Common Infections — MCQs
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A 28-year-old woman presents with a 3-day history of painful swelling in her right axilla. She has no fever. Examination reveals a 2cm tender, erythematous, fluctuant nodule in the axilla with surrounding induration. There is no lymphadenopathy and no evidence of ascending lymphangitis. She has a past medical history of similar lesions in both axillae over the past 2 years. What is the most likely diagnosis?
A 67-year-old man with type 2 diabetes presents with a 4-day history of severe pain, swelling, and erythema of his left foot following a minor cut. Examination reveals a dusky, violaceous discolouration with bullae containing dark fluid, crepitus on palpation, and anaesthesia of the overlying skin. Temperature is 38.9°C, heart rate 118/min, blood pressure 98/62 mmHg. Blood tests show lactate 4.2 mmol/L, creatinine 178 μmol/L (baseline 92), and creatine kinase 3,420 U/L. What is the single most important immediate management step?
According to current UK antimicrobial guidance, what is the recommended duration of antibiotic therapy for an immunocompetent adult with uncomplicated cellulitis of the lower limb showing good clinical response?
A 36-year-old woman with systemic lupus erythematosus on prednisolone 20mg daily and mycophenolate mofetil presents with a 5-day history of painful vesicular rash in a dermatomal distribution on the right side of her chest. Several vesicles have coalesced and there is involvement crossing the midline anteriorly. She has no visual symptoms. Temperature is 37.8°C. What is the most appropriate management?
A hospital antimicrobial stewardship team reviews audit data showing that 45% of patients receiving antimicrobials for more than 5 days lack documented indication, review dates, or stop/review dates in their medical records. Which intervention, according to evidence-based antimicrobial stewardship practice, would most effectively address this documentation deficiency?
A 41-year-old man who works as a fishmonger presents with a 48-hour history of a painful, rapidly spreading erythematous swelling on his right hand following a puncture injury from a fish bone. The affected area has violaceous bullae and is exquisitely tender. He is systemically well with temperature 37.4°C. Blood tests show WCC 11.2 × 10⁹/L and CRP 28 mg/L. Which organism is most likely responsible?
Which of the following antimicrobial prescribing practices best demonstrates the 'Start Smart - Then Focus' antimicrobial stewardship principle of 'review and revise' at 48-72 hours?
A 33-year-old woman presents to the Emergency Department with a 12-hour history of severe pain and swelling of her left breast. She is 3 weeks postpartum and exclusively breastfeeding. On examination, there is a 4cm fluctuant, erythematous, tender mass in the upper outer quadrant of the left breast. Temperature is 38.7°C. What is the most appropriate management?
A 54-year-old man with known cirrhosis (Child-Pugh class B) presents with a 3-day history of fever, abdominal pain, and confusion. He has tense ascites. Diagnostic paracentesis reveals ascitic fluid with neutrophil count of 320 cells/mm³, protein 18 g/L, and glucose 3.8 mmol/L. Blood cultures are pending. According to antimicrobial stewardship principles and current evidence, what is the most appropriate initial antibiotic regimen?
A 78-year-old woman with chronic obstructive pulmonary disease is admitted with acute exacerbation. She is started on amoxicillin 500mg three times daily. On day 5 of admission, she develops watery diarrhoea (5 episodes in 24 hours). Temperature is 38.2°C. Abdominal examination reveals mild lower abdominal tenderness but no peritonism. Blood tests show WCC 16.8 × 10⁹/L (neutrophils 14.2 × 10⁹/L). What is the most appropriate next step in management?
Common Infections UK Medical PG Practice Questions and MCQs
Question 191: A 28-year-old woman presents with a 3-day history of painful swelling in her right axilla. She has no fever. Examination reveals a 2cm tender, erythematous, fluctuant nodule in the axilla with surrounding induration. There is no lymphadenopathy and no evidence of ascending lymphangitis. She has a past medical history of similar lesions in both axillae over the past 2 years. What is the most likely diagnosis?
- A. Hidradenitis suppurativa (Correct Answer)
- B. Furunculosis
- C. Cat scratch disease
- D. Lymph node abscess
- E. Mycobacterial lymphadenitis
Explanation: ***Hidradenitis suppurativa*** - This chronic inflammatory condition is characterized by **recurrent painful nodules**, abscesses, and sinus tracts in **apocrine gland-bearing areas** like the axillae, groin, and gluteal cleft. - The history of similar lesions over **2 years** in both axillae, presenting as a tender, erythematous, fluctuant nodule without fever or significant lymphadenopathy, is classic for **hidradenitis suppurativa**. *Furunculosis* - These are acute deep-seated **follicular infections** (boils) caused by *Staphylococcus aureus* and typically resolve without recurrence in the same specific locations. - While presenting as a tender nodule, furuncles lack the **chronic, relapsing-remitting course** and specific involvement of **apocrine gland-rich areas** seen in this patient. *Cat scratch disease* - Caused by **Bartonella henselae**, it typically presents with **regional lymphadenopathy** proximal to a cat scratch or bite, not recurrent primary skin nodules. - The enlarged lymph nodes are usually tender, firm, and often solitary, distinct from the **fluctuant, recurring axillary skin lesions** described. *Lymph node abscess* - This involves a suppurative infection of a **lymph node itself**, often secondary to a draining infection, and is typically accompanied by systemic signs like **fever** and significant lymphadenopathy. - The presentation here is a primary **skin lesion** with no lymphadenopathy and a history of recurrence, which differentiates it from a single, deep-seated lymph node abscess. *Mycobacterial lymphadenitis* - Also known as **scrofula**, this condition presents as an **indolent, non-tender,
Question 192: A 67-year-old man with type 2 diabetes presents with a 4-day history of severe pain, swelling, and erythema of his left foot following a minor cut. Examination reveals a dusky, violaceous discolouration with bullae containing dark fluid, crepitus on palpation, and anaesthesia of the overlying skin. Temperature is 38.9°C, heart rate 118/min, blood pressure 98/62 mmHg. Blood tests show lactate 4.2 mmol/L, creatinine 178 μmol/L (baseline 92), and creatine kinase 3,420 U/L. What is the single most important immediate management step?
- A. Urgent surgical referral for debridement/amputation and broad-spectrum antibiotics including clindamycin (Correct Answer)
- B. CT imaging of the foot to delineate extent of infection before surgical intervention
- C. Intravenous flucloxacillin and metronidazole with close observation for 24 hours
- D. Ultrasound of the foot to confirm presence of gas and guide antibiotic selection
- E. Blood cultures, commence broad-spectrum antibiotics, and arrange MRI within 6 hours
Explanation: ***Urgent surgical referral for debridement/amputation and broad-spectrum antibiotics including clindamycin***- The patient's presentation with **dusky skin**, **bullae**, **crepitus**, **skin anaesthesia**, and signs of **septic shock** (hypotension, tachycardia, elevated lactate) is highly indicative of **necrotizing fasciitis**, a surgical emergency requiring immediate debridement.- **Broad-spectrum antibiotics** covering Gram-positive, Gram-negative, and anaerobic organisms are essential, with **clindamycin** specifically included for its ability to inhibit bacterial **toxin production** and modulate the severe inflammatory response. *CT imaging of the foot to delineate extent of infection before surgical intervention*- While CT imaging can confirm the presence of **fascial fluid** or **gas**, it must **never delay urgent surgical exploration and debridement**, which is the definitive diagnostic and therapeutic step.- In a patient with clear clinical signs of necrotizing fasciitis and **hemodynamic instability**, delaying surgery for imaging significantly increases morbidity and mortality. *Intravenous flucloxacillin and metronidazole with close observation for 24 hours*- This antibiotic regimen is **insufficient**, as flucloxacillin primarily covers *Staphylococcus* and *Streptococcus*, and it lacks adequate **broad-spectrum coverage** for potential polymicrobial infections including Gram-negative bacteria, and it does not include an agent for **toxin suppression**.- **Close observation for 24 hours** is inappropriate and dangerous; necrotizing fasciitis progresses rapidly, and a delay of even a few hours can lead to extensive tissue loss, limb amputation, or death. *Ultrasound of the foot to confirm presence of gas and guide antibiotic selection*- Ultrasound has **limited sensitivity** for detecting subtle **subcutaneous gas** and may not reliably define the extent of fascial involvement, making it an unreliable primary diagnostic tool in this context.- Antibiotic selection for suspected necrotizing fasciitis must be **empiric and broad-spectrum** and initiated immediately; waiting for imaging to guide this decision is a critical delay. *Blood cultures, commence broad-spectrum antibiotics, and arrange MRI within 6 hours*- While **blood cultures** and **broad-spectrum antibiotics** are important initial steps, arranging an **MRI within 6 hours** will cause an unacceptable delay in definitive surgical management.- MRI, though sensitive for soft tissue infection, often **overestimates the extent** and is not indicated when the clinical picture is clear and demands immediate surgical intervention.
Question 193: According to current UK antimicrobial guidance, what is the recommended duration of antibiotic therapy for an immunocompetent adult with uncomplicated cellulitis of the lower limb showing good clinical response?
- A. 3 days
- B. 5 days (Correct Answer)
- C. 7 days
- D. 10 days
- E. 14 days
Explanation: ***5 days*** - Current **NICE** and **PHE** guidance recommends a **5-day course** of antibiotics for uncomplicated cellulitis in immunocompetent adults who show a **good clinical response**. - Evidence demonstrates that shorter courses are **non-inferior** to longer treatments, effectively reducing antibiotic exposure and the risk of **antimicrobial resistance**. *3 days* - A **3-day duration** is generally insufficient for the eradication of bacteria in skin and soft tissue infections like **cellulitis**. - This short duration is more commonly associated with uncomplicated **urinary tract infections** in women, not skin infections. *7 days* - While previously common, a **7-day course** is now reserved for cases where there has been a **slow clinical response** by day 5. - For an immunocompetent patient responding well, extending treatment to 7 days provides no additional benefit over **5 days**. *10 days* - A **10-day course** represents outdated practice for uncomplicated infections and increases the risk of **antibiotic-associated side effects**. - This duration might only be considered in **complicated infections** or cases involving specific pathogens like **Group A Streptococcus** with associated complications. *14 days* - **14 days** of therapy is unnecessarily long for simple cellulitis and significantly increases the likelihood of **Clostridioides difficile** infection. - Such prolonged courses are typically reserved for **immunocompromised patients** or deep-seated infections like **osteomyelitis**.
Question 194: A 36-year-old woman with systemic lupus erythematosus on prednisolone 20mg daily and mycophenolate mofetil presents with a 5-day history of painful vesicular rash in a dermatomal distribution on the right side of her chest. Several vesicles have coalesced and there is involvement crossing the midline anteriorly. She has no visual symptoms. Temperature is 37.8°C. What is the most appropriate management?
- A. Oral aciclovir 800mg five times daily for 7 days
- B. Intravenous aciclovir 10mg/kg three times daily (Correct Answer)
- C. Oral valaciclovir 1g three times daily for 7 days
- D. Topical aciclovir cream five times daily with oral analgesia
- E. Oral famciclovir 500mg three times daily for 7 days
Explanation: ***Intravenous aciclovir 10mg/kg three times daily*** - This patient is **severely immunocompromised** due to systemic lupus erythematosus, moderate-dose **prednisolone** (20mg daily), and **mycophenolate mofetil**, which warrants intravenous therapy for Herpes Zoster. - Features such as **crossing the midline** and coalescing vesicles in an immunocompromised host indicate a high risk of **disseminated disease** or visceral involvement, requiring high-bioavailability systemic treatment. *Oral aciclovir 800mg five times daily for 7 days* - While a standard dose for **immunocompetent** patients, oral aciclovir has poor **bioavailability** compared to the intravenous route. - In this scenario, the severity of immunosuppression and the clinical presentation require the higher serum levels provided by **IV aciclovir**. *Oral valaciclovir 1g three times daily for 7 days* - Valaciclovir offers better absorption than oral aciclovir but is still insufficient for an immunocompromised patient with **extensive dermatomal involvement** or risk of dissemination. - Guidelines prioritize **parenteral therapy** in patients receiving multiple immunosuppressants or showing signs of severe local disease. *Topical aciclovir cream five times daily with oral analgesia* - **Topical therapy** is completely inadequate for the treatment of **Herpes Zoster** and does not prevent post-herpetic neuralgia or systemic spread. - Management must involve **systemic antiviral agents** to inhibit viral replication within the nervous system and skin. *Oral famciclovir 500mg three times daily for 7 days* - Famciclovir is an alternative oral prodrug, but like other oral agents, it is reserved for **uncomplicated shingles** in the immunocompetent. - The presence of **systemic lupus** and current medication use (Mycophenolate) makes the patient too high-risk for **oral-only** therapeutic strategies.
Question 195: A hospital antimicrobial stewardship team reviews audit data showing that 45% of patients receiving antimicrobials for more than 5 days lack documented indication, review dates, or stop/review dates in their medical records. Which intervention, according to evidence-based antimicrobial stewardship practice, would most effectively address this documentation deficiency?
- A. Implementing mandatory infectious diseases consultation for all patients on antibiotics for >5 days
- B. Introducing antimicrobial prescription charts with mandatory fields for indication, review date, and duration (Correct Answer)
- C. Sending weekly email reminders to all prescribers about documentation requirements
- D. Restricting antibiotic prescribing to consultants and registrars grade ST4 and above
- E. Conducting monthly teaching sessions for junior doctors on antimicrobial prescribing
Explanation: ***Introducing antimicrobial prescription charts with mandatory fields for indication, review date, and duration*** - This is a system-level **structural intervention** that creates a 'hard stop' at the point of prescribing, ensuring compliance with **antimicrobial stewardship (AMS)** guidelines. - Evidence shows that forcing the inclusion of **indication and stop/review dates** significantly improves documentation compared to passive reminders or education alone. *Implementing mandatory infectious diseases consultation for all patients on antibiotics for >5 days* - This approach is **resource-intensive** and impractical for most hospital environments due to the high volume of antibiotic use. - It acts more as a **clinical review mechanism** rather than a solution for the specific documentation deficiency identified in the audit. *Sending weekly email reminders to all prescribers about documentation requirements* - Email reminders are considered a **weak, passive intervention** that does not integrate into the clinical workflow or force a change in habit. - Prescribers often experience **notification fatigue**, leading to these reminders being ignored without improving documentation accuracy. *Restricting antibiotic prescribing to consultants and registrars grade ST4 and above* - Such restrictions are typically reserved for **broad-spectrum or high-cost antibiotics** and are not an appropriate solution for general documentation issues. - This intervention could lead to **treatment delays** and does not address the underlying lack of structure in the documentation process itself. *Conducting monthly teaching sessions for junior doctors on antimicrobial prescribing* - While **education** is a core component of AMS, it is rarely sufficient as a standalone strategy to ensure long-term behavioral change in documentation. - Teaching sessions address **knowledge gaps** but fail to provide the **system enablers** required to facilitate routine clinical documentation tasks.
Question 196: A 41-year-old man who works as a fishmonger presents with a 48-hour history of a painful, rapidly spreading erythematous swelling on his right hand following a puncture injury from a fish bone. The affected area has violaceous bullae and is exquisitely tender. He is systemically well with temperature 37.4°C. Blood tests show WCC 11.2 × 10⁹/L and CRP 28 mg/L. Which organism is most likely responsible?
- A. Vibrio vulnificus
- B. Pasteurella multocida
- C. Streptococcus pyogenes
- D. Staphylococcus aureus
- E. Erysipelothrix rhusiopathiae (Correct Answer)
Explanation: ***Erysipelothrix rhusiopathiae*** - This organism causes **erysipeloid**, a localized skin infection classic in **fishmongers** and meat handlers following a **puncture injury** from fish bones or scales. - It typically presents as a painful, **violaceous (purplish)**, spreading erythema on the hands, often with mild systemic symptoms and a lack of significant suppuration.*Vibrio vulnificus* - While associated with seawater and shellfish, it typically causes much more **severe, necrotizing soft tissue infections** and hemorrhagic bullae. - Usually presents in patients with **liver disease** or immunosuppression with profound **systemic toxicity** and sepsis.*Pasteurella multocida* - This organism is classically associated with **animal bites or scratches**, particularly from **cats and dogs**, rather than fish-related injuries. - It typically presents with a very rapid onset of infection, often within **24 hours** of the injury.*Streptococcus pyogenes* - Commonly causes cellulitis and erysipelas, but these are typically associated with **high fever**, significant systemic toxicity, and bright red rather than **violaceous** erythema. - While it can cause necrotizing fasciitis, the occupational link to a fish bone and the patient's **systemically well** status makes it less likely.*Staphylococcus aureus* - A frequent cause of skin infections, it primarily leads to **localized abscess formation** or impetigo rather than broad, violaceous spreading lesions. - It lacks the specific **occupational association** with raw fish and sea life compared to Erysipelothrix.
Question 197: Which of the following antimicrobial prescribing practices best demonstrates the 'Start Smart - Then Focus' antimicrobial stewardship principle of 'review and revise' at 48-72 hours?
- A. Continuing intravenous meropenem for hospital-acquired pneumonia despite clinical improvement and negative cultures because the patient remains pyrexial
- B. Switching from intravenous co-amoxiclav to oral amoxicillin for community-acquired pneumonia following clinical improvement and ability to tolerate oral intake (Correct Answer)
- C. Extending a 5-day course of ciprofloxacin to 10 days for uncomplicated urinary tract infection because the patient had microscopic haematuria
- D. Adding azithromycin to amoxicillin for community-acquired pneumonia despite clinical improvement to 'cover atypical organisms'
- E. Continuing flucloxacillin for cellulitis despite complete resolution of erythema because the baseline creatine kinase was mildly elevated
Explanation: ***Switching from intravenous co-amoxiclav to oral amoxicillin for community-acquired pneumonia following clinical improvement and ability to tolerate oral intake*** - This demonstrates **antimicrobial de-escalation**, a core component of the "Focus" step, which involves switching from **IV to oral (IVOS)** therapy when clinical criteria are met. - By narrowing the spectrum (removing anaerobic coverage of clavulanate) and switching route, it reduces **antibiotic resistance**, side effects, and costs. *Continuing intravenous meropenem for hospital-acquired pneumonia despite clinical improvement and negative cultures because the patient remains pyrexial* - This describes **inappropriate broad-spectrum misuse**; pyrexia alone without other markers of infection does not justify continuing a carbapenem if cultures are negative. - Stewardship guidelines advise **narrowing the spectrum** or stopping therapy if infection is unlikely after 72 hours of review. *Extending a 5-day course of ciprofloxacin to 10 days for uncomplicated urinary tract infection because the patient had microscopic haematuria* - **Microscopic haematuria** is common in cystitis and does not warrant extending therapy beyond the standard evidence-based duration. - Proper stewardship focuses on **shorter durations** of therapy to minimize the selection of resistant bacteria. *Adding azithromycin to amoxicillin for community-acquired pneumonia despite clinical improvement to 'cover atypical organisms'* - Adding a second agent when a patient is already improving is an **unnecessary escalation** of therapy and violates the "review and revise" principle. - Stewardship encourages **rationalizing therapy** based on microbiology and clinical response rather than adding unnecessary empirical coverage. *Continuing flucloxacillin for cellulitis despite complete resolution of erythema because the baseline creatine kinase was mildly elevated* - Antibiotics should be stopped when the **clinical infection has resolved**; an isolated mildly elevated CK is not an indication for continued antimicrobial therapy. - This practice leads to **unnecessary antibiotic exposure**, increasing the risk of healthcare-associated infections like C. difficile.
Question 198: A 33-year-old woman presents to the Emergency Department with a 12-hour history of severe pain and swelling of her left breast. She is 3 weeks postpartum and exclusively breastfeeding. On examination, there is a 4cm fluctuant, erythematous, tender mass in the upper outer quadrant of the left breast. Temperature is 38.7°C. What is the most appropriate management?
- A. Oral flucloxacillin and advise to continue breastfeeding from both breasts
- B. Intravenous flucloxacillin and advise to stop breastfeeding from the affected breast
- C. Ultrasound-guided aspiration or incision and drainage, plus oral flucloxacillin (Correct Answer)
- D. Oral co-amoxiclav and advise complete cessation of breastfeeding
- E. Oral erythromycin and advise to express and discard milk from the affected breast
Explanation: ***Ultrasound-guided aspiration or incision and drainage, plus oral flucloxacillin*** - The presence of a **fluctuant mass** and fever in the context of mastitis indicates a **breast abscess**, which requires surgical or needle **drainage** for resolution. - **Flucloxacillin** is the first-line antibiotic choice to cover **Staphylococcus aureus**, and patients should be encouraged to **continue breastfeeding** to prevent further engorgement. *Oral flucloxacillin and advise to continue breastfeeding from both breasts* - While antibiotics and continuing breastfeeding are vital, they are insufficient for an **abscess**; antibiotics cannot effectively penetrate a **walled-off collection** of pus. - This management is appropriate for simple **lactational mastitis** without a fluctuant mass or collection. *Intravenous flucloxacillin and advise to stop breastfeeding from the affected breast* - Stopping breastfeeding on the affected side is contraindicated as it leads to **milk stasis**, which can worsen the infection and exacerbate the **abscess**. - Intravenous antibiotics may be required for severe systemic sepsis, but the definitive treatment for the localized mass remains **drainage**. *Oral co-amoxiclav and advise complete cessation of breastfeeding* - **Co-amoxiclav** provides unnecessarily broad coverage (including anaerobes) for a typical **S. aureus** breast infection and is not first-line. - **Cessation of breastfeeding** is unnecessary and harmful, as it increases the risk of further abscess formation and compromises the **milk supply**. *Oral erythromycin and advise to express and discard milk from the affected breast* - **Erythromycin** has less predictable efficacy against **Staphylococcus aureus** compared to penicillinase-resistant penicillins like flucloxacillin. - There is no clinical indication to **discard milk**, as the milk remains safe for the infant and expressing is essential to **decompress** the breast tissue.
Question 199: A 54-year-old man with known cirrhosis (Child-Pugh class B) presents with a 3-day history of fever, abdominal pain, and confusion. He has tense ascites. Diagnostic paracentesis reveals ascitic fluid with neutrophil count of 320 cells/mm³, protein 18 g/L, and glucose 3.8 mmol/L. Blood cultures are pending. According to antimicrobial stewardship principles and current evidence, what is the most appropriate initial antibiotic regimen?
- A. Intravenous cefotaxime 2g three times daily (Correct Answer)
- B. Intravenous piperacillin-tazobactam 4.5g three times daily
- C. Intravenous meropenem 1g three times daily
- D. Oral ciprofloxacin 500mg twice daily
- E. Intravenous co-amoxiclav 1.2g three times daily
Explanation: ***Intravenous cefotaxime 2g three times daily***- Third-generation cephalosporins are the **gold-standard empirical treatment** for community-acquired **spontaneous bacterial peritonitis (SBP)**, effectively covering common pathogens like **E. coli, Klebsiella**, and **S. pneumoniae**.- This patient's ascitic fluid **neutrophil count of 320 cells/mm³** (>250 threshold) confirms SBP, and cefotaxime provides excellent **ascitic fluid penetration** and a proven mortality benefit.*Intravenous piperacillin-tazobactam 4.5g three times daily*- This provides an unnecessarily broad spectrum including **Pseudomonas** coverage, which is generally not required for **community-acquired SBP**.- According to **antimicrobial stewardship**, it should be reserved for **healthcare-associated infections** or patients with recent broad-spectrum antibiotic exposure.*Intravenous meropenem 1g three times daily*- Carbapenems are **ultra-broad-spectrum antibiotics** and are inappropriate as first-line therapy for non-refractory, community-acquired SBP.- Overuse of meropenem promotes the development of **carbapenem-resistant Enterobacteriaceae (CRE)** and should be avoided unless **multidrug-resistant organisms** are highly suspected.*Oral ciprofloxacin 500mg twice daily*- Oral fluoroquinolones are primarily used for **SBP prophylaxis** (primary or secondary) rather than the treatment of an acute, symptomatic infection with systemic features like **fever** and **confusion**.- There is increasing **bacterial resistance** to quinolones among enteric gram-negative bacilli, making them less reliable for initial empiric therapy in severe cases.*Intravenous co-amoxiclav 1.2g three times daily*- While it covers some gram-negatives and anaerobes, it has **inferior clinical evidence** and penetration compared to third-generation cephalosporins for treating SBP.- In many regions, **resistance rates** for common enteric bacteria to amoxicillin-clavulanate are higher than to **cefotaxime**, reducing its effectiveness for empiric SBP treatment.
Question 200: A 78-year-old woman with chronic obstructive pulmonary disease is admitted with acute exacerbation. She is started on amoxicillin 500mg three times daily. On day 5 of admission, she develops watery diarrhoea (5 episodes in 24 hours). Temperature is 38.2°C. Abdominal examination reveals mild lower abdominal tenderness but no peritonism. Blood tests show WCC 16.8 × 10⁹/L (neutrophils 14.2 × 10⁹/L). What is the most appropriate next step in management?
- A. Continue amoxicillin and send stool for culture and Clostridioides difficile testing
- B. Stop amoxicillin, start oral metronidazole, and send stool for C. difficile testing
- C. Stop amoxicillin, start oral vancomycin, and send stool for C. difficile testing (Correct Answer)
- D. Continue amoxicillin, start loperamide, and send stool for culture
- E. Stop amoxicillin, start intravenous metronidazole and vancomycin immediately
Explanation: ***Stop amoxicillin, start oral vancomycin, and send stool for C. difficile testing*** - The patient presents with classic symptoms of **Clostridioides difficile infection (CDI)** following antibiotic use, including **watery diarrhoea**, fever, and **leukocytosis** (WCC 16.8 × 10⁹/L). - Current clinical guidelines recommend **oral vancomycin** as first-line treatment for an initial episode of CDI, especially with indicators of severity like high WCC, and the causative antibiotic (**amoxicillin**) should be discontinued immediately. *Continue amoxicillin and send stool for culture and Clostridioides difficile testing* - Continuing the inciting antibiotic significantly increases the risk of **disease progression** and treatment failure in CDI. - Management must begin with the removal of the **precipitating factor** (amoxicillin) alongside diagnostic testing, not before. *Stop amoxicillin, start oral metronidazole, and send stool for C. difficile testing* - **Oral metronidazole** is no longer recommended as first-line therapy for CDI due to its inferiority to vancomycin in achieving clinical cure. - Metronidazole is now typically reserved for scenarios where vancomycin is unavailable or contraindicated in **non-severe** cases, or as an adjunct in fulminant disease. *Continue amoxicillin, start loperamide, and send stool for culture* - **Loperamide** and other anti-motility agents are generally **contraindicated** in suspected CDI as they can precipitate **toxic megacolon** by inhibiting toxin clearance. - Stool culture is non-specific for CDI; specific **C. difficile toxin** or PCR testing is required for diagnosis. *Stop amoxicillin, start intravenous metronidazole and vancomycin immediately* - **Intravenous metronidazole** in combination with **oral/rectal vancomycin** is reserved for **life-threatening (fulminant)** CDI with ileus, hypotension, or other signs of systemic toxicity. - This patient's symptoms represent severe CDI but do not indicate fulminant disease, and intravenous vancomycin has poor penetration into the gut lumen.
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