3. Salmonella
3
• 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.
4. Enteric Fever Typhoid Fever
4
• 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
5. Morphology of Salmonella
• Gram negative bacilli
• 1-3 / 0.5 microns,
• Motile by peritrichous
flagella
5
6. Cultural Characters
6
• 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
7. Enrichment Medium
7
• Liquid Medium
• Selenite F medium
• Tetrathionate broth
• Above medium are used for isolation of
Salmonella from contaminated specimens
• Particularly stool specimens..
8. Identifying Enteric Organisms
8
• 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
9. Biochemical Characters
• Glucose ,Mannitol ,Maltose produce A/G
• Salmonella typhi do not produce gas
• Lactose/Salicin/sucrose not fermented.
• Indole –
• Methyl Red +
• V P -
• Citrate +
• Urea –
• H2S – produced by Salmonella typhi
• Paratyphi A do not produce H2S
11
10. Antigenic structure of
Salmonella
10
• 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.
11. Salmonella Antigenic
Structure
11
• 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,
12. Antigens – Salmonella
12
• 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
13. Antigenic Variation in
Salmonella
• May be phenotypic / Genotypic
• H to O = loss of Flagella
May be phase variation from I to II
V to W variation S to R variation
13
14. Classification of
Salmonella
• Classified on the basis of
Kauffmann-White Scheme
• Structure of 0 and H antigens are taken
into consideration,
• More than 2000 species
characterized.
14
17. Pathogenicity
17
• Salmonella are definite parasites to humans.
• Eg S.typhi.
• S.paratyphi A, B ,C Other groups Salmonella
• The important clinical syndromes
Enteric fever, Septicemias, gastroenteritis.
19. CAUSE
BACTERIA
• Cause by Bacteria -Salmonella
Typhi.
• Family-Enterobacteriacea.
• Gram negative bacilii.
• Best grows at 37 C.
TRANSMISSION
• faecal-oral route.
• close contact with patients
or carriers.
• contaminated water and food.
• flies and cockroaches.
21. What Arethe Symptomsof
TyphoidFever?
Incubation period is
typically about 10-14
days but can be longer,
and the onset may be
insidious.
Symptoms are often
non- specific and
clinically non-
distinguishable from
other febrile illnesses.
However, clinical
severity varies and
severe cases may lead
to serious complications
22. With appropriate antibiotic therapy, most patients recover from the
disease.
However, 30% of people who do not receive therapy will die.
Annually, in the United States, there are about 300-400 cases and
only one or two deaths each year.
Most of those who got sick had failed to receive a vaccination prior
to travel.
Typhoid fever kills hundreds of thousands of people annually each
year. Most deaths occur in developing countries where the disease
is common. With adequate treatment, less than 1% of victims
should die.
There is a concern that multi-antibiotic-resistant strains of
bacteria are becoming more common worldwide.
WhatIsthe Prognosisof TyphoidFever?
23. Epidemiology
23
• Developed countries - Controlled.
• Water supply/ Sanitation /Economically
poor.
• S.typhi and S.paratyphi are prevalent in
India
• Previously Typhi are more common
Paratyphoid A on raise.
• Age 5 – 20 years, Sanitation
24. Epidemiology (Contd)
24
• Bacilli persist in the Gall bladder and kidney
• Food handlers spread the infection
• Cooks great role
• S.typhi and S.paratyphi in humans
• S.para B in Animals,
• Typhoid spread through Water, Milk, Food HIV
patients potentially susceptible for Typhoid
disease.
25. Immunity in Typhoid
• Typhoid
bacilli are
Intracellular
pathogens
• Cell mediated
immunity is
crucial 27
26. CLINICALFEA
TURES
• Slowly rising (stepladder fashion) of
temperature for 4-5 days
• Abdominal pain & myalgia
• Malaise
• Headache
• Constipation
• Relative bradycardia
• Signs and symptoms of 1st week progress
• Delirium, complications, then coma &
death (if untreated)
Stage 1 (1ST WEEK)
Stage 2 (2ND WEEK)
• Rose spots may appear
on the upper abdomen &
on the back of sparse
• Cough
• Splenomegaly
• Abdominal distension with
tenderness
• Diarrhea
End of 1ST WEEK
End of 2ND WEEK
27. • Febrile become toxic & anorexic
• Significant weight loss
• Typhoid state (Apathy, confusion & psychosis)
• High risk (5-10%) of hemorrhage and perforation may cause death
Stage 3 (3RD WEEK)
Stage 4 (4TH WEEK)
Recoveryperiod
If the individual survives to the fourth week, the fever, mental state,
and abdominal distension slowly improve over a few days.
Intestinal and neurologic complications may still occur in surviving
untreated
individuals.
Weight loss and debilitating weakness last months.
Some survivors become asymptomatic S typhi carriers and have the
potential to transmit the bacteria indefinitely.
29. Diagnosis &Investigation
• Bloodculture
• Specific serologic test
Identify Salmonella antibodies / antigens
[ Fluorescent antibody study to look for
substances that are specific to Typhoid
bacteria ]
Widal Test and ELISA
• Urine and Stool Culture (2nd & 3rd week)
• Marrow Culture*
- 90%sensitive unless until after 5days
commencement of antibiotic
• Punch-biopsy samplesof rose spotsCulture
- 63%sensitive
• Clotculture
*culture maybe obtained from CSF
,peritoneal fluid,
mesenteric LNs,resected intestine, gallbladder,
pharynx, tonsils, abscess,bone
30.
31. Diagnosis and Treatment
31
• Isolation by
culturing
• Rarely need
antibiotics.
• More frequent in
Developed
nations.
32. Clot culture
• Clot cultures are
more productive in
yielding better
results in isolation.
• A blood after
clotting, the clot is
lysed with
Streptokinase ,but
expensive to
perform in
developing
countries.
44
33. Bactek and Radiometric based
methods are in recent use
33
• Bactek methods in
isolation of
Salmonella is a rapid
and sensitive method
in early diagnosis of
Enteric fever.
• Many Microbiology
Diagnostic
Laboratories are
upgrading to Bactek
methods
34. TREATMENT
•Activity – rest is helpful
•Medical care
oAntibiotic
oCorticosterois ( for severetyphoidfever)
oAntipyretics
•Diet - fluid and electrolytes should be
monitored. Soft digestible diet is preferable in
absence of abdominal distension and ileus
•Surgical care – in casesof intestinal perforation
35. Antibiotic
Chloramphenicol (500mgqid)
Ampicillin ( 750mgqid)
Co-trimoxazole ( 2 tablets/ ivbds)
Fluoroquinolone (Drug of choice) – ciprofloxacin (500mgbds)
3rd generation cephalosporin – ceftriaxone, cefotaxime (alternative)
Azithromycin ( 500mg once daily) alternativewhen fluoroquinolone
resistant ispresent
Treatment should be continued for 14days
• Chroniccarriers were formerly treated for 4 weekswith ciprofloxacin but
mayrequire analternative agent and duration, asguided byantimicrobial
sensitivity testing.
• Cholecystectomymaybe necessary.
Resistance in
many areas of
the world,
especially India &
South-east Asia
36. Vaccines
36
• An Inject able vaccine Typhium Vi
• Contains purified Vi polysaccharide
antigen from S.typhi strain Ty2
• A single dose, subcutaneous route
• Given to children > 5 years
• Immunity lasts for 2- 3 years.
• Follow a booster
37. Coalition against Typhoid
37
• Since May 2011, the
Coalition against Typhoid
(CaT) has featured
monthly articles in the
WHO’s Global
Immunization Newsletters
(GIN). The articles,
written by CaT members
from around the world,
highlight important work
being done to accelerate
adoption of typhoid
vaccines.
39. ANTIMICROBIAL RESISTANCE TYPHOID FEVER
• Mechanisms of antibiotic resistance in S.typhi is mediated by two
factors
• Acquisition of foreign genes via plasmids
• Mutation on chromosome.
• Resistance can be achieved by horizontal acquisition of resistance
genes, mobilized via insertion sequences, transposons and
conjugative plasmids, by recombination of foreign DNA in to the
chromosome, or by mutations in different chromosomal loci.
40. MULTI-DRUG RESISTANCE
• Under the process of HGT, it is possible for bacteria to acquire
multiple resistance genes thereby protecting them from multiple
classes of antimicrobials. When this occurs, this is an example of
multidrug resistance, or MDR.
• Multidrug resistant non-typhoidal Salmonella strains are typically
resistant to chloramphenicol, ampicillin, and trimethoprim plus
possibly others.
• As AMR and MDR continue to spread among Salmonella strains and
other bacterial species, the burden of disease caused by these
pathogens will worsen.
• The following graphic demonstrates one simple scenario of how AMR
can develop and spread.
43. Different drug resistance of S.typhi
• Resistance to sulfonamides is mediated by a
plasmid encoded transport system that actively
exports the drug out of the cell (Denyeret al, 2011).
• Many genes, such as plasmid mediated
ßlactamases,tetracycline-resistance genes,and
aminoglycoside-modifying enzymes, are organized
on transposons(Richardetal., 2007).
44. Different drug resistance of S.typhi
• The chromosomal mediated drug resistance phenomen on against
fluoroquinolones has been reported recently as a result of selective
pressure on the bacterial population due to their uncontrolled use. This
has been attributed toasingle point mutation in the quinolone resistance
determining region(QRDR) of the topoisomerase gene gyrA, which
encodes DNA gyrase.
• Resistance to trimethoprim is due primarily to mutations in the
chromosomal gene that encodes dihydrofolate reductase, the enzyme
that reduces dihydrofolate to tetrahydrofolate. Also, resistance to
sulfonamides has been found to be mediated by a chromosal mutation in
the gene coding for the target enzyme dihydropteroate synthetase,
which reduces the binding affinity of the drug.
