Infectious Disease
Infectious Disease
We live in a world of bacteria and viruses.
- So why is it sometimes we get sick?
- We know three things are necessary for an infectious disease to develop.
---A susceptible host.
---The agent of the disease.
---Proper environmental factors.- So, if the bugs are on our skin, in our GI tracts and up our noses, what constitutes an infection?
- An infection results when a microbial agent causes disease or injury in the course of its growth, cellular metabolism or reproduction .
The three elements needed for an infection.
- Here are a few host factors. ---Immune susceptibility.
---Nutritional status.
---Breaks in skin or mucosa.
---Being in the wrong place at the wrong time.
- Here are a few things the bugs bring to the scene.
---Size
---Adhesive proteins
---Toxins
---Antibiotic resistance- Environmental factors.
---Reservoir and/or vector, if needed.
---People in close proximity.
---The proverbial 'dirty toilet seat.'
---Inappropriate use of antibiotics.
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Case Report:
Jennifer is a three year-old little girl who presents with:
- Two-day history of low grade fever and vomiting.
- Diarrhea started this morning.
- Upper respiratory symptoms
---cough
---nasal discharge
---pharyngitis
- Three other children at the new daycare have had similar symptoms.
- Her physical exam revealed:---A few small cervical lymph nodes.
---Mildly reddened pharyngeal mucosa.
---Mild to moderate abdominal tenderness to palpation
---Temperature of 100.2- Her doctor ordered:
---A CBC
---Throat culture
---Stool for culture and Rotavirus by ELISA
So what do you think Doc?
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Infectious Disease
Answer:
[HIDE]Jennifer has a viral gastroenteritis
• Viral gastroenteritis is a major cause of illness in infants and young children.
o Diarrhea can result in severe dehydration
o Metabolic acidosis
o Hemoconcentration and even risk of thrombosis (stroke, believe it or not).
• Rotavirus is probably the most common agent. Others include:
o Norwalk viruses
o Coronaviruses
o Adenoviruses
• Viral diarrhea results from
o Death of mature epithelial cells, which causes
Decreased absorption of sodium and water
Reduced ability to absorb carbohydrates
• Bacterial diarrhea is different:
o Often toxin mediated
o Toxins actually cause active secretion of water and electrolytes.
• Mother's milk contains antibodies; don't see the disease until child is weaned.
o By the age of 4 or 5 most children have developed their own antibodies.
Diagnosis and treatment of viral gastroenteritis
• Antigen detection
• Immunoassay (ELISA) techniques.
o Viral cultures are not practical.
o Look for viral antigens in stool.
o Commercial kits available for
rotavirus
adenovirus
o Immunoassay (ELISA) techniques require a large number of viral particles.
• Immune electron microscopy improves sensitivity.
o Expensive and not readily available.
o Uses antibodies to clump viral particles
• Serological conversion (looking for antibodies) is of limited value.
o Infection is resolved by the time antibodies appear in the patient.
• Treatment and prevention:
o Strictly observe universal precautions to prevent spread.
o Fluid and electrolyte management; prevent or correct serious dehydration.
o Perhaps a vaccine in the future, but none right now.
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