infectious disease Flashcards
how long does HIV seroconversion take?
It typically occurs 3-12 weeks after infection
what are the features of acute schistosomiasis syndrome (katayama fever)?
fever
urticaria/angioedema
arthralgia/myalgia
cough
diarrhoea
eosinophilia
what is the treatment for acute schistosomiasis
praziquantel
what are the factors which reduce vertical transmission of HIV?
- maternal antiretroviral therapy
- mode of delivery (caesarean section)
- neonatal antiretroviral therapy
- infant feeding (bottle feeding)
what is the monod sign?
a mass within a cavity with a ‘Monod sign’ (the crescent of the surrounding air
Angola is an area with a high prevalence of TB and the chest x-ray findings are typical of aspergilloma
what is the CNS lymphoma associated with?
EBV - epstein barr virus
what is the treatment for CNS lymphoma?
steroids ( may significantly reduce tumour size)
chemotherapy (methotrexate)
what is the pathology behind progressive multifocal leukoencephalothy?
due to infection of oligodenrocytes by JC virus ( a polyoma DNA virus)
-widespread demyelination
what is the differene on thallium SPECT scan for toxoplasmosis and lymphoma?
Thallium SPECT negative - toxoplasmosis
Thallium SPECT positive - Lymphoma
what is lemierre syndrome?
Infectious thrombophlebitis of the internal jugular vein.
what is the cause of peritonsillar abscess?
Secondary to a bacterial sore throat caused by Fusobacterium necrophorum leading to a peritonsillar abscess
combination of spread of the infection laterally from the abscess and compression lead to thrombosis of IJV
what are the features of lemierre’s syndrome?
Patients will present with a history of bacterial sore throat followed by neck pain, stiffness and tenderness (may be mistaken for meningitis) and systemic involvement (fevers, rigors, etc)
Septic pulmonary emboli may also occur
What are the features of Disseminated gonococcal infection ?
- tenosynovitis
- migratory polyarthritis
- dermatitis (lesions can be maculopapular or vesicular)
what are the features of congenital CMV infection?
- growth retardation,
- pinpoint petechial ‘blueberry muffin’ skin lesions
- microcephaly
- sensorineural deafness,
- encephalitiis (seizures)
- hepatosplenomegaly
what is the typical pattern of presentation of yellow fever?
Yellow fever typically presents with flu like illness → brief remission→ followed by jaundice and haematemesis
The first stage classically causes a non-specific illness which is often described as ‘flu-like’ with fever, malaise, nausea, myalgia and headache. This stage is due to the circulating virus in the bloodstream (viraemic stage).
There is then a recovery stage when the viraemia clears
Around 15% of patients progress after about 3-7 days after the onset of symptoms which presents with fever, nausea and vomiting, acute kidney injury, hepatitis with jaundice, and haemorrhage.
what is the cause of spread of yellow fever?
zoonotic infection: spread by Aedes mosquitos
incubation period = 2 - 14 days
what vaccines are contrindicated in patients with HIV?
Cholera CVD103-HgR
Influenza-intranasal
Poliomyelitis-oral (OPV)
Tuberculosis (BCG)
what is seen under the microscope in a diagnosis of BV?
gram positive coccobacilli
what are the malignancies associated with EBV infection?
- Burkitt’s lymphoma*
- Hodgkin’s lymphoma
- nasopharyngeal carcinoma
- HIV-associated central nervous system lymphomas
how is lassa fever contracted?
Lassa fever is contracted by contact with the excreta of infected African rats (Mastomys rodent) or by person-to-person spread
what is the cause of leprosy?
Granulomatous disease primarily affecting the peripheral nerves and skin. It is caused by Mycobacterium leprae.
what are the features of leprosy?
- patches of hypopigmented skin typically affecting the buttocks, face, and extensor surfaces of limbs
- sensory loss
what is the treatment for leprosy?
rifampicin, dapsone and clofazimine
what UTI causes present with nitrate negative, leucocyte positive urine dip?
Gram negative organisms test positive on the nitrite test as they convert nitrates to nitrites for energy. Gram positive organisms are unable to reduce nitrate to nitrite and therefore, test negative
what UTI causes present with nitrate negative, leucocyte positive urine dip?
Gram negative organisms test positive on the nitrite test as they convert nitrates to nitrites for energy. Gram positive organisms are unable to reduce nitrate to nitrite and therefore, test negative
what is the treatment of pneumocystis jiroveci?
- co-trimoxazole
- In severe cases - IV pentamidine
- Steroids if hypoxic (if pO2 < 9.3kPa - they reduce the risk of respiratory failure)
what are the false positive causes of non-treponemal tests?
pregnancy
SLE, anti-phospholipid syndrome
tuberculosis
leprosy
malaria
HIV
what are the different tests you can do for testing for syphilis?
Treponemal specific testing - Tp-EIA trep.pallidum enzyme immunoassay
Non-treponemal tests - VDRL, RPR - rapid plasma reagin
what does it mean when there is a Positive non-treponemal test + negative treponemal test?
consistent with a false-positive syphilis result e.g. due to pregnancy or SLE
what does it mean when there is a Negative non-treponemal test + positive treponemal test ?
successfully treated syphilis
what are the list of bacteriostatic medications?
CORe - ChlORamphenicol
Medical - Macro
TRAinee - TeTRAcycline
to
SPecialty - SulPhonamide
TRaInee - TRImethoprim
what is the cause of rocky mountain spotted fever?
Rickettsia Ricketsii - ticks
What is the cause of Q fever?
Coxiella burnetti
what is the general pattern of HIV?
NRTIs end in ‘ine’
Pis: end in ‘vir’
NNRTIs: nevirapine, efavirenz
what is the organism causing disease in cat scratch disease?
Gram negative rod Bartonella henselae
Features
-fever
- history of a cat scratch
- regional lymphadenopathy
- headache, malaise
what are the features of dengue fever?
Retro-orbital headache, fever, facial flushing, rash, thrombocytopenia in returning traveller → ?dengue
dengue virus is a RNA virus of the genus Flavivirus
transmitted by the Aedes aegypti mosquito
incubation period of 7 days
what is the features of severe dengue?
- Disseminated intravascular coagulation (DIC) resulting in:
thrombocytopenia
spontaneous bleeding - 20-30% - dengue shock syndrome
what are the investigations results of dengue?
- Typically blood results: leukopenia, thrombocytopenia, raised aminotransferases
- Diagnostic tests: serology
nucleic acid amplification tests for viral RNA
NS1 antigen test
what are the gram negative cocci which cause pneumonia?
Moraxella catarrhalis - Gram-negative cocci
what organism is isolated from animal bites?
Pasteurella multocida
what medication is used in animal bites if co-amoxiclav cannot be taken due to allergies?
doxycycline + metronidazole
what is immune reconstitution inflammatory syndrome?
Immune reconstitution inflammatory syndrome can occur in HIV positive patients when starting anti-retrovirals; this is an immune phenomenon that results in the clinical worsening of a pre-exisiting opportunistic infection
how does botulinum toxin work?
irreversibly blocks the release of acetylcholine
what are the features of bolutism?
- patient usually fully conscious with no sensory disturbance
- flaccid paralysis - descending
- diplopia
- ataxia
- bulbar palsy
what is the cause of lyme disease?
Borrelia burgdorferi and is spread by ticks.
what is the typical rash seen in lyme disease called?
‘bulls-eye’ rash is typically at the site of the tick bite
typically develops 1-4 weeks after the initial bite but may present sooner
what are the cardiovascular features of lyme disease?
- heart block
- peri/myocarditis
what is seen in hepatocytes in yellow fever?
Councilman bodies (inclusion bodies) may be seen in the hepatocytes
what are the side effects of trimethoprim?
- myelosupression
- transient rise in creatinine -
trimethoprim competitively inhibits the tubular secretion of creatinine resulting in a temporary increase which reverses upon stopping the drug
trimethoprim blocks the ENaC channel in the distal nephron, causing a hyperkalaemic distal RTA (type 4). It also inhibits creatinine secretion, often leading to an increase in creatinine by around 40 points (but not necessarily causing AKI)
what is the cause of scrub typhus?
caused by Orientia tsutsugamushi
reservoir/vector: harvest mites on humans or rodents
what is the difference between scrub typhus and anthrax?
A black eschar with oedema is characteristic of anthrax. There are occasional outbreaks in central Asia and Africa (ref: WHO). The cutaneous form is the most common, caused by handling infected animals resulting in farmers being at risk. In this case, anthrax would need to be considered and ruled out first.
Scrub typhus would also give an eschar but would be accompanied by other symptoms such as muscle pain, cough, and GI upset.
what is the treatment for scrub typhus?
doxycycline
what are the features of african typanosomiasis or sleeping sickness?
- trypanosoma chancre- painless subcutaneous nodule at site of infection
- intermittent fever
- enlargement of posterior cervical lymph nodes - winterbottom sign
- central nervous system involvement : somnolence, headaches, mood changes
what is the treatment for african trypanosomiasis?
- IV pentamidine or suramin : early disease
- IV melarsoprol - later disease
what are the features of Chagas diseas?
Acute phase -
cutaneous manifestation -
1. chagoma (an erythematous nodule at site of infection)
2. Romana sign - unilateral painless oedema of the eyelid and periocular tissue
chronic phase:
1. Chagas cardiomyopathy - biverticular dilative cardiomyopathy
2. Gastrointestinal tract - achalsia - damage to the submucosal and myenteric plexus
what is the management of american trypanosomiasis?
- Acute phase - benznidazole or nifurtimox
what is the cause of leptospirosis?
spirochaete Leptospira interrogans
spread by contact with infected rat urine.
what are the features of leptospirosis?
Early phase:
- fever
- flu like symptoms
- subconjunctival suffusion/ haemorrhage
Second immune phase (Weil’s disease)
- AKI (seen in 50% patients)
- hepatitis: jaundice, hepatomegaly
- aseptic meningitis
what is the most common cause of larva migrans?
Ancylostoma braziliense
what is the treatment for plasmodium ovale and vivax?
patients with ovale or vivax malaria should be given primaquine following acute treatment with chloroquine to destroy liver hypnozoites and prevent relapse
what is the cause of leprosy?
Mycobacterium leprae
what are the features of leprosy?
- patches of hypopigmented skin typically affecting the buttocks, face, and extensor surfaces of limbs
- sensory loss
what is the treatment for leprosy?
rifampicin, dapsone and clofazimine
what are the features of leprosy in patients with low degree of cell mediated immunity?
lepromatous leprosy
- extensive skin involvement
- symmetrical nerve involvement
what are the features of leprosy in patients with high degree of cell mediated immunity?
- limited skin disease
- assymmetric nerve involvement - hypesthesia
- hair los
what is the mode of action of ribavrin?
Guanosine analog which inhibits inosine monophosphate (IMP) dehydrogenase, interferes with the capping of viral mRNA
what vaccines should be avoided in immunocompromised ?
You Musn’t Prescribe BCG Incase They RIP Stat= Yellow fever, MMR, Polio, BCG, Influenza, Typhoid, Rotavirus, Shingles’
what is the screening test used for HIV?
HIV-1/2 Ab/Ag Immunoassay
what are the conditions where tetracyclines (doxy) are used?
acne vulgaris
Lyme disease
Chlamydia
Mycoplasma pneumoniae
what are the side effects of tetracyclines?
- discolouration of teeth: therefore should not be used in children < 12 years of age
- photosensitivity
- angioedema
- black hairy tongue
what is the treatment for lyme disease for a pregnant woman?
amoxicillin
