Infectious Disease Flashcards
What causes scarlet fever?
Streptococcus pyogenes
You are a surgical house officer and have been bleeped to see a 34 year old man who is post op day 1 following abdominal surgery. He complains of intense pain around his leg. On examination it is erythematous. His temperature is 38.3, HR 160, BP 135/96. He is a known diabetic and heavy drinker. What is the most appropriate management?
IV morphine and urgent referral for surgical debridement
This patient has necrotising fasciitis
What are risk factors for necrotising fasciitis?
Abdominal surgery
Diabetes
Alcoholism
Malignancy
What 4 drugs are used to treat TB?
Rifampicin
Isoniazid
Pyrazinamide
Ethambutol
What is a main side effect of ethambutol? What should be done before commencing treatment?
Toxic optic neuropathy
Test visual acuity and colour vision before treatment
What test should be performed prior to commencing rifampicin, isoniazid and pyrazinamide treatment?
LFTs as they can cause hepatitis
What type of bacteria is E.coli?
Gram negative bacilli
What is infectious mononucleosis?
Glandular fever
Self limiting infection due to Epstein Barr virus
Low grade fever, sore throat, lethargy
How do you diagnose glandular fever?
Monospot test
What happens if you prescribe amoxicillin to patients with glandular fever?
Severe rash
What is leptospirosis?
Weils disease
Infection caused by spirochaetes
Due to contact with infected urine, usually from rats
Mild flu like symptoms, jaundice, meningitis and renal failure in severe cases
How long after HIV exposure is post exposure prophylaxis effective for?
Most effective within an hour of infection
After 72 hours, effectiveness is very limited
What are the 3 most common chase of lung infection in people with cystic fibrosis?
Staph aureus
Haemophillus influenza
Pseudomonas aeruginosa: rusty coloured sputum
What sort of infections are people with a splenectomy susceptible to? And why
Encapsulated organisms for example h. Influenza and strep pneumoniae
Because spleen provides environment where encapsulated organisms are opsonised
What is antimicrobial stewardship?
Organisational approach to promoting and monitoring judicious use of antimicrobials to preserve their future effectiveness
What are the principles of antimicrobial stewardship?
How: Prescribe only when needed, Review need for abx in accordance with local formularies and guidelines
Why: Optimise therapy for individual patients, Prevent overuse, misuse, abuse, Minimise development of resistance at patient and
community levels
Who has responsibility for antimicrobial stewardship?
Clinicians
Society: Demand and supply
Politicians
Corporations
Why is antimicrobial stewardship important?
Optimise therapy for individual patients
Minimise side effects
Microbiome: all antibiotics, limit with narrower spectrum
Allergy and intolerance, specific contraindications and interactions
Prevent overuse, misuse, abuse
Minimise development of resistance at patient and community levels
How can we limit the need for antimicrobials?
Prevention and control of infection: No infection means no antibiotic needed, No multi-resistant organism means narrower spectrum antibiotic can be used
List resources available to aid optimal antimicrobial prescribing
TARGET antibiotics toolkit: treat antibiotics responsibly guidance, education and tools
NICE guidelines
Department of health antimicrobial stewardship guide
Local primary and secondary care guidance
What is contained in the TARGET toolkit?
Commissioner resources Information for patients Audit tools Training resources Self assessment National antibiotic management guidance
List the principal considerations required before commencing antibiotic therapy
Absorption (How can I get it into my patient?)
Distribution (does it get where I want it to?)
Predictably sensitive? (is resistance likely to be a problem before or after treatment?)
Adverse effects (common, particular patient group?)
Interaction with other drugs (prescribed or otherwise)
Metabolism and excretion (how does the drug get out? Is that a problem in my patient?)
What are beta lactam antibiotics?
Penicillins and their derivatives
Cephalosporins (ceph/ cef….)
Carbapenems (-penems)
Monobactams (aztreonam)
Describe the absorption profiles of the beta lactam antibiotics
Penicillins: Penicillin V/ phenoxymethylpenicillin low absorption from GI tract, Amoxicillin better, Penicillin G/ benzylpenicillin no absorption so given IV
Cephalosporins: Limited number available orally, generally good absorption for those that are (cefalexin), Most IV only e.g. ceftriaxone
Carbapenems: No oral formulation
Aztreonam: Also IV only
Describe the distribution profile of beta lactam antibiotics
Generally good penetration to body tissues
Penicillins don’t cross the blood-brain barrier well unless the meninges are inflamed
Do not get inside individual host cells
Poor activity against bacteria that live intracellularly, Legionella is classic example
Describe the mechanism of action of beta lactam antibiotics. What implication does this have?
Interruption of cell wall synthesis
So NO activity against bacteria without a cell wall (Mycoplasma, Chlamydia)
What is the difference between a bacteriostatic and bacteriocidal antibiotics?
Bacteriostatic: inhibiting the growth of a bacterium
Bactericidal: killing the bacterium
What is the minimum inhibitory concentration?
Lowest concentration of an antibiotic which inhibits visible growth of bacteria
What is minimum Bactericidal concentration?
Lowest Concentration of an antibiotic that kills 99.9% of a population of bacteria
What is the breakpoint in terms of antibiotic sensitivity?
Minimum inhibitory concentration cut-off which separates strains where there is a high likelihood of treatment succeeding from those where treatment is more likely to fail
How does resistance to beta lactams occur?
Intrinsic: No cell wall, Strictly intracellular bacteria, No target for the specific drug
Acquired: Stop the drug getting in, Break it down, Change the target, Pump it out
Describe the forms of acquired antibiotic resistance that occurs with beta lactams and what can be done about this
Enzyme which breaks the antibiotic down (e.g. Staphylococcal penicillinase), use an enzyme inhibitor to restore susceptibility (co-amoxiclav)
Alteration in target site (e.g. MRSA), need to find a new target for a different antimicrobial
What are some adverse effects of beta lactam antibiotics?
Generally safe and well-tolerated: low rates renal of hepatotoxicity, neurotoxicity, Jaundice with flucloxacillin and co-amoxiclav
Diarrhoea with any, especially broad spectrum (C difficile particular association with cephalosporins)
IgE-mediated allergy in 5-10% patients
Are beta lactam antibiotics teratogenic?
No
Which drugs might interact with beta lactams?
Anticoagulants
Oral contraceptive (not contraindicated)
Anti-epileptics
How are beta lactams excreted?
In urine
Excretion rates very rapid for older penicillins, so need to be given frequently
4-hourly for benzylpenicillin in severe infection
Pencillin V given qds
At what level of renal function do you need to adjust the dose of beta lactams?
Only in very poor renal function
GFR less than 10
What are potential complications of meningococcal disease?
Septic shock Hypotension Acidosis DIC Hearing loss Motor and cognitive disability Blindness Ischaemic injury to skin/extremities
What is Waterhouse friderichsens syndrome?
Bilateral adrenal haemorrhage typically caused by fulminant meningococcal infection
What are risk factors for the development of meningococcal disease?
Young age Complement deficiency Asplenia or hyposplenia Residence in dormitory Globulin deficiency Close contact with invasive meningococcal infection Household crowding Travel to endemic area Lab worker
What are risk factors for toxic shock syndrome?
Diabetes mellitus Alcoholism Trauma Surgical procedures, particularly vaginal delivery, c section, hysterectomy Single tampon use for consecutive days Highly absorbent tampons
What are potential complications of toxic shock syndrome?
Bacteraemia Acute respiratory distress syndrome DIC Renal failure Waterhouse friderichsen syndrome Wound sequelae requiring major surgery
How many days pen V should be prescribed for streptococcal sore throat?
10 days
A 23 year old with fever sore throat and swollen neck and groin nodes, what is the most likely diagnosis?
Glandular fever
What is the test for glandular fever?
Monospot
Paul Bunnell
A mum brings a 4 year old boy to GP with right earache and fever for 24 hours. This morning it has started to discharge pus, what is the most likely diagnosis?
Otitis media with perforation
What tests can be done for streptococcal infection?
ASOT - antistreptolysin O titre
Anti DNAase B titre
What can cause laryngitis?
Complication of URTI
Parainfluenza
Measles
What should be done to treat acute laryngotracheobronchitis?
Nebulised adrenaline
Oral/IM corticosteroids
Oxygen
Fluids
What should be done to treat acute epiglottitis?
Endotracheal intubation
IV ceftazidime
In which patients is an inflenza vaccine recommended?
Over 65s CHD Lung disease CKD Diabetes Immunosuppressed
How do you treat sinusitis?
Nasal decongestant
Co amoxiclav
Fluticasone proprionate (corticosteroid) nasal spray
Steam inhalation
What do you do to manage recurrent sinusitis or if there is an orbital cellulitis complication?
Refer to ENT for CT of paranasal sinuses
