ID Flashcards
What is seen on CSF analysis in bacterial meningitis?
Cloudy appearance
Low glucose (50% plasma)
High protein
10-5000 PMNs
What is seen on CSF analysis in viral meningitis?
Glucose 60-80% plasma
Normal/high protein
15-1000 lymphocytes
What is seen on CSF analysis in tuberculous meningitis?
Slightly cloudy, fibrin web
Low glucose (50% plasma)
High protein
30-300 lymphocytes
What is the treatment of TB meningitis?
Usual therapy + prednisolone
12 months
What is the most common cause of viral meningitis?
Enterovirus e.g. Coxsackie
Which lobes does HSV-1 encephalitis affect?
Temporal and frontal
How is HSV encephalitis diagnosed?
LP - viral CSF picture
PCR for HSV
CT: medial temporal and inferior frontal petechial haemorrhages
EEG: lateralised periodic discharges at 2Hz
What is the cause of Japanese encephalitis and how is it transmitted?
Flavivirus
Transmitted by culex mosquitos which breed in rice paddy fields
Reservoir hosts - aquatic birds
Amplification hosts - pigs
What are the symptoms of Japanese encephalitis that differentiate it from other forms of encephalitis?
Parkinsonian features
Acute flaccid paralysis
What type of virus is hepatitis B?
dsDNA hepadnavirus
Which is the first serological marker to appear in hepatitis B and indicates ongoing infection?
HBsAg
What are the characteristics of anti-HBs?
Implies immunity - exposure or immunisation
Negative in chronic disease
What are the characteristics of anti-HBc?
Present for around 6 months; implies previous or current infection
Negative if immunised (c=caught)
What hepatitis serology is expected to be seen in patients who have only been immunised against hepatitis B?
Anti-HBs
What are the complications of hepatitis B?
Chronic hepatitis and fulminant liver failure
Glomerulonephritis
Polyarteritis nodosa
Cryoglobulinaemia
What level of anti-HBs shows adequate response to vaccination?
> 100
What are the features of chronic hepatitis B?
Transaminitis
Ground glass appearance of liver
HBsAg and anti-HBc
What is the treatment of chronic hepatitis B?
48 weeks pegylated IFN-a
Synthetic thymidine nucleoside analogue e.g. tenofovir, entecavir
What type of virus is hepatitis C?
RNA flavivirus
What is the serology of hepatitis C?
HCV RNA detected
anti-HCV antibodies (remain if patients clear the virus)
What percentage of patients clear hepatitis C?
33%
66% develop chronic hepatitis C, 50% of these develop end stage liver disease
What are the risk factors for developing chronic hepatitis C?
Asymptomatic in acute stage
Co-existing hepatic pathology
HIV
African American
What are the complications of chronic hepatitis C?
Arthritis Sjogren's syndrome Cirrhosis and HCC Type 2 cryoglobulinaemia PCT Membranoproliferative GN Autoimmune thyroid disease
What does management of hepatitis C depend on?
Viral genotype
What is the treatment of hepatitis C?
2DAAS +/- ribavarin
E.g. Harvoni (ledipasvir (NS5A inhibitor) and sofosbuvir (NS5B inhibitor)
What is HCC screening in hepatitis C?
6 monthly AFP, liver USS
In which patients does hepatitis E carry risk of significant mortality?
Pregnancy
What is the mechanism of action of rifampicin?
Inhibits bacterial DNA dependent RNA polymerase, preventing transcription of DNA into mRNA
What are the side effects of rifampicin?
Hepatitis
Orange/pink secretions
Flu like
P450 inducer
What is the mechanism of action of isoniazid?
Inhibits mycolic acid synthesis
What are the side effects of isoniazid?
Peripheral neuropathy (prevent with pyridoxine)
Hepatitis
Agranulocytosis
P450 inhibitor
What is the mechanism of action of pyrazinamide?
Converted into pyrazinoic acid which inhibits fatty acid synthase
What are the side effects of pyrazinamide?
Hyperuricaemia
Arthralgia/myalgia
Hepatitis
What is the mechanism of action of ethambutol?
Inhibits arabinosyl transferase which polymerises arabinose into arabian
What are the side effects of ethambutol?
Retrobulbar optic neuritis
Needs dose adjustment in renal impairment
Name 5 skin disorders associated with TB.
Lupus vulgaris Erythema nodosum Scarring alopecia Scrofuloderma Verrucosa cutis Gumma
What is the general treatment of HIV?
2NRTIs + PI/NRTI
Give some examples of NRTIs and their side effects.
Zidovudine: anaemia, myopathy, black nails
Tenofovir: renal impairment, osteoporosis
General: peripheral neuropathy
Give some examples of NNRTIs and their side effects.
Nevirapine, efavirenz
P450 induction, rashes
Give some examples of protease inhibitors and their side effects.
Ritonavir: P450 inhibitor
Indinavir: renal stones, high bilirubin
General: diabetes, hyperlipidaemia, buffalo hump and central obesity
Give some examples of integrase inhibitors.
Raltegravir, elvitegravir
What is the cause of progressive multifocal leukoencephalopathy?
Infection of oligodendrocytes by JC virus
What is seen on CT or MRI in PML?
Widespread demyelination, single/multiple lesions
What is seen on CT in cerebral toxoplasmosis?
Single or multiple ring enhancing lesions
What is the treatment of cerebral toxoplasmosis?
Sulfadiazine and pyrimethamine
Which virus is primary CNS lymphoma associated with?
EBV
Which imaging modality is positive in primary CNS lymphoma?
Thallium SPECT
How is cryptococcal meningitis diagnosed?
High opening pressure CSF, India ink test positive
What is the cause of AIDs dementia?
HIV virus itself
What is post exposure prophylaxis?
Combo PO antiretrovirals for 4 weeks
Serological testing at 12 weeks post completion
What are the symptoms of HIV seroconversion illness?
Glandular fever type
1-4 weeks after infection
Maculopapular rash
Suggests the beginning of HIV antibody production
What is tested in suspected HIV seroconversion illness?
P24 antigen
HIV PCR
Antibodies negative up to 3 months
Which HIV patients should have prophylaxis against PCP pneumonia?
CD4 count <200
How is PCP pneumonia diagnosed?
CXR: bilateral interstitial pulmonary infiltrates
BAL silver staining: cysts
Sputum culture
What is the treatment of PCP pneumonia?
Co-trimaxazole
IV pentamidine if severe
If PCP patients are hypoxic <9.3kPa, what is added to treatment?
Steroids
What type of virus is HIV?
RNA retrovirus
Which cells does HIV virus infect?
CD4 T cells, macrophages, dendritic cells
How does HIV virus replicate?
After entering a cell, reverse transcriptase creates dsDNA from RNA for integration into the host cell’s genome
Which vaccines are contraindicated in HIV?
Cholera
Intranasal influenza
Oral polio
BCG
How is latent TB diagnosed, and when is a false negative likely?
Mantoux skin test –> if positive then IFN-gamma blood test used.
Mantoux test false -ve: miliary TB, sarcoid, lymphoma, HIV, <6 months
How is active TB diagnosed?
3x sputum culture
More sensitive than sputum smear with Ziehl-Neelson stain
What is the treatment of active TB?
Rifampicin and isoniazid for 6 months
Pyrazinamide and ethambutol for first 2 months
What is the treatment of latent TB?
3 months isoniazid and rifampicin, or 6 months isoniazid
What are the features of strep pneumonia CAP?
Rapid onset
High fever
Pleuritic chest pain
Herpes labialis
What are the causes of infectious mononucleosis?
EBV or HH4
How is infectious mononucleosis diagnosed?
Atypical lymphocytes
Transient rise in ALT
Haemolytic anaemia secondary to cold agglutins (IgM)
Maculopapular rash after amoxicillin
What is the cause of anthrax and how does it cause disease?
Bacillus anthracis (gram +ve rod)
Produces tripartite protein toxin: protective factor, oedema factor (increased cAMP) and lethal factor (which is toxic to macrophages)
What are the features of anthrax?
Painless black eschar which can cause oedema, compartment syndrome, fever
Necrotising fasciitis
GI bleeding
What is the treatment of anthrax?
Ciprofloxacin
What is the reaction caused by release of endotoxins following bacterial death after first dose of antibiotics?
Jarisch-Herxheimer reaction
What is the treatment of lassa fever?
Ribavarin
How is dengue fever transmitted?
Aedes aegypti mosquito
What are the symptoms of dengue fever?
Retro-orbital headache
Fever, myalgia
Facial flushing and maculopapular rash
What may Dengue fever progress to?
Dengue haemorrhagic fever (form of DIC) –> dengue shock syndrome
What are the features of Chikungunya fever?
Rapid fever
Debilitating joint pain
Palmar/plantar rash
What are the features of Lassa fever?
Mucosal bleeding
Mastomys rodent
What are the features of Yellow fever?
5 day duration
Non specific symptoms
What are the features of leprosy?
Hypopigmented skin with sensory loss
Lepromatous leprosy/multibacillary: extensive, symmetric nerve involvement
Tuberculoid leprosy/paucibacillary: limited skin disease, asymmetric nerve involvement
What determines severity of leprosy?
Degree of cell mediated immunity
What is the treatment of leprosy?
Rifampicin, dapsone, clofazimine
How does the rabies virus cause disease?
Animal bite –> virus travels up nerve axons towards CNS
What are the features of rabies?
Prodromal headache/fever
Hydrophobia and muscle spasms
Hypersalivation
What is seen in infected neurons in rabies?
Negri bodies (cytoplasmic inclusion bodies)
What is the treatment of rabies?
2 further doses of vaccine
If not vaccinated, human rabies Ig with full vaccine course
What are the features of typhoid?
Relative bradycardia
Abdo pain and distension
Rose spots
How is typhoid diagnosed?
Large volume blood culture
What are the 3 serotypes of e coli?
O - lipopolysaccharide layer
K - capsule
H - flagellin
Which type of e.coli causes neonatal meningitis?
K1
Name some gram +ve bacteria.
Cocci - staph + strep
Bacilli - anthrax, listeria, diphtheria, clostridium
Name some gram -ve bacteria.
Cocci - neisseria, moraxella
Bacilli - e.coli, hib, pseudomonas, salmonella, shigella
What are the 7 live attenuated vaccines?
BCG MMR Intranasal influenza Oral rotavirus Oral polio Yellow fever Oral typhoid
What is the mechanism of action of aciclovir?
Guanosine analogue, phosphorylated by thymidine kinase which inhibits viral DNA polymerase
What is a side effect of aciclovir?
Crystalline nephropathy
What is the pathophysiology of botulism?
Clostridium botulinum produces botulinum toxin, a neurotoxin which irreversibly blocks the release of ACh
What are the features of botulism?
Fully conscious with no sensory disturbance
Flaccid paralysis
Bulbar palsy
Dysarthria, diplopia, ataxia
What is the treatment of botulism?
Botulism antitoxin
What is Lemierre’s syndrome?
Thrombophlebitis of the internal jugular vein secondary to peritonsillar abscess –> septic PE
What is the pathophysiology of diphtheria?
Corynebacterium diphtheria releases exotoxin encoded by b-prophage, which inhibits protein synthesis by catalysing ADP-ribosylation of elongation factor EF2
What are the features of diphtheria?
Diphtheric membrane on tonsils
Cervical lymphad
Neuritis
Heart block
What is the treatment of diphtheria?
IM penicillin
Diphtheria antitoxin
What are the 2 reproductive cycles in falciparum malaria?
Exo-erythrocytic cycle in hepatocytes
Erythrocytic cycle in red blood cells
What are the features of falciparum malaria?
Schizonts on blood film Parasitaemia >2% Hypoglycaemia Acidosis Fever>39 Severe anaemia
What are schizonts on blood film?
Indicates imminent schizogony and consequentially significant rise in parasitaemia
What is Blackwater fever?
Acute renal failure secondary to large intravascular haemolysis
Urine black/dark red (haemoglobinuria)
What is the treatment of falciparum malaria?
Uncomplicated: ACTs e.g. artesunate + mefloquine
Complicated: IV artesunate
What is the treatment of severe parasitaemia >10% in falciparum malaria?
Exchange transfusion
What is the most common type of non falciparum malaria?
Vivax
What are the characteristics of knowlesi malaria?
Very fast erythrocytic cycle (24 hours) with end stage involves lysis of RBCs and release of additional parasites
Therefore produces very high parasite counts in a short space of time
Which malaria is associated with nephrotic syndrome?
Malariae
What is the treatment of non falciparum malaria?
Chloroquine (unless resistant - ACT)
What medication is added in vivax/ovale malaria and why?
Primaquine
To destroy liver hypnozoites and prevent relapse
What is the cause and risk factor for melioidosis?
Gram -ve burkholderia pseudomallei in East Asia and Northern Australia
RF: diabetes
What is the treatment of melioidosis?
10 days IV ceftazidime/carbapenem
Followed by 20 weeks oral maintenance phase
What is the cause of traveller’s diarrhoea?
Enterotoxigenic e.coli
What are the features of amoebiasis?
Long incubation
RUQ pain - liver abscess with anchovy sauce aspirate
What is the treatment of amoebiasis?
Metronidazole and tinidazole, followed by luminal amoebicide (diloxanide furoate)
How is leptospirosis spread?
Infected rat urine
What are the early features of leptospirosis?
Fever, flu like, subconjunctival injection
Lasts a week
What are the features of second immune phase of leptospirosis (Weil’s disease)?
AKI
Hepatorenal syndrome
Aseptic meningitis
What is the treatment of leptospirosis?
High dose ben pen or doxy
What is the cause of Q fever?
Coxiella burnetti
Rickettsia ricketsii causes which illness?
Rocky mountain spotted fever
What are the features of endemic typhus?
Rickettssi typhi
Flea vector
Central rash –> peripheral
What are the 2 forms of trypanosomiasis and what are they spread by?
African (sleeping sickness) –> tsetse fly
American (Chagas disease) –> triatomine bug
What are the features of African trypanosomiasis?
Intermittent fever
Trypanosoma chancre
Posterior cervical lymphad
Somnelence, reversal of sleep-wake cycle
What is the treatment of African trypanosomiasis?
IV pentamidine/suramin
If CNS involvement: IV melarosprol
What is the Romana sign?
Chagoma and periorbital oedema seen in acute phase of American trypanosomiasis
What are the chronic features of Chagas’ disease?
Myocarditis + dilated cardiomyopathy
Megaoesophagus and megacolon
What spreads leishmaniasis?
Sandfly bite
What are the 3 forms of leishmaniasis?
Cutaneous
Mucocutaneous
Visceral
What are the features of visceral leishmaniasis?
Caused by leishmania donovani Fevers, rigors Massive splenomegaly and hepatomegaly Weight loss Grey skin (kala-azar) Pancytopenia
How does toxoplasma gondii cause disease?
Oocysts release trophozoites which migrate around the body including to the eye, brain or muscle
What are the forms of toxoplasmosis?
Immunocompetent: asymptomatic/self limiting
HIV: cerebral/chorioretinitis
Congenital (transplacental spread): neuro and ophthalmic damage
What is the pathognomonic rash of strongyloidiasis?
Larvae currens
What is the treatment of strongyloidiasis?
Ivermectin
What is Katayama fever?
Acute schistosomiasis syndrome - fever, urticaria, arthralgia, cough, diarrhoea, eosinophilia
Which form of schistosoma causes terminal haematuria and is a risk factor for squamous cell bladder cancer?
Schistosoma haematobiu,
What do schistosoma mansoni and japonicum do?
Mature in the liver
Travel through the portal system to inhabit the distal colon
Cause hepatosplenomegaly, portal vein congestion, cor pulmonale
What is the commonest cause of visceral larva migrans?
Toxocara canis
Which tapeworm causes cysticercosis and what is the treatment?
Taenia solium
Niclosamide
What is the treatment of schistosomiasis?
Praziquantel
What is the cause of a painless ulcer (chancre)?
Syphilis
Treponema pallidum
What is the cause of a painful chancroid with ragged border?
Haemophilus ducreyi
What disease does chlamydia trachomatis cause?
Lymphogranuloma venereum
What are the stages of lymphogranuloma venereum?
Small painless ulcer
Painful inguinal lymphad
Proctocolitis
What is the treatment of LGV?
Doxycycline
What is the cause of granuloma inguinale?
Klebsiella granulomatis
What is the treatment of PID?
PO olfloxacin + PO metro
OR
IM ceftriaxone + PO doxy + PO metro
What is the treatment of chlamydia?
7 days doxycycline
What is the treatment of gonorrhoea?
IM ceftriaxone 1g