Infection session 1 Flashcards
(16 cards)
What is an infection? What is disease caused by?
- Invasion of a host’s tissues by micro-organisms
- microbial multiplication, toxin, host response. –> not just the treatment of the organism but also the management of the host’s body response as well.
How do people get infections?
There is a source and it can get to a person several ways
- Through an intermediary (vector/other person)
- It is on a person but it is then transferred to another region of the body where it causes damage (E coli in peritoneum, Strep pneumonae in lungs {instead of throat})
- Environment: water, food, air surfaces
- Different methods of transmission: contact, aerosol, sexual, etc.
- Zoonosis
- Range and duration of bacteria are important wrt response
What is the microbiota?
- Commensal organisms: not harmful (even beneficial) when are in right place, can be very harmful in wrong place
- Micro-organisms carried on skin and mucosal surfaces
- Response depends on organism host and your immune system
What are the modes of transmission of infection and disease?
- Contact: direct, indirect, vector
- Inhalation: droplets, aerosols
- Ingestion: fecal-oral transmission (norovirus)
- Vertical transmission: mother to child, before birth (congenital syphillis, HIV)
What is the sequence of events for causing disease? (before host response)
-Exposure –> Adherence –> invasion –> multiplication –> Dissemination
What are virulence factors? How do these tie with the sequence of events for causing disease before host response)
- Step after the dissemination of the disease
- Virulence factors are molecules produced by pathogenic bacteria, viruses, fungi, and protozoa that add to their effectiveness and enable them to achieve the following: colonization of a niche in the host (this includes attachment to cells)
- Exotoxins: cytolytic, AB toxins, superantigens, enzymes
- Endotoxins
How does host cellular damage occur? What kinds are there? What is it the result of?
It is the result of the virulence factor and the sequence of events leading to dissemination of disease in the body
- Can be direct (ie from the toxins)
- Can be a consequence of host immune response.
Give an example of a pathogen that uses the exposure –> dissemination pathway
- Viruses: have to replicate within the cell (incomplete particles otherwise) and subvert the cell in order to make more copies.
- They need to bind to a specific cell structure so they stimulate the host cell to engulf/absorb the virus in the cell.
Give an example of a pathogen that produces exotoxins
Bacteria release exotoxins as part of the pathogenic process.
What factors (3) determine whether a pathogen is successful in creating infection? What are some of the factors (2) determines how a patient gets this infection?
- Virulence factors, inoculum size, antimicrobial resistance
- Site of infection, co-morbidities
What are the three main steps when determining whether somebody has an infection?
- History
- Examination
- Investigations
Describe what is included in history (when trying to determine if somebody has an infection)
- Symptoms: focal, systemic, severity, duration
- Potential exposures
Describe what is included in examinations (when trying to determine if somebody has an infection)
-Organ dysfunction, any visible signs
Describe what is included in investigations (when trying to determine if somebody has an infection)
-Specific, supportive
Give examples of some supportive investigations and their function
- FBC: neutrophils, lymphocytes, WBC, platelets
- CRP: acute inflammation marker
- Blood chemistry: liver and kidney function tests (organ shutdown)
- Imaging: x ray, MRI
- histopathology
How can we try and identify pathogens in pts we suspect have infections?
- Bacteriology: swabs, fluids tissues
- Antigen/antibody Detection
- Nucleic acid detection
- Microscopy (stains), Cultures and ABX susceptibility
