Hospital Acquired Infections And Adaptive Immune System Flashcards
What is a hospital acquired infection?
Infections arising as a consequence of providing health care
The infection was not present or incubating on admission
Onset at least 48 hours after admission
What are the commonest types of hospital acquired infections?
UTIs
GI problems
Surgical wound infections
Name some viruses that were/are notorious for hospital spread and state which have available vaccines
HepB (vaccine)
Norovirus
Influenza (vaccine)
Chicken pox (vaccine)
Give examples of common bacteria causing HAQ infection
Staph aureus (inc MRSA) Clostridium difficile E-coli Klebsiella pneumoniae Pseudomonas aureginosa
Name some features of clostridium difficile
Gram positive
Anaerobic
Produces spores - can survive for months in a clinical environment
Give some risk factors for HAQ infection
Extremes of age Obesity/malnourished Diabetes Cancer Immunosuppressed Smoker Surgical patient Emergency admission
What are the 4 Ps of infection prevention and control?
Patient
Pathogen
Practice
Place
Name some interventions we do for the patient to reduce change of HAQ infection
Optimise pt conditions (good nutrition, controlled diabetes) Antimicrobial prophylaxis Skin preparation Hand hygiene MRSA screens Disinfectant body wash
Give 2 methods of ward deep cleaning and explain why they are impractical
Steam cleaning
Hydrogen peroxide vapour
Difficult because need whole wards clear of people for days at a time
Describe the I-Five pathway for dealing with HAQ infections
Identify (A-F) Isolate Investigate Inform (infection control/other HCPs) Initiate (appropriate treatment)
What does the A-F stand for when trying to identify HAQ infections?
A - abroad (travel Hx) B - blood borne infections C - colonised D - diarrhoea/vomiting E - expectorating (coughing up) F - funny looking rash (Things to look for)
Describe the pathway for suspected C. Diff infection
Send stool sample (look for CDT)
Take blood samples for WCC, urea, creatinine and albumin
Isolate patient and inform infection control
Stop: antibiotics, PPIs, laxatives, immunosuppressants, opioids
Ensure regular assessment
What features would make a case of C. Diff infection severe?
Sepsis Temp >38.5 Evidence of severe colitis Albumin <25 WBC > 15 Acute rising serum creatinine
What is the treatment for severe C. Diff infections?
Oral vancomycin for 10 days
Needs daily assessment and review
What is the treatment for non-severe C. Diff infection?
Metronidazole (oral) for 10 days
Regular assessment
When can patients who’ve had a C. Diff infection mix with other patients again?
No diarrhoea for at least 48 hours
How are T cells activated?
By antigen presenting cells
What is the difference between intracellular and extracellular microbes?
Replicate inside/outside the host cells
What are the 3 stages that an APC goes through after contact with a pathogen?
Capture
Processing
Presentation
Give some features of APCs
Located in strategic places (where B and T cells are)
Pathogen capture - can use phagocytosis or macropinocytosis
Diversity in pathogen sensors (PRRs)
Where are dendritic cells found?
Lymph nodes
Mucous membranes
Blood
Where are Langerhans’ cells present?
Skin
Which type of APC presents to both T and B cells?
Dendritic cell
Extracellular microbes trigger which immunity first?
Humoral immunity
Antibodies and complement
Intracellular microbes trigger which immunity?
Cell-dependent immunity
CD8 cells, macrophages and antibodies
Where do we find MHC class I molecules?
All nucleated cells
Where do we find MHC class II molecules?
Antigen presenting cells and B cells
Give the key features of MHC molecules
Codominant expression - both parental genes are expressed to increase the number of different MHC molecules
Polymorphic genes - many different alleles of each gene therefore different individuals have different presentations of antigens
Can accommodate many peptides - broad specificity
MHC class I presents peptides from …
Intracellular microbes
MHC class II presents peptides form …
Extracellular microbes
MHC class I mainly activates which type of cell?
CD8+ T cells
MHC class II mainly activates which type of cell?
CD4+ T cells (helper)
What is the function of the MHC molecules?
Bind peptide fragments derived from pathogens
Display these fragments on the cell surface for recognition by appropriate T cells
How can MHC molecules cause organ rejection?
MHC/HLA mismatch
Recognises as foreign so attacks it
How do T lymphocytes recognise antigens?
Have antigen receptors called T cell receptors (TCRs)
Recognise the MHC-peptide complex
How are T cells activated?
Not easily
Must have TCR bound to MHC-peptide complex and co-stimulatory signals before the T cells will proliferate and differentiate
Extracellular microbes stimulate the production of which TH molecules?
TH2 and TH17
Intracellular microbes stimulate the production of which TH molecule?
TH1
What is the role of TH1?
Helps with T cell differentiation
What is the role of TH2?
Activation of eosinophils, B cells and mast cells
What is the role of TH17?
Chemotaxis to get neutrophils to site of infection for phagocytosis
Which type of immunoglobulin is most abundant in the primary response to an infection?
IgM
Which type of immunoglobulin is more abundant in the secondary response to an infection?
IgG
How can we tell whether something is a primary or secondary response to infection?
Measure the IgG and IgM levels
What is the role of IgG?
Opsonin
Activates complement
Neonatal immunity as transfers from maternal blood
Toxin/virus neutralisation
What is the role of IgA?
Mucosal immunity - prevents the microbes from attaching
What is the role of IgE?
Immunity against helminths (worms)
Mast cell degranulation in allergies
What is the role of IgM?
Complement activation
