Micro Flashcards
Adult onset Still’s disease and MAS
Very high ferritin
EBV Serology
PCR is pointless in healthy person
Viral Capsid Antigen (VCA) - with symptoms
EP Nucleic Antibody (EBNA) - later
Bartonella
Cat scratch illness, regional adenopathy, sometimes PUO
Sometimes HSM and haem abnormalities.
Diagnosis by serology
Brucella
Must have exposure (farm animal contact or unpasteurised milk)
LFTs rise. Diagnosis by serology.
PET CT
All activated leukocytes demonstrate increased FDG uptake
IGRA
Test for latent TB
TTE (transthoracic echocardiogram)
Useful in IE
5-10% have negative BCs because of abx or Fastidious organisms (HACEK) or Aspergillus, Bartonella, Brucella, Coxiella, Rickettsia, Mycobacteria, Nocardia, Chlamydia
(IV drug user may take abx themselves and not tell you – linezolid)
HACEK
Haemophilus, Aggregatibacter
Cardiovacterium
Eikenelia
Kingella
Dukes Criteria
2 major or 1 major + 3 minor criteria
Major
Persistent bacteraemia (>2 BC pos)
Echocardiogram: vegetation
Positive serology for Bartonella, Coxiella or Brucella
Minor Predisposition (murmur, IVDU) Inflammatory markers (fever , CRP high) Immune complexes: splinters, RBCs in urine Embolic phenomena: Janeway lesions, CVA Atypical echo 1 positive BC
Giant Cell arteritis
>50y Jaw claudication Headache ESR >45 High risk of sight impairment / stroke Temporal biopsy gold standard
Adult onset Stills disease
Salmon pink rash (macular papular)
Very high ferritin
Which of the following malignancies is least likely to be associated with fevers
Lymphoma Renal cell carcinoma Leukaemia Hepatocellular carcinoma Adenocarcinoma of the lung
Adenocarcinoma of the lung
African tick bite fever
Ricketssia
Lyme disease, ticks
Borrelia
Cyclist, Richmond, insect bite
Borrelia Lyme disease (tick bites)
safari, TseTse fly, Winterbottom’s sign
Trypanosoma brucei
- sleeping sickness
Goat, Unpasteurized milk, back pain + discitis
Brucellosis
Comma, oxidase +ve, bloody foul diarrhoea, a/w Guillain-Barre, Reiters
Campylobacter
Slow onset fever, constipation, bradycarida, splenomegaly, rose spots
Salmonella typhi or paratyphi
Non-bloody diarrhoea, poultry/eggs/meat
Salmonella enteritedes
Bartonella henselae – cat scratch disease
Macule at site of innoculation
Becomes pustular
Regional adenopathy
Progress to systemic symptoms in 14%
Mx: erythromycin, doxycycline
Bartonella henselae – bacillary angiomatosis
Occurs in immunocompromised - HIV
Skin papules
Disseminated multi-organ and vasculature involvement
Mx: Erythromycin, Doxycycline PLUS rifampicin
Cats/ undercooked meat, obligate intracellular parasite
Toxoplasmosis (T. gondii)
toxoplasmosis features
Fever Adenopathy Still-birth Progressive visual, hearing, motor, & cognitive issues Seizures (immunocompromised) Neuropathies (immunocompromised)
toxoplasmosis management
Spiramycin
Pyrimethamine plus sulfadiazine – don’t give to pregnant woman – treatment for immunosupressed head toxo
anti-O-polysaccharide Ab, normal WCC
Brucellosis
Brucellosis treatment
Doxycycline PLUS
Gentamicin OR Rifampicin
Back pain, undulant fever (peaks in evening), focal abscess (psoas)
Brucellosis
Rhabdo virus, warm blooded animals, Negri bodies, fatal encephalitis
Rabies
Fever, polyarthralgia, maculopapular rash becomes purpuric, may progress to endocarditis, transmitted by rats
Rat bite fever
Spirillosis or streptobacillosis
mx: penicillin
Natural reservoir of influenza A viruses
Ducks
Influenza virus infection causes respiratory disease because
influenza virus requires activation by host cell proteases that are only expressed in the respiratory tract
Haemagglutinin must be cleaved in two in order for fusion event (release genome) to take place
Requires human airway tryptase
Some avian viruses have mutations which allow them to be cleaved in any part of the body = very pathogenic
Binds sialic acis on host cell allowing entry of virus
Haemagluttinin
Cleaves sialic acid residues, exposes host cell receptors, disrupts mucin barrier
Neuroaminidase
Gene in all human influenza viruses
PB2 627K
Avian virus gene
PB2 627E
Human H5N1 and H7N9 (avian flu) infections associated with severe disease gene mutation
PB2 E627K mutation - allows avian virus to infect humans
Lysine residue in a PB2 gene = hallmark
Features of HA and NA that affect influenza transmission
Receptor binding - HA adapted to binding
Virion stability - HA adapted to fusion at lower pH (mucus is acidic)
NA stalk length
Swine flu
pH1N1
similar to H1N1 in 1920 - people alive at this time were relatively protected
severe outcomes from pH1N1
High dose, route of exposure
Mutant virus (D225G mutation)
Bacterial superinfection
Co morbidity: Asthma, pregnancy, obesity, diabetes
Genetic predisposition: IFITM3 mutation; ethnic bias
IFITM3
Gene normally protective against viral infection
Loss = increase susceptibility
Higher prevalence in China and Japan
Antiviral for flu - Targets M2 ion channel
Amantadine – old fashioned drug
Single amino acid mutation in M2 (S31N) renders virus resistant
Does not work against influenza B or pH1N1 or seasonal H3N2
Antiviral for flu - Neuraminidase inhibitors
Tamiflu (oseltamivir) oral – largely available in UK
Relenza (zanamivir) inhaled or iv formulation
Peramivir iv
Antiviral for flu - Polymerase inhibitors
Favipiravir (licensed in Japan excluding pregnant women - teratogenic)
Baloxavir (licensed in Japan)
Currently license in Japan (particularly in pandemic)
Seasonal Influenza vaccine
A purified fraction containing HA and NA of an inactivated virus
Given to at risk groups
Short term strain specific immunity
Seasonal Influenza vaccine - children
Live attenuated vaccine, also tri or quadrivalent
Cold adapted virus limited to URT (sprayed up nose)
Broader immunity including cellular response
Malaria - P. Falciparum
Length of rhythm - 48h (tertian)
Blood film = young trophozites (rings), crescent-shaped gametocytes
Malaria - P. Vivax
Length of rhythm - 48h
Chronic liver stage (hypnozites)
Blood film = Schuffners dots, >20 merozites/ schizont
Malaria - P. Ovale
Length of rhythm - 48h
Chronic liver stage (hypnozites)
Blood film = Schuffners dots
Malaria - P. Malariae
Length of rhythm - 72h (quartan)
Benign
Similar morphology to P. Knowlesi
Malaria - P. Knowlesi
Behaves like falciparum
Increasing incidence in SE Asia
1-2 cases/year UK
Malaria treatment - non-falciparum
Chloroquine (3d)
Primaquine (14 days) - for liver stage
Complications - rare (splenic rupture = fatal)
Malaria treatment - falciparum
Mild: oral
First line = Malarone (Atovoquone/ Proguanil)
Severe (>2% parasitaemia)
IV Artesunate
Dengue Fever
Vector - Aedes mosquito
Flavivirus
Short incubation, urban disease
Usually mild/ self limiting - fever, rash, arthralgia
Already infected with different serotype = increased risk of dengue haemorrhagic fever and shock (bleeding, complications)
Tx - supportive, no specific antiviral tx
Typhoid
Salmonella Typhi or Paratyphi
Typhoid Clinical features
Insidious onset (incubation 7-18d) High, prolonged fever Headache Rose spots (minority) Constipation Complications - GI bleeding, perforation, encephalopathy
Typhoid Tx
Empiric ceftriaxone (2g IV OD) Azithromycin (500mg BD 7days)
Mononucleosis
EBV, CMV Tonsillar enlargement with exudates atypical lymphocytosis monospot IgM + EBV/CMV
Ricketssial Disease
obligate intracellular bacteria
fever, headache, myalgia +/- eschar
vectors - ticks/ lice/ mites
tx - doxyxycline
Entameoba Histolytica
MSM food, water, soil motile trophozite in stool - 4 nuclei flask-shaped ulcer dysentery, wind, tenesmus wt loss RUQ pain (liver anscess) tx: metronidazole
Giardia lamblia
travellers/hikers/MSM/mental hospitals
pear shaped trophozite in stool - 2 nuclei
malabsorption - foul-smelling non-bloody diarrhoea
ELISA string test
tx: metronidazole
Cryptosporidium parvum
jejunum severe diarrhoea immunocompromised oocytes in stool tx: paromomycin
Kinyoun acid fast stain
tests for oocytes in stool in Cryptosporidium parvum
Katayama fever
acute schistosomiasis
eosinophilia a/w invasive helminth
Cholera toxin mechanism (secretory diarrhoea)
cAMP opens Cl- channel on enterocytes
Efflux Cl to lumen; loss of H20 and electrolytes
Superantigens mechanism (diarrhoea)
Directly bind T cell receptors and MHC molecules
Outside peptide binding site
» massive cytokine production (CD4+)
Systemic toxicity and suppression of adaptive immune response
S. Aureus food poisoning
Shed via skin into food Virulence factor - Protein A Catalase, coagulase +ve, clusters Beta haemolytic Vomiting, watery diarrhoea, non-bloody diarrhoea Tx: self limiting
Bacillius cereus
reheated rice - spores superantigen short incubation period - 4hrs watery non bloody diarrhoea Tx: self limiting
Clostridia Botulinum
Canned food - honey in children, beans in students
Blocks Ach release - descending paralysis (botulinism)
Tx: antitoxin
Clostridia Perfringens (food poisoning)
reheated food/ meat
enterotoxin/ super antigen acts on small bowel
incubation 8-16h
watery diarrhoea, cramps, little vomiting (lasts 24h)
prolonged - gas gangrene - gut necrosis?
Clostridia Difficile
anaerobe
abx related colitis (cephalosporins/ fluorquinolones)
pseudomembrnaous colitis
Tx: metronidazole (stop causative abx)
Listeria monocytogenes
febrile gastroenteritis Beta haemolyitc Aesculin positive with tumbling motility refrigerated food/ unpasteurised dairy/ veg perinatal infection, immunocompromised Tx: ampicillin
ETEC
toxigenic
travellers diarrhoea
EIEC
invasive dysentary
EHEC
haemorrhagic
O157:H7 shiga-like verocytotoxin causes HUS
petting zoo - very unwell (ICU)
EPEC
infantile diarrhoea (P for paeds)
Shigella
distal ileum and colon
Inflammation, fever pain, bloody diarrhoea
Shiga enterotoxin
Yersinia enterocolitis
Mesenteric adenitis w necrotising granulomas
A/w reactive arthritis and erythema nodosum
Food contaminated w domestic animal excreta
Virbriosis Cholera
rice water stool
cAMP binds Cl channels - increas Cl in lumen (loos H20/ electrolytes)
massive diarrhoea without inflammation
supportive tx
Vibriosis Parahaemolyticus
Ingestion of raw undercooked seafood (Japan) 3/7 diarrhoea self limiting salty agar tx: doxycycline
Vibriosis vulnificus
cellulitis in shellfish handlers
tx: doxycycline
HIV - fatal septicaemia w D+V
Campylobacter jejuni
curved/comma/ S shaped unpasteurised milk, food eg poultry bloody foul smelling diarrhoea prodrome: headache fever, cramps oxidase +ve, motile, sensitive to nalidixic acid
A/w Guillain-Barre, reactive arthritis (Reiter’s)
Listeria
watery diarrhoea, little vomiting
perinatal infection, immunocompromised
febrile gastroeneteritis (outbreaks)
unpasteurised dairy, refrigerated food, vegetables
Norovirus
adult outbreaks
vomiting
Rotavirus
dsRNA “wheel like”
<6yrs
secretory, diarrhoea no inflammation
watery diarrhoea by stimulation of eneteric nervous system
exposure to natural infection twice = life long immunity
Adenovirus
types 40, 41
cause non bloody diarrhoea in <2yrs
Sporadic CJD
80%
Somatic PRNP mutation or spontaneous conversion
Rapid progressive dementia (myocoluns, cortical blindness, LMN signs)
45-75y
Survival - 6m
Sporadic CJD Investigations
EEG - periodic triphasic changes
MRI - Highlighting basal ganglia (may be normal)
14-3-3 protein +ve
129 codon MM (most)
Post mortem - spongiform vacuolation, PrP amyloid plaques
Variant CJD
Acquired - exposure to Bovine Spongiform Encephalitis
Anxiety/paranoia/hallucinations + neuro symptoms
later - chorea, ataxia, dementia
30yrs
Survival - 14m
Variant CJD Investigations
EEG - non specific slow waves
MRI - posterior thalamus (pulvinar sign)
129 codon MM (all)
Post mortem - PrPsc 4t detectable in CNS, florid plaques
Iatrogenic CJD
Inoculation - surgery
Progressive ataxia
Later - dementia and myoclonus
Progression - depends on route of inoculation (CNS - fastest)
Kuru CJD
Acquired CJD
Cannibalism
Progressive cerebellar syndrome
Death within 2y
Gerstmann Straussler-Scheinker Syndrome
Inherited CJD Autosomal dominant 20-60y Survival - 5y Dysarthia - progresses to cerebellar ataxia (+ dementia)
Fatal Familial Insomnia
Inherited CJD Inherited CJD Autosomal dominant Insomnia + paranoia - hallucinations + wt loss Mute Survival 1-18m
Inherited CJD investigations
MRI - high signal in basal ganglia
129 codon homozygosity - earlier onset
