L1 - An Introduction to infection Flashcards
Define infection
Invasion of a hosts tissues by micro-organisms
What is the term ‘microbiota’ used to describe?
The micro-organisms which exist on our skin and mucosal surface which are normally harmless
How can micro-organisms from the microbiota become harmful?
When they are transferred to an abnormal site e.g. from the skin to the GI tract during surgery
Name two mechanisms by which an infection can be spread (modes of transmission) from an intermediary
1) physical contact
2) airborne
3) vector e.g. mosquito
Infection can be gotten from the environment as well rather than an intermediary, give two environmental transmissions of infection
1) ingestion if contaminated food/water
2) inhalation of contaminated air by environmental organisms rather than intermediaries
3) contact with contaminated surfaces including medical devices
Horizontal transmission can be subcategorised into contact, inhalation and ingestion. What’s the difference between direct and indirect contact transmission?
Direct is the result of physical contact between two people
Indirect transmission is when the environment acts as a temporary reservoir for the microorganism
If a disease is spread by airborne transmission it can be spread as a droplet or an aerosol, describe the difference
Droplets drop - don’t go much further than a metre or two,
Aerosols remain suspended in the air and can stay viable there for some time, all that’s needed is it to be breathed in later for it to cause infection
What is vertical transmission? Give an example of how
Vertical transmission is mother to child at or before birth.
At birth - on the way out through the birth canal and vagina, newborn will be coated in microbes
Before birth - if uterine membranes are compromised
Complete the following describing how micro-organisms cause disease - > 1) Exposure 2) ? 3) invasion 4) Multiplication 5) ?
2) adherence - describes the micro-organisms sticking to mucosal membranes - eyes/ears/nose
Virulence factors are released by microbes during infection. Give and explain the two types of virulence factors
Exotoxins - these potentiate the microbes viability in the host. Released by the bacteria
Endotoxins - normal constituents of the invading microbes, normally part of the LPS in gram negative bacteria which can be recognised by the hosts immune system causing an immune response. Released when bacteria die
Disease determinants can be to do with the pathogen or the patient. Give an example of a disease determinant to do with the pathogen and one to do with the patient
Pathogen
1) virulence factors
2) inoculum size - amount/number of microorganisms
3) antimocrobial resistance
Patient
1) site of infection
2) co-morbidities
There are three major things we need to do to find out if an individual has an infection - complete
1)
2) examination - e.g. observe them, organ distinctions etc
3) investigations
1) History - ask about potential exposures and symptoms.
In regard to symptoms, is it focal I.e. localised or systemic. How long have they been going on? How sever are the symptoms
Investigations, the third step of finding if an individual is infected are investigations. Name two supportive and two specific investigations which can be carried out
Supportive
Full blood count, CRP levels, liver and kidney function tests e.g. u and e test - urea and electrolytes, imaging e.g. MRI/x-ray, histopathology
Specific Swabs from broken skin in skin disease Tissue samples during surgery Bacterial cultures Microscopy Antigen detection Nucleic acid detection
Name a way to detect a specific virus in a patient
Virus Antigen detection
Detection of antibodies to the virus
Detection of viral nucleic acids
Name three questions you can ask a patient about history when trying to discern an infection
Symptoms - duration Severity Focal or systemic Potential exposures
