Session 1 Flashcards
What two things are essential for an infection to occur?
- Microbe
- Host
What is an infection?
An invasion of a host’s tissues by microorganisms and disease caused by; microbial multiplication, toxins and a host response.
Describe how a patient can in effect ‘give themselves’ an infection?
Due to microbiota
- These are microorganisms carried on skin and mucosal surfaces
- Normally harmless or even beneficial
- Transfer to other sites can be harmful
- e.g. urinary tract infection
How do people get infections?
- Physical contact may be required
- Airborne spread may be sufficient
- Vector may be necessary
- Ingesting contaminated food/water
- Inhalation of contaminated air
- Contact with contaminated surfaces
What are the different modes of transmission?
- Horizontal transmission
- Vertical transmission
Horizontal transmission
- Contact (direct, indirect and vectors)
- Inhalation (droplets and aerosols)
- Ingestion (faecal oral route)
Vertical transmission
- Mother to child, before or after birth
How do microorganisms cause disease?
- Exposure
- Adherence
- Invasion
- Multiplication
- Dissemination
What are the two main categories of disease determinants?
- Pathogen
- Patient
Pathogen disease determinants
- Virulence factors
- Inoculum size
- Antimicrobial resistance
Patient disease determinants
- Site of infection
- Co-morbitites
How do we know patients have an infection?
- Take a history (symptoms and potential exposures)
- Examination
- Investigations
What are the two types of investigations you could do?
- Supportive
- Specific
Supportive investigations
These are trying to find out how unwell the patient is
- Full blood count
- CRP
- Blood chemistry - test liver and kidney function
- Imaging - X ray, ultrasound, MRI
- Histopathology
Specific investigations
Help identify the cause of the infection
- Include bacteriology and virology
Bacteriology
- Specimen types include swabs, fluids, tissues
- ‘M,C&S’ - microscopy, culture and sensitivities
- Antigen detection
- Nucleic acid detection
What is virology?
Methods of diagnosing and identifying viruses
How can be identify the virus that causes the infection?
- Antigen detection of the virus
- Antibody detection (patient’s response)
- Detecting the viral nucleic acid (DNA and RNA)
What are the most relevant things to look out for in a FBC when looking for signs of infection?
Mainly WBC and neutrophils but lymphocyte count is also relevant
In a FBC, what is white blood cell differential?
This looks at the type of white blood cells present. 5 different typed - neutrophils, lymphocytes, monocytes, eosinophils and basophils.
What would happen to the WBC count in someone with infection?
Increased
What would happen to the neutrophil count in someone with infection?
Increased in some bacterial infections
NB. neutrophils are a dynamic population that varies somewhat from day to day
