Infectious diseases Flashcards
What are some congenital and acquired causes of immunocompromise?
Congenital: B-cell defect, T-cell defect, Complement deficiency, phagocyte deficiencies
Acquired: Malnutrition, HIV, Diabetes, Drugs, Cancer
Give some examples of neutropenic defects causing immunosuppression.
Aplastic anaemia
Chemotherapy (doxorubicin, cyclophosphamide)
Leukaemia
Give some examples of cell defects causing immunosuppression.
Chemotherapy (azathioprine, bleomycin)
HIV/CMV/EBV infection
Malnutrition
Lymphoma
Give some examples of humoral defects causing immunosuppression.
Multiple myeloma
Chronic lymphocytic leukaemia
Chemotherapy (Azathioprine, methotrexate)
Splenectomy
What is infectious mononucleosis?
Glandular fever
Triad of fever, pharyngitis, lymphadenopathy with atypical lymphocytosis
Caused by Epstein Barr virus via saliva
What is pyrexia of unknown origin?
A temperature of >/=38.3 degrees for >/=3 weeks with no identifiable cause after 3 days of hospital evaluation or 3 outpatient visits.
Infection, inflammation, neoplastic, miscellaneous
What blood results may help aid a diagnosis of malaria?
Hypoglycaemia, acidosis and anaemia
What are some complications of severe malaria?
Shock, renal failure, severe anaemia, acidosis, pulmonary oedema
What are the types of plasmodium that cause malaria?
Plasmodium Falciparum- most common cause of severe malaria. Drug resistant
Plasmodium vivax - persistent liver infection, can relate months after initial infection, chloroquine resistant
Plasmodium ovale - persistent liver infection, no drug resistance
Plasmodium malaraie - no liver infection and no resistance
What is Viral Haemorrhagic fever?
A group of serious illness caused by particular viruses.
Ebola, Lassa fever, Marburg, Crimean-congo fever
How does VHF cause illness?
The virus invades the body and lives in macrophages and dendritic cells where it multiples.
It then disseminates into organ systems
This triggers the innate immune response and cytokines and NO is released.
Replication and tissue damage and there is increased permeability of the vessels - DIC
What is dysentry?
Infection of the intestine causing diarrhoea containing blood and mucous
Bacillary caused by Shigella
Ameobic caused by entameobic histolytica
What are some differences in dysentry caused by shigella and caused by entameobic histolytica?
Shigella - 10 loose movements a day with small amounts of stool. Fresh blood coloured and no odour. more pus and mø - risk of HUS
Ameobic - 6-8 loose movement but copious amounts of stool which is dark with a foul odour. more eosinophils and red cell clumps.
What is Leprosy?
Also known as Hansens disease.
A chronic infection with mycobacterium leprae characterised by one or more of the following:
- Hypopigmented or erythematous skin lesions with loss of sensation
- Peripheral nerve damage -> loss of sensation
- Muscle weakness in hands, feet or face
- Paraesthesia (tingling of hands and feet)
What is cholera?
A secretory diarrhoeal illness caused by the gram -ve comma shaped bacilli vibrio cholerae bacteria.
Cholera Enterotoxin stimulate continuous stimulate of adenylate cyclase causing water to be secreted from the intestinal cells in to the lumen and then salt follows. (small bowel)
Shock, dehydration, vomiting, RICE WATER STOOL*, circulatory collapse.
Give IV fluids
What is meningitis?
Inflammation of the meninges (± cerebrum is encephalitis)
Usually a triad: Fever, nuchal rigidity, altered mental state
Meningiococcal rash (non-blanching petechial rash)
(Confusion indicated encephalitis)
What bacteria can cause meningitis?
Nesseria meningitdis - Gram negative diplococci
Streptococcal pneumonia - Gram positive diplococci
Listeria monocytogenes - Gram positive rod
70% of patients with streptococcal pneumoniae caused meningitis have underlying disease, give some examples.
Middle ear disease Head injury (CSF leak) Alcohol Neurosurgery Immunocompromised
What signs are diagnostic of meningitis?
Kernig’s sign - Inability or reluctance to fully extend the knee when the hip is flexed at 90 degrees.
Brudzinskis sign - Spontaneous flexion of the hips when the neck is passively flexed. Examines nuchal rigidity
When might a LP be contraindicated?
GCS=12, papilloedema, immunocompromised, seizures, Coagulopathy (INR>/=1.5), Infection if LP site or abscess, Severe sepsis, respiratory or cardiac compromise
From CSF results how can you tell a bacterial and viral meningitis apart?
Bacteria: Neutrophils - Raised protein, reduced glucose. Cloudy
Viral - Lymphocyes - Raised protein, normal glucose. Clear
How would you treat bacterial meningitis?
N. meningiococcal - IV Ceftriaxone 2g/12hours for 5-7 days
S. pneumococcal - IV Ceftriaxone 2g/12h for 10-14 days
L. monocytogenes - IV Amoxicillin 2g/4h for 21 days
If penicillin allergy - Chlorampenicol (for ceftriaxone) and Co-trimoxazole (for amxo)
PLUS
IV dexamthasone** 10mg/6hr for 4 days
What prophylaxis can you give for someone in contact with someone with meningitis?
Rifampicin or Ciprofloxacin
What are some complications of meningitis?
Purpura fulminants
Deafness (CN palsies)
Seizures
What is progressive multifocal leukoencephalopathy?
Progressive motor dysfunction
Clumsiness, trouble speaking, Partially blind, AMS
Due to JC virus
In immunocompromised, HIV, anti-TNF, transplant
What is Tuberculosis?
A bacterial infection passed on by inhaling tiny droplets from the cough or sneeze of an infected person. Bacilli - Mycobacterium tuberculosis
What is latent TB?
You have the bacteria but it is dormant, surrounded by immune cells in an ceaseating granuloma. It is not transmissible in this stage
How might TB present?
90% have pulmonary TB: Haemoptysis, SoB, cough, sputum
CONSTITUTIONAL SYMPTOMS V IMPORTANT**
Weight loss, night sweats, malaise, loss of appetite, fever and chills, lymphadenopathy, fatigue
What are some high risk factors for TB?
Silicosis, AIDS or HIV and not on antiviral therapy, CKD requiring dialysis, TNF inhibitors, immunosuppressed
What CXR findings are shown in TB?
Consolidation, cavitation, fibrosis, calcification
What is shown on a TB histology?
Caseating granuloma
How would you investigate for TB?
- Mantoux test/ tuberculin skin test (TB antigen injected intradermally, strong +ve indicates active TB. +ve if immunity or had BCG)
- If this is +ve - Interfernon gamma release assay
- If CXR suggests TB - >/=3 sputum samples with at least one form early morning before starting treatment. Use for MC&S for Acid fast bacillus resistance
- Quantiferon TB gold - measures delayed hypersensitivity developed after contact with TB
- PCR and culture of fluids if not pulmonary
What treatment is used in TB?
2 months of all 4 drugs then 4 more months of RI
RIPE
Rifampicin - 600mg PO 3x wk
Isoniazid - 15mg/kg PO 3x wk - give with pyridoxine 10mg/24h for peripheral neuropathy
Pyrazinamide - 2.5g PO 3x wk
Ethambutol - 30mg/kg PO 3x wk
List the SE of the TB drugs.
Rifampicin - Orange bodily secretions, Increases LFTs, decreases platelets. Interfere with warfarin and OCP
Isoniazid - Vit B6 def (dermatitis), peripheral neuropathy, increases LFTs
Pyrazinamide - gout, raised lactate, arthralgia, hepatitis
Ethambutol - Toxic optic neuropathy
What are teh 4 populations of cells in TB and which antibiotic targets them?
Actively growing - isoniazid
Dormant
Semi-dormant but inhibited by an acid environment - pyrazinamide
Semi-dormant with spurts of active metabolism - rifampicin
Multi-drug resistant TB is resistant to isoniazid and rifampicin, what treatment can u give?
Pyrazinamide + 4 second line agents
- Fluoroquinolone
- Injectable - amikacin, kanamycin
- Ethionamide
- cycloserine
What does AIDS mean?
Its a combination of potetially life-threatening infections and cancers that develop when someones immune system has been damaged by HIV
How might you diagnose HIV?
Viral load - aim of tx is to keep it at an undetectable level - <200 copies /mL
CD4 count - Lower means you are at risk of opportunistic infection. <200 cells/mm3 is bad.
If you have an undetectable viral load for 6 months and continue with treatment you are not at risk of passing it on during sex