Infectious diseases Flashcards
(42 cards)
Hepatitis viruses, how are the spread?
HAV - faecal oral
HBV - blood products, IV drug users, sexual intercourse, direct contact
HCV - blood products, IV drug users, sexual intercourse, acupuncture
HDV - with HBV
The hepatitis viruses: DNA or RNA?
HAV - RNA HBV - DNA HCV - RNA flavivirus HDV - incomplete RNA virus (only exists with HBV) HEV - RNA virus (similar to HAV)
Hepatitis A - what are its symptoms, how long is the incubation period and how can you detect an infection and recent infection?
Incubation 2-6 weeks
Prodromal symptoms - fever, malaise, anorexia, nausea, arthralgia
Jaundice +/- hepatomegaly,
AST and ALT rise day 22-40 after exposure and return to normal over 5-20 weeks
IgM rises from day 25 and signifies recent infection
IgG remains detectable for life
Self limiting usually - NEVER results in chronic liver disease
What are the 4 main organisms that cause TB, and what are the features of the bacteria?
Mycobacterium tuberculosis
Mycobacterium bovis
Mycobacterium africanum
Mycobacterium microti
They are obligate aerobes, facultative intracellular pathogens, usually infecting mononuculear phagocytes. They grow slowly, 12-18hr generation time and have a high lipid cell wall.
What are the different clinical types of TB?
Primary TB -
Alveolar macrophages ingest bacteria, the bacilli proliferative inside and cause release of chemoattractants and cytokienes. This leads to inflammatory cell infiltrate in the lungs and the hilar lymph nodes.
Delayed hypersensitivity reaction occurs resulting in the necrosis and granulomas seen: central areas of necrotic tissue surrounded by epitheliod cells and langhans giant cells
Latent TB - cell mediated immune memory to the bacteria
Reactivated TB - can occur in HIV ,immunosuppression, DM, malnutrition and ageing.
TB can occur in any organ:
Potts disease = TB in bone
Millary TB = a result of haematogenous dissemination of the TB
Lupus vulgaris = skin TB
How do you treat TB?
Rifampicin
Isoniazid
Pyrazinamide
Ethambutol
All 4 for 2 months and only R and I for 4 months.
Pyridoxine (vit B6) should be given throughout
What are the side effects of the anti TB drugs?
Rifampicin:
Hepatitis (ok if AST rises, need to stop if bilirubin increases), orange discolouration of urine and tears, inactivation of the pill
Isoniazid:
Hepatitis, neuropathy, agraulocytosis
Ethambutol:
Optic neuritis - colour vision is the first to go
Pyrazinamide:
Hepatitis, arthralgia
Hepatitis C - what are its symptoms, how long is the incubation period and how can you detect an infection and recent infection?
Early infection is often mild or asymptomatic
85% develop chronic infection - 20-30% develop cirrhosis and 1-3% of those develop HCC
No infection = -ve AntiHCV and -ve HCV RNA
Early acute phase = -ve AntiHCV and +ve HCV RNA
Infection = +ve AntiHCV and +ve HCV RNA
Resolution = +ve AntiHCV and -ve HCV RNA
When treating prognosis is measured using the viral load and patients can have a Rapid Virological response (RVR) an Early Virological response (EVR) or a Sustained Virological response (SVR), people have an undetectable viral load at 4, 12 or over 24 weeks of treatment.
A partial responder is someone who gets an EVR but is not undetectable by 24weeks, and a null responder is someone who doesn’t get an EVR,
What symptoms and signs would make you treat a patient for meningitis?
Headaches with leg pains, cold hands and abnormal skin colour
Meningism - neck stiffness, photophobia, Kernig’s sign
Decreased consciousness level
Seizures or focal neurological signs
Petchial rash
Signs of sepsis
What would a lumbar puncture show in bacterial, viral and TB meningitis?
Bacterial:
Turbid, 90-1000+ polymorphs.
Glucose 1.5g/l of protein
Viral:
Usually clear with 50-1000 mononuclear cells
Glucose >1/2 of the plasma glucose
What are the different manifestations of herpes simplex virus?
- Genital/ oral herpes
- Gingiovostomatitis - ulcers in the mouth
- Herpetic whitlow - vesicles on the fingers
- Eczema herpeticum - HSV infection of eczematous skin
- HSV meningitis - uncommon but self limiting
- HSV keratitis - corneal dendritic ulcers
- Systemic infection - fever, sore throat lymphadenopathy, if not immunocompromised may go unnoticed, can be life threatening
- HSV encephalitits - usually HSV1. spreads from cranial nerve ganglia to frontal and temporal nerves. Fever, fits, odd behaviour. PCR on CSF. NEEDS IV ACICLOVIR ASAP
What are the complications of influenza?
Bronchitis, pneumonia, sinustitis, otitis media, encephalitis, pericarditis
Reye’s syndrome - coma and high LFTs
What does toxoplasmosis do to the eye?
Granulomatous uveitits
Necrotizing retinitis
If congenital presents with choriodretinitis, posterior uveitis and may cause cataract
How does congenital CMV present?
Jaundice, hepatosplenomegly purpura,
Mental retardation, cerebral palsy, epilepsy, and eye problems
How can you distinguish between patients who have been infected with hep B and are now carriers, those currently infected and those who have been vaccinated?
Test different things:
Liver function tests - abnormal when someone is acutely infected or they have the chronic disease.
HepB surface antigen - is only detected when patients are infected as its found on the virus.
+ve incubation, acute infection and chronic infection
HepB e antigen - detected when the virus is replicating.
+ve incubation and acute infection. If the virus is reactivating in chronic infection
Anti HepB core IgM - acute antibody against the core.
+ve acute infection and some chronic infections
Anti HepB core IgG - chronic antibody against the core.
Present in acute infections, chronic infections and fully recovered infections.
Anti HepB surface - is a sign of immunity
+ve in fully recovered infections and vaccinated patients
How do the two different modes of transmission of Hep B affect the end result?
Vertical transmission from mother to fetus is the most common mode of transmission.
90% of the children have no acute episode and therefore dont clear the virus so have the chronic infection
If a adult patient develops an acute infection >90% will clear the virus.
What are the complications of Hep B?
Fulminant hepatic failure Replapse Prolonged cholestasis Chronic hepatitis Cirrhosis Hepatocellular carcinoma -10 fold if HepB Surface antigen +ve, 60 fold increase if HepB surface antigen and HepB e antigen +ve Glomerulonephritis Cryoglobulinaemia
Glandular fever: What causes it? How do you test for it? What happens with the bloods? What are the complications?
Epstein Barr virus
Mono spot test
Blood film shows lymphocytosis
Complications:
CNS - meningitis, encephalitis, ataxia, cranial nerve lesions, GBS, chronic fatigue
Thrombocytopenia, ruptured spleen, upper airways obstruction, hepatitis, myo or pericarditis, renal failure, autoimmune haemolysis, erythema multiforme.
DO NOT GIVE AMPLICILLIN OR AMOXICILLIN TO PTS WITH A SORE THROAT, IF THEY HAVE EBV THEY WILL DEVELOP A SEVERE RASH
What bacteria grow gram +ve cocci in clusters?
Staphlococcus aureas or coagulase negative staphs (epidermidis)
What bacteria grow gram +ve cocci in chains?
Streptococcus - group a, or beta haemolytic strep
What bacteria grow gram +ve cocci in pairs?
Streptococcus pneumoniae or enterococcus
What bacteria grow as gram +ve rods?
Small and thin - diphtheroid or propionibacterium (contaminants in blood cultures normally)
Large with spores - clostridium or bacillus
What bacteria grow as gram -ve cocci?
Neisseria meningitides and Neisseria gonorrhoeae
Moraxella spp
What bacteria grow as gram -ve rods?
Coliforms - E coil, klebsiella, enterobacter, proteus Pseudomonas Haemophilus influenzae Salmonella, shigella, campylobacter Legionella, pertussis
