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Flashcards in Path - Microbiology Deck (129)
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1

Match each numbered class of antibiotic with its lettered mechanism of action/ description

1. Beta lactams
2. Oxazolidinones
3. Glycopeptides
4. Aminoglycosides & tetracyclines
5. Macrolides & chloramphenicol
6. Fluoroquinolones
7. Nitroimidazoles
8. Rifamycins
9. Sulphonamides and diaminopyrimidines

A. Inhibits a subunit of DNA gyrase to disrupt DNA replication
B. Binds to pentapeptides to prevent them from being used to form peptidoglycan
C. Binds to the 50s subunit of bacterial ribosomes
D. Interferes with folic acid metabolism, indirectly affecting DNA replication
E. Binds to the 30s subunit of bacterial ribosomes
F. Inactivates transpeptidases which are important for incorporating peptidoglycan into the bacterial cell wall
G. Binds to the 23s component of the 50s subunit of bacterial ribosomes to prevent formation of the initiation complex
H. Produces an active intermediate under anaerobic conditions which causes DNA strand breakage
I. Inhibits protein synthesis by binding to DNA-dependent RNA polymerase thereby inhibiting initiation

1. Beta lactams - F. Inactivates transpeptidases which are important for incorporating peptidoglycan into the bacterial cell wall

2. Oxazolidinones - G. Binds to the 23s component of the 50s subunit of bacterial ribosomes to prevent formation of the initiation complex

3. Glycopeptides - B. Binds to pentapeptides to prevent them from being used to form peptidoglycan

4. Aminoglycosides/ tetracyclines - E. Binds to the 30s subunit of bacterial ribosomes

5. Macrolides/ chloramphenicol - C. Binds to the 50s subunit of bacterial ribosomes

6. Fluoroquinolones - A. Inhibits a subunit of DNA gyrase to disrupt DNA replication

7. Nirtoimidazoles - H. Produces an active intermediate under anaerobic conditions which causes DNA strand breakage

8. Rifamycins - I. Inhibits protein synthesis by binding to DNA-dependent RNA polymerase thereby inhibiting initiation

9. Sulphonamides and diaminopyrimidines - D. Interferes with folic acid metabolism, indirectly affecting DNA replication

2

A patient being treated for a separate infection develops diarrhoea, fever, and nausea. They are diagnosed with moderate pseudomembranous colitis.

Which would be the most appropriate antibiotic to give?

A. Ceftriaxone
B. Metronidazole
C. Gentamicin
D. Vancomycin
E. Cefotaxime

B. Metronidazole

Metronidazole is used to treat mild-moderate C. difficile colitis, with vancomycin and fidaxomicin being reserved for severe disease. This is partially to avoid resistance to vancomycin developing, and partially because it is nephrotoxic and requires careful monitoring of the patient's renal function. Cephalosporins should not be used in this case as they are associated with causing C. difficile colitis. Most antibiotics have some association with C. diff diarrhoea, especially: clindamycin, cephalosporins, fluoroquinolones, and broad spectrum penicillins (the broader the spectrum, the more likely diarrhoea is).

3

A known cystic fibrosis patient presents to hospital with purulent cough, fever, and fatigue. Pseudomonas infection is diagnosed.

What would be the most appropriate antibiotic to give?

A. Tetracycline
B. Cefotaxime
C. Ketoconazole
D. Vancomycin
E. Gentamicin

E. Gentamicin

Though they are ototoxic and nephrotoxic, and so levels must be monitored, gentamicin and tobramycin (both aminoglycosides) are particularly effective against P. aeruginosa infection.

Pseudomonas can be treated with aminoglycosides (e.g. amikcacin, gentamicin, tobramycin) or with broad-action beta lactams (tazocin, meropenem, ceftazidime) or fluoroquinolones (ciprofloxacin).

4

Match the numbered example to the lettered mechanism of resistance (lettered options may be used more than once)

1. ESBL E. coli resistance to ceftriaxone
2. Resistance to macrolides
3. Resistance to trimethoprim and sulphonamides
4. MRSA resistance to flucloxacillin
5. Resistance to Rifampicin


A. Impaired uptake of the antibiotic
B. Alteration of the target
C. Enzymatic inactivation of the antibiotic
D. Enhanced antibiotic efflux
E. Bypass of antibiotic-sensitive step

1. ESBL E. coli resistance to ceftriaxone - C. Enzymatic inactivation of the antibiotic
2. Resistance to macrolides - B. Alteration of the target
3. Resistance to trimethoprim and sulphonamides - E. Bypass of antibiotic-sensitive step
4. MRSA resistance to flucloxacillin - B. Alteration of the target
5. Resistance to Rifampicin - B. Alteration of the target

ESBL stands for extended-spectrum beta lactamase, and organisms which produce it can inactivate a wide range of antibiotics including third generation cephalosporins.

Flucloxacillin-resistant strains (e.g. MRSA) have altered transpeptidase enzymes (penicillin-binding proteins) which prevent beta-lactams from binding. However Flucloxacillin is stable against beta lactamases.

NB: If in doubt, say altered target

5

A woman is brought to hospital with suspected meningitis. Blood is taken and an LP is performed before commencement of empirical antibiotics. Upon analysis the CSF shows clear fluid with raised lymphocyte and protein counts, but normal glucose.

What is the most likely causative organism?

A. Haemophilus influenzae
B. Streptococcus pneumoniae
C. Mycoplasma tuberculosis
D. Enterovirus
E. Herpes simplex

D. Enterovirus

This is a case of aseptic meningitis: viral meningitis. It is so named because the causative organism does not cause sepsis, and is the most common form of CNS infection. This CSF result usually indicates viral meningitis, for which non-polio enteroviruses (i.e. echoviruses and coxsackie viruses) are responsible for 80-90% of cases. This condition most frequently occurs in children under 1 year old, and presents with photophobia, neck stiffness, and photophobia, and a non-specific rash may also be seen. However the course of the disease is self-limiting and resolves in 1-2 weeks.

It is worth looking up and memorising the CSF findings in each different type of meningitis.

6

A 65 year-old man, who is a big fan of unpasteurised cheese, presents with headache and neck stiffness. Blood cultures produce a Gram-positive rod.

What is the most likely causative organism?

A. Listeria monocytogenes
B. Cryptococcus neoformans
C. Haemophilus influenzae
D. Streptococcus pneumoniae
E. Neisseria meningitidis
F. Escherichia coli
G. Mycobacterium tuberculosis

A. Listeria monocytogenes

Listeria monocytogenes is one of the three most common causes of meningitis in immunocompromised (including elderly and very young) patients along with group B Streptococcus and Escherichia coli. The relatively advanced age (>50) of the patient, his penchant for unpasteurised cheese, and the presence of a Gram-positive rod imply the cause is Listeria monocytogenes.

7

A 33 year-old man presents with headache and neck stiffness. Treating a CSF sample with the Indian ink stain reveals the causative organism.

What is the most likely causative organism?

A. Listeria monocytogenes
B. Cryptococcus neoformans
C. Haemophilus influenzae
D. Streptococcus pneumoniae
E. Neisseria meningitidis
F. Escherichia coli
G. Mycobacterium tuberculosis

B. Cryptococcus neoformans

The India ink stain is useful for staining the polysaccharide capsule surrounding Cryptococcus neoformans (which is a yeast). Cryptococcus is a less common cause of meningitis and should not occur unless the patient is in some way immunocompromised. Accordingly, this patient should be offered an HIV test.

8

Which option describes the best treatment for meningitis to be given as soon as blood cultures and CSF have been taken if the causative organism is unknown?

A. Meropenem 6g/d or Ceftazidime 6g/d
B. Aciclovir 10mg/kg I.V. tds, Ceftriaxone 2g I.V. bd with Amoxicillin 2g I.V. 4-hourly if >50 or immunocompromised
C. Ceftriaxone 4g/d or Chloramphenicol 75-100mg/kg/d
D. Ampicillin 12g/d plus Gentamicin or Benzylpenicillin 18-24 mg/d
E. Ceftriaxone 2g I.V. bd with Amoxicillin 2g I.V. 4-hourly if >50 or immunocompromised

E. Ceftriaxone 2g I.V. bd with Amoxicillin 2g I.V. 4-hourly if >50 or immunocompromised

The management protocol for meningitis is to immediately take blood cultures and perform an LP. An LP must not be performed if there are signs of raised intra-cranial pressure (decreased GCS, papilloedema on fundoscopy, seizures, or focal neruological deficits). As soon as this has been done, empirical treatment with Ceftriaxone 2g I.V.bd with Amoxicillin 2g I.V. 4-hourly if >50 or immunocompromised is begun. Once culture results are available and the organism is known, more targeted antibiotic regimes can be started. Aciclovir is added to this starter regime if there is suspicion of viral meningio-encephalitis.

NB: Amoxicillin is added in very young or elderly or immunocompromised patients as they are vulnerable to listeria monocytogenes, which will not be killed by Ceftriaxone.

NB: Ceftriaxone is not used in neonates because it displaces bilirubin from albumin which may cause biliary sludging - cefotaxime is used instead

9

A 19 year-old man returns from holiday in Spain. Four weeks later, he develops a hot, swollen, painful, red knee joint, with an effusion. The knee is tapped, and 20ml of cloudy yellow fluid is withdrawn. Microbiology reveals Gram-negative intracellular diplococci.

What is the most likely causative organism?

A. Neisseria meningitidis
B. Haemophilus influenzae
C. Streptococcus viridans
D. Escherichia coli
E. Streptococcus pneumoniae
F. Neisseira gonorrhoeae
G. Staphylococcus Aureus

F. Neisseria gonorrhoeae

STIs can lead to septic arthritis if untreated, and this should be suspected particularly in young patients or patients with a suspicious sexual/ travel history.

10

A previously well 19 year-old student arrives in casualty septic, pyrexial, and confused, with a temperature of 39 degrees. He has a stiff neck, and an LP is performed

Which of the following is the LP most likely to show?

A. Gram positive bacilli
B. Gram negative bacilli
C. Gram positive coccobacilli
D. Gram negative cocci in large clusters
E. Gram positive cocci in chains

E. Gram positive cocci in chains

Gram positive cocci in chains implies the pathogen is Streptococcus pneumoniae - one of the three most commonly responsible pathogens in meningitis of immunocompetent patients along with Neisseria meningitidis and Haemophilus influenzae. The three most common organisms causing meningitis in immunocompromised patients are group B Strep (Streptococcus agalactiae), Listeria monocytogenes, and Escherichia coli.

'A' describes Listeria and 'B' describes E. coli. 'C' incorrectly describes H. influenzae, as it is actually a Gram negative coccobacillus. 'D' incorrectly describes N. meningitidis, which is a Gram negative diplococcus.

11

A 6 year-old boy arrives in casualty septic, pyrexial, and confused with a temperature of 39 degrees. He has a stiff neck, and a lumber puncture reveals Gram-negative coccobacilli.

What is the most likely causative organism?

A. Neisserisa meningitidis
B. Haemophilus influenzae
C. Streptococcus viridans
D. Escherichia coli
E. Streptococcus pneumoniae
F. Neisseira gonorrhoeae
G. Staphylococcus Aureus

B. Haemophilus influenzae

Haemophilus influenzae is a coccobacillus, and so is halfway between a rod and a coccus. Haemophilus influenzae is one of the three main causes of meningitis in immunocompetent individuals (the other two being Streptococcus pneumoniae and Neisseria meningitidis). The main three causes of meningitis which only occur in immunocompromised patients are E. coli, Group B Streptococci (S. agalactiae), and Listeria. These organisms most commonly cause meningitis in neonates.

12

A 22 year-old has a mild fever for several months, and no cause can be found. After 2 months, blood cultures come back positive for Gram-positive cocci.

What is the most likely causative organism?

A. Neisserisa meningitidis
B. Haemophilus influenzae
C. Streptococcus viridans
D. Escherichia coli
E. Streptococcus pneumoniae
F. Neisseira gonorrhoeae
G. Staphylococcus Aureus

C. Streptococcus viridans

Streptococcus viridans is a slow-growing organism which can cause low-level systemic infection. It normally resides in the mouth, hence dental surgery may allow it to enter the bloodstream. Streptococcus viridans causes subacute bacterial endocarditis as bacteria in the bloodstream adhere to heart valves (usually the mitral, but the tricuspid in IVDU).

Subacute bacterial endocarditis requires prior damage of the heart valves in order to take hold. The extracellular matrix of the valves is accordingly damaged by the body's inflammatory response (hence subacute bacterial endocarditis is classified as a type III hypersensitivity reaction). Subacute bacterial endocarditis usually affects the mitral valve because it is constantly subjected to the high pressures of the left heart, and so is slightly damaged even in healthy people, which makes it easier for bacteria to infect.

NB: This is not to be confused with rheumatic fever: a type II hypersensitivity reaction occurring after Streptococcus pyogenes infection.

13

A 35 year-old patient presents with clustered red pustules on his skin, fever, abdominal pain, and blood in the stool. A routine HIV test is positive. During the history the patient reveals they bought a kitten several months ago.

What is the most likely diagnosis?

A. Toxoplasmosis
B. Viral haemorrhagic fever
C. Q fever
D. Bacilliary angiomatosis
E. Brucellosis

D. Bacilliary angiomatosis

This infection has been caused by Bartonella henselae, which is a slightly curved Gram-negative rod. Bartonella is found on cat's paws, particularly in kittens (which also scratch more than adult cats as they cannot retract their claws). Bartonella usually only causes Cat-scratch disease, which features a macule (later pustule as the centre ulcerates) at the site of inoculation, along with regional adenopathy and systemic flu-like symptoms. In some, rarer cases, Cat-scratch disease can cause more severe manifestations e.g. pneumonia, arthritis, hepatitis.

In immunocomprimised patients, Bartonella can cause bacilliary angiomatosis - the formation of vascular lesions within multiple organ systems leading to bleeding. The skin is most often involved, but almost any organ system can be affected (hence the GI bleeding in this patient.

14

Why should vancomycin not be given orally apart from in case of pseudomembranous colitis?

A. It is enterotoxic
B. It is not absorbed from the gut
C. It undergoes extensive first-pass metabolism
D. It has been known to rarely cause osteonecrosis of the jaw
E. The oral form is too expensive

B. It is not absorbed from the gut

Vancomycin is always given I.V. because it cannot be absorbed form inside the gut. The exception to this is when treating pseudomembranous colitis, as in that case it is ideal to not absorb the vancomycin.

15

A 30 year-old man presents with jaundice and haemoptysis. He has felt 'run-down' since returning from a canoeing trip to the USA a little over a month ago. On questioning he admits to having muscle aches (especially in his calves), and headaches. On examination there is hepatomegaly and conjunctival suffusion. He reveals that his trip was to a remote region with a lot of rodents, and that there was heavy rainfall during his stay.

What is the most likely causative organism?

A. Rabies lyssavirus
B. Bacillus anthrax
C. Brucella melitensis
D. Bartonella henselae
E. Leptospira interrogans
F. Coxiella burnetii
G. Borrelia burgdorferi

E. Leptospira interrogans

Leptospirosis (also known as Weil's disease) usually presents with sudden onset headache, fever, chills, abdominal pain, muscle pain in the lower limbs (particularly the calf muscle), and conjunctival suffusion (resembles conjunctivitis, but without inflammatory exudates - virtually pathognomic of leptospirosis). The gold standard for diagnosing L. interrogans infection is microscopic agglutination testing.

Jaundice, severe haemoptysis, cardiac arrhythmia, acute renal failure, a maculopapular rash, and rarely mental state changes may all occur in advanced disease. Leptopspirosis consists of two phases: the initial acute/ septic phase features the flu-like symptoms, and the immune phase afterwards which features the more severe and rarer symptoms.

Risk factors include travel to tropical/ endemic regions, travel/ residence in flooding regions especially after heavy rainfall, water sports, and exposure to infected animal urine (particularly rats). Leptospirosis is diagnosed using the Faine's criteria adopted by the WHO which accounts for clinical, epidemiological, and laboratory findings. Leptospira interrogans can inhabit freshwater for long period of time.

16

A 25 year-old man presents to his GP with lethargy for a month accompanied by headaches and fever. On examination, he had a temperature of 39 degrees and splenomegaly. He has recently travelled to Italy. Small Gram-negative coccobacilli were seen on culture with Castaneda's medium.

What is the most likely causative organism?

A. Rabies lyssavirus
B. Bacillus anthrax
C. Brucella melitensis
D. Bartonella henselae
E. Leptospira interrogans
F. Coxiella burnetii
G. Borrelia burgdorferi

C. Brucella melitensis

Brucella is a Gram negative intracellular coccobacillus which causes a zoonotic infection. Brucellosis typically causes undulating fevers, headache, arthralgia, night sweats, and anorexia in its initial stages. Later the infection may become more serious and lead to neural infection, endocarditis, liver abscesses, spondylitis, and epididymo-orchitis.

17

A 22 year-old student presents to her GP upon return from a biology field trip with a lesion on her leg which is 5cm in diameter and flat, with a red edge and a dim centre. She also mentions feeling tired and suffering form headaches. On examination, the GP noted a fever of 38 degrees and an irregular heart rate.

What is the most likely causative organism?

A. Rabies lyssavirus
B. Bacillus anthrax
C. Brucella melitensis
D. Bartonella henselae
E. Leptospira interrogans
F. Coxiella burnetii
G. Borrelia burgdorferi

G. Borrelia burgdorferi

This is a history of Lyme disease. The best known feature of Lyme disease is an expanding rash known as erythema migrans (seen in ~80% of patients); it has a target/ bullseye appearance and is caused by infection of the skin by Borrelia. The rash appears within the first couple of weeks after a tick-bite, and is accompanied by generic flu-like symptoms.

Once disseminated, Borrelia can cause neurological compliations (facial palsy, radiculopathy, meningitis, encephalitis, peripheral neuropathy), cardiological complications (myocarditis leading to abnormal rhythms - palpitations), and arthritis.

18

A tanner on holiday from India presents to hospital with an ulcerating papule on his hand. On inspection of the ulcer, the centre was black and necrotic. Gram-positive rods grew on blood agar culture and responded to treatment with large doses of penicillin.

What is the most likely causative organism?

A. Rabies lyssavirus
B. Bacillus anthrax
C. Brucella melitensis
D. Bartonella henselae
E. Leptospira interrogans
F. Coxiella burnetii
G. Borrelia burgdorferi

B. Bacillus anthrax

A tanner works with animal hides, which provide a perfect environment for Bacillus anthrax to proliferate, and so the occupation in this case gives a strong clue.

19

A 49 year-old man was admitted from A&E with a 3-day history of worsening right arm pain and a 1-day history of hypersalivation, agitation, and generalised muscle twitching. Vital signs and blood tests were normal but he later became confused. He developed renal failure and died four days later.

What is the most likely causative organism?

A. Rabies lyssavirus
B. Bacillus anthrax
C. Brucella melitensis
D. Bartonella henselae
E. Leptospira interrogans
F. Coxiella burnetii
G. Borrelia burgdorferi

A. Rabies lyssavirus

Rabies lyssavirus is transmitted through saliva, and once a person is infected the virus enters their peripheral nervous system and spreads to their CNS. There is an incubation period of 1-3 months, but once the virus spreads to the CNS and the patient become symptomatic, the patient almost invariably dies - only a handful of people have ever survived symptomatic rabies.

Vaccination provides some protection, and prognosis is good if treatment is started before symptoms begin. If unvaccinated, the patient will need three doses of vaccine along with human rabies immunoglobulin, which is 100% effective if given within 14 days If already vaccinated, a person need only receive post-exposure vaccination to be treated.

Symptoms begin with generic flu-like symptoms, then progress to behavioural changes with aggression, paranoia, terror, paralysis, delerium, and eventually coma and death. A treatment known as the Milwaukee protocol was tried which involved placing patients in a chemically induced coma and giving anti-viral treatment, but was not successful and is no longer tried.

Don't get rabies kids

20

A French farmer visiting family in the UK presents with fever and fatigue of two weeks duration. He also admits a dry cough and some abdominal pain. Examination reveals reduced chest expansion and crackles on auscultation, as well as tenderness over the right hypochondriac region and hepatomegaly. The farmer keeps a range of livestock for breeding and has close contact with the animals including assisting in their giving birth.

What is the most likely causative organism?

A. Coxiella burnetii
B. Borrelia burgdorferi
C. Leptospira interrogans
D. Staphylococcus aureus
E. Streptococcus viridans

A. Coxiella burnetii

Coxiella burnetti causes Q fever. Q fever is difficult to distinguish from other infections, particularly brucellosis as it shares the same reservoirs (goats, cattle) and has a similar presentation (pneumonia, flu-like illness, hepatitis). Q fever may also result in focal infections in a wide variety of systems. Around 5% of Q fever cases will proceed to a chronic infection, which confers an increased chance of developing endocarditis. Q fever is a significant problem in pregannt women, and has a distinct presentation.

21

Why is penicillin less effective on infections with a high bacterial load?

A. The bacteria form dense populations which physically prevents drugs from reaching the centre
B. Horizontal gene transmission of resistance genes is more likely in these populations
C. There is a greater concentration of beta-lactamase produced
D. Greater populations are more likely to include other bacterial species which are not susceptible to penicillin
E. Penicillin is only active whilst bacteria are replicating which occurs less when their numbers are greater

E. Penicillin is only active whilst bacteria are replicating which occurs less when their numbers are greater

As bacterial numbers increase, their rate of growth slows, as resources become more scarce. Penicillin only affects bacteria in the growth phase, and so if the bacteria are not growing at a significant rate, penicillin will have no effect.

22

Which of the following options most accurately describes a prion disease?

A. A disease with a genetic form inherited in an autosomal recessive fashion
B. A sub-variant of amyloidosis
C. Disease caused by alpha-helical configured proteins
D. A pure protein infectious agent which causes untreatable neurodegeneration
E. A progressive neurodegenerative condition similar to dementia, causing steady decline over many years

D. A pure protein infectious agent which causes untreatable neurodegeneration

Prion diseases are caused by the presence of misfolded proteins (prions) in the CNS which cause rapid and untreatable neurodegeneration.

The aetiology of prion disease is not thoroughly understood, as it is incredibly rare (~1 in a million). What is known is that the prion protein (PrP) exists in normal organisms and is not harmful, though its normal function is unknown. PrP can become misfolded to produce a prion. A prion is distinguished by its beta-sheet configuration (PrP normally has an alpha-helical configuration) which makes it incredibly resistant to proteases, which means it accumulates in the CNS, then aggregates to form PrP amyloid plaques which cause neurodegeneration (however prion disease is separate from amyloidosis). Prions are somehow able to misfold other PrP to also become prions, and so behave like infectious agents.

The resilience of prions means that they cannot reliably be removed from surgical instruments, even with extreme heat or radiation. Any instruments used in surgery on a prion-infected patient must be destroyed.

Whilst prion disease is steadily progressive, once symptoms begin it progresses rapidly, causing death in 3 months - 2 years depending on the type. However incubation periods may be extremely extensive, with periods of 45 years being reported amongst Kuru patients in Papua New Guinea.

23

What is the most common form of prion disease?

A. Kuru
B. Iatrogenic Creutzfeld-Jacob disease
C. Gerstmann-Straussler-Sheinker syndrome
D. Variant Creutzfeld-Jacob disease
E. Sporadic Creutzfeld-Jacob disease

E. Sporadic Creutzfeld-Jacob disease

Sporadic CJD represents ~80% of all prion disease, and affects older people (mean age of onset is 65). SCJD causes rapid dementia with myoclonus, cortical blindness, lower motor neuron signs, and akinetic mutism (dysarthria with akinesia/ ataxia). The cause of sCJD is unknown.

Signs of sCJD include: incresed signal in the basal ganglia on MRI, periodic triphasic complexes on EEG, presence of S100 and 14-3-3 neurodegenerative markers, and spongiform vacuolation and PrP amyloid plaques on biopsy.

24

Which statement is false of sporadic Creutzfeld-Jacob disease?

A. Median survival time after diagnosis is <6 months
B. Tonsillar biopsy can be diagnostic
C. EEG usually shows periodic complexes
D. Mean age of onset is 65
E. CSF markers (S100, 14-3-3) of neuronal damage may be elevated

B. Tonsillar biopsy is diagnostic

Tonsillar biopsy is of no use in sCJD, but is 100% sensitive and specific in variant CJD.

25

Which statement is true of variant Creutzfeld-jacob disease?

A. The disease mainly affects elderly people
B. vCJD is more rapidly progressive than sporadic CJD
C. The initial symptoms are always neurological
D. An MRI typically shows the pulvinar sign
E. EEG is usually abnormal

D. An MRI typically shows the pulvinar sign

Variant CJD occurs in younger people (median onset is 26) and is slower progressing than sCJD. It usually presents with psychiatric symptoms (anxiety, paranoia, hallucinations, dysphoria) and neurological symptoms appear later (peripheral neuropathy, ataxia, myoclonus, chorea, dementia).

Signs of vCJD include: a positive tonsillar biopsy (100% sensitive and specific in vCJD), increased signal form the pulvinar nuclei in the posterior thalamus on MRI (pulvinar sign), and florid plaques seen on biopsy.

All bar one patients who have been known to contract vCJD have had the methyinine-methyinine polymorphism at codon 129 of the PRNP gene. It is not known why this association exists.

26

Which of the following statements is true?

A. The vast majority of cases of variant CJD have been found to be MM at codon 129 of the PRNP gene
B. Familial prion disease does not cause ataxia
C. In familial prion disease, mutations are usually inherited recessively
D. Familial CJD is more rapidly progressive than sporadic CJD
E. Variant CJD can be indicated by increased signal in the basal ganglia on MRI scans

A. The vast majority of cases of variant CJD have been found to be MM at codon 129 of the PRNP gene

All but one case

27

A 13 year-old patient presents with throat pain and fever. They deny cough, and examination shows tonsillar exudate. Their modified centor score is 5.

Which treatment should be given?

A. Benzylpenicillin
B. Valaciclovir
C. Co-amoxiclav
D. Vancomycin
E. Aciclovir

A. Benzylpenicillin

This is most probably a case of bacterial pharyngitis, as indicated by a high centor score, as a score of 3-4 indicates a 32-56% chance of a Streptococcal cause. As a result, benzylpenicillin should be given for 10 days.

28

A 78 year-old man is admitted to A&E with cough, dyspnoea, and confusion. His respiratory rate is 33 and his BP is 85/55. He is given an urgent chest X-ray and diagnosed with pneumonia.

How should this patient be managed?

A. Dishrge home with instructions to family to monitor him and return if symptoms don't improve, give oral amoxicillin with erythromycin
B. Admit to a respiratory ward and give oral amoxicillin and clarithromycin
C. Consider ICU admission and give I.V. co-amoxiclav with clarithromycin
D. Admit to HDU and begin I.V. vancomycin
E. Admit to ICU, take blood cultures, then immdeiately start I.V. ceftriaxone with amoxicillin

C. Consider ICU admission and give I.V. co-amoxiclav with clarithromycin

A CURB-65 score would be used to calculate the predicted mortality, and by extension the severity of this patient's disease.

Confusion - new onset, defined by an AMTS of 8 or less
Urea - Serum conc. > 7mmol/L
Respiratory rate - >30 breaths per minute
Blood pressure - less than 90 systolic or 60 diastolic
65 - aged 65 or over

This patient has a CURB-65 score of 4 and so should be given I.V. co-amoxiclav with clarithromycin and should be admitted to ITU. A score of 0 or 1 indicates possible home-based care, 2 indicates hospital-based care, and 3 or more indicates ITU admission. It is important to monitor for sepsis and remember the Sepsis 6:

Monitor urine output
Take blood cultures
Serial lactate measurements
Give oxygen
Give empirical antibiotics
Give I.V. saline

29

A 65 year-old woman presents with jaundice and abdominal swelling. Examination reveals spider naevi and palmar erythema. She has a mild alcohol history, and denies I.V. drug use. She has three children, the first of which was a difficult birth with significant post-partum haemorrhage when she was 21. She mentions she has recently returned from holiday and that she had seafood from a questionable vendor.

What is the most likely cause of her symptoms?

A. Hepatitis A
B. Hepatitis B
C. Hepatitis C
D. HIV
E. Cytomegalovirus

C. Hepatitis C

This is a clinical picture of a woman with acute-on-chronic liver failure (also known as decompensated liver failure) as indicated by ascites (low albumin), spider naevi and palmar erythema (high oestrogens as the liver can no longer metabolise them). The seafood is a red herring (badoom cha) because though that could infect this patient with hepatitis A, it is a self-limiting illness that could not cause this extent of damage.

This woman most likely contracted hepatitis C from contaminated blood products given when she gave birth to her first child, as this was before the advent of hepatitis C screening in the UK (1991).

30

Why would amoxicillin be given in addition to ceftriaxone to treat meningitis?

A. Because ceftriaxone is not effective against Listeria
B. Because they have synergistic killing effects on bacteria
C. To give enhanced Gram negative cover
D. Because amoxicillin is effective against organisms which produce ESBLs
E. To cover atypical organisms

A. Because ceftriaxone is not effective against Listeria

Ceftriaxone is a third generation cephalosporins with good Gram positive and negative cover, but does not protect against Listeria, an important cause of meningitis in newborns and immunocompromised patients. Cheese may be contaminated with Listeria, and is an important clue in the history.