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salmonella spp.ppt

  1. Typhoid/ Enteric fever Dr. Jyotsna Agarwal Professor, Dept. Microbiology KGMU 1
  2. 2 • Salmonella is Gram-negative, rod-shaped • Facultative anaerobe in family Enterobacteriaceae • Motile, Non lactose fermenting • Over 2400 serotypes Salmonella
  3. 3  Faeco-oral transmission  Refrigeration does not kill bacteria, Heat at 600C destroys
  4. 4 Clinical Syndromes of Salmonella Salmonellosis = Generic term for disease Enteritis (acute gastroenteritis) Enteric fever (prototype is typhoid fever and less severe paratyphoid fever) Septicemia (particularly S. choleraesuis, S. typhi, and S. paratyphi) Asymptomatic carriage (gall bladder is the reservoir for Salmonella typhi)
  5. 5 Enteritis( Food Poisoning)  Most common form of salmonellosis with foodborne outbreaks and sporadic disease  High infectious dose (108 CFU)  Poultry, eggs, etc. are sources of infection  6-48h incubation period  Nausea, vomiting, nonbloody diarrhea, fever, cramps, myalgia and headache common  Many species of salmonella can cause this (eg. S. typhimurium) except S. typhi
  6. 6 Pathogenesis  Bacteria penetrates intestinal cell in ileocaecal region  Inflammatory response to bacterial multiplication in the cell  Prostaglandins secreted  Increase in C-AMP
  7. 7 Clinical Syndromes- Enteric fever  S. typhi causes typhoid fever S. paratyphi A, B and C cause milder form of enteric fever called paratyphoid fever  Infectious dose large = 106 CFU  Fecal-oral route of transmission  Person-to-person spread by chronic carrier  Fecally-contaminated food or water  Food handlers contaminate food  10-14 day incubation period
  8. 8  Virtually non existent in developed world  In developing countries endemic  Typhoid more common than paratyphoid
  9. 9 Pathogenesis of Enteric fever M cells on Peyers patches Invade intestinal lining cells bloodstream (primary bacteremia) Phagocytosis Transported (R E system), continue to replicate
  10. 10 Pathogenesis contd…  Second week: re-enter bloodstream (secondary bacteremia) endotoxemia  Second to third week: gallbladder, secreted in bile, re-infect intestinal tract
  11. 11  Complications: Intestinal haemorrhage, perforation, cholecystitis  Less commonly: Bronchopneumonia, arthritis, osteomyelitis
  12. 12 Asymptomatic Carriage  Chronic carriage in 1-5% of cases following S. typhi or S. paratyphi infection (Temporary carrier>12 months shedding)  Gall bladder usually the reservoir  Chronic carriage with other Salmonella spp. occurs in <<1% of cases and does not play a role in human disease transmission Epidemiology & Clinical Syndromes
  13. 13 Early 1900- Mary Mallon
  14. 14 Virulence factor •Encapsulation , antigenic mimicry, masking •Evasion or incapacitation of phagocytosis • Mechanisms enabling an invading microorganism to resist being ingested and lysed by lysosomes intracellular survival and multiplication •Endotoxin
  15. 15 Diagnosis of Typhoid Fever  Clinical:  For Lab diagnosis, specimen & diagnostic tests according to duration of fever: 1. Blood for Culture 2. WIDAL 3. Stool culture 4. Urine culture
  16. 16 Blood Culture  In blood culture bottle  Repeated cultures may be required  Subculture on MacConkey medium (NLF colony)  Clot culture- put clot in blood culture bottle, lyse it with streptokinase in B/C bottle  Use serum for WIDAL
  17. 17  Selective media for subculture from blood culture bottle: MacConkey, Wilson Blair, Tellurite blood agar  Enrichment broth for culture of stool/urine: Selenite F broth, Tetrathionate broth
  18. 18 Serological test- WIDAL  For detecting antibody  Agglutination test 1. Endemic titre 2. Paired sera  For carriers - antibody against Vi antigen  Rapid test- Typhi dot
  19. 19 Treatment, prevention & control of salmonella infections Enteritis:  Antibiotics not recommended for enteritis because prolong duration  Control by proper preparation of poultry & eggs Enteric fever:  Antibiotics- Chloramphenicol, cipriflox, Ceftriaxone  Identify & treat carriers of S. typhi & S. paratyphi  Vaccination can reduce risk of disease for travellers in endemic areas
  20. Salmonella vaccines  TAB: Salmonella typhi, paratyphi A &B, killed whole cell  Oral Ty21-A: Live attenuated, Salmonella typhi vaccine  Vi capsular polysaccharide vaccine 20
  21. Summary- Enteric fever  S. typhi / S. paratyphi  Mode of spread /Pathogenesis  Clinical features / Complications  Laboratory diagnosis  Treatment/vaccines 21