Session 5 - Hospital Acquired Infections and Adaptive Immunity Flashcards Preview

Phase 1 - S2 Infection (M) > Session 5 - Hospital Acquired Infections and Adaptive Immunity > Flashcards

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What are hospital acquired infections?

An infection that has taken place and/or originated in a hospital setting.


What are the most prevalent types of hospital acquired infections?

  • Urinary Tract Infections
  • Pneumonia
  • Surgical wound infections
  • Skin and soft tissue infections
  • Primary bloodstream infections
  • Gastro-intestinal infections


Give examples of viruses that can cause a hospital acquired infection

  • Blood borne viruses (Hep B, C, HIV)
  • Norovirus
  • Influenza
  • Chickenpox


Give examples of bacteria that can cause a hospital acquired infection

  • Staph. aureus 
    • inclusive of the MRSA strain
  • Clostridium difficile
  • E. coli
  • Klebsiella pneumoniae
  • Pseudomonas aeruginosa
  • Mycobacterium tuberculosis


Give examples of fungi that can cause a hospital acquired infection

  • Candida albicans
  • Aspergillus species


Give examples of parasites that can cause a hospital acquired infection

  • Malaria


What general patient measures can we take to prevent hospital acquired infections?

  • Optimise the patient's conditions
  • Antimicrobial prophylaxis
  • Skin preparation
  • Hand hygiene


What specific patient measures can we take to prevent hospital acquired infections?

  • Conduct MRSA screens
  • Mupirocin nasal ointment
  • Disinfectant body wash
  • Halting patient to patient transmission by isolation of infected patients and protection of susceptible patients


What measures can be taken to prevent healthcare worker to patient spread of infection?

Healthcare workers:

  • Should be healthy
    • disease free
    • vaccinated
  • Should use good practice methods
    • good clinical techniques (sterile non-touch)
    • hand hygiene
    • PPE
    • anti-microbial perscribing


What environmental interventions can be taken in order to prevent hospital acquired infections?

  • Cleaning
    • disinfectants
    • steam cleaning
    • hydrogen peroxide vapour
  • Medical devices
    • single use equipment
    • sterilisation
    • decontamination
  • Good food hygiene practice


What is the adaptive immune response?

The second part of the immune response that follows the innate immune response.


When does adaptive immunity come into action?

Adaptive immunity begins if the innate immune and inflammatory response are unable to clear the infection. It is a more specific form of immunity.


How is the adaptive immune response activated?

Antigens are presented to the adaptive immune system by APC (antigen presenting cells) with digested antigens travel to the lymph nodes.


What are the different antigen presenting cells (APCs)?

  • Dendritic cells
  • Langerhans' cells
  • Macrophages
  • B cells 


What do APC cells do when they reach the lymph nodes?

They present the antigen to the naive T helper cells by the MHC molecules present on the T cell's surface.

This activates the naive T helper cells and allows them to mature into active T helper cells.


What are the different MHC molecules and in which types of cells are they found?

MHC molecules come in two different classes:

  • MHC I
    • found on all nucleated cells
  • MHC II
    • found on dendritic cells, macrophages, and B cells


What are the key features of MHC I and MHC II?

  • They have co-dominant expression
  • They are polymorphic genes (different alleles for everyone)
  • They have different main functions:
    • MHC I: present peptides from intracellular microbes
    • MHC II: present peptides from extracellular microbes


Which T cells recognise MHC I molecules?

CD8+ T cells


Which T cells recognise MHC II molecules?

CD4+ T cells


What are some clincal problems with MHC molecules?

Is a major cause for organ transplant rejection due to conflicting MHC molecules from the donor and the patient.


What do CD4 T cells do in the adaptive immune response?

Activate humoral immunity to act on extracellular microbes:

  • B cells
  • Complement system


What do CD8 T cells do in the adaptive immune response?

Activate cell-dependent immunity for intracellular microbes:

  • B cell activation
  • Completment system
  • Macrophages 
  • Cytotoxic T cells

CD4 T cells are needed to activate CD8 T cells, therefore MHC II is needed for activation.


How are B cells activated?

B cells are activated by T cells, which encourage them to start producing antibodies.


What do B cells produce to help fight infections?

B cells produce various different kinds of immunoglobulin antibodies that have different functions.


What are the different kinds of immnoglobulin antibodies and what are their functions?

  • IgA
    • mucosal immunity
  • IgE
    • immunity against helminths 
    • mast cell degranulation (allergies)
  • IgG
    • Fc-dependent phagocytosis
    • complement activation
    • neonatal immunity
    • toxin/virus neutralisation
  • IgM
    • complement activation


What are the differences in antibody concentrations between first and second exposure to the same infection?

First exposure: IgM concentration will be higher than IgG concentration to fight the infection.

Second exposure: results in a faster response, therefore IgG will be higher than IgM because it is better at fighting infections.


Why is IgG better than IgM at fighting infections?

Due to it's structure, it can enter a cell and act on intracellular pathogens.


What is the isotype switch?

This is when B cells change the kind of immunoglobulin they are secreting. 

This happens when B cells switch from IgM to IgG molecules when an infection lasts for a long time.


How can you test if a person has been exposed to a certain pathogen before using immunoglobulins?

Test for the presence of that pathogen's IgG levels.

If IgG is present in the patient, they have been previously exposed to the pathogen.