infection PT 1 2016 modif

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Question 1 of 153

5490

At what CD4 count should highly active anti-retroviral treatment (HAART) commence in

asymptomatic HIV patients?

Explanation

Timing of treatment in human immunodeficiency virus infection

A number of cohorts exist, providing important data on the natural history and

progression of HIV infection

Multiple logistic regression can and has been used to determine the optimal point at

which to start HAART, and it appears that the point where the benefit of HAART

outweighs the risk is around 350 mm

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152 Responses Incorrect:

153 Responses Total:

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8/9/2016 MyPastest

Question 2 of 153

A 22-year-old woman returns from a holiday on the Kenyan coast She develops a fever,

deteriorates over the next 48 h and becomes unconscious and unrousable She has acute

renal failure Which one of the following options is the most appropriate investigation?

Explanation

Complications in malaria treatment

The patient in the present case has extremely severe falciparum malaria, with cerebralmalaria (coma) and renal failure (usually pre-renal) needing renal replacement therapyPatients with full-blown cerebral malaria are at an increased risk of fitting, which may

be treated with diazepam

Administration of prophylactic anticonvulsants may be associated with an increased

mortality

Exchange transfusion is recommended for a parasitaemia > 10% with complications (or

> 30% if no other complications)

Treatment of the malaria is with IV quinine, which increases insulin secretion and the

sensitivity of cells to insulin and can cause hypoglycaemia

Malaria itself can cause hypoglycaemia too, so blood glucose should be monitored

Computed tomography (CT) scan, head

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8/9/2016 MyPastest

Question 3 of 153

Which one of the following organisms is the most frequent cause of hospital-acquired

infections and is also developing increasing resistance to antimicrobial agents?

Explanation

Staphylococcus aureus infection

Epidemiological studies of Staphylococcus aureus infection, and increasingly these

concern meticillin-resistant Staph aureus (MRSA) strains, require typing methods to

distinguish between epidemic and endemic strains

Staph aureus is part of the normal flora in some individuals; about 25% of people carry

the organism permanently, a similar proportion never do, and the rest do so

intermittently

Common carriage sites are the nose, axillae, perineum and toe webs

Nasal carriage rates vary from 10% to 40% in normal adults outside a hospital

environment, but higher rates are often found in hospital patients, particularly those

who have been in hospital for several weeks

High carriage rates are also found in those with skin diseases such as eczema, those

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Chronic fatigue syndrome

A diagnosis of chronic fatigue syndrome (CFS) requires the presence of unexplained

chronic fatigue for more than six months

Although several formal definitions exist, cardinal features of CFS (besides fatigue)

include impaired memory or concentration, sore throats, myalgia, arthralgia, headaches,unrefreshing sleep and post-exertion malaise

CFS is a diagnosis of exclusion, which requires the absence of any other underlying

organic or psychiatric problem

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become unwell over the last 24 h On admission he looks unwell and has a temperature of 39

°C He has a pulse rate of 110 bpm Examination is otherwise unremarkable Which one of thefollowing options is the most appropriate next step?

Explanation

Malaria/Viral Haemorrhagic Fever Differential

The most likely diagnosis in the present case is malaria, in the current climate howeverthe major concern is for viral haemorrhagic fever, in particular a differential of Ebola,

and as such guidance has changed from that previously recommended

In the past, in someone returning from rural Sierra Leone guidance was send only onesample for malaria (if positive for malaria, can relax and treat for malaria)

New guidance dictates that if suspicion of viral haemorrhagic fever, then don't even

take a single sample to avoid exposure risk for lab staff, send directly to an isolation

unit (Royal Free, Newcastle, Liverpool, Sheffield) - so this would encompass anyone

Send samples for FBC, clotting, U&Es, LFTs and a malaria film to the lab

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An irregular plaque like lesion with central scarring is suggestive of lupus vulgaris

This is the commonest manifestation of cutaneous tuberculosis

Ringworm infection

Ringworm (Tinea corporis) infection usually presents with slightly itchy, asymmetrical

scaly patches that show central clearing and an advanced scaly raised edge

Occasionally vesicles or pustules may be seen in the edge

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Rashes in anti-retroviral therapy

Maculopapular rash an important and frequently encountered problem in anti-retroviraltherapy

Nevirapine is a non-nucleoside reverse-transcriptase inhibitor, a class of drugs well

recognised to cause maculopapular rashes This is the rationale for starting low-dose

therapy with nevirapine in the first 2 weeks

Zidovudine and lamivudine are nucleoside reverse-transcriptase inhibitors, which are

less frequently associated with rashes

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multiple, shallow and tender ulcers at the skin and mucous membrane of the vagina The

most probable diagnosis is:

Explanation

Genital herpes

Underlying causes

Infectious aetiologies of genital ulcers include herpes simplex virus (HSV), chancroid

(Haemophilus ducreyi), granuloma inguinale (Calymmatobacterium granulomatis),

syphilis (Treponema pallidum), HIV-specific ulcers (acute HIV infection or late HIV), and lymphogranuloma venereum (LGV, Chlamydia trachomatis serovars L1–3)

Non-infectious aetiologies include fixed drug reactions, Behçet’s disease, neoplasms,

and trauma

It is particularly important to consider these alternative causes if evaluations for the

infectious aetiologies do not lead to a diagnosis

HIV infection should always be considered and tested for

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chancroid often presents with deep, undermined and purulent ulcers

When a painless, indurated, clean-based ulcer is present, the diagnosis of syphilis is

more likely

Laboratory investigations

A number of laboratory tests can be used to make an accurate diagnosis:

Gram stain and culture on selective media (for H ducreyi)

Tzanck preparation, direct fluorescence antibody (DFA), and viral culture (for

HSV)

serological tests (for syphilis and LGV)

darkfield microscopy (for syphilis)

tissue biopsy (syphilis, granuloma inguinale)

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A backpacker who has recently returned from Indonesia is diagnosed as having as a nocardialinfection What would be the best technique for isolating and culturing the organism?

Explanation

Culture techniques for pathogenic organisms

Nocardia spp use paraffin as a source of carbon for growth

In this technique, a paraffin wax-coated glass rod is placed in the inoculated

carbon-free broth

Nocardia grow on the rod at the air–liquid interface

They are relatively slow to grow in blood cultures

Footpads of mice are used to grow of Mycobacterium leprae

Cell culture techniques are used to isolate Chlamydia trachomatis

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A 42-year-old single man who has been living in Thailand returns to the UK for a medical

consultation as he has deteriorating health He admits to engaging in casual sexual

relationships during his time in the country Over the past few weeks he has begun sufferingincreasing night sweats, weight loss and diarrhoea On examination his BP is 105/65 mmHg,pulse is 85/min and regular There is peripheral lymphadenopathy and right upper quadrantpain on abdominal examination His BMI is 21

Stool culture and microscopy negative for cysts and ovae

Which of the following is the most likely diagnosis?

9 9 +

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Explanation

The answer is Mycobacterium avium complex (MAC)

-The implication of this man’s gradually deteriorating health during his stay in Thailand is that

he has developed AIDS and the GI upset seen here is related to MAC Serological testing toconfirm the diagnosis of MAC is under development, currently culture of AAFB is required toconfirm its presence This patient should of course also have an HIV test Typically patientsare treated with combination antimicrobials, (a macrolide, Ethambutol and Rifampicin)

Blastomycosis is manifest by predominant respiratory symptoms, as is histoplasmosis

Cryptosporidium is diagnosed by the presence of oocysts on stool culture, and CMV is

associated with a more acute presentation than that seen here

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A patient presents with diarrhoea and vomiting He is jaundiced Hepatitis A infection is

diagnosed Which one of the following modes of transmission is most likely?

Explanation

Hepatitis A infection

Hepatitis A virus causes a self-limiting hepatitis

This RNA virus is acquired orally

The incubation period is between 2 and 6 weeks

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A 32-year-old man from Uganda is referred to hospital with a high eosinophil count by his GPfollowing routine blood tests He is entirely asymptomatic and has no past medical history ofnote Which of the following organisms is LEAST likely to be responsible?

Explanation

Eosinophilia

Aetiology

Eosinophilia is associated with tissue-invasive helminths: strongyloidiasis, Wucheria

infection, schistosomiasis could all present in this way and should be screened for hereOther notes

Entamoeba histolytica is associated with a spectrum of illness, including colitis, liver

abscess, extra-gastrointestinal disease (central nervous system (CNS), pulmonary

involvement) and asymptomatic infection Leukocytosis may occur but eosinophilia isNOT a feature

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African tick typhus

Diagnostic considerations in the present case

Both the eschar and travel history are very suggestive of African tick typhus

However, malaria should be excluded

Causative organism

The organism most commonly involved is Rickettsia conorii

Treatment

Treatment is with doxycycline, which often results in a very quick resolution of

symptoms and fever

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A 20-year-old woman presents to casualty with fever, diarrhoea, myalgia and a diffuse rashthat started 6 h ago She recovered from a similar episode 6 months ago She is currently

menstruating and is using tampons On examination her temperature is 40.1 °C, blood

pressure 80/50 mmHg, pulse 140/min Which one of the following options is the most likelydiagnosis?

Explanation

Toxic shock syndrome

Epidemiology

In the late 1970s there was an epidemic of toxic shock syndrome associated with

menstruation and tampon use

Toxic shock syndrome has also been described in non-menstruating women and in men,

in association with a wide variety of conditions and operations

Additionally, it has been reported in association with burns in children

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of treatment is supportive

Anti-staphylococcal antibiotics should be given to eradicate Staphylococcus aureus

from the local site; bacteraemia has rarely been reported in toxic shock syndrome

The staphylococci isolated are usually resistant only to penicillin

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A 20-year-old backpacker from Australia returns from a 3-month journey to Guatemala Shewas fully vaccinated prior to travel and took malaria prophylaxis She is vegetarian and atemainly salads and fruit while on holiday On her return, she has severe diarrhoea that has notresponded to a course of ciprofloxacin and metronidazole On examination she is dehydratedbut relatively well and apyrexial Which treatment is most likely to be effective?

Explanation

Cyclospora cayetanensis infection

Epidemiology

Cyclospora cayetanensis infection is a protozoan infection associated with eating

Guatemalan fruit (especially raspberries) and presents with a similar history to infection

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A 25-year-old lawyer from Edinburgh was brought into hospital with a 3-day history of

increasing shortness of breath and fevers She recently received a diagnosis of Cushing’s

disease and is awaiting treatment Initial examination revealed a respiratory rate of 20 breathsper minute and bilateral sparse crackles, with a characteristic buffalo hump and centripetalobesity Chest X-ray revealed sparse perihilar shadowing only She has been on the

admission’s ward for 2 days and is being treated with intravenous cefotaxime and oral

clarithromycin Overnight, she has deteriorated and arterial blood gases reveal a p (O ) of 6.5

on 24% oxygen Which one of the following management options is most appropriate?

Although classically associated with HIV infection (and a CD4 count < 200 cells/mm ),

Pneumocystis infection also occurs in patients who are immunosuppressed for other

reasons, eg post bone-marrow transplantation and those on high-dose steroids;

2

Increase the oxygen to 100% and arrange admission to medical HDU for closer

monitoring, and change the antibiotics to iv Tazocin

Increase the oxygen to 100% and arrange admission to medical HDU, adding

co-trimoxazole, amphotericin and switching to iv Tazocin

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In addition to increasing the oxygen to 100% and arrange admission to medical

high-dependency unit (HDU) and iv co-trimoxazole, amphotericin should also be considered,

as she is also likely to be at risk of a fungal infection

However, this is less likely than Pneumocystis jirovecii (PCJ; formerly Pneumocystis

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A 45-year-old man of Sudanese origin is admitted with a history of low-grade fever for over 7days He migrated to the UK 1 year ago and has a past history of well-controlled asthma Histemperature chart shows that on some days there is a doubled rise in his temperature during

24 h Examination shows a massively enlarged spleen and mild hepatomegaly His full bloodcount shows a mild microcytic and hypochromic anaemia along with granulocytopenia andthrombocytopenia Which one of the following investigations will establish a diagnosis?

Explanation

Visceral leishmaniasis

The diagnosis in the present case is visceral leishmaniasis

Causative organism

It is caused by infection with Leishmania donovani

L donovani is found in the Mediterranean and Red Sea area, Sudan, India, China and

South America

The organism multiplies in the monocytes and macrophages in various organs,

especially in the liver and spleen (which become enlarged), the bone marrow, lymphoidtissue and the small intestinal mucosa

Incubation period

The incubation period may be up to 10 years with an insidious onset and low-grade

Bone marrow aspirate

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fever

Clinical features and prognosis

The temperature typically rises twice in 24 h

The spleen and liver are enlarged and if not treated the patient becomes wasted

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A 25-year-old man presents to the GP with a history of severe diarrhoea which contained

occasional flecks of blood This was accompanied by unpleasant gripping abdominal pain Itcame on some 6–7 h after eating a rice-based dish He had eaten the food from a local

Chinese takeaway His flatmate had had similar symptoms after visiting the same takeaway afew days earlier and these resolved within a day

Which one of the following is the most likely causative organism?

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A 17-year-old girl who started medical school 2 weeks ago presents with fever, confusion,

hypotension (75/50 mmHg) and a rapidly spreading purpuric rash over her whole body

Which one of the following options is the investigation most likely to deliver a rapid

diagnosis? (Ceftriaxone has already been commenced)

The patient needs immediate intensive care unit (ITU) care

A CT scan will delay this

Other considerations

A lumbar puncture (LP) will probably be contraindicated as she will undoubtedly be

thrombocytopenic and/or have a disseminated intravascular coagulation (DIC)

High-dose steroids probably worsen the outcome

She should be in respiratory isolation for 24 h

Meningococcal PCR is now a standard investigation

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Trachoma is a chronic keratoconjunctivitis that affects more than 500 million people

worldwide, mainly in the developing countries Some seven million people are blind as a result

of it Which one of the following organisms is most likely to be responsible for this infection?

Explanation

Trachoma

Trachoma is a chronic keratoconjunctivitis caused by Chlamydia trachomatis, believed

to affect some 500 million people, of whom 7 million are blind and 10 million have somevisual impairment

After cataracts, it is the most common cause of blindness world-wide, but is now

confined largely to developing countries

Herpes simplex virus

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