Salmonella

Question 0

What family are salmonella bacteria part of and what are the lab characteristics?

Answer 0

Enterobacteriiaceae - gram negative

Question 1

Which salmonella species cause enteric fever in humans?

Answer 1

Salmonella Typhi - typhoid fever
Salmonella Paratyphi (A-C) - paratyphoid fever
*disease syndrome caused by these organisms is ENTERIC FEVER

Question 2

Which salmonella cause gastroenteritis in humans?

Answer 2

Non-typhoidal salmonellas

*food-poisoning group

Question 3

What kind of disease is salmonella?

Answer 3

An ingestion disease.

Water, milk, food (contaminated)

Question 4

Infection with salmonella can result in three patterns of illness. Name them.

Answer 4

1. Enteric fever (typhoid or paratyphoid)
2. Gastroenteritis (food poisoning)
3. Extra intestinal infection - associated with poor host response

Question 5

How is S.Typhi spread?

Answer 5

Is an infection of man only therefore:

• hands
• food
• water
• milk

Question 6

Lab characteristics of S.Typhi?

Answer 6

Gram-negative bacilli
non-sporulating
motile

Question 7

Outline the pathogenesis of S.Typhi.

Answer 7

Invades S.I. > multiplies in mesenteric lymph glands > enters bold stream via thoracic duct > infection of organs > organisms localise in R.E.S > organisms released from R.E.S > septicemia (fever onset) > re-infection of organs

Question 8

What part of the body is particularly affected by Enteric fever?

Answer 8

Peyers patches:

- inflammatory response can result in ulceration and perforation

Question 9

How can S.Typhi infection be chronic?

Answer 9

Long term survival of the organism in the gallbladder.

Question 10

What allows S.Typhi to spread around the body despite efforts from the immune system?

Answer 10

1. S.Typhi can survive in phagocytes
2. Lipopolysaccharide endotoxins
3. Microcapsule - protects against the llytic activity of complement and impedes phagocytosis

Question 11

Pathology of S.Typhi?

Answer 11

Ulceration of peyers patches in ileum. Perforation = peritonitis
Mesenteric lymph nodes:
- enlarged, soft and red due to hyperplasia, hyperaemia and edema
Spleen:
- enlarged and soft

Question 12

Histologically, what is the pathology with regards to S.Typhi?

Answer 12

Histiocytes
Lymphocytes
Plasma cells
*polymorphs not prominent

Question 13

When can one expect complications of enteric fever?

Answer 13

Usually two weeks after onset.

Question 14

What are some complications of enteric fever?

Answer 14

Perforation > peritonitis
Haemorrhage > eroded blood vessel in base of ulcer
Typhoid pneumonitis
Thrombosis
Cholecystitis (allow organisms to persist)
Typhoid hepatitis
*can also affect the heart + meninges

Question 15

Incubation period of enteric fever?

Answer 15

1-3 weeks.

Question 16

Clinical presentation of enteric fever?

Answer 16

Insidious onset of:

• headache
• step-like temperature
• bradycardia
• malaise, anorexia

Question 17

What may happen if enteric fever is allowed to become severe?

Answer 17

Apathy
Delirium
Stupor

Question 18

What skin sign could one see with regards to enteric fever?

Answer 18

Rose-colored rash on the abdomen.

Question 19

What is the most striking clinical feature of enteric fever?

Answer 19

Septicemia

Question 20

Is enteric fever associated with gastroenteritis?

Answer 20

Varying degrees - classical pea-soup like stool

*patient may be constipated or have normal stools

Question 21

How does one diagnose S.Typhi?

Answer 21

Isolation of causative organism > culture

Serology

Question 22

What specimens can be used to try to culture S.Typhi?

Answer 22

Blood - initial disease levels are high
Stool - only in third week of illness
Urine - excretion with S.Typhi often intermittent
Bone marrow aspirate

Question 23

What serological test can be used to try to identify S.Typhi? Is it reliable?

Answer 23

Widal agglutination test.

Unreliable and often difficult to interpret.

Question 24

What is the Widal agglutination test? When may it be difficult to interpret the test result?

Answer 24

Test for antibodies to both the O and H antigens. | *difficult to interpret when a person has relieved a Typhoid vaccine

Question 25

What factors should one consider whenever interpreting a serological test?

Answer 25

1. Antibodies in the population at risk 2. Previous innoculations (vaccines) 3. Antibiotic therapy (may modify the response) 4. At what stage of the disease the blood was taken for serology

Question 26

Once someone has had enteric fever can they get it again?

Answer 26

Only rarely.

Question 27

Who gets the vaccine for S.Typhi?

Answer 27

Travellers to endemic areas.

Question 28

What antibiotics are used to treat enteric fever?

Answer 28

Quinolones. Amoxicillin Cotrimoxazole

Question 29

With regards to doses of organisms required to cause disease, where does S.Typhi stand?

Answer 29

Low dose is sufficient.

Question 30

What would Typhoid Mary be referred to today?

Answer 30

A chronic excretor of S.Typhi (gallbladder). | Cholecystectomy required today.

Question 31

Pathogenesis of gastroenteritis caused by non-typhoidal salmonella?

Answer 31

Organisms multiply in S.I. > invade gut wall (pinocytosis) > migrate to lamina propria > inflammatory response

Question 32

Clinical features of gastroenteritis due to non-typhoidal salmonella?

Answer 32

Asymptomatic Gastroenteritis (watery to dysenteric stools) Fever + abdominal cramps + nausea/emesis + myalgia

Question 33

What does the Diarrhoea in gastroenteritis due to non-typhoidal salmonella look like?

Answer 33

Loose or watery Blood is rare Pus may be present

Question 34

How to diagnose gastroenteritis due to non-typhoidal salmonella?

Answer 34

Organism cultured form the stool fairly readily.

Question 35

Treatment of non-typhoidal salmonella induced gastroenteritis?

Answer 35

Supportive care - illness is self-limiting | Antibiotics in the immunocompromised

Question 36

What antibiotics can be used to treat gastroenteritis due to non-typhoidal salmonella?

Answer 36

Quinolones | Or amoxicillin or cotrimoxazole

Question 37

Who are at risk of invasive disease with regards to salmonella?

Answer 37

Immunocompromised. HIV PATIENTS

Question 38

What can happen in invasive disease regarding salmonella?

Answer 38

Pneumonia. Meningitis. Damage at atherosclerotic lesions.

Question 39

How to treat invasive salmonella in HIV patients?

Answer 39

Third generation cephalosporins followed by oral Quinolones.