Infectious disease Flashcards
Which stain is used to differentiate between gram positive and gram negative bacteria? What is the result?
Crystal violet stain. Gram positive bacteria are stained but gram negative don’t
What is the name for rod shaped bacteria?
Bacilli
What is the name for circular shaped bacteria?
Cocci
What is the counterstain called which identifies gram negative bacteria? What colour does it turn?
safarin. Red/ pink
What is the difference in cell structure between gram positive and a negative bacteria?
Gram positive have a thick peptidoglycan cell wall
Name 3 gram-positive cocci?
Staphylococcus
Streptococcus
Enterococcus
What does MRSA stand for?
Methicillin- resistant staphylococcus aureus
Name 3 antibiotic treatment options for MRSA
Doxycyline
Clindamycin
Vancomycin
What are the 2 broad mechanisms of actions of antibiotics?
Bactericidal
Bacteriostatic
Which bacteria does amoxicillin cover?
Streptococcus, listeria and enterococcus (all gram +ve)
Which bacteria does co-amoxiclav cover?
Staphylococcus, haemophilus and e.coli
Which bacteria does tazocin cover?
Pseudomonas
Which bacteria does meropenem cover?
ESBLs (extended spectrum beta lactamases) These are bacteria which produce an enzyme which makes them resistant to beta lactamases
Which bacteria do teicoplanin and vancomycin cover?
MRSA
Which bacteria do clarithromycin and doxycyline cover?
Atypical bacteria
Why is oedema a feature of sepsis?
Massive cytokine release occurs in response to pathogen. This causes the endothelial lining of cells to be more permeable leading to fluid leakage.
What can oedema cause in sepsis and why?
tissue hypoxia because fluid leakage creates a space between vessels and tissue
Why does DIC occur in sepsis?
Coagulation system is activated leading to deposition of fibrin throughout the circulation system. This causes platelets to be used up
Why is blood lactate high in sepsis?
Hypo-perfusion of tissues causes tissues to switch to anaerobic respiration. A by-product of anaerobic respiration is lactate
What are the two main symptoms which measure if a patient is in septic shock?
Systolic blood pressure less than 90
Hyperlactaemia (>4mmol/L)
How is septic shock managed?
IV fluid boluses to improve BP and perfusion. If this doesn’t wrk then use inotropes (such as noradrenalin) to stimulate the CV system, increase BP and perfusion
How is severe sepsis defined?
When sepsis is present and results in organ dysfunction
What is the screening tool for sepsis used in hospitals?
NEWS (national early warning score)
What is often the first sign if sepsis?
Tachypnoea
Investigations for sepsis?
FBC (asses neutrophils) U&Es for kidney function LFTs CRP Clotting (DIC) Blood cultures ABG (lactate, pH and glucose)
What is the sepsis 6?
Three tests:
- Blood lactate
- Blood cultures
- Urine output
Three treatments:
- O2 (94-98% target)
- Empirical broad spectrum antibiotics
- IV fluids
What is neutropenic sepsis?
Sepsis in a patient with a low neutrophil count of less than 1x10^9/L
Which 2 bacteria most commonly cause chest infections?
- Streptococcus pneumonaie (50%)
2. Haemophilus influenzae (20%)
What is the most appropriate initial antibiotic in the community for a chest infection?
Amoxicillin
Which bacteria most commonly cause UTIs?
E.coli
What are the 4 main symptoms of pyelonephritis?
Fever
Loin pain
Haematuria
Renal angle tenderness
What would show on a urine dipstick if someone has a UTI?
Nitrites
Leukocytes
What length of antibiotic treatment should women be put on for UTI?
3 days
What length of antibiotic treatment should women who are immunosupressed or have abnormal kidney function be put on for UTI?
5-10 days
What length of antibiotic treatment should men, pregnant women or people with catheter related UTIs be put on for UTI?
7 days
Which antibiotics are the initial choices for UTI?
Trimethoprim
Nitrafurantoin
Which antibiotic for UTI is avoided in the third trimester?
Nitrofurantoin, causes haemolytic anaemia in newborns
Which antibiotic for UTI is avoided in the first trimester?
Trimethoprim due to anti-folate effects
What does a gold-yellow crust indicate?
Staphylococcus aureus infection
What is the name of the classification used for cellulitis?
Eron classification
Which antibiotic is most commonly used for cellulitis?
Flucloxacillin. Very effective against staph
Which bacteria most commonly causes bacterial tonsillitis?
Group A strep (mainly streptococcus pyogenes)
Which bacteria most commonly causes otitis media, sinusitis and tonsilitis?
Streptococcus pneumoniae
Whats the first line antibiotic for tonisilitis?
Phenoxymethylpenicillin
What is the first line antibiotic for sinusitis?
Phenoxymethylpenicillin
What is the most common causative organism of septic arthritis?
Staphylococcus aureus
What is the management of septic arthritis?
Joint aspiration PRIOR to abx
Start empirical abx (often flucloxacillin plus rifampicin)
Who is the flu vaccine given to for free?
Aged 65+ Young children Pregnant women Chronic health conditions Healthcare workers
How do you diagnose the flu?
Viral nasal or throat swabs
Then PCR
What are the 3 most common causes of viral gastroenteritis?
Rotavirus
Norovirus
Adenovirus
What is a complication of E.coli and why does this mean that antibiotic therapy is contraindicated?
Haemolytic uraemic syndrome. the use of antibiotics increase the risk of HUS so shouldn’t be used
What are the symptoms of e.coli gasteroenteritis?
Bloody diarrhoea, vomiting and abdo cramps
Whats the most common cause of travellers diarrhoea?
campylobacter jejuni
Which bacteria often causes gastroenteritis after the patient eats rice?
Bacillus cereus
What is the treatment for giardia?
Metronidazole
Which bacteria most commonly causes meningococcal septicaemia?
neisseria meningitidis and streptococcus pneumoniae
What causes the non-blanching rash in meningitis?
DIC and subcutaneous haemorrhages
What are the two special tests for meningeal irritation?
Kerning’s test
Brudzinski’s test
What should be given as a stat dose in a primary care setting if meningitis is suspected?
IM benzylpenecillin
When is a lumbar puncture contraindicated
if there is purpura
Which antibiotics should be used if the patient <3 months and has meningitis?
Cefotaxime and amoxicillin
Which antibiotics should be used if the patients is >3months and has meningitis?
Ceftriaxone
Which medication is given alongside abx to children with meningitis? Why?
Steriod to reduce the chance of hearing loss and neuro damage
What should be given as post exposure prophylaxis to meningitis contacts? Within what time frame?
People who have been in close contact 7 days prior should be given a single dose of ciprofloxacin
What are the features bacterial meningitis lumbar puncture?
Cloudy, high protein, low glucose, high WCC (neutrophils)
What are the features viral meningitis lumbar puncture?
Clear, normal protein, normal glucose, high WCC (lymphocytes)
Which bacteria causes TB?
Mycobacterium tuberculosis
Which stain should be used for mycobacterium tuberculosis? What colour does it turn them?
Zeihl-Neelsen stain. Red against a blue background
What does active TB mean?
There is active infection in various areas of the body
What does latent TB mean?
There has been active TB. Now the immune system has managed to encapsulate sites of infection and stop the progression of the disease
What is secondary TB?
When latent TB reactivates
What is miliary TB?
Severe TB
What is a cold abscess?
A firm and painless abscess caused by TB, usually in the neck
What kind of vaccine is the BCG vaccine?
Live attenuated
How do you test if someone has antibodies to TB?
Mantoux test
What are the symptoms of TB?
Lethargy Fever Night sweats Weight loss Erythema nodosum Lymphadenopathy
How do you investigate TB?
Check for immune response (mantoux test or interferon gamma release assay)
Use Ziehl-Neelsen stain
Chest X-Ray
Cultures
What is the interferon-gamma release assay test used for?
To confirm a diagnosis of latent TB in patients who have had a positive mantoux test
What might primary TB show on a chest X-ray?
Consolidation
Pleural effusions
Hilar lymphadenopathy
What may reactivated TB show on a chest X-ray?
Patchy or nodular consolidation with cavitation (gas filled spaces) in the lungs
What may disseminated Miliary TB show on chest X-ray?
Millet seeds, uniformly distributed throught the lung fields
How can latent TB be managed?
Isoniazid and rifampicin for 3 months or just isoniazid for 6 months
How should acute TB be managed?
RIPE: Rifampicin for 6 months Isoniazid for 6 months Pyrazinamide for 2 months Ethambutol for 2 months
What should always be prescribed alongside isoniazid?
Pyridoxine (vitamin B6) because isoniazid can cause peripheral neuropathy
Where should patients with active TB be treated?
In hospital negative pressure rooms until they are established on treatment
What is a side effect of rifampicin?
Red/ orange discolouration of secretions.
What is a side effect of isoniazid?
Peripheral neuropathy. Pyridoxine should be prescribed alongside
What is a side effect of pyrazinamide?
Hyperuricaemia. This can result in gout
What is a side effect of ethambutol?
Colour blindness and reduced visual acuity
What kind of virus is HIV?
It is an RNA retrovirus
Which cells in the body does HIV attack?
CD4 T helper cells
Name some AIDS-defining illnesses
Kaposi's sarcoma PCP Cytomegalovirus infection Candidiasis (oesophageal or bronchial) Lymphomas Tuberculosis
How long can a HIV antibody test be negative for following exposure?
3 months
Which test for HIV can give a positive result faster than an antibody test?
p24 antigen
What does PCR testing for HIV RNA show?
Viral load
What 2 things do you monitor in HIV?
CD4 count
Viral load
How is HIV treated?
Antiretroviral therapy until they have a normal CD4 count and an undetectable viral load
Which type of vaccines should HIV patients avoid?
Live vaccines
What is the current post exposure prophylaxis regime for HIV?
Truvada and raltegravir for 28 days
How is malaria spread?
Through bites from the female anopheles mosquitoes
What are the symptoms of malaria?
Fever, sweats and rigors Malaise Myalgia Headache Vomiting
What are the signs of malaria?
Pallor due to anaemia
Hepatosplenomegaly
Jaundice
How do you diagnose malaria?
Malaria blood film
How do you exclude malaria?
3 malaria blood films over 3 consecutive days
How do you treat malaria?
If uncomplicated, oral quinine sulphate
If severe, IV artesunate
