salmonella_lecture S. Paraty.S.typhi.ppt

TAB: Salmonella typhi, paratyphi A &B, killed whole cell
Oral Ty21-A: Live attenuated, Salmonella typhi vaccine
Vi capsular polysaccharide vaccine
Salmonellosis = Generic term for disease


Enteritis (acute gastroenteritis)

Enteric fever (prototype is typhoid fever and less severe paratyphoid fever) : Body temperature increase 101 F.

Septicemia (particularly S. choleraesuis, S. typhi, and S. paratyphi): When bacteria, viruses, or fungi spread into the bloodstream and cause a severe infection.

Asymptomatic carriage (gall bladder is the reservoir for Salmonella typhi. Salmonella is a type of bacteria commonly associated with foodborne illnesses. It can cause an infection called salmonellosis, which typically results from consuming contaminated food or water. Key points about Salmonella include:

Sources: It is often found in raw or undercooked meat, poultry, eggs, and unpasteurized milk or juice. Contaminated water and contact with infected animals (especially reptiles and birds) can also be sources.

Symptoms: Common symptoms of salmonellosis include diarrhea, fever, abdominal cramps, and vomiting. Symptoms usually appear 6 hours to 6 days after infection and last 4-7 days.

Prevention: Safe food handling practices can reduce the risk of infection. This includes cooking meat thoroughly, avoiding raw eggs, washing fruits and vegetables, and maintaining good hand hygiene.

Vulnerable Groups: Infants, elderly individuals, and people with weakened immune systems are at higher risk of severe illness.1. Types of Salmonella
There are two main species of Salmonella:

Salmonella enterica: Responsible for most human infections.
Salmonella bongori: Primarily affects cold-blooded animals.
S. enterica has many subspecies and serotypes, including Salmonella Typhimurium and Salmonella Enteritidis, which are the most common causes of foodborne illness in humans.

2. Transmission
Contaminated food and water: Salmonella bacteria live in the intestines of animals and humans, and they are usually transmitted through the consumption of food or water that has been contaminated by feces.
Animal contact: Handling animals like reptiles (e.g., turtles), birds, and their environments can also spread the bacteria.
3. Symptoms of Salmonellosis
Gastrointestinal distress: Diarrhea, nausea, vomiting, fever, and abdominal cramps are common. In some cases, the illness can lead to dehydration, especially in vulnerable populations.
Severity: While most people recover without treatment, the infection can be more severe in young children, the elderly, and immunocompromised individuals. In rare cases, it can lead to sepsis (bloodstream infection) or reactive arthritis.
4. At-Risk Foods
Raw poultry and eggs: Contamination often occurs at the farm level, but cross-contamination can also happen during food preparation.
Raw or undercooked meat: Cooking food to the correct temperature is essential to kill Salmonella.
Unwashed produce: Bacteria can transfer from the soil or water to fruit

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. 4
Clinical Syndromes of Salmonella
Salmonellosis= Generic term for disease
Enteritis(acute gastroenteritis)
Enteric fever(prototype is typhoid feverand
less severe paratyphoid fever) : Body
temperature increase 101 F.
Septicemia(particularly S. choleraesuis, S. typhi,
and S. paratyphi): When bacteria, viruses, or
fungi spread into the bloodstream and cause a
severe infection.
Asymptomatic carriage(gall bladder is the
reservoir for Salmonella typhi)

5. 5
Enteritis( Food Poisoning)
Most commonform of salmonellosis with
foodborne outbreaksand sporadic disease
High infectious dose(10
8
CFU)
Poultry, eggs, etc. are sources of infection
6-48h incubation period
Nausea, vomiting, nonbloodydiarrhea, 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
ileocecal region

Inflammatory response to bacterial
multiplication in the cell

7. 7
Clinical 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

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
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 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

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Early 1900- Mary Mallon

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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

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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

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Treatment, 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

17. Salmonella vaccines

TAB: Salmonella typhi, paratyphi A &B, killed whole
cell

Oral Ty21-A: Live attenuated, Salmonella typhi
vaccine

Vi capsular polysaccharide vaccine
17

18. Summary- Enteric fever

S. typhi / S. paratyphi

Mode of spread /Pathogenesis

Clinical features / Complications

Laboratory diagnosis

Treatment/vaccines
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