Salmonella Flashcards
What family are salmonella bacteria part of and what are the lab characteristics?
Enterobacteriiaceae - gram negative
Which salmonella species cause enteric fever in humans?
Salmonella Typhi - typhoid fever
Salmonella Paratyphi (A-C) - paratyphoid fever
*disease syndrome caused by these organisms is ENTERIC FEVER
Which salmonella cause gastroenteritis in humans?
Non-typhoidal salmonellas
*food-poisoning group
What kind of disease is salmonella?
An ingestion disease.
Water, milk, food (contaminated)
Infection with salmonella can result in three patterns of illness. Name them.
- Enteric fever (typhoid or paratyphoid)
- Gastroenteritis (food poisoning)
- Extra intestinal infection - associated with poor host response
How is S.Typhi spread?
Is an infection of man only therefore:
- hands
- food
- water
- milk
Lab characteristics of S.Typhi?
Gram-negative bacilli
non-sporulating
motile
Outline the pathogenesis of S.Typhi.
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
What part of the body is particularly affected by Enteric fever?
Peyers patches:
- inflammatory response can result in ulceration and perforation
How can S.Typhi infection be chronic?
Long term survival of the organism in the gallbladder.
What allows S.Typhi to spread around the body despite efforts from the immune system?
- S.Typhi can survive in phagocytes
- Lipopolysaccharide endotoxins
- Microcapsule - protects against the llytic activity of complement and impedes phagocytosis
Pathology of S.Typhi?
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
Histologically, what is the pathology with regards to S.Typhi?
Histiocytes
Lymphocytes
Plasma cells
*polymorphs not prominent
When can one expect complications of enteric fever?
Usually two weeks after onset.
What are some complications of enteric fever?
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
Incubation period of enteric fever?
1-3 weeks.
Clinical presentation of enteric fever?
Insidious onset of:
- headache
- step-like temperature
- bradycardia
- malaise, anorexia
What may happen if enteric fever is allowed to become severe?
Apathy
Delirium
Stupor
What skin sign could one see with regards to enteric fever?
Rose-colored rash on the abdomen.
What is the most striking clinical feature of enteric fever?
Septicemia
Is enteric fever associated with gastroenteritis?
Varying degrees - classical pea-soup like stool
*patient may be constipated or have normal stools
How does one diagnose S.Typhi?
Isolation of causative organism > culture
Serology
What specimens can be used to try to culture S.Typhi?
Blood - initial disease levels are high
Stool - only in third week of illness
Urine - excretion with S.Typhi often intermittent
Bone marrow aspirate
What serological test can be used to try to identify S.Typhi? Is it reliable?
Widal agglutination test.
Unreliable and often difficult to interpret.
What is the Widal agglutination test? When may it be difficult to interpret the test result?
Test for antibodies to both the O and H antigens.
*difficult to interpret when a person has relieved a Typhoid vaccine
What factors should one consider whenever interpreting a serological test?
- Antibodies in the population at risk
- Previous innoculations (vaccines)
- Antibiotic therapy (may modify the response)
- At what stage of the disease the blood was taken for serology
Once someone has had enteric fever can they get it again?
Only rarely.
Who gets the vaccine for S.Typhi?
Travellers to endemic areas.
What antibiotics are used to treat enteric fever?
Quinolones.
Amoxicillin
Cotrimoxazole
With regards to doses of organisms required to cause disease, where does S.Typhi stand?
Low dose is sufficient.
What would Typhoid Mary be referred to today?
A chronic excretor of S.Typhi (gallbladder).
Cholecystectomy required today.
Pathogenesis of gastroenteritis caused by non-typhoidal salmonella?
Organisms multiply in S.I. > invade gut wall (pinocytosis) > migrate to lamina propria > inflammatory response
Clinical features of gastroenteritis due to non-typhoidal salmonella?
Asymptomatic
Gastroenteritis (watery to dysenteric stools)
Fever + abdominal cramps + nausea/emesis + myalgia
What does the Diarrhoea in gastroenteritis due to non-typhoidal salmonella look like?
Loose or watery
Blood is rare
Pus may be present
How to diagnose gastroenteritis due to non-typhoidal salmonella?
Organism cultured form the stool fairly readily.
Treatment of non-typhoidal salmonella induced gastroenteritis?
Supportive care - illness is self-limiting
Antibiotics in the immunocompromised
What antibiotics can be used to treat gastroenteritis due to non-typhoidal salmonella?
Quinolones
Or amoxicillin or cotrimoxazole
Who are at risk of invasive disease with regards to salmonella?
Immunocompromised. HIV PATIENTS
What can happen in invasive disease regarding salmonella?
Pneumonia.
Meningitis.
Damage at atherosclerotic lesions.
How to treat invasive salmonella in HIV patients?
Third generation cephalosporins followed by oral Quinolones.
