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Infection, Pharmacology & VTE MCQs

Practice Set 38 of 68

This practice set contains high-yield board review questions covering key concepts in Infection, Pharmacology & VTE. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 741

Topic: Infection, Pharmacology & VTE

Which of the following is an absolute contraindication to performing a Debridement, Antibiotics, and Implant Retention (DAIR) procedure for a periprosthetic joint infection?

. Symptom duration of 2 weeks
. Infection with a fluoroquinolone-sensitive organism
. A radiographically loose femoral component
. Patient age greater than 80 years
. Serum CRP of 150 mg/L

Correct Answer & Explanation

. A radiographically loose femoral component

Explanation

A loose prosthesis is an absolute contraindication for a DAIR procedure, as biofilm cannot be adequately eradicated and the implant requires revision for mechanical stability. DAIR is best reserved for acute infections (<3-4 weeks) with well-fixed implants.

Question 742

Topic: Infection, Pharmacology & VTE

A 42-year-old woman presents with diffuse skin thickening extending proximal to her elbows and knees. She complains of progressive dyspnea on exertion. Serologic testing is positive for Anti-Scl-70 antibodies. What is the most likely pulmonary complication associated with this specific autoantibody profile?

. Pulmonary arterial hypertension without parenchymal disease
. Spontaneous pneumothorax
. Interstitial lung disease (pulmonary fibrosis)
. Asthma
. Pulmonary embolism

Correct Answer & Explanation

. Interstitial lung disease (pulmonary fibrosis)

Explanation

Anti-Scl-70 (anti-topoisomerase I) antibodies are associated with diffuse cutaneous systemic sclerosis, which carries a high risk of interstitial lung disease (pulmonary fibrosis). In contrast, anti-centromere antibodies (CREST) are more associated with isolated pulmonary arterial hypertension.

Question 743

Topic: Infection, Pharmacology & VTE

Biofilm formation plays a critical role in the pathogenesis of periprosthetic joint infections. Within a mature biofilm, which characteristic best explains the extreme resistance of the embedded bacteria to systemic antibiotic therapy?

. Rapid exponential replication of the bacteria
. High metabolic rate demanding constant nutrient influx
. The bacteria enter a dormant, stationary growth phase
. The complete absence of an exopolysaccharide matrix
. Increased cell-wall permeability to large molecules

Correct Answer & Explanation

. The bacteria enter a dormant, stationary growth phase

Explanation

Bacteria within a mature biofilm exhibit a markedly altered phenotype, entering a dormant, stationary growth phase. Because most antibiotics target active cell division and metabolic processes, these dormant bacteria are highly resistant to standard antimicrobial therapy.

Question 744

Topic: Infection, Pharmacology & VTE

A 68-year-old man undergoes DAIR for an acute hematogenous periprosthetic joint infection of his knee. Intraoperative cultures grow methicillin-sensitive Staphylococcus aureus (MSSA). Which of the following oral antibiotic regimens is best supported by evidence for long-term suppression after initial IV therapy?

. Cephalexin alone
. Ciprofloxacin alone
. Amoxicillin alone
. Dicloxacillin and rifampin
. Ciprofloxacin and rifampin

Correct Answer & Explanation

. Ciprofloxacin and rifampin

Explanation

Rifampin has excellent biofilm penetration and is highly effective against staphylococcal species in PJI. It must be combined with a companion drug (such as a fluoroquinolone like ciprofloxacin) to prevent the rapid emergence of resistance.

Question 745

Topic: Infection, Pharmacology & VTE

Which of the following antibiotics is most critical to include in the treatment regimen for a retained total joint arthroplasty infected with methicillin-sensitive Staphylococcus aureus, owing to its efficacy against biofilm-associated bacteria?

. Vancomycin
. Linezolid
. Rifampin
. Ciprofloxacin
. Daptomycin

Correct Answer & Explanation

. Rifampin

Explanation

Rifampin has unique activity against staphylococcal species residing within a mature biofilm. It is universally recommended as an adjunct in the medical management of staphylococcal PJI treated with debridement and implant retention.

Question 746

Topic: Infection, Pharmacology & VTE

Staphylococcus epidermidis is a common pathogen in periprosthetic joint infections. Which of the following components is primarily responsible for the structural integrity of the biofilm produced by this organism?

. Protein A
. Polysaccharide intercellular adhesin (PIA)
. Alpha-toxin
. Panton-Valentine leukocidin
. Lipoteichoic acid

Correct Answer & Explanation

. Polysaccharide intercellular adhesin (PIA)

Explanation

The biofilm of S. epidermidis is primarily composed of polysaccharide intercellular adhesin (PIA), which is synthesized by the icaADBC operon. This extracellular polymeric substance protects the bacteria from host immune responses and antibiotics.

Question 747

Topic: Infection, Pharmacology & VTE

In a patient undergoing Debridement, Antibiotics, and Implant Retention (DAIR) for a periprosthetic joint infection, which of the following factors is considered an absolute contraindication to the procedure?

. Age greater than 65 years
. Infection with Streptococcus species
. Duration of symptoms less than 7 days
. Presence of a draining sinus tract
. Exchange of modular components

Correct Answer & Explanation

. Presence of a draining sinus tract

Explanation

The presence of a sinus tract indicates a chronic infection with an established, mature biofilm. This is an absolute contraindication to a DAIR procedure, as eradication cannot be achieved without complete implant removal.

Question 748

Topic: Infection, Pharmacology & VTE

A 65-year-old male with diabetes lacks protective sensation to the 5.07 monofilament and has developed a plantar neuropathic ulcer under the first metatarsal head. The physician is considering a total contact cast (TCC) to offload the ulcer. Which of the following is an absolute contraindication to the use of a TCC in this patient?

. The presence of a superficial, uninfected Wagner Grade 1 ulcer
. A history of prior neuropathic arthropathy
. Active deep infection with palpable bone at the ulcer base
. Mild peripheral edema
. Patient age greater than 60 years

Correct Answer & Explanation

. Active deep infection with palpable bone at the ulcer base

Explanation

Correct Answer: Active deep infection with palpable bone at the ulcer baseTotal contact casting (TCC) is the gold standard for offloading plantar neuropathic ulcers. However, it has strict contraindications. Absolute contraindications include active deep infection (e.g., abscess, osteomyelitis, palpable bone), severe peripheral arterial disease (ischemia), and deep tracking sinus tracts. Applying a cast over an active deep infection can lead to rapid progression of the infection, sepsis, and limb loss. Superficial, uninfected ulcers (Wagner Grade 1) are the primary indication for TCC.

Question 749

Topic: Infection, Pharmacology & VTE

A 54-year-old diabetic male who failed 5.07 monofilament screening presents with a foot ulcer. Examination reveals an ulceration on the plantar aspect of the foot that extends deep to the joint capsule, exposing the flexor tendon, but there is no evidence of abscess, osteomyelitis, or gangrene. According to the Wagner classification system, what grade is this ulcer?

. Grade 1
. Grade 2
. Grade 3
. Grade 4
. Grade 5

Correct Answer & Explanation

. Grade 2

Explanation

Correct Answer: Grade 2The Wagner classification is used to grade diabetic foot ulcers. Grade 0: Pre-ulcerative lesion, healed ulcer, or presence of bony deformity. Grade 1: Superficial ulcer without subcutaneous tissue involvement. Grade 2: Deep ulcer penetrating to tendon, bone, or joint capsule, but without deep infection or osteomyelitis. Grade 3: Deep ulcer with osteomyelitis, abscess, or joint sepsis. Grade 4: Localized gangrene (e.g., forefoot or heel). Grade 5: Extensive gangrene involving the entire foot.

Question 750

Topic: Infection, Pharmacology & VTE

A 60-year-old poorly controlled diabetic presents with a swollen, erythematous, and warm right foot with bounding pulses and no open ulceration. When the affected leg is elevated for 10 minutes, the erythema resolves completely. What is the most likely diagnosis?

. Acute cellulitis
. Deep vein thrombosis
. Acute Charcot neuroarthropathy
. Osteomyelitis
. Critical limb ischemia

Correct Answer & Explanation

. Acute Charcot neuroarthropathy

Explanation

In a neuropathic foot, a warm, red, swollen presentation can be Charcot neuroarthropathy or infection. Erythema that resolves with elevation (dependent rubor) strongly suggests acute Charcot rather than cellulitis.

Question 751

Topic: Infection, Pharmacology & VTE

During the physical examination of a chronic diabetic foot ulcer, a sterile blunt probe is introduced into the wound. The examiner feels a hard, gritty surface. This 'probe-to-bone' test has the highest positive predictive value for which condition?

. Malignant transformation (Marjolin's ulcer)
. Underlying osteomyelitis
. Acute Charcot neuroarthropathy
. Deep vein thrombosis
. Necrotizing fasciitis

Correct Answer & Explanation

. Underlying osteomyelitis

Explanation

A positive probe-to-bone test, where a sterile blunt probe touches a hard, gritty surface, is highly specific and has a high positive predictive value for underlying osteomyelitis in the setting of a diabetic foot ulcer.

Question 752

Topic: Infection, Pharmacology & VTE

Which of the following radiographic findings is typically the earliest sign of osteomyelitis in a patient being evaluated for a chronic diabetic foot ulcer?

. Complete bone resorption of the metatarsal head
. Focal osteopenia and subtle periosteal reaction
. Gas outlining the fascial planes
. Pathologic fracture with severe displacement
. Sclerosis of the medullary canal

Correct Answer & Explanation

. Focal osteopenia and subtle periosteal reaction

Explanation

The earliest radiographic signs of osteomyelitis include focal osteopenia, cortical erosion, and subtle periosteal reaction. These changes typically require 10-14 days of progressive infection to become visible on plain radiographs.

Question 753

Topic: Infection, Pharmacology & VTE

Total Contact Casting (TCC) is considered the gold standard for offloading plantar diabetic foot ulcers. Which of the following is an absolute contraindication for applying a TCC?

. Wagner Grade 1 ulcer on the plantar hallux
. Wagner Grade 2 ulcer without clinical signs of infection
. Presence of active deep space infection or osteomyelitis
. Loss of protective sensation in the contralateral foot
. History of previous successful TCC treatment

Correct Answer & Explanation

. Presence of active deep space infection or osteomyelitis

Explanation

Total contact casting relies on enclosing the foot to redistribute pressure. It is absolutely contraindicated in the presence of active deep infection, untreated osteomyelitis, severe ischemia, or highly exuding wounds due to the risk of enclosing an active infection.

Question 754

Topic: Infection, Pharmacology & VTE

A patient with long-standing diabetes is evaluated for progressive foot deformity. The examiner notes profound sensory loss and a 'rocker-bottom' deformity. Radiographs show tarsometatarsal destruction, fragmentation, and new bone formation. What is the most likely diagnosis?

. Gouty arthropathy
. Rheumatoid arthritis
. Charcot neuroarthropathy (coalescence phase)
. Acute hematogenous osteomyelitis
. Severe osteoarthritis

Correct Answer & Explanation

. Charcot neuroarthropathy (coalescence phase)

Explanation

The combination of profound sensory loss, rocker-bottom deformity, and radiographic findings of destruction, fragmentation, and bony consolidation (new bone formation) is hallmark for the coalescence/remodeling phases of Charcot neuroarthropathy.

Question 755

Topic: Infection, Pharmacology & VTE

What is the primary goal of anatomical reduction and rigid internal fixation in adult both bones forearm fractures?

. Facilitate early weight-bearing.
. Minimize operative time.
. Promote secondary bone healing.
. Restore full pronation and supination.
. Prevent osteomyelitis.

Correct Answer & Explanation

. Restore full pronation and supination.

Explanation

The primary goal of anatomical reduction and rigid internal fixation in adult diaphyseal forearm fractures is to restore full pronation and supination (Option D). The forearm requires precise anatomical alignment to allow for the complex coupled motion of the radius and ulna around each other. Any significant malreduction, especially rotational, will severely compromise this function. Rigid fixation also aims for primary bone healing, and while minimizing operative time and preventing osteomyelitis are important surgical considerations, they are not theprimary goalfor functional outcome. Early weight-bearing (Option A) is not typically a goal for forearm fractures.

Question 756

Topic: Infection, Pharmacology & VTE

A patient presents with a 'fight bite' over the dorsal aspect of the fifth MCP joint. During surgical exploration, purulent material is found tracking along the extensor digitorum communis tendon into the wrist. This finding is indicative of:

. A. Isolated cellulitis
. B. Septic arthritis of the MCP joint
. C. Tenosynovitis of the extensor tendon sheath
. D. Osteomyelitis of the fifth metacarpal head
. E. Localized abscess formation

Correct Answer & Explanation

. C. Tenosynovitis of the extensor tendon sheath

Explanation

Purulent material tracking along the extensor digitorum communis tendon into the wrist is a classic sign of extensor tenosynovitis. While other pathologies like septic arthritis and osteomyelitis can coexist or develop from tenosynovitis, the direct observation of pus within the tendon sheath extending proximally confirms tenosynovitis. Cellulitis (A) is a superficial soft tissue infection. Septic arthritis (B) involves the joint space. Osteomyelitis (D) involves bone infection. A localized abscess (E) would be a circumscribed collection of pus, but its extension along a tendon sheath points specifically to tenosynovitis.

Question 757

Topic: Infection, Pharmacology & VTE

What is the typical duration of intravenous antibiotic therapy for established septic arthritis of the MCP joint secondary to a human bite, assuming no osteomyelitis is present?

. A. 24-48 hours, followed by oral antibiotics for 5 days.
. B. 3-5 days, followed by oral antibiotics for 1-2 weeks.
. C. 7-10 days, followed by oral antibiotics for 2-4 weeks.
. D. 4-6 weeks of intravenous antibiotics only.
. E. 6-8 weeks of combined intravenous and oral antibiotics.

Correct Answer & Explanation

. C. 7-10 days, followed by oral antibiotics for 2-4 weeks.

Explanation

For established septic arthritis without associated osteomyelitis, the typical duration involves initial intravenous antibiotics for 7-10 days, followed by a transition to oral antibiotics for an additional 2-4 weeks, for a total course of 3-4 weeks. The exact duration may vary based on clinical response, pathogen, and host factors. Shorter courses (A, B) are often insufficient for deep-seated joint infections. Prolonged IV antibiotics for 4-6 weeks (D) or 6-8 weeks (E) are more typical for osteomyelitis, not isolated septic arthritis.

Question 758

Topic: Infection, Pharmacology & VTE

Which of the following physical examination findings is most indicative of septic arthritis of an MCP joint in a patient with a suspected fight bite?

. A. Pain localized to the skin laceration with normal range of motion.
. B. Warmth and erythema extending to the forearm.
. C. Significant pain with passive range of motion of the affected MCP joint.
. D. Paresthesias in the digit distal to the wound.
. E. Visible pus exuding from the wound without joint involvement.

Correct Answer & Explanation

. C. Significant pain with passive range of motion of the affected MCP joint.

Explanation

Significant pain with passive range of motion (PROM) of the affected joint is a classic and highly sensitive sign of septic arthritis. Any attempt to move the joint will stretch the inflamed and distended joint capsule, causing severe pain. Pain localized to the skin (A) suggests superficial involvement. Warmth and erythema extending to the forearm (B) indicate cellulitis/lymphangitis, which may or may not involve the joint. Paresthesias (D) suggest nerve injury, not primarily septic arthritis. Visible pus (E) from the wound suggests infection but does not specifically localize it to the joint unless it is directly from within the joint space.

Question 759

Topic: Infection, Pharmacology & VTE

What is the primary role of an MRI in the acute evaluation of a complicated fight bite injury to the hand?

. A. To definitively identify bacterial species present in the wound.
. B. To assess the extent of soft tissue edema and inflammation only.
. C. To detect early osteomyelitis, tenosynovitis, or joint capsule violation not clear on plain radiographs.
. D. To guide placement of external fixators for unstable fractures.
. E. To measure nerve conduction velocity for suspected nerve injury.

Correct Answer & Explanation

. C. To detect early osteomyelitis, tenosynovitis, or joint capsule violation not clear on plain radiographs.

Explanation

MRI is highly sensitive for detecting early osteomyelitis, tenosynovitis, and joint capsule violations, as well as foreign bodies not visible on X-ray, and delineating fluid collections (abscesses). While plain radiographs are initial, MRI provides superior soft tissue and bone marrow detail when deep infection or complex involvement is suspected but not definitively clear from clinical exam and X-rays. It does not identify bacterial species (A) or measure nerve conduction (E). While it shows edema (B), its utility extends far beyond that. External fixator guidance (D) is not its primary role in the acute phase of an infection.

Question 760

Topic: Infection, Pharmacology & VTE

Which of the following is considered a poor prognostic indicator in a fight bite injury to the hand?

. A. Young patient age.
. B. Injury sustained over the index finger MCP joint.
. C. Delayed presentation (>24 hours) with signs of deep infection.
. D. Superficial laceration without joint involvement.
. E. Absence of associated fracture.

Correct Answer & Explanation

. C. Delayed presentation (>24 hours) with signs of deep infection.

Explanation

Delayed presentation (>24 hours) coupled with signs of deep infection (e.g., septic arthritis, osteomyelitis, tenosynovitis) is a significant poor prognostic indicator for fight bite injuries. The longer the infection is allowed to progress without definitive treatment, the greater the risk of irreversible joint damage, functional loss, and limb-threatening complications. Young age (A) is generally a good prognostic indicator. The location (B) is common but not inherently prognostic. Superficial wounds (D) and absence of fracture (E) are typically associated with better outcomes.

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