Infection Flashcards
How is infective endocarditis diagnosed?
Duke Criteria:
- Definitive endocarditis then the one of the following bullet points is needed:
- Two major criteria
- One major & 3 minor
- Five minor criteria
Major Criteria:
- Persistently positive blood cultures
- Specific imaging findings → eg, vegetation seen on echo, new valvular regurgitation
Minor Criteria:
- Predisposition → eg, IVDU, heart valve pathology
- Fever >38
- Vascular phenomena →Splenic infarct, Janeway lesions
- Immunological phenomena → Osler’s nodes, Roth spots, glomerulonephritis
- Microbiological → positive cultures not qualifying for major criteria
How is infective endocarditis managed?
- Admission
- IV broad-spectrum antibiotics → can be changed depending on cultures
- 4 weeks with native heart valves, 6 weeks with prosthetic heart valves
- Typically IV for 2 weeks before changing to oral
- Surgery may be required if heart failure, large vegetations, infections not responding to antibiotic
What are the 3 most common causes of viral meningitis?
- Enterovirus (eg, coxsackievirus)
- HSV
- Varicella zoster virus
What are the two special examination tests that indicate meningitis?
Kernig’s test - involves lying the patient on their back, flexing one hip and knee to 90 degrees and then slowly straightening the knee whilst keeping the hip flexed at 90 degrees. This creates a slight stretch in the meninges. Where there is meningitis, it will produce spinal pain or resistance to movement.
Brudzinski’s test - involves lying the patient flat on their back and gently using your hands to lift their head and neck off the bed, flexing their chin to their chest. A positive test, indicating meningitis, is when this causes the patient to flex their hips and knees involuntarily.
When does physiological jaundice present in a newborn?
2nd or 3rd day of life -> jaundice in first 24hrs of life is always pathological
What are the causes of unconjugated neonatal jaundice?
Increased haemolysis:
- Haemolytic disease of the newborn (rhesus, ABO incompatibility)
- Excessive bruising
- Spherocytosis
- G6PD deficiency (fragile RBCs)
Impaired conjugation:
- Physiological
- Breast milk
- Gilbert’s syndrome
What are the causes of conjugated neonatal jaundice?
Intrahepatic:
- Infection
- Metabolic disease
Extrahepatic:
- Biliary atresia
- Cysts
- Intestinal obstruction
What is haemophilia A & B? How are they inherited?
Haemophilia A - factor 8 deficiency
Haemophilia B - factor 9 deficiency
X-linked recessive
How is haemophilia managed?
- Recombinant synthetic factor
- On demand for bleeding episodes
- Targeted prophylaxis → surgery/dental work
- Primary prophylaxis → severe haemophilia
- Physiotherapy → helps them to keep their joints & muscles in good condition
Describe the stages of HIV infection.
- 1 - Primary HIV infection (seroconversion)
- HIV binds to CD4 receptor found on the surface of T-helper lymphocytes, monocytes, macrophages & dendritic cells.
- The infected CD4 cells die & release new virions, which disseminate through the blood to infect more CD4 cells
- 2-4 weeks after exposure
- Seroconversion illness → the immune response to this infection can cause mild-to-moderate non-specific symptoms (flu-like)
- Highly infectious at this stage due to high viral load.
- 2 - Chronic HIV infection (asymptomatic infection/clinical latency)
- The immune response controls the virus, limiting symptoms despite a low level of viral infection
- Can continue for 10-15 years
- Still infectious
- 3 - Acquired immunodeficiency syndrome (AIDS)
- Occurs when the CD4 count <200 as the HIV infection has compromised the ability of the immune system to replenish CD4 cells.
- The individual is now susceptible to opportunistic infection & malignancy
What are the investigations for HIV diagnosis & monitoring?
- Fourth-generation laboratory test
- Checks for antibodies to HIV & the p24 antigen
- Window period of 45 days → a negative result before this is not reliable
- Point of care test for HIV antibodies
- Gives a result within minutes
- 90-day window period
Monitoring:
- CD4 count
- Normal → 500-1200 cells/mm
- Risk of opportunistic infections → <200 cells/mm
- Viral load
- Testing for HIV RNA per ml of blood
- Undetectable → <20 copies/ml
- If untreated, this can be in the hundreds of thousands
How does mumps present?
- 20% of those infected are asymptomatic
- Prodrome → initial period of flu-like symptoms prior to parotid swelling:
- Fever
- Muscle aches
- Lethargy
- Reduced appetite
- Headache
- Dry mouth
- Parotid gland swelling → unilateral or bilateral, associated pain
- Symptoms of complications
- Abdominal pain → pancreatitis
- Testicular pain & swelling → orchitis
- Confusion, neck stiffness, headache → meningitis or encephalitis
How is mumps managed?
- Notify public health
- Supportive management
- Rest, fluids, analgesia
- Self-limiting, most recover in 1-2 weeks
- Remain off school/work for 5 days following the development of parotitis
How is Lyme Disease managed?
- Localised disease → oral doxycycline 100mg BD (or oral amoxicillin 500mg-1g TDS) for 21 days
- Cardiac involvement → IV ceftriaxone 2g OD for 21 days
- Neurological involvement → oral doxycycline
