Infection and immunity Flashcards
What type of bacteria is staph aureus? What infections is it associated with?
Gram positive cocci
Grape shaped
Septic arthritis
Hospital acquired pneumoniaf
Impetigo
Cellulitis
What type of bacteria is coagulase negative staph?
What infections is it associated with?
Gram positive cocci
Eg staph saprophyticus and staph epidermis
UTI
Prosthetic devices via biofilms
What type of bacteria is strep pneumoniae?
What infections is it associated with?
Group A strep
Gram positive cocci
Chains
Community acquired pneumonia
Meningitis
ENT infection
What type of bacteria is strep pyogenes?
What infections is it associated with?
Group A strep
Gram positive cocci
Necrotising fasciitis
Strep throat
What type of bacteria is strep viridans?
What infections is it associated with?
Gram positive cocci
Endocarditis
What type of bacteria is clostridium difficile?
What infections is it associated with?
Gram positive bacilli
GI
What type of bacteria is TB?
Acid fast bacilli
Mycobacterium
What type of bacteria is neisseria meningitidis?
What infections is it associated with?
Gram negative diplococci
Meningitis
What type of bacteria is neisseria gonorrhoea?
What infections is it associated with?
Gram negative diplococci
STI
Septic arthritis
What type of bacteria is haemophilus influenzae?
What infections is it associated with?
Gram negative cocci
Community acquired pneumonia
Bronchiectasis/COPD flare
What type of bacteria is Escherichia Coli?
What infections is it associated with?
Gram negative bacilli
UTI
Traveller’s diarrhoea
Meningitis (neonates)
What type of bacteria are pseudomonas aeruginosa and burkholderia cepacia?
What infections is it associated with?
Gram negative bacilli
CF pneumonia
Which organisms are most commonly associated with bronchiolitis?
Respiratory syncytial virus
Which organisms are most commonly associated with community acquired pneumonia?
Strep pneumoniae
Haemophilus influenzae
(Staph aureus)
Which organisms are most commonly associated with hospital acquired pneumonia?
Staph aureus
Pseudomonas aeruginosa
Which organisms are most commonly associated with pneumonia in alcoholics?
Klebsiella pneumoniae
Which organisms are most commonly associated with CF flares?
Staph aureus Haemophilus influenzae Aspergillus fumigatus Pseudomonas aeruginosa Burkholderia cepacia
Which organisms are most commonly associated with COPD or bronchiectasis flares?
Haemophilus influenzae
Which organisms are most commonly associated with endocarditis?
Strep viridans
Staph aureus
Coagulase negative staph (on prosthetic valves)
Which organisms are most commonly associated with meningitis at various ages?
Neonates - E coli and group B strep
Elderly - Listeria monocytogenes
Everyone else - Strep pneumoniae, Neisseria meningitidis, Haemophilus influenzae
Which organisms are most commonly associated with septic arthritis?
Staph aureus
Strep A
Neisseria Gonorrhoea
Which organisms are most commonly associated with necrotising fasciitis?
Strep pyogenes
Which organisms are most commonly associated with dog bite?
Pasturella multocida
Clostridium tetani
Which organisms are most commonly associated with UTI?
E Coli
Strep saprophyticus
Which organisms are most commonly associated with acne?
Propioni acnes
Which organisms are most commonly associated with impetigo?
Staph aureus
Which organisms are asplenic patients most susceptible to?
Encapsulated eg neisseria meningitidis
Spleen releases complement including opsonins.
Therefore
Decrease in ability to recognise microbes (particularly because no visible pamp without opsonin) and decrease in ability to recruit phagocytes.
Which infections do you not give first line amoxicillin/co-amoxiclav?
Endocarditis - vancomycin
Meningitis - ceftriaxone
C diff - metronidazole
UTI - trimethoprim
What is the triple therapy for h pylori?
LAC - 14 days
Lansoprazole
Amoxicillin
Clarithromycin
What is the standard treatment for TB?
RIPE
Rifampicin
Isoniazid
Pyrazinamide
Ethanbutol
All 4 for 2 months
RI for 4 further months
What are the side effects of the TB drugs?
Rifampicin - hepatitis, orange secretions, CYP inducer
Isoniazid - peripheral neuropathy, give vit B6, CYP inhibitor
Pyrazinamide - hepatitis, gout
Ethanbutol - optic neuritis - acuity and colour blindness
What is the treatment for a CURB 1-2 pneumonia?
Amoxicillin or doxycycline
What is the treatment for a CURB 3+ pneumonia?
Co amoxiclav + clarithromycin
or
Doxycycline + clarithromycin
What is the treatment for septic arthritis?
Co amoxiclav or clindamycin
What is the treatment for centor 3 or 4 tonsillitis?
Penicillin V or erythromycin
What is the mechanism of action of penicillin?
Beta lactam that inhibits the transpeptidase that catalyzes the final step in cell wall biosynthesis, the cross-linking of peptidoglycan
What is the mechanism of action of vancomycin?
Glycopeptide
Inhibits cell wall synthesis
What is the mechanism of action of gentamicin?
Aminoglycoside
Inihibits protein synthesis
What is the mechanism of action of erythromicin?
Macrolide
Inhibits protein synthesis
What is the mechanism of action of ciprofloxacin?
Quinolone
Inhibits DNA synthesis
What is the mechanism of action of trimethoprim?
Folic acid antagonist
What is the difference between amoxicillin and co amoxiclav?
Clavulanic acid to inhibit beta lactamase in penicillin resistant bacteria
Which antibiotics are most associated with a risk of c diff?
Cephalosporins eg ceftriaxone
Clindamycin
Penicillins
What is a hypersensitivity reaction/
An antigen specific immune response that is inappropriate or excessive.
Describe the Gell and Coombs classification of hypersensitivity reactions
I - atopy and anaphylaxis II - transfusion reaction, Goodpastures III - SLE IV - Contact dermatitis, scabies, TB V - Grave's disease, myaesthenia gravis
Describe the pathophysiology of anaphylaxis
Phase 1
Silent 1st exposure, TH2 phenotype of CD4 T cell tells B cell to switch IGm to IGe
This primes the mast cells
Phase 2
Antigen crosslinking on the primed mast cells causes them to release histamine, leukotrienes and prostaglandins
What is the treatment for anaphylaxis?
0.5mg IM adrenalin (can have several doses) 100mg IV hydrocortisone oxygen fluid monitor airway
Describe the pathogenesis of TB
Type 4 hypersensitivity reaction (T cell mediated)
Mycobacteria detected and phagocytosed inside macrophage where they multiply and are taken to lymph nodes. In the lymph node this is the Ghon complex.
Either then primary TB (mild)
Or T cells send it latent
Then can have secondary disease (severe)
What is miliary TB?
Secondary active disease that is disseminated across the body
Usually in immunocompromised
What does a negative quantiferon test mean?
Never had TB
What does a positive quantiferon test mean?
Latent or active TB
What does a negative mantoux mean?
Never vaccinated or exposed to TB
Give BCG
What does a positive mantoux mean?
Either vaccinated already or exposed to TB in some way
Do not give BCG
Describe the histology of TB
Caseous necrosis and granulomas (epithelioid histiocytes) with Langhan’s giant cells
Describe how TB appears in radiology?
Patchy consolidation with cavitating lesions
Hilar lymphadenopathy
Describe the HIV stages?
Acute phase 1 - asymptomatic 2 - CD4 <500 3 - CD4 <350 4 - CD4 <200
At what stage should antiretrovirals be started for HIV?
At diagnosis
What conditions are commonly seen at CD4 counts <500, <200, <100?
<500 - Candidiasis, TB, Herpes zoster, leukoplakia, Kaposi’s sarcoma
<200 - Pneumocystis jirovecii pneumonia (PCP), toxoplasmosis
<100 - Cytomegalovirus, meningitis, oesophageal candidiasis
Which type of pneumonia is associated with HIV?
Pneumocystis jirovecii pneumonia (PCP)
How would the results of hepatitis B serology look in a patient who is immune due to infection?
HBsAg (exposure) - positive
antiHBs (immunity) - positive
How would the results of hepatitis B serology look in a patient who is immune due to vaccination?
HBsAg (exposure) - negative
antiHBs (immunity) - positive over 100
How would the results of hepatitis B serology look in a patient who has active disease?
HBsAg (exposure) - positive
antiHBs (immunity) - negative
antiHBc - positive IgM
How would the results of hepatitis B serology look in a patient who has chronic disease?
HBsAg (exposure) - positive
antiHBs (immunity) - negative
antiHBc - positive IgG
Which antibiotics can you give in general instead of co-amoxiclav in penicllin allergic patients?
Cefuroxime (cephalosporin generally for lung but be careful in severe/proper allergy)
Clindamycin (macrolide generally for MSK)
Doxycycline (tetracycline generally low risk for c diff)