Infectious Diseases MCQs ( Set 1)
This is MCQs set 1 of infectious diseases of Medicine. Answers with explanation is given at the end of each MCQ.
1- A 50 year old woman returned from Sri Lanka several days ago. She presents to hospital with headaches, myalgia and a fever of 38.5°C.Examination reveals multiple petechiae.
Her bloods show Hb 13 g/dl, WCC 11 x 109/L, platelet count 70 x 109/L. Thick and thin films for malaria are negative.
Which one of the following infections is most likely?
1- Plasmodium malariae
2- Brucella
3- Rickettsia
4- Plasmodium ovale
5- Dengue fever
Answer: 5- Dengue fever
Dengue fever is a condition caused by an RNA arbovirus which is common in tropical and subtropical areas, particularly India, South East Asia and the Pacific. Fevers, joint pains, myalgia, rash and retro-orbital pain are common. A petechial rash suggests the possibility of impending serious sequelae (dengue haemorrhagic fever/shock syndrome) and indicates that she has been previously infected with another serotype.
2- A 75 year old woman presents with a Two day history of confusion. She had complained to her husband of a headache and neck stiffness. A lumbar puncture was performed. CSF microscopy revealed: WBC 650 cells/mL (<5) 90% neutrophils
A few Gram positive diplococci on staining. What is the likely cause of her meningitis?
1- Listeria monocytogenes
2- Streptococcus pneumoniae
3- Neisseria meningitidis
4- HIV
5- Herpes simplex
Answer: 2- Streptococcus pneumoniae
Streptococci are gram positive cocci. Pneumococcal meningitis is commoner in older patients. Neisseria meningitidis are gram negative diplococci, whilst listeria monocytogenes is a small gram positive bacillus.
3- A 40 year old man presented to hospital with fever, intermittent rigors and lethargy. He had returned from a holiday to West Africa six months previously.
What is the likely diagnosis?
1- Plasmodium falciparum malaria
2- Plasmodium ovale malaria
3- Typhoid fever
4- Brucellosis
5- Leishmaniasis
Answer: 2- Plasmodium ovale malaria
Plasmodium ovale malaria and its cyclic paroxysms occur every 48 hours (tertian fever). Plasmodium ovale is the rarest of the four species and is apparently more restricted in distribution.However, it is common in the West African countries of Ghana, Liberia, and Nigeria.
4- A 31-year-old white male presented to a general practitioner with a tw o-day history of fever, headaches, generalised aches and pains, lethargy and loss of appetite. He had travelled to Papua New Guinea 2 months ago.A full blood count showed: lymphocytes, 0.71 x 10 9 /L; neutrophils, 1.95 x 10 9 /L; and platelets, 33 x 10 9 /L; (normal, 150-450 x 10 9 /L). Haemoglobin concentration was in the normal range. Blood film shows schizonts.
Which one of the following is the most likely organism?
1- Schistosoma
2- Mycobacterium tuberculosis
3- Pasteurella
4- Plasmodium vivax
5- Leptospira
Answer: 4- Plasmodium vivax
The history and FBC count is most consistent with malaria. In this case, vivax malaria.
5- A 19 year old female has a several day history of urethral discharge. Mid stream urine is negative. A swab was sent but no organisms were grown.
Which one of the following should be prescribed?
1- Penicillin V
2- Trimethoprim
3- Metronidazole
4- Doxycycline
5- Ciprofloxacin
Answer: 4- Doxycycline
The diagnosis is non gonococcal urethritis. This is commonly due to Chlamydia. Treatment of choice is doxycycline.