Infection Session 4- Healthcare Infections And Adaptive Immunity Flashcards
What are healthcare infections?
Infections arising as a consequence of providing healthcare, so for hospital patients the infection was neither present nor incubating at time of admission
Why are healthcare infections important?
Frequent
Impact on health
Impact on healthcare organisations
Preventable
Give some examples of healthcare infection pathogens
Hep C HIV Norovirus MRSA E coli Malaria Candida Albicans C diff
What can make a patient more at risk of a healthcare infection?
Extremes of age Obesity/malnourished Diabetes Cancer Immunosuppression Smoker Surgical patient Emergency admission
What general patient interventions can prevent healthcare infections?
Optimise patient’s condition- smoking, nutrition, diabetes
Antimicrobial prophylaxis
Skin preparation
Hand hygiene
What specific patent interventions can prevent healthcare infections?
MRSA screens
Mupirocin nasal ointment
Disinfectant body wash
What can be done to prevent patient to patient transmission of healthcare infections?
Vaccination Good clinical techniques Hand hygiene PPE Antimicrobial prescribing
What environmental interventions can be done to prevent healthcare infections?
Wash hand basins
Cleaning- disinfectants, steam cleaning and H2O2 vapour
Medical devices- single use equipment, sterilisation and decontamination
Appropriate kitchen and ward food facilities
Good food hygiene practice
Positive/negative pressure rooms
What are the five I’s when it comes to healthcare infections?
Identify Isolate Investigate Inform Initiate treatment
Describe the main features of antigen presenting cells
Strategic location (B+T cell interaction)
Pathogen capture
Diversity in pathogen sensors (PRRs)
Where can antigen presenting cells be found?
Skin
Mucous membranes
Lymphoid organs
Blood circulation
What methods of pathogen capture can antigen presenting cells do?
Phagocytosis
Macropinocytosis
Name the different types of antigen presenting cells
Dendritic cells
Langerhans’ cells
Macrophages
B cells
Where are dendritic cells found and what do they present to?
Lymph nodes, mucous membranes, blood
Present to T+B cells
Where are Langerhans’ cells found and what do they present to?
Skin
Present to T cells
Where are macrophages found and what do they present to?
Various tissues
Present to T cells
Where are B cells found and what do they present to?
Lymphoid tissue
Present to T cells
What substances are involved in humoral immunity?
Antibodies
Complement
What substances are involved in cell-dependant immunity?
Cytotoxic T cells (CD8+ T cells)
Macrophages
Antibodies
Where are class I + II major histocompatability complexes found?
Class I- found on all uncleared cells
Class II- found on dendritic cells, macrophages and B cells
What are the key features of MHC class I and II?
Co-dominant expression- both parental genes are expressed to increase number of different MHC molecules
Polymorphic genes- different alleles among different individuals to increase presentation of different antigens/microbes
What is the main difference between class I + class II MHC?
Class I present peptides from intracellular microbes
Class II present peptides form extracellular microbes
What is the significance of the structure of the peptide binding cleft?
Variable region with highly polymorphic residues so have a broad specificity- many peptides presented by the same MHC molecule.
Which T cells are activated by MHC class I?
CD8+
Which T cells are activated by MHC class II?
CD4+
Describe the antigen presenting features
Both self and non self peptides are presented
All peptides from the same microbe are presented by different MHC molecules
Susceptibility to infections depends on the types on MHC molecules
What clinical problems are associated with MHC molecules?
Major causes for organ transplant rejection- HLA molecules mismatch between donor and recipient
HLA association and autoimmune disease
Which microbes are extracellular or intracellular?
Extracellular- bacteria, parasites, worms and fungi
Intracellular- viruses, bacteria, protozoa
What do CD4+ and CD8+ differentiate into?
CD8+ becomes cytotoxic T cells
CD4+ become TH1,2 and 17 cells
Which T helper cells are activated by extracellular microbes?
TH2 and TH17
Which T helper cells are present in response to intracellular microbes?
TH1
What do TH1 do?
Activate B cells and macrophages
Assist antigen presenting cells to activate CD8+
What do TH2 do?
Activate eosinophils, B cells and mast cells
What do TH17 do?
Activate neutrophils
What are the different antibodies and what are their functions?
IgG- Fc dependant phagocytosis, complement activation, neonatal immunity, toxin/virus neutralisation
IgE- immunity against helminths, mast cell degranulation
IgA- mucosal immunity
IgM- complement activation
Describe the characteristics of C. Diff
Watery diarrhoea Severe abdominal pain Loss of appetite Fever Blood in stools Weight loss
How is C. Diff caused?
C. Diff is a minor component in normal flora of large intestine so when other flora are cleared the c diff is no longer competing for resources so can grow and cause infection.
Which antibiotics can cause C. Diff?
Amoxicillin
Ampicillin
Cephalosporins
Clindamycin
Describe the characteristics of MRSA
Causes bacteraemia and infective endocarditis
Describe the characteristics of norovirus
Acute gastroenteritis Nausea Vomiting Diarrhoea Abdominal cramps Abdominal pain Mucus in stool Headache and fever
