Theme 3 Lecture 16: Investigations of specific infections Flashcards
What is meant by the specificity of a test?
the proportion of people without the disease who have a negative test
What is meant by the sensitivity of a test?
the proportion of people with the disease who have a positive test
How do you work out the sensitivity of a test?
true positive / (true positive + false negative)
How do you work out the specificity of a test?
true negative / (true negative + false positive)
What is M,C & S?
- Microscopy - cell count, gram stain, direct visualisation of organisms
- Culture - difficult culture media, slopes
- Sensitivity - EUCAST dict testing, strips
In a blood test for detection of immunity, what does the presence of IgG show?
previous infection
In a blood test for detection of immunity, what does the presence of IgM show?
current infection (or reactivation)
What is the pathology of meningitis?
inflammation of the meninges/ brain parenchyma
What is the most frequent cause of meningitis and encephalitis?
viral infection - HSV most likely
Would you perform an LP on a patient with a suspected brain abcess?
no because of increased intracranial pressure
What are the symptoms of upper respiratory tract infections?
cold, sore throat, ear infections
What are the symptoms of lower respiratory tract infections?
bronchitis, pneumonia
What are the symptoms of community acquired pneumonia?
shortness of breath, cough, sputum, fever
-changes on chest X-ray confirm pneumonia
What is atypical pneumonia?
- can present with some unusual symptoms - arthralgia, myalgia
- if patient has failed usual antibiotic treatment or radiological features are unusual
Which viruses can we test for using PCR?
- COVID-19
- influenza A/B
- parainfluenza
- RSV
- adenovirus
- metapneumovirus
- rhinovirus
What are: 1. typical pneumonia 2. atypical pneumonia 3. viral pneumonia caused by?
- bacterial infection
- bacterial infection
- viruses
Which tests tell us if a patient has had TB in the past, even if they are not showing symptoms?
- mantoux
- IGRA’s
- T-spot/ quantiferon
What is the mode of transmission of TB?
Requires exposure then reactivation
Which fungal infections are common in an immunocompromised host?
- aspergillus fumigatus
- crytococcosis
- mucormycosis
Which bacterial infections are common in an immunocompromised host?
nocardia sp
gram negatives - resistant
Name 3 localised skin and soft tissue infection?
- impetigo - spots on face and back
- erysipelas - deep tissue infection
- cellulitis
Name 2 severe/extensive skin and soft tissue infection?
- necrotising fasciitis
- diabetic foot infection
What are the 4 types of urinary tract infections?
- lower UTI
- upper UTI
- prostatitis
- epididymo-orchitis
Which 3 antibiotics increase resistance?
- amoxicillin
- trimethoprim
- nitrofurantoin
What is prostatitis?
- bacterial inflammation in the prostate
- suspect in men with recurrent UTIs
What is epididymo-orchitis?
inflammation of the epididymis and/or testicles
What are some examples of GI tract infections?
- infectious diarrhoea - viral gastroenteritis, bacterial, parasitic infection, C-difficile
- liver abscess
- biliary tract infection
- diverticulitis
What are some bacterial causes of community acquired gastroenteritis?
salmonella sp sigella sp E.coli campylobacter sp C.difficile
What are some viral causes of community acquired gastroenteritis?
rotavirus, norovirus
What are some parasitic causes of community acquired gastroenteritis?
cryptosporidium, giardia
What is a self-limiting disease?
a disease that can resolve without treatment
What are the signs of diverticulitis?
fever
abdo pain
diarrhoea
How can you test for HIV?
HIV Ab/Ag combined test
HIV PCR
how do we test for Hep C?
- look for antibody to see if patient has been exposed to virus
- then do PCR if antibody test is +ve
- to see if they have active infection
What is the positive predicted value?
the probability that people with a positive test truly have the disease
What is the negative predicted value?
the probability that people with a negative test truly don’t have the disease
Name an organism that is a cuase of ‘atypical pneumonia’
legionella pneumonphila
What are the most appropriate tests for a patient with suspected TB?
Chest X-ray and 3 sputum samples for AAFB MC&S
What tests would you perform if a patient presents to A&E with headache, neck stiffness, fever, photophobia
blood cultures, throat swabs (can pick up neisseria meningitidis), CSF, blood for PCR
How do we diagnose UTIs?
- go off symptoms
- antibiotics are not necessary if there are no symptoms
