Infection Session 4 Flashcards
What broad types of infection account for the majority of healthcare acquired infections?
UTI
URT
GI infections
Give some examples of healthcare infection viruses.
Hep B&C HIV Norovirus Influenza Chickenpox
Give some examples of healthcare infection bacteria.
Staph aureus inc. MRSA C.diff E.coli Klebsiella pneumoniae Mycobacterium tuberculosis
Give some examples of healthcare infection fungi.
Candida albicans
Aspergillus sp.
What are the 4 P’s of infection prevention and control?
Patient
Pathogen
Practice
Place
What general patient interventions can be used in infection prevention and control?
Optimise pt condition
Antimicrobial prophylaxis
Skin preparation
Hand hygiene
What specific patient interventions can be used in infection prevention and control?
MRSA screens
Mupirocin nasal ointment
Disinfectant body wash
How can pt–>pt spread of healthcare acquired infection be prevented?
Isolate infected pts
Protect susceptible pts
Use +ve and -ve pressures
What practice factors can be used in infection prevention and control?
Healthy healthcare workers
Effective policies and implementation e.g. Hand washing, surgical technique, Abx prescribing
Effective organisational structure and engagement
Leadership at all levels
What pathogen factors should be considered in infection prevention and control?
Virulence factors
Ecological interactions w/other bacteria, Abx and disinfectants
What interventions can be implemented when considering place in infection prevention and control?
Built environment: single rooms, toilets, hand basins
Variable features: furnishings
Cleaning w/disinfectants, steam and H2O2 vapour
Single-use medical devices where possible
Hygienic food provision
Will an immune response be mounted if you have any number of T cells and tumour cells/pathogens?
No, need an APC present
Where are APCs located?
Strategically where B and T cells are present in lymphoid tissue (ALT), lymphoid organs and blood
What can carry out phagocytosis for whole microbes and macropinocytosis for soluble particles such as toxins?
APCs
Where are dendritic cells located?
Lymph nodes
Mucosa
Blood
What is included in the term ‘healthcare infections’?
Infection not incubating or present on admission to hospital (onset at least 48hrs after admission)
Infections in hospital visitors
Infections in healthcare workers
What allows APCs to detect both extracellular and intracellular pathogens?
Diversity in pathogen recognition receptors
Where are Langerhans cells found?
Skin
Where are B cells found?
Lymphoid tissues
What do B cells signal?
Switch from IgM to IgG production
How are MHC genes expressed?
Co-dominant, 3 paternal and 3 maternal
Do MHC genes show variance across the population?
Yes, they are polymorphic
Describe the peptide binding cleft of an MHC.
Variable region with polymorphic residues
What characteristic of MHCs means many peptides are presented by the same MHC molecule?
Broad specificity
What does having co-dominant expression, polymorphic genes, variable peptide binding cleft and broad specificity confer in MHCs?
Increase in diversity to more likely to present protein
Where are class I MHCs found?
All nucleated cells
What peptides do class I MHCs present?
Intracellular peptides
What is the responsive T cell to class I MHCs?
CD8+
Where are class II MHCs found?
Dendritic cells
Macrophages
B cells
What peptides do class II MHCs present?
Extracellular microbe
What are the responsive T cells to class II MHCs?
CD4+
What is unique about the MHCs found on dendritic cells?
Nucleated cells so have both class I and class II
Are self and non-self peptides presented by APCs?
Yes
Why are all peptides from the same microbe presented using different MHC molecules?
Increase chances of T cell activation
What type of microbial protein is the endogenous pathway used for?
Intracellular
Which MHC class does the endogenous pathway of antigen presentation use?
Class I
What type of microbial protein does the exogenous antigen processing pathway present?
Extracellular
Which MHC class does the exogenous antigen processing pathway use?
Class II
What is the importance of MHC molecules in Elite Controllers and Long Term Non-Progressors?
Allow them to keep viral load low
How is an effective T cell response brought about in an HIV infected individual?
MHC molecules possessed by individual present key viral peptides that the virus cannot mutate due to their essential nature
Why do Rapid Progressors who are infected with HIV not mount a T cell response?
Their MHC molecules present less critical peptides which the virus can mutate so they are not recognised
Which viral proteins are essential for viral entry in HIV infection?
Docking and transmembrane glycoproteins
What can cause organ transplant rejection?
HLA molecule mismatch b/w donor and recipient
Graft vs host reaction
Which two autoimmune diseases are associated with specific HLA molecules?
Ankylosing spondylitis
Insulin-dependent DM
What causes Guillan Barré syndrome?
Campylobacter jejuni has a microbial protein similar to myelin associated gangliosides so the microbial protein is assumed to be self
In what conditions is cross-reactivity between microbial and host antigens seen?
Rheumatic heart disease
Guillan-Barré syndrome
T1DM
What extracellular microbes may have their proteins presented by the exogenous pathway?
Bacteria
Parasites
Worms
Fungi
What microbes may have their proteins presented by the endogenous pathway?
Viruses
Bacteria
Protozoa
Which type of immunity do CD4+ cells stimulate?
Humoral
What type of immunity do CD8+ T cells stimulate?
Cell-dependent
How do the components of humoral and cell dependent immunity compare?
Both have antibodies and complement
Cell dependent also has macrophages and cytotoxic T cells
What are the two main types of T cells?
T-helper and cytotoxic T cells
Why can T cells produce a range of cytokines?
They have a range of cellular responses
What is required for full activation of a naïve CD4+ T cells?
Cross-stimulation
Which two T cells are produced from an exposed naïve CD4+ T cell to deal with extracellular microbes?
TH2
TH17
Which T cell is produced following exposure of a naïve CD4+ T cell in order to clear intracellular microbes?
TH1
Why is TH1 produced for intracellular microbes when a naïve CD4+ T cell is activated?
Best type for differentiation into cytotoxic T cells
What are the T cell responses against intracellular microbes?
Cytotoxic T lymphocytes –> perforin granzymes
B cells –> isotype switching of antibodies to IgG
Cytokine release –> macrophages –> kill opsonised microbes
Which cell type do long-term HIV survivors maintain high levels of to prevent progression to AIDS?
Cytotoxic T lymphocytes
What are the T cell responses against extracellular microbes?
TH2 –> eosinophils for parasites, B cells for antibody and mast cells for local inflammation
TH17 –> neutrophils for phagocytosis
How does the primary and secondary response to antigen exposure by antibodies compare?
Secondary is faster, stronger, longer duration and higher affinity due to isotype switch from IgM –> IgG
Which antibody response has greater levels of total antibody and IgG but lower levels of IgM?
Secondary
How does the activation capacity of IgG and IgM differ?
IgG v. good in activating opsonisation
IgM v. good at activating complement
What are the immune functions of IgG?
Fc-dependent phagocytosis
Complement activation
Neonatal immunity
Toxin/virus neutralisation
What is the immune function of IgA?
Prevent microbes binding to mucosa
What are the immune functions of IgE?
Immunity against helminths
Mast cell degranulation
What is the immune function of IgM?
Complement activation
Why is IgM better than IgG at complement activation?
It is pantomeric
How are immune deficiencies treated?
Take pool of antibodies from ~1000 pts to build a profile for a pt who cannot make antibodies (immunoglobulin therapy)
What can antibody-based diagnostic tests be used for?
Infectious diseases
Autoimmune diseases
Blood type
HLA type
When might an antibody transfer be used?
To confer passive immunisation for immediate protection if a pregnant lady is found to be not immune to varicella zoster
