Immun / Path Flashcards
What causes a positive coagulase test?
The conversion on fibrinogen to insoluble fibrin
What colour go gram positive organisms stain and why?
Purple
Peptidoglycan layer
What organism does the optochin test identify?
Streptococcus pneumoniae
What is the antibiotic used for treatment of staphylococcal pneumonia?
Flucloxacillin and Rafampicin
What kind of bacteria is E.coli?
Gram negative bacilli
What colour would E.coli colonies show as on MacConkey’s agar?
What does this colour tell you about E.coli bacteria?
Pink
Lactose fermenting bacteria
What agar plate is used to determine if the bacteria has simple or fastidious growth requirements?
Chocolate agar
How would you treat traveller’s diarrhoea?
Oral rehydration
Antimotility agents e.g. loperamide
Clostridium difficile is an infective cause of diarrhoea, name 2 antibiotics that can cause C.diff infection
co-amoxiclav
cephalosporins e.g. cephalexin
ciprofloxacin
clindamycin
Following a venepuncture, bleeding is stopped by…
Platelet and fibrin plug formation over the area of damaged endothelial wall
What does TLR2 detect?
Lipoeichoic acid on gram positive bacteria
What does TLR1 detect?
Malaria
What does TLR4 detect?
Lipopolysaccharide on gram negative bacteria
What does TLR5 detect?
Flagellin
What does 1,3 beta-D-glucan assay detect?
Aspergillus fumigatus, Candida albicans, and pneumocystis jirovecii
Describe how cholera causes diarrhoea
Toxin degranualtion of ion transport in endothelial cells
1st line antibiotic for chest infection?
Amoxicillin / Clarithromycin / Doxycycline
What is myocolic acid and what does it do?
In the cell wall of pathogens, allows them to resist phagocytic killing
How does flucloxacillin work?
Disrupts peptidoglycan
What is the mechanism of amoxicillin antibiotic resistance?
Βeta lactamase hydrolysis
What sputum smear confirms TB diagnosis?
Acid fast bacilli
What its the most common causative organism of CAP?
Describe the microscopy
Streptococcus pneumoniae
Gram positive cocci, α haemolytic, optochin sensitive
What is the second most common cause of CAP?
Chlamydophila pneumoniae
Young adult presents with CAP, haemolytic anaemia, raynauds.
Most likely causative organism?
Mycoplasma pneumoniae
What kind of pneumonia does Haemophilus influenza cause? Describe the microbiology.
Why is it now rare?
CAP
Gram negative coccobacilli
Rare due to Hib vaccine
When might Staphylococcus aureus cause CAP?
As a complication of recent influenza infection
What 3 gram negative causative organisms are common in HAP?
Pseudomonas aeruginosa, E.coli, Klebsiella pneumoniae
What is CLED agar mostly used for?
Urinary bacterial infections i.e. differentiating E.coli which is yellow on CLED agar
What is MacConkey used for?
Testing lactose fermenting
Pink = Lactose fermenting e.g. E.coli
Yellow/colourless = non-lactose fermenting e.g. salmonella, shigella
How do you differentiate between Salmonella and Shigella on microscopy?
XLD agar
Red with black centres = Salmonella
Red only = Shigella
What is the agar used for fungus?
Sabourard agar
How is S.aureus differentiated from other staphs on microscopy?
- Coagulase test: S.aureus is coagulase positive, the others are negative
- Blood agar culture: S.aureus is gold, others are colourless
What are the sterile sites of the body?
- blood
- CSF
- pleural fluid
- peritoneum
- joints
- urinary tract
- lower respiratory tract
Gram negative, lactose fermenting. What could it be?
- E.coli
- Klebsiella
What are the two main approaches for diagnosing viral infection?
Viral detection via PCR, e- microscopy
Serology testing via ELISA, immunoflourescence etc
How does serology work?
Detects immunoglobulins against the virus
Throat infection / glandular fever.
How do you determine the causative organism?
- Black charcoal swab is used to exclude S.pyogenes
- EBV is diagnosed via blood tests: IgM +ve = acute infection, IgG +ve = chronic/prior infection
What is the characteristic feature of cytomegalovirus?
Owl eye inclusion bodies
What are the 4 main AIDS defining illnesses?
- Cytomegalovirus
- PCP (pneumocystis pneumonia)
- Oral candida
- Lymphoma
How is CMV treated in AIDS pts?
IV ganciclovir (antiviral)
What are the 3 HIV markers tested for in blood?
HIV immunoglobulin
HIV RNA
P24 antigen
Is TLR3 intracellular or extra cellular?
Intracellular
Where is TLR5 expressed ?
Type II dendritic cells in the terminal ileum
Which TLRs are intracellular?
3,7,8,9
What makes mycoplasma resistant to β-lactam antibiotics?
They lack a cell wall
How do β-lactam antibiotics work?
Act by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls
What is the mechanism of dubutamine?
β1-agonist
Treatment of cardiogenic shock
Bacterial meningitis diagnosis. Which cell type would be expected to predominate in the CSF?
Neutrophils
What type of hypersensitivity is SLE?
Type III
Involving damage to tissues to tissues mediated by the deposition of antibody-antibody complexes, resulting in activation of complement.
Which peripheral leukocyte can become pulmonary macrophages?
Monocytes
which antibody response is the initial response to virus?
IgM
What type of immunity is antibody transfer from mother to in fact during breastfeeding?
Naturally acquired, passive
What is secreted by virally infected cells as part of a signalling mechanism?
Interferon-α
Which cell in the normal lymph node is a specialised, highly efficient antigen-presenting cell (APC) found mostly in areas of T-cell concentration?
Dendritic cells
Which is the most common causative organism of traveller’s diarrhoea?
Enterotoxigenic Escherichia coli (ETEC)
Which pathogen is most commonly isolated in cases of chronic diarrhoea associated with HIV?
Campylobacter
What cells express MHC-1?
All nucleated cells
Explain the difference between pharmacodynamics and pharmacokinetics
pharmacodynamics = what the drug does to the body
pharmacokinetics = what the body does to the drug
What are the properties of mycobacterium ?
- slow growing
- predominantly immobile
- rod shaped
- intracellular
- gram positive
Meningitis prophylaxis?
Ciprofloxacin
Malaria prophylaxis?
Doxycycline
What types of hypersensitivity reaction is anaphylaxis and what immunoglobulin is involved?
Type I
IgE
Explain the mechanism of re-exposure in anaphylaxis
- allergen binds to IgE
- receptor cross linking causes a cascade
- mast cell degranulation of histamine
What microorganism causes complicated malaria?
Plasmodium falciparum
Stages of malaria
- Expo-erythrocytic stage
- Endo-erythrocytic stage
- Dormant stage
Give 2 examples of organisms that can cause UTIs and their gram stain
- Escherichia coli- gram –ve rod (lactose- fermenting)
- Klebsiella pneumoniae- gram –ve cocci
Give an example of an upper UTI and a lower UTI
Upper: pyelonephritis, ureteritis
Lower: urethritis, cystitis
Give 4 examples of antibiotics that can be used to treat UTI
- nitrofurantoin
- trimethoprim
- amoxicillin
- cefalexin
What is the name of the criteria used in infective endocarditis diagnosis?
Modified Dukes criteria
Name the two major Dukes criteria
- blood culture positive >12hrs apart
- evidence of endothelial involvement on ECHO
List some minor Dukes criteria
- fever >38 degrees C
- vascular phenomena e.g. Janeway lesions
- evidence from immunology e.g. Roth spots, Oslers nodes, glomerulonephritis
- predisposing factor e.g. IVDU, prosthetic valve
Microscopy of streptococcus pneumoniae?
Gram positive cocci in chains
Αlpha haemolytic
What is the mechanism of action of erythromycin ?
Macroglide - inhibits protein synthesis by acting on the 50s subunit of ribosomes
Which immunoglobulin provides immunity to parasites ?
IgE
