Mock Infectious Diseases Module 4

An 83-year-old man with advanced chronic obstructive pulmonary disease (COPD) and poorly controlled diabetes mellitus presents to the emergency department with severe pneumonia. He is febrile and tachypnoeic and has a productive cough with purulent sputum.

His chest X-ray shows bilateral infiltrates. He was hospitalised two months ago for a COPD exacerbation and treated with intravenous antibiotics, during which Pseudomonas aeruginosa was isolated from sputum culture.

Considering his clinical history, what is the strongest single risk factor for his current respiratory infection with Pseudomonas aeruginosa?

Which of the following is the most common cause of recurrent bacterial meningitis?

Which of the following characteristics is not considered a risk factor for the development of human papillomavirus (HPV)–related cancer?

An 18-year-old woman became sexually active two years ago. Over the past six months she has had two sexual partners who intermittently used condoms. She has not received HPV vaccination but has previously received Hepatitis B vaccine.

She is asymptomatic and examination is unremarkable. Based on routine screening recommendations, which infections should this patient be tested for?

Fidaxomicin is capable of eradicating which type of bacteria?

Which of the following antibiotics is least useful in the treatment of methicillin-resistant Staphylococcus aureus (MRSA)?

A 28-year-old man presents with a two-week history of fever, sore throat, myalgia, and a maculopapular rash following a high-risk sexual exposure.

Which of the following clinical features, if present, is most specific for acute HIV-1 infection (acute retroviral syndrome) as opposed to a common viral exanthem?

A 25-year-old renal transplant recipient on mycophenolate and sirolimus attends for pre-travel advice.

Which of the following vaccines is contraindicated?

Which of the following dental procedures does NOT require infective endocarditis prophylaxis (in an at-risk patient)?

Which of the following Aedes mosquitoes is the principal vector for Zika virus?

Regarding the rash of Mpox (monkeypox), all of the following statements are true except:

Which of the following statements regarding Candida auris is incorrect?

Statins are recommended for primary cardiovascular prevention in many people with HIV and because all statins are metabolised to some degree by CYP3A4, which statin must be avoided in a person taking a protease-inhibitor– or cobicistat-boosted regimen?

What is the primary indication for the use of lefamulin?

A 68-year-old man is admitted with fever and dysuria three weeks after returning from an elective surgical procedure in India. Urine culture grows Escherichia coli with the following susceptibility profile:

Molecular testing detects an NDM-1 gene.

What is the biochemical mechanism by which this enzyme confers resistance to the affected agents?

A 24-year-old man who injects drugs presents with a fluctuant abscess over the right forearm and fever. Blood cultures are collected. Gram stain of the drained pus shows Gram-positive cocci in clusters. Culture grows Staphylococcus aureus with the following results:

Which genetic element is most likely responsible for this resistance phenotype?

A 55-year-old woman on haemodialysis via a tunnelled catheter develops rigors during dialysis. Blood cultures from two sites grow MRSA.

A transthoracic echocardiogram is normal. She is started on vancomycin. The catheter is removed.

On day 4, repeat blood cultures remain positive. Vancomycin trough is therapeutic and the isolate’s vancomycin minimum inhibitory concentration is 1.5 mg/L. She has no rash or renal impairment.

Which is the most appropriate next step in management?

A 62-year-old man with acute myeloid leukaemia is neutropenic following induction chemotherapy. He develops fever.

A midstream urine specimen collected while asymptomatic (no dysuria, frequency or suprapubic pain) grows Enterococcus faecium that is vancomycin resistant (vanB). Blood cultures are pending.

He has a peripherally inserted central catheter in situ. Chest imaging is clear. He is commenced on piperacillin-tazobactam per the febrile neutropenia protocol.

Regarding the vancomycin-resistant enterococcus in the urine, what is the most appropriate initial action?

A 70-year-old woman with a biliary stent develops cholangitis. Blood cultures grow Enterobacter cloacae with the following initial susceptibilities:

She is commenced on ceftriaxone. After 4 days of clinical improvement she deteriorates, and repeat blood cultures grow Enterobacter cloacae now resistant to ceftriaxone and ceftazidime.

What is the mechanism responsible for this change in susceptibility?

A 58-year-old man presents with fever and flank pain. He is haemodynamically stable. Urine and blood cultures both grow Escherichia coli with the following results:

The isolate is confirmed as an ESBL producer. He is diagnosed with an ESBL E. coli bacteraemia secondary to pyelonephritis.

Which is the most appropriate definitive therapy?

A 45-year-old woman presents with dysuria, urinary frequency and suprapubic discomfort, without fever or systemic features. She has no flank pain.

Urine culture grows Escherichia coli confirmed as an ESBL producer with the following results:

She is diagnosed with ESBL E. coli cystitis and is otherwise well with normal renal function (eGFR >60 mL/min/1.73m²).

Which is the most appropriate treatment?

A 72-year-old man is transferred from an overseas hospital and develops a hospital-acquired pneumonia with bacteraemia.

Blood cultures grow Klebsiella pneumoniae resistant to all penicillins, cephalosporins and carbapenems.

The reference laboratory confirms a KPC-2 carbapenemase.

Ceftazidime-avibactam susceptibility is pending.

Which is the most appropriate targeted therapy?

An 80-year-old woman is transferred to your intensive care unit directly from a hospital in a European country where a Candida auris outbreak has been reported.

She is intubated with a central venous catheter and urinary catheter in situ. She currently has no signs of infection. Screening swabs are pending.

What is the most appropriate immediate infection prevention measure?

A 66-year-old man is admitted from a residential aged care facility with septic shock (lactate 4.8 mmol/L; reference <2.0 mmol/L), hypotension requiring noradrenaline, and a presumed urinary source.

He was hospitalised in Southeast Asia two months ago. He has been colonised with an ESBL-producing E. coli on a prior urine culture.

Local rates of ESBL in urinary E. coli exceed 10%. Blood cultures are collected and empirical therapy must be commenced immediately.

Which is the most appropriate empirical antimicrobial choice?

A 68-year-old woman presents to the emergency department with a 3-week history of gradually worsening bilateral lower limb redness, warmth and swelling extending from the ankles to the mid-shins.

She reports mild discomfort but denies fever, rigors or systemic symptoms.

Her history includes obesity (BMI 38 kg/m²), type 2 diabetes mellitus and chronic venous insufficiency. She was commenced on oral flucloxacillin by her general practitioner 5 days ago with no improvement.

On examination, she is afebrile (36.8°C) and haemodynamically stable. Both lower limbs demonstrate symmetrical erythema, hyperpigmentation, induration and pitting oedema, with associated haemosiderin staining and scaling. There is no discrete area of demarcation, no lymphangitis and no regional lymphadenopathy.

Investigations:

Venous duplex ultrasound demonstrates chronic venous insufficiency with no evidence of deep vein thrombosis.

Which is the most appropriate next step in management?

A 54-year-old man presents with a 24-hour history of severe pain in his left thigh. Two days earlier he sustained a minor abrasion while gardening.

He is febrile (38.9°C), tachycardic (heart rate 122/min), and hypotensive (blood pressure 88/52 mmHg).

Examination reveals pain that appears disproportionate to the modest overlying erythema, with associated violaceous discolouration and early bullae formation. There is a serosanguineous discharge from the wound.

Investigations:

Gram stain of wound fluid shows Gram-positive cocci in chains. He is taken urgently for surgical exploration, which confirms necrotising fasciitis, and empirical broad-spectrum antibiotics are commenced.

In addition to the primary antibiotic regimen and surgical debridement, adding which of the following agents is most likely to reduce mortality in this patient?

A 59-year-old woman presents with her fourth episode of left lower limb cellulitis in the past 18 months. Each episode has responded to oral flucloxacillin.

Her history includes chronic lymphoedema following pelvic surgery and prior radiotherapy, and she has recurrent tinea pedis.

On this presentation she has a well-demarcated area of erythema, warmth and tenderness over the left shin. She is systemically well and afebrile.

Investigations:

The current episode is treated successfully with a course of oral antibiotics.

In addition to treating her tinea pedis and optimising her lymphoedema management, which of the following is the most appropriate intervention to reduce the risk of future recurrence?

A 72-year-old man presents to the emergency department with a 3-day history of productive cough, fevers and increasing breathlessness. He has a background of hypertension and takes amlodipine.

On examination he is alert but slightly confused (new onset per his wife), with a respiratory rate of 32/min, blood pressure of 96/58 mmHg, heart rate of 104/min, temperature 38.6°C and oxygen saturation 91% on room air. Auscultation reveals bronchial breathing at the right base.

Investigations:

Chest x-ray demonstrates right lower lobe consolidation.

Based on the appropriate severity assessment, which is the most appropriate management plan?

A 58-year-old woman is admitted with moderate-severity community-acquired pneumonia. Blood cultures taken on admission subsequently grow Streptococcus pneumoniae. The laboratory reports the following susceptibility for the isolate:

She has no penicillin allergy and is clinically improving on intravenous benzylpenicillin.

Which of the following statements best explains why intravenous benzylpenicillin remains appropriate for this isolate?

A 64-year-old man was admitted 5 days ago with moderate-severity community-acquired pneumonia and commenced on intravenous benzylpenicillin plus oral doxycycline, later switched to oral amoxicillin. He has improved substantially.

Urinary pneumococcal antigen was positive; blood cultures and Legionella urinary antigen were negative.

His current observations are: temperature 36.7°C, heart rate 74/min, respiratory rate 16/min, blood pressure 128/76 mmHg and oxygen saturation 97% on room air. He has been afebrile for 72 hours and is eating and mobilising well.

Investigations today:

There is no evidence of empyema, lung abscess or metastatic infection.

Which is the most appropriate management regarding antibiotic duration?