Infectious Disease Teaching Flashcards
What is tuberculosis (TB)? (cause, outcomes, risk factors, transmission, symptoms, diagnosis, treatment)
Cause
- Bacteria Mycobacterium tuberculosis complex
Transmission
Transmission- via inhalation of droplet nuclei
Risk factors
- Poverty and overcrowding •Undernutrition
- Alcohol misuse
- HIV → increases risk of developing active infection →TB is the leading killer of people with HIV
- Silicosis
- CKD
- DM
- Smoking
- Immunosuppression
Symptoms
- Fever, night sweats, weight loss,malaise
- Pulmonary (85%)- Productive cough, haemoptysis
- Extra-pulmonary • Backpain
- Lymphadenopathy • Meningitis
- Genitourinary
Infection
- 1/4 of the world pop. have been infected with tuberculosis → 5–10% lifetime risk of falling ill with TB
Diagnosis
- Traditional ZN stain
- Auramine stain
Active TB
Sputum smear (3x sputums = 72% sensitive)
Sputum culture- gold standard but slow, required for sensitivity testing
Sputum PCR
• GeneXpert MTB/RIF
- 100% sensitive on smear positive sputum samples
- 70% sensitive if smear negative • Detects resistance to rifampicin • Quick and easy to perform
- Tuberculosis culture
Can be very slow
Traditionally use egg based Lowenstein- Jensen media
• Isolates are sent to Birmingham Reference Laboratory
Genotypic +/- phenotypic sensitivity testing
Whole genome sequencing
Treatment
Standard treatment of drug sensitive TB
• Isoniazid and rifampicin- 6 months • Pyrazinamide and ethambutol- first
2 months
- MDR TB
- Resistance to isoniazid and
rifampicin
- XDR TB
- Additional resistance to injectable second line drug and fluoroquinolone
What is miliary TB?
Miliary TB = disseminated haematogenous spread of TB
Explain HIV (types, transmission, symppptoms)
Types
- HIV-1
- HIV-2- less common, mostly in West Africa, less transmissible, slower disease progressions
Transmission
• Sexual
- Perinatal
- Bood transfusion
- Sharing needles
- Occupational e.g. NSI, splash
Symptoms
Symptoms depend on stage of infection
most infectious shortly after infection
many unaware of status until later stages
In the first few weeks after initial infection some experience an influenza- like illness including fever, headache, rash or sore throat
= seroconversion illness
As infection progressively weakens the immune system
- swollenlymphnodes • weightloss
- fever
- diarrhoea
• cough
Without treatment risk of severe illnesses such as TB, Cryptococcal meningitis, severe bacterial infections, lymphomas and Kaposi’s sarcoma
What is this condition?
Karposi’s Sarcoma
• Caused by human herpes virus 8
(HHV-8)
- Purple or brown lesions or patches occurring on the legs, face, mouth and genitalia
- Causes small blood vessels to grow abnormally
- Diagnosis confirmed on biopsy
What is this condition?
Oral Hairy Leucoplakia
- Caused by Epstein-Barr virus
- Found almost exclusively in people with HIV
- Adherent corrugated white patches on lateral parts of tongue that cannot be scrapped off
What is this condition?
Oesophageal Candidiasis
• White, plaques on the buccal and
pharyngeal mucosa
- Lesions can be scrapped off
- Can cause pain on eating and swallowing, which can result in weight loss
- One of the commonest infections in people living with HIV
What is this condition?
Cryptosporidium
Protozoan infection, acquired through ingestion of contaminated water or food
Self-limiting in immunocompetent people, but causes chronic diarrhoea, abdominal cramps and weight loss in people with HIV
- Occurs when CD4 <200 cells/mm3
- Diagnosed on stool microscopy or PCR
What is this condition?
Toxoplasmosis
A protozoan parasite, commonest cause of brain lesion in people with HIV
Usually due to reactivation of previous infection, causes focal neurological symptoms, fever, seizures
• Can also cause chorioretinitis
What is this condition?
Shingles
• Caused by herpes zoster infection
Painful vesicular lesions occur in a dermatomal distribution
Complications include post- herpetic neuralgia, blindness and meningitis
What is this condition?
Pneumocystis jiroveci pneumonia
- Commonest cause of infection in patients with HIV
- Presents with progressive dyspnoea, fever, malaise
Desaturation on exertion, CXR shows diffuse alveolar infiltrates
Diagnosis is by PCR of induced sputum or BAL or histology
What is this condition?
- Progressive multifocal leukoencephalopathy
- Rare brain and spinal cord disease is caused by JC virus, seen almost exclusively in people with HIV.
Symptoms include loss of muscle control, paralysis, blindness, speech problems and altered mental state.
This disease often progresses rapidly and may be fatal.
What is this condition?
Mycobacterium tuberculosis
- Symptoms in the lungs include cough, tiredness, weight loss, fever, haemoptysis and night sweats.
- Organisms are acid fast bacilli
What is this condition?
CMV
• Herpes virus
- Viral infection that can cause pneumonia, colitis, encephalitis and retinitis.
- Can cause blindness if not treated promptly.
What is this condition?
Cryptococcus neoformans
Common cause of meningitis in
HIV
Presents with insidious onset of fever, headache, visual change, neck stiffness, cranial nerve deficit, seizures
Associated with CD4 count <100 cells/mm3
• Diagnosed by India ink staining of CSF or antigen test
Explain infective endocarditis (what it is, risk factors, symptoms, causes, diagnosis, treatment)
What it is
Infection of the endocardial surface of the heart
• Alteration of the valve surface >> deposition of platelets and fibrin >> colonisation by
bacteria >> development of vegetation • Native or prosthetic valve
Risk factors
- Congenital heart disease • Rheumatic heart disease • IVDU
- Mitral valve prolapse
- IV devices
Symptoms
Fever, rigors, malaise, dyspnoea, anorexia
and weight loss
Causes
- 80% of infections are due to Strep (streptococcus viridans) or Staphs (staphylococcus aureus)
Specific clinical findings
- Roth Spots
- Janeway lesions
- Splinter haemorrhages
- Osler’s nodes
Diagnosis
- 3 sets of blood cultures and echocardiogram required
-
Duke’s criteria
- 2 major criteria
- OR one major and 3 minor criteria
- OR 5 minor criteria
Treatment
- Depends on:
- Causative organism
- Native or prosthetic valve
- Patient factors e.g. renal function, allergies
Usually 4-6 weeks intravenous antibiotics
May require therapeutic drug monitoring
May require surgery
