A 55-year-old woman with type 2 diabetes presents with necrotising fasciitis of the right thigh following minor trauma. She is hypotensive (BP 85/50 mmHg), tachycardic (HR 125/min), and has crepitus extending proximally. Blood results show lactate 4.2 mmol/L, creatinine 185 μmol/L, and WCC 22 × 10⁹/L with left shift. What is the most appropriate immediate antimicrobial regimen?
Q242
A 32-year-old injection drug user presents with a painful, fluctuant swelling on his left forearm. Incision and drainage is performed, yielding 15mL of purulent material. Gram stain shows gram-positive cocci in clusters. The patient is otherwise well with normal observations. Which empirical antibiotic regimen is most appropriate pending culture results?
Q243
A 68-year-old diabetic patient with hospital-acquired pneumonia has been receiving intravenous piperacillin-tazobactam for 5 days. Blood cultures grow Pseudomonas aeruginosa sensitive to all tested antibiotics. The patient has clinically improved, is apyrexial for 48 hours, and inflammatory markers are trending downward (CRP decreased from 185 to 65 mg/L). Which action best demonstrates appropriate antimicrobial stewardship?
Q244
A 45-year-old man presents to the Emergency Department with a 2-day history of increasing pain, swelling, and redness of his right lower leg. He has a temperature of 38.5°C. Examination reveals a well-demarcated area of erythema extending from the ankle to mid-calf with associated warmth and tenderness. There is no crepitus or bullae. His inflammatory markers show CRP 145 mg/L and WCC 14.2 × 10⁹/L. What is the most appropriate initial antibiotic choice?
Common Infections UK Medical PG Practice Questions and MCQs
Question 241: A 55-year-old woman with type 2 diabetes presents with necrotising fasciitis of the right thigh following minor trauma. She is hypotensive (BP 85/50 mmHg), tachycardic (HR 125/min), and has crepitus extending proximally. Blood results show lactate 4.2 mmol/L, creatinine 185 μmol/L, and WCC 22 × 10⁹/L with left shift. What is the most appropriate immediate antimicrobial regimen?
A. Intravenous flucloxacillin and clindamycin
B. Intravenous benzylpenicillin and clindamycin
C. Intravenous piperacillin-tazobactam, clindamycin, and vancomycin (Correct Answer)
D. Intravenous meropenem alone
E. Intravenous co-amoxiclav and metronidazole
Explanation: ***Intravenous piperacillin-tazobactam, clindamycin, and vancomycin***
- In a diabetic patient with **Type 1 (polymicrobial)** necrotising fasciitis, broad-spectrum coverage including **MRSA**, **Gram-negatives**, and **anaerobes** is essential for survival.
- **Clindamycin** is added specifically for its **antitoxin effect** by inhibiting bacterial protein synthesis and suppressed toxin production from Group A Streptococcus.
*Intravenous flucloxacillin and clindamycin*
- This regimen provides good coverage for **Group A Streptococcus** and **Staphylococcus aureus**, but lacks essential **Gram-negative** and **anaerobic** coverage.
- In a patient with **diabetes** and sepsis, the risk of polymicrobial infection is high, making this spectrum too narrow.
*Intravenous benzylpenicillin and clindamycin*
- This is the standard treatment for **Type 2 (monomicrobial)** necrotising fasciitis caused by Group A Streptococcus.
- It fails to cover **Gram-negative bacilli** and **Staphylococcus aureus**, which are common in necrotising fasciitis following minor trauma in diabetics.
*Intravenous meropenem alone*
- While **meropenem** provides excellent broad-spectrum coverage, it does not possess the **antitoxin properties** that clindamycin offers.
- Monotherapy lacks specific **MRSA coverage**, which is a significant concern in patients with co-morbidities like **diabetes mellitus**.
*Intravenous co-amoxiclav and metronidazole*
- This combination provides some Gram-negative and anaerobic coverage but is insufficient for the **high bacterial load** and severity of this surgical emergency.
- It lacks the **anti-toxin effect** of clindamycin and does not provide adequate protection against resistant organisms like **MRSA**.
Question 242: A 32-year-old injection drug user presents with a painful, fluctuant swelling on his left forearm. Incision and drainage is performed, yielding 15mL of purulent material. Gram stain shows gram-positive cocci in clusters. The patient is otherwise well with normal observations. Which empirical antibiotic regimen is most appropriate pending culture results?
A. Oral flucloxacillin alone
B. Oral co-amoxiclav and doxycycline
C. Intravenous vancomycin
D. Oral flucloxacillin and rifampicin
E. No antibiotics required following adequate drainage (Correct Answer)
Explanation: ***No antibiotics required following adequate drainage***- For a **simple cutaneous abscess** in an immunocompetent patient with normal observations, **incision and drainage** is considered definitive treatment without the need for antibiotics.- Clinical guidelines suggest that once **source control** is achieved, antibiotics offer minimal benefit unless there is evidence of **systemic inflammatory response** or extensive surrounding **cellulitis**.*Oral flucloxacillin alone*- While **flucloxacillin** is excellent for **Gram-positive cocci** like MSSA, it is unnecessary for a localized, drained abscess in a stable patient.- Overuse of antibiotics in cases where **surgical drainage** is sufficient contributes to the development of **antimicrobial resistance**.*Oral co-amoxiclav and doxycycline*- This combination provides broad coverage, including against **MRSA** (via doxycycline), but is not indicated for a simple, well-drained **skin and soft tissue infection**.- Broad-spectrum agents like **co-amoxiclav** increase the risk of side effects and **Clostridioides difficile** infection without providing clinical benefit in this scenario.*Intravenous vancomycin*- **Intravenous vancomycin** is reserved for severe, life-threatening infections or cases where **MRSA** is suspected and the patient is **haemodynamically unstable**.- This patient has **normal observations** and is "otherwise well," making inpatient parenteral therapy inappropriate and unnecessary.*Oral flucloxacillin and rifampicin*- **Rifampicin** is rarely used as a primary agent for skin infections and is typically reserved for **prosthetic joint infections** or adjunctive treatment in specialized cases.- Adding a second agent increases the risk of **drug-drug interactions** and hepatotoxicity without improving outcomes for a **drained abscess**.
Question 243: A 68-year-old diabetic patient with hospital-acquired pneumonia has been receiving intravenous piperacillin-tazobactam for 5 days. Blood cultures grow Pseudomonas aeruginosa sensitive to all tested antibiotics. The patient has clinically improved, is apyrexial for 48 hours, and inflammatory markers are trending downward (CRP decreased from 185 to 65 mg/L). Which action best demonstrates appropriate antimicrobial stewardship?
A. Continue IV piperacillin-tazobactam for a total of 14 days
B. Switch to IV meropenem for broader coverage
C. Switch to oral ciprofloxacin to complete the course (Correct Answer)
D. Stop all antibiotics as the patient has improved
E. Add IV gentamicin for synergistic effect
Explanation: ***Switch to oral ciprofloxacin to complete the course***
- Antimicrobial stewardship emphasizes an **IV-to-oral switch** when a patient is clinically stable, afebrile, and can tolerate oral medications.
- **Oral ciprofloxacin** has excellent bioavailability and is a highly effective agent against **Pseudomonas aeruginosa**, allowing for safe and efficient completion of treatment while reducing risks associated with prolonged IV access.
*Continue IV piperacillin-tazobactam for a total of 14 days*
- Continuing IV therapy beyond clinical stability increases the risk of **catheter-related bloodstream infections** and prolongs hospital stay/costs.
- For most hospital-acquired pneumonias, a **7-day course** of antibiotics is typically sufficient, especially for gram-negative organisms like Pseudomonas, unless complicated by abscess or empyema.
*Switch to IV meropenem for broader coverage*
- Escalating to a **carbapenem** when the organism is known and sensitive to a narrower-spectrum agent like piperacillin-tazobactam promotes **antibiotic resistance**.
- Broadening coverage is unnecessary as the patient is **clinically improving**, and the specific pathogen and its sensitivities are already known.
*Stop all antibiotics as the patient has improved*
- Stopping therapy after only 5 days for a **Pseudomonas aeruginosa** infection, even with improvement, carries a high risk of **treatment failure** and clinical relapse.
- Standard guidelines recommend completing a defined course of treatment (typically **7 days**) to ensure pathogen eradication and prevent resistance development.
*Add IV gentamicin for synergistic effect*
- **Double coverage** or synergistic therapy is generally not necessary for a stable patient with known sensitivities, especially after clinical improvement.
- Adding **gentamicin** significantly increases the risk of serious adverse effects such as **nephrotoxicity** and ototoxicity without providing additional clinical benefit in this context.
Question 244: A 45-year-old man presents to the Emergency Department with a 2-day history of increasing pain, swelling, and redness of his right lower leg. He has a temperature of 38.5°C. Examination reveals a well-demarcated area of erythema extending from the ankle to mid-calf with associated warmth and tenderness. There is no crepitus or bullae. His inflammatory markers show CRP 145 mg/L and WCC 14.2 × 10⁹/L. What is the most appropriate initial antibiotic choice?
A. Intravenous flucloxacillin (Correct Answer)
B. Oral amoxicillin
C. Intravenous co-amoxiclav
D. Oral doxycycline
E. Intravenous meropenem
Explanation: ***Intravenous flucloxacillin***
- The patient presents with systemic features of infection (**fever**, **high CRP**, and **leukocytosis**), necessitating **intravenous therapy** for moderate-to-severe cellulitis.
- **Flucloxacillin** is the first-line choice as it provides targeted coverage against the most common causative organisms: **Staphylococcus aureus** and **Streptococcus pyogenes**.
*Oral amoxicillin*
- Amoxicillin is ineffective against **Staphylococcus aureus** because the bacterium produces **beta-lactamases** that destroy the antibiotic.
- Oral administration is inappropriate here due to the patient's **systemic toxicity** and the severity of clinical markers.
*Intravenous co-amoxiclav*
- While effective, **co-amoxiclav** provides unnecessarily broad-spectrum coverage, including against **anaerobes**, which are not typically involved in uncomplicated cellulitis.
- It is usually reserved for **facial cellulitis**, animal bites, or cases where **Gram-negative** organisms are suspected.
*Oral doxycycline*
- **Doxycycline** is generally used as a second-line oral therapy for patients with a **penicillin allergy** but is not the primary choice for acute systemic infection.
- The clinical severity (CRP 145) requires the rapid onset and bio-availability of **injectable antibiotics** rather than oral agents.
*Intravenous meropenem*
- **Meropenem** is a broad-spectrum **carbapenem** reserved for life-threatening infections or multi-drug resistant organisms.
- Using it for standard cellulitis violates **antimicrobial stewardship** principles and risks increasing bacterial resistance.
