Common Infections Practice Questions

Question 1

A 65-year-old man with diabetes presents with a non-healing foot ulcer for 3 months. X-ray shows osteolytic changes in the underlying bone. MRI confirms osteomyelitis. What is the most appropriate treatment duration for antibiotics?

Accepted Answer

12 weeks total therapy

Answer

2 weeks IV

Answer

4 weeks IV

Answer

6 weeks IV

Answer

4-6 weeks IV followed by 2-6 weeks oral

Question 2

A 16-year-old boy presents with a 1-week history of sore throat and fever. He has developed a widespread maculopapular rash after taking amoxicillin prescribed by his GP. What is the most likely underlying diagnosis?

Accepted Answer

Infectious mononucleosis

Answer

Penicillin allergy

Answer

Scarlet fever

Answer

Kawasaki disease

Answer

Stevens-Johnson syndrome

Question 3

A 35-year-old man with HIV infection (CD4 count 80 cells/mm³, viral load 125,000 copies/mL, not on antiretroviral therapy) presents with a 4-week history of headache, fever, and confusion. CT head shows basal meningeal enhancement and multiple small nodules. Lumbar puncture shows: opening pressure 32 cmH2O, CSF white cells 45/mm³ (80% lymphocytes), protein 1.2 g/L, glucose 1.9 mmol/L (serum glucose 5.4 mmol/L). India ink stain is positive. Cryptococcal antigen is positive in both CSF and serum at titres of 1:2048 and 1:1024 respectively. He is started on liposomal amphotericin B and flucytosine. Which one of the following additional interventions has been shown to improve survival in this patient?

Accepted Answer

Performing daily therapeutic lumbar punctures until opening pressure normalizes

Answer

Commencing antiretroviral therapy immediately alongside antifungal treatment

Answer

Adding adjunctive dexamethasone 0.4 mg/kg daily for 6 weeks

Answer

Adding adjunctive interferon-gamma to enhance immune response

Answer

Inserting a ventriculoperitoneal shunt to manage hydrocephalus

Question 4

A 25-year-old woman presents with a 2-week history of sore throat, fever, and fatigue. She has cervical lymphadenopathy and splenomegaly. Her throat swab is negative for Group A Streptococcus. What is the most likely diagnosis?

Accepted Answer

Infectious mononucleosis

Answer

Viral pharyngitis

Answer

Bacterial pharyngitis

Answer

Diphtheria

Answer

Candidiasis

Question 5

A 31-year-old man presents with fever, sore throat, and a widespread maculopapular rash after taking amoxicillin prescribed by his GP. What is the most likely underlying diagnosis?

Accepted Answer

Infectious mononucleosis

Answer

Penicillin allergy

Answer

Scarlet fever

Answer

Kawasaki disease

Answer

Stevens-Johnson syndrome

Question 6

A 58-year-old man with diabetes presents with severe foot pain and a deep ulcer exposing bone. X-ray shows osteolytic changes. What is the most likely complication?

Accepted Answer

Osteomyelitis

Answer

Cellulitis

Answer

Charcot arthropathy

Answer

Peripheral arterial disease

Answer

Deep vein thrombosis

Question 7

A 34-year-old woman with Crohn's disease on adalimumab presents with a 10-day history of multiple painful nodules on both shins. The lesions are 2-4cm in diameter, raised, tender, and erythematous without ulceration or pustulation. She reports associated joint pains in her knees and ankles but no fever. Recent colonoscopy showed active inflammation. Blood tests reveal WCC 11.2 × 10⁹/L, CRP 78 mg/L, ESR 65 mm/hr. What is the most likely diagnosis?

Accepted Answer

Erythema nodosum

Answer

Cellulitis secondary to immunosuppression

Answer

Pyoderma gangrenosum

Answer

Sweet's syndrome (acute febrile neutrophilic dermatosis)

Answer

Subcutaneous nodular panniculitis from adalimumab injection sites

Question 8

A 72-year-old man with chronic obstructive pulmonary disease is admitted with an exacerbation and started on prednisolone 30mg daily. On day 3 of admission, he develops a painful, erythematous rash on his right shin. The affected area is warm and tender with a well-demarcated, raised border and has a characteristic orange-peel (peau d'orange) appearance. His temperature is 38.4°C. Blood tests show WCC 16.2 × 10⁹/L, CRP 128 mg/L. Which organism is most likely responsible for this infection?

Accepted Answer

Streptococcus pyogenes (Group A Streptococcus)

Answer

Staphylococcus aureus

Answer

Pseudomonas aeruginosa

Answer

Haemophilus influenzae

Answer

Pasteurella multocida

Question 9

A 61-year-old man presents with a 4-day history of a painful red swelling on his upper back. On examination, there is a 5cm area of indurated, erythematous skin with multiple pustular openings discharging purulent material from several adjacent hair follicles. His temperature is 37.8°C. He has well-controlled type 2 diabetes. What is this lesion called?

Accepted Answer

Carbuncle

Answer

Furuncle

Answer

Hidradenitis suppurativa

Answer

Folliculitis

Answer

Erysipelas

Common Infections

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