Serious & Notifiable Infections Practice Questions

Q: A 62-year-old man with diabetes presents with a foot ulcer and fever. X-ray shows bone destruction. Blood cultures grow Staphylococcus aureus. What is the recommended antibiotic duration?

8-12 weeks. ***8-12 weeks***- This prolonged duration is typically recommended for **diabetic foot osteomyelitis (DFO)**, especially when complicated by **Staphylococcus aureus bacteremia** and radiographic evidence of **bone destruction**.- The extended treatment ensures adequate eradication of bacteria from the poorly vascularized bone, which is crucial in diabetic patients prone to **recurrence**.*2 weeks*- This duration is vastly insufficient for established **osteomyelitis**, which requires prolonged therapy due to poor antibiotic penetration into bone and the potential for **biofilm** formation.- A 2-week course is generally reserved for uncomplicated **soft tissue infections** or **cellulitis**, not for deep bone infections with systemic involvement.*4 weeks*- While sometimes used for acute, uncomplicated osteomyelitis without extensive bone involvement, **4 weeks** is typically inadequate for severe cases like **DFO** with **bacteremia** and significant **bone destruction**.- In such complex scenarios, a shorter course significantly increases the risk of **treatment failure** and **relapse**.*6 weeks*- **6 weeks** is considered the standard minimum duration for acute, uncomplicated osteomyelitis, particularly after successful **surgical debridement** of infected bone.- However, for complicated DFO with **S. aureus bacteremia** and significant bone destruction, a longer course, often up to 12 weeks, is frequently necessary, especially if debridement is limited.*6 months*- This exceptionally long duration is generally reserved for very specific, highly refractory infections, such as **tuberculosis osteomyelitis**, or for chronic suppressive therapy in certain **prosthetic joint infections**.- It is typically excessive for **Staphylococcus aureus** DFO when managed with appropriate initial therapy and a standard prolonged course (8-12 weeks).

Q: A 22-year-old student presents with fever, headache, and a petechial rash on her legs. CSF shows: protein 2.1 g/L, glucose 1.8 mmol/L (serum 5.2), WCC 850 (90% neutrophils). What is the most likely organism?

Neisseria meningitidis. ***Neisseria meningitidis***- The classic presentation of fever, headache, and a **petechial rash** (indicating **meningococcemia**) in a young adult is highly characteristic of *Neisseria meningitidis* infection.- The CSF profilehigh protein, **low glucose** (low CSF/serum ratio), and **high white cell count** with **predominantly neutrophils** (90%)-is consistent with acute bacterial meningitis caused by this organism.*Streptococcus pneumoniae*- While *Streptococcus pneumoniae* is a common cause of bacterial meningitis with a similar CSF profile (high protein, low glucose, neutrophilic pleocytosis), it is less typically associated with a fulminant **petechial rash**.- This organism often affects extremes of age (very young or elderly) or individuals with specific risk factors such as **pneumonia**, **otitis media**, or **CSF leaks**.*Haemophilus influenzae*- *Haemophilus influenzae* type b (HiB) was a major cause of meningitis in **unvaccinated children** before widespread vaccination, making it less common in immunocompetent young adults.- Although it can cause bacterial meningitis with similar CSF findings, the striking **petechial rash** and patient's age make *Neisseria meningitidis* a more likely diagnosis.*Listeria monocytogenes*- *Listeria monocytogenes* typically causes meningitis in specific vulnerable populations, including **neonates**, the **elderly**, pregnant women, or the **immunosuppressed**.- Given the patient is a healthy 22-year-old student, *Listeria* is a less probable cause compared to *Neisseria meningitidis*.*Enterovirus*- **Enteroviruses** cause **aseptic (viral) meningitis**, which is characterized by a different CSF profile than seen here.- Viral meningitis typically presents with **normal CSF glucose**, normal or mildly elevated protein, and a **lymphocytic pleocytosis** (lymphocyte predominance), which contradicts the 90% neutrophil count in this case.

Q: A 37-year-old man presents with acute onset severe headache, fever, and neck stiffness. Lumbar puncture shows lymphocytic pleocytosis with normal glucose. HSV PCR is positive. What is the most appropriate treatment?

IV aciclovir. ***IV aciclovir*** - The clinical presentation (acute severe headache, fever, neck stiffness) and cerebrospinal fluid (CSF) findings (**lymphocytic pleocytosis**, **normal glucose**) are highly suggestive of **viral meningoencephalitis**. - A positive **HSV PCR** in the CSF confirms **Herpes Simplex Virus (HSV) encephalitis**, a severe and potentially fatal condition that necessitates immediate high-dose intravenous **aciclovir**. *IV ceftriaxone* - Ceftriaxone is an antibiotic primarily used for **bacterial meningitis**, which typically presents with **neutrophilic pleocytosis** and **low CSF glucose**. - It is ineffective against **viral infections** like HSV, making it an inappropriate treatment for confirmed HSV encephalitis. *IV ampicillin* - Ampicillin is another antibiotic used to treat specific forms of **bacterial meningitis**, particularly covering *Listeria monocytogenes*. - It does not have antiviral activity and therefore is not an effective treatment for **HSV encephalitis**. *Supportive care only* - **HSV encephalitis** carries a high risk of mortality and significant neurological sequelae if left untreated with specific antiviral agents. - Relying solely on supportive care is insufficient and would be detrimental in a confirmed case of HSV encephalitis. *IV immunoglobulin* - Intravenous immunoglobulin (IVIG) is typically used in the management of certain **immunodeficiency syndromes** or **autoimmune disorders**. - It has no established role or efficacy in the **acute treatment** of viral encephalitis, including that caused by HSV.

Q: 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?

12 weeks total therapy. ***12 weeks total therapy***- The treatment duration for confirmed **diabetic foot osteomyelitis (DFO)** without amputation or with residual infected bone often requires 10–12 weeks or 3 months of total antibiotic therapy (IV and/or oral) to achieve cure and prevent relapse.- Prolonged treatment is crucial because of the **poor vascular supply** in diabetic feet and the low penetration of antibiotics into the avascular, infected bone. *2 weeks IV*- This duration is insufficient for bone infection, as antibiotics require extended time to reach therapeutic concentrations within the **avascular, necrotic bone**.- **Acute uncomplicated cellulitis** or soft tissue infection might be treated in 2 weeks, but not osteomyelitis. *4 weeks IV*- A 4-week course might be considered sufficient only if the infected bone has been completely removed during **surgical debridement** (e.g., partial foot amputation), which is not guaranteed by the prompt.- This duration drastically increases the risk of **relapse** in confirmed, non-surgically cleared osteomyelitis. *6 weeks IV*- This is the standard duration for **vertebral osteomyelitis** or chronic osteomyelitis where adequate surgical debridement was achieved, often substituting for the total 12-week regimen.- However, for conservative management of **DFO**, guidelines often recommend a total of 10–12 weeks (IV and oral) to maximize bone penetration. *4-6 weeks IV followed by 2-6 weeks oral*- While this combination (totaling 6–12 weeks) is a common strategy, it is less definitive than the 12-week option and can be interpreted as potentially insufficient depending on the chosen duration (e.g., 6 weeks total is too short).- The **IDSA guidelines** often suggest at least 6 weeks following resection of infected bone, but up to 12 weeks is recommended if bone cannot be fully resected or infection is severe.

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

Osteomyelitis. ***Osteomyelitis***- The combination of a **deep ulcer exposing bone** and radiologic evidence of **osteolytic changes** strongly indicates infection and destruction of the bone itself.- In patients with **diabetes**, foot ulcers often progress rapidly from soft tissue infection to bone infection due to underlying neuropathy and vascular disease.*Cellulitis*- Cellulitis is a superficial soft tissue infection characterized by erythema, swelling, and warmth, typically without **ulceration exposing bone**.- It affects the dermal and subcutaneous layers and does not cause **osteolytic changes** on X-ray.*Charcot arthropathy*- Charcot foot involves **neuropathic joint destruction** and deformity (e.g., *rocker-bottom* foot), but typically presents with little pain and diffuse bony fragmentation, rather than a localized deep, infected ulcer causing severe pain and lytic changes.- Although common in diabetes, pure Charcot arthropathy is usually sterile; the presence of a deep, draining ulcer points strongly to a progressive infection.*Peripheral arterial disease*- While PAD often contributes to ulcer formation (ischemic ulcers), these ulcers are typically **dry**, **punched-out**, and associated with diminished or absent pedal pulses.- PAD causes ischemia, but the identification of a deep ulcer exposing bone and active **osteolytic changes** points primarily toward a severe, established bone infection.*Deep vein thrombosis*- DVT involves clotting in a deep vein, presenting primarily with **unilateral swelling**, pain, and warmth in the leg (often calf or thigh).- It does not cause localized deep foot ulcers or underlying **osteolytic changes** in the bone.

Question 1

A 62-year-old man with diabetes presents with a foot ulcer and fever. X-ray shows bone destruction. Blood cultures grow Staphylococcus aureus. What is the recommended antibiotic duration?

Accepted Answer

8-12 weeks

Answer

2 weeks

Answer

4 weeks

Answer

6 weeks

Answer

6 months

Question 2

A 22-year-old student presents with fever, headache, and a petechial rash on her legs. CSF shows: protein 2.1 g/L, glucose 1.8 mmol/L (serum 5.2), WCC 850 (90% neutrophils). What is the most likely organism?

Accepted Answer

Neisseria meningitidis

Answer

Streptococcus pneumoniae

Answer

Haemophilus influenzae

Answer

Listeria monocytogenes

Answer

Enterovirus

Question 3

A 37-year-old man presents with acute onset severe headache, fever, and neck stiffness. Lumbar puncture shows lymphocytic pleocytosis with normal glucose. HSV PCR is positive. What is the most appropriate treatment?

Accepted Answer

IV aciclovir

Answer

IV ceftriaxone

Answer

IV ampicillin

Answer

Supportive care only

Answer

IV immunoglobulin

Question 4

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 5

A 58-year-old woman 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

Serious & Notifiable Infections — MCQs

Serious & Notifiable Infections — MCQs

On this page

Practice by Chapter

Want unlimited practice?