acid and gas • Further identification done by slide agglutination tests Dr.T.V.Rao MD 10
11. Biochemical Characters • Glucose ,Mannitol ,Maltose produce A/G • Salmonella typhi do not produce gas • Lactose/Salicin/sucrose not fermented. • Indole – • Methyl Red + • VP - • Citrate + • Urea – • H2S – produced by Salmonella typhi • Paratyphi A do not produce H2S Dr.T.V.Rao MD 11
12. Resistance of Salmonella • 55º c – 1 hour • 60º c – 15 MT • Boiling ,Chlorination, Pasteurization Destroy the Bacilli. Dr.T.V.Rao MD 12
13. Antigenic structure of Salmonella • Two sets of antigens • Detection by serotyping • 1 Somatic or 0 Antigens contain long chain polysaccharides ( LPS ) comprises of heat stable polysaccharide commonly. • 2 Flagellar or H Antigens are strongly immunogenic and induces antibody formation rapidly and in high titers following infection or immunization. The flagellar antigen is of a dual nature, occurring in one of the two phases. Dr.T.V.Rao MD 13
14. Salmonella Antigenic Structure • H – Flegellar antigens • O – Somatic antigen, • Vi – Surface antigen in some species only • H antigens also called flegellar antigens, heat labile protein, • Boiling destroys antigenicity • When mixed with Antiserum produces agglutination and fluffy clumps are produced • H antigens are strongly immunogenic Induces antibodies rapidly, Dr.T.V.Rao MD 14
15. Antigens – Salmonella ( cont ) • O Antigens • Forms integral part of Cell wall, • Like Endotoxin • 0 Antigens unaffected by boiling. • When mixed with antiserum produce chalky clumps are formed, take more time reaction, at high temp 50º – 55º c • O antigens are less immunogenic. than H antigens Dr.T.V.Rao MD 15
16. Antigen (Vi) – Salmonella ( contd ) • Vi antigens • Many strains in S.typhi covers the O antigens- prevents agglutination. • Resembles like K antigens • Destroyed after boiling at 60º c / 1 hour. • Vi a polysaccharide • Acts as virulence factor, protects the bacilli against Phagocytosis and activity of Complement • Poorly immunogenic • Low titer of antibodies are produced, Not diagnostic Dr.T.V.Rao MD 16