investigation of specific infections Flashcards
what is the main function of testing?
to identify the cause, treatment and risk of the patient
what is the issue with testing?
no test is infallible - there will be a positive and negative error rate for all
when should you not do a test?
if it does not add to the management or prognosis
what types of sampling are there?
local and general
what is local sampling?
it is sampling from the source of infection - assist with the diagnosis and identify appropriate treatment
what is general sampling?
it is part of sepsis investigation and includes blood cultures such as FBCs, U&Es, LFTs, clotting and CRP
what is meningitis?
it is inflammation of the meninges that is caused by bacteria, viruses, mycobacteria, fungi and parasites
how would you identify meningitis?
through a lumbar puncture to sample CSF, blood cultures - CRP, glucose, LFTs, U&Es and FBCs, blood culture for bacterial PCR for N meningitidis or S pneumoniae, and CSF cryptococcal antigen or TB culture PCR in immunosupressed
what is encephalitis?
it is inflammation of the brain that is usually viral - herpes
how would you test for encephalitis?
CSF requesting viral PCR specifically
`what is the cause of brain abscesses?
there is a wide aetiology including bacteria, mycobacterial, fungal and parasitic
what can help to identify brain abscess?
the history - ear, sinuses, blood and post op
what should be discouraged in identifying brain abscess?
lumbar puncture as it is rarely positive and high risk
what should be done to identify brain abscess?
local sampling
pus - biopsy or drainage - gram, culture, sensitivity and PCR
blood cultures
what are the characteristics of healthy CSF?
the opening pressure should be 5-20 cmH20
the appearance should be clear
the WBC count should be <3x10^6/L
there should not be any cell differentiation
the protein should be from 0.2-0.5g/L
the glucose in CSF:blood should be 0.6
what are the characteristics of CSF in viral infection?
the opening pressure should be normal or slightly raised
the appearance should be clear
the WBC count should be <1000x10^6/L
the cell differentiation should be mainly lymphocytes
the protein should be <1g/L
the glucose in CSF: blood should be >0.6
what are the characteristics of CSF in bacterial infection?
the opening pressure >30cmH20 the appearance of CSF turbid the WBC count >500x10^6/L the cell differentiation is mainly polymorphs the protein >1g/L the glucose in CSF:blood <0.4
what are the characteristics of CSF in fungal and TB infection?
the opening pressure if variable - however if it is a crypto fungal infection it is greatly increased
the appearance of CSF is variable
the WBC is variable
the cell differentiation is mainly lymphocytes
the protein is <0.5g/L
the glucose in CSF:blood is less than 0.4
what are the two most common infections of the ear?
acute otitis media and externa
how will you manage media?
clinical diagnosis - viral or bacterial
if the ear drum is perforated then send a pus sample off
how will you manage externa?
ear swab to identify the cause and sensitivity
what is the most common nose infection?
sinusitis/rhino-sinusitis
majority are viral or secondary bacterial
caused by upper respiratory tract flora
what is the management if suspected sinusitis?
swab in all cases - except severe as this is unhelpful
severe cases - pus from operative sinus lavage and FBC and blood cultures
what are the most common throat infections?
pharyngitis - viral and bacterial sore throat
diphtheria