1. Enteric fever 1
Prabin Shah
BScMLT, MSc(Biochemistry)

2. 
 Typhoid fever, commonly just typhoid, is a common
worldwide illness, transmitted by the ingestion of
food or water contaminated with the feces of an
infected person.
 This fever received various names, such as gastric
fever, the bends, abdominal typhus, infantile
remittent fever, slow fever, nervous fever,
pathogenic fever, etc.
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INTRODUCTION

3. The salmonella bacilli was first
described by Salmon and Smithin the
year 1885.
In 1906, Irish immigrant Mary Mallon
worked as a cook and was a carrier. Thus
earned the nickname "Typhoid Mary.
She died of a stroke after 23 years.
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History

4.  The term enteric fever or typhoid fever refers
to a communicable disease, found only in man
and includes both typhoid fever caused by
S.Typhi and paratyphoid fever caused by
S.Paratyphi A, B and C .
 It is an acute generalized infection of the
reticulo-endothelial system, intestinal
lymphoid tissue, and the gall bladder.
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DEFINITION

5. 
 GNB
 Motile
 Non sporing
 Non capsulated
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MORPHOLOGY

6. 
 Killed at 60°C in 15 mins
 Boiling, chlorination of water and pasteurisation of
milk also destroys the bacilli.
 Survive in water and ice for weeks
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RESISTANCE

7. 
 3 types of antigens;
1. Flagellar antigen ‘H’
2. Somatic antigen ‘O’
3. Surface antigen ‘Vi’
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ANTIGENIC STRUCTURE

8. 
"O"-group
Sero type "O" antigens
Phase 1 (motile)
"H" antigens
Phase 2 (non-
motile) "H"
antigensOld New
A 2 S.Paratyphi A 1,2,12 a no phase 2 antigen
B 4 S. Paratyphi B 1,4,5,12 b 1,2
S. Typhimurium 1,4,5,12 i 1,2
C1 7 S. Paratyphi C 6,7 c 1,5
S. Colerae-suis 6,7 c 1,5
C2 8 S.muenchen 6,8 d 1,2
S.newport 6,8,20 e, h 1,2
D 9 S. Typhi 9,12,Vi d no phase 2 antigen
S. Enteritidis 1,9,12 g,m no phase 2 antigen
S. Gallinarum 1,9,12 no phase 1 antigen no phase 2 antigen
S. Pullorum (1),9,12 no phase 1 antigen no phase 2 antigen
E1 3,10 S. Anatum 3,10 e,h 1,6

9.  H antigen( flagellar antigen)
Ag is present in the flagella
Heat labile protein
Strongly immunogenic
Produces large, loose, fluffy clumps.
 O antigen
Lipo polysaccharide
Identical to endotoxin
Heat stable
Produces compact, chalky, granular clumps.
Less immunogenic
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10.  Vi antigen
Surface antigen enveloping the O Ag is referred to
as Vi Ag.
Heat labile
Acts as virulence factor by inhibiting phagocytosis,
resisting complement activation and bacterial lysis.
Poorly immunogenic.
Not helpful in the diagnosis of enteric fever.
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11. 
1. ENTERIC FEVER
i. TYPHOID FEVER
ii. PARATYPHOID FEVER
2. SEPTICAEMIA
3. GASTROENTERITIS
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PATHOGENESIS

12. 1. TYPHOID FEVER
The name typhoid was coined by Louis in 1829.
Caused by S.typhi
Acquired by the ingestion of contaminated food and
water
IP: 7-14 days
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ENTERIC FEVER

13.  Enteric fever is endemic in all parts of india.
 Typhoid fever occurs in 2 epidemiological types;
1. endemic( occurs through out the year)
2. epidemic( occur in endemic or non-endemic areas)
13
Epidemiology

14. 1. Convalescent carriers
 shed the bacilli in feces for 3 weeks to 3 months.
2. Temporary carriers
 Shed the bacilli for more than 3 months but less than a year.
3. Chronic carriers
 Shed the bacilli over an year
4. Fecal carrier
 the bacilli that persist in kidney or gall bladder are eliminated through feces
5. Urinary carrier
 bacilli eliminated through urine, associated with urinary lesion such as calculi.
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Types of carriers

15. Bacilli attaches to the epithelial cells of the intestinal villi in
the small intestine.
Penetrates to the lamina propria and sub mucosa
Phagocytosed by the neutrophils and macrophages
Bacteria resists and it enters into the mesenteric lymph
nodes and multiply there via the thoracic duct and enters
into the blood stream.
A transient bacteremia follows and the internal organs like
liver, gall bladder, spleen, bone marrow, lungs and kidney
get infected.
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Sequence of infection

16. Clinical features include;
 Mild pyrexia
 Headache
 Malaise
 Anorexia
 Coated tongue
 Abdominal discomfort with constipation/diarrhea
 Congestion of mucous membranes
 Hepatosplenomegaly with soft and palpable spleen.
 Step ladder pyrexia with relative bradycardia and
leucopenia.
 Skin rashes known as rose spots may appear on the 2nd
and 3rd week.
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17. Rose spots
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18. 2. PARATYPHOID FEVER
 Milder form than typhoid fever.
 Caused by S.paratyphi A,B and C
 Other salmonella causing enteric fever are;
S.dublin
S.barielly
S.sendai
S.enteritidis
S.typhimurium
S.eastbourne
S.saintpaul
S.panama
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19. I. Specimen collection
Blood
Faeces
Urine
Aspirated duodenal fluid
Bile
Bone marrow
Rose spots
Pus from suppurative lesions
CSF
Sputum
At autopsy cultures may be obtained from the gall
bladder, liver, spleen, and mesenteric lymph nodes.
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LAB DIAGNOSIS

20. Duration of disease Specimen
examination
% positivity
1st week Blood culture 90
2nd week Blood culture
Faeces culture
Widal test
75
50
Low titre
3rd week Widal test
Blood culture
Faeces culture
80-100
60
80
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Specimens collection based on
different phases of enteric fever

21.  Gram stain is done
GNB
Non capsulated
Motile with peritricous flagella except
gallinarum and pullorum.
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II. Microscopy

22. 
 Grows on ordinary media
 Opt temp: 37°C
 pH: 6-8
 Aerobic and facultative anaerobic.
On nutrient agar
Colonies are 2-3mm in diameter, circular,
translucent, grey white in color, low
convex and smooth.
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III. Culture

23. On MacConkey’s agar and DCA
Colorless colonies due to NLF colonies.
Selective media
Wilson and Blair bismuth sulphite medium
Jet black colonies with metallic sheen are formed due to
formation of hydrogen sulphide.
Xylose lysine deoxycholate (XLD)
Red colonies with black centres are seen
Enrichment media
Selenite F broth
Tetrathionate broth (TTB) 23

24. Enteric fever 24

25.  Ferments glucose and mannitol forming acid and gas except
S.typhi produces only acid but no gas.
 Catalase positive
 Oxidase negative
 Indole is not produced
 Produces H2S in TSI agar except S. paratyphi A and S.
cholerae-suis.
 Utilise citrate (except S.typhi & S.paratyphi A)
 MR positive
 VP negative
 Urea not hydrolysed
 Nitrate reduction test is positive
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IV. BIOCHEMICAL REACTIONS

26. S.typhi S.Paratyphi
A
S.Paratyphi
B
S.Paratyphi
C
Glucose A AG AG AG
Mannitol A AG AG AG
Lactose - - - -
Sucrose - - - -
Indole - - - -
Citrate - - + +
MR + + + +
VP - - - -
H2S + - ++ +
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Biochemical rxns to differentiate
btw salmonella species

27. 
 Positive in 90% of the cases in the first week of fever.
 75% in second week
 60% in third week
Procedure
10ml of blood collected under aseptic
conditions and transferred into blood
culture bottles.
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Blood culture

28.  Blood has to be diluted with the culture media in the
ratio of 1:10.
 Then incubated at 37°C overnight.
 Subculture done on BA and MCA
 More preferred method is the Castaneda’s method of
blood culture.
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29. 
 Salmonella are shed in faeces during the infection and
convalescence phase too.
 Generally faeces culture turn positive in the second week
of infection.
 Sample is inoculated into one tube each of selenite and
tetrathionate broth(enrichment media)
 Plated onto MCA, DCA, XLD, and Wilson-Blair medium.
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Faeces culture

30. 
 Frequency of getting a positive result is less when
compared to that of blood and faeces.
 Generally seen as positive in the 2nd and 3rd weeks.
 Urine samples are centrifuged and deposit is
inoculated into both enrichment and selective
medium.
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Urine Culture

31. 
 5ml of blood is withdrawn aseptically into sterile
container and allowed to clot.
 Clot is broken up with a sterile glass rod and added
to bile broth containing streptokinase(100units/ml)
which digests the clot causing its lysis and thereby
the bacteria are released from the clot.
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Clot culture

32. 
 It is an agglutination test for the detection of
agglutinins (H and O) in patients with enteric fever.
 The antibodies begin to appear in serum at the end
of 1st week and rise during the 3rd week of enteric
fever.
 2 specimens of sera are collected at an interval of 7 to
10 days to demonstrate the rising Ab titre.
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WIDAL TEST

33.  2 types of tubes;
 Dreyer’s tube
 Felix tube
 Equal vol of 0.4ml of serial dilution of the serum(1:10 to
1:640) and the H and O antigens are mixed and
incubated at 37°C for 4 hrs and read after overnight
incubation in room temp.
 Control tubes with antigen and normal saline are
included to check for auto agglutination.
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Procedure

34.  H agglutination - formation of loose, cotton wool
clumps
 O agglutination – granular deposit at the bottom of the
tube
 High dilution with carpet formation indicates the
antibody titre against that particular Ag.
 Control tubes will show a compact deposit (button
formation).
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35.  A loopful of the growth from nutrient agar slope is emulsified in
2 drops of saline on a slide.
 One emulsion acts as a control and other as a test.
 Agglutination is first carried out with the polyvalent O and the
polyvalent H antisera.
 Positive agglutination indicates that the isolate belong to genus
salmonella.
 Then if S.typhi is suspected, agglutination with O anti serum is
done.
 Prompt agglutination indicates that the isolate belong to group
D salmonella.
 S.typhi is confirmed by the agglutination with O anti serum.
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SLIDE AGGLUTINATION TEST

36. Vaccinations
i. TAB vaccine
 heat killed
 Polyvalent vaccine
 Dose schedule: 2 doses of 0.5ml at an interval of 4-6
weeks S/C followed by booster every 3 years.
ii. Purified Vi polysaccharide vaccine(typhim-Vi)
 Dose schedule: single dose of 25µg injected I/M or S/C
 Causes minimal reaction.
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PROPHYLAXIS

37. iii. Live Oral typhoid vaccine
 Stable mutant of S.typhi
 Dose schedule: 3 doses on days 1,3,5 should be taken an
hour before food, with a glass of water or milk.
 Oral (typhoral) vaccine is available as capsule.
 On ingestion, it initiates infection but self destructs after
4-5 cell divisions and thus cannot induce any illness.
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38. 
 Antibiotics such as;
 Chloramphenicol
 Streptomycin
 Tetracycline
 Ampicillin
 Amoxycillin
 Cotrimoxazole
Are found effective in the treatment of typhoid fever.
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Treatment

39. 
 Showed resistance to chloramphenicol.
 Chloramphenicol resistant typhoid fever appeared in
kerala in 1972.
 Multi drug resistant S.typhi is also becoming a major
problem in india.
 These may cause nosocomial salmonellosis as
septicaemia, meningitis, and suppurative lesions.
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Drug resistance

40. 
 A zoonotic disease
 Caused by S.typhi, S.typhimurium, S.enteritidis,
S.indiana, S.newport, S.agona.
 Sources: poultry, meat, milk, eggs.
 Clinical features: diarrhea, vomiting, fever,
abdominal pain.
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Gastroenteritis

41. 
 Certain salmonella may cause septicaemia with
suppurative lesions such as deep abscess, osteomyelitis ,
pneumonia, endocarditis and meningitis.
 S.cholerae suis is the most important causative agent of
salmonella septicaemia.
 Fulminating blood infection.
 Treatment with chloramphenicol.
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Septicaemia

42. 
1. Text book of microbiology
Ananthnarayan and Paniker’s
2. Text book of microbiology
C.P. Baveja
3. Mackie and McCartney
4. google
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REFERENCE

43. 
THANK YOU
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