salmonella spp.ppt

enteric bacteria

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
60
0
C destroys

4. 4Clinical Syndromes of Salmonella
Salmonellosis= Generic term for disease
Enteritis(acute gastroenteritis)
Enteric fever(prototype is typhoid feverand
less severe paratyphoid fever)
Septicemia(particularly S. choleraesuis, S. typhi,
and S. paratyphi)
Asymptomatic carriage(gall bladder is the
reservoir for Salmonella typhi)

5. 5Enteritis( Food Poisoning)
Most commonform of salmonellosiswith
foodborneoutbreaksand sporadic disease
High infectious dose(10
8
CFU)
Poultry, eggs, etc. are sources of infection
6-48h incubation period
Nausea, vomiting, nonbloodydiarrhea, fever,
cramps, myalgiaand 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. 7Clinical Syndromes-Enteric fever
S. typhicauses typhoid fever
S. paratyphiA, B and C cause milder form of
enteric fever called paratyphoid fever
Infectious doselarge= 10
6
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 onPeyers 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. 12Asymptomatic Carriage
Chronic carriage in 1-5% of casesfollowing S.
typhior S. paratyphiinfection (Temporary
carrier>12 months shedding)
Gall bladderusually the reservoir
Chronic carriage with other Salmonellaspp.
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. 14Virulence 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
Subcultureon 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. 19Treatment, prevention & control of
salmonella infections
Enteritis:
Antibiotics not recommendedfor enteritis
because prolong duration
Control by proper preparation ofpoultry & eggs
Enteric fever:
Antibiotics-Chloramphenicol, cipriflox,
Ceftriaxone
Identify & treat carriersof S. typhi& S.paratyphi
Vaccinationcan reduce risk of disease for
travellersin endemic areas

20. Salmonella vaccines
TAB: Salmonella typhi, paratyphi A &B, killed whole
cell
Oral Ty21-A: Live attenuated, Salmonella typhi
vaccine
Vicapsular polysaccharide vaccine
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21. Summary-Enteric fever
S. typhi / S. paratyphi
Mode of spread /Pathogenesis
Clinical features / Complications
Laboratory diagnosis
Treatment/vaccines
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