Menu

Infection, Pharmacology & VTE MCQs

Practice Set 64 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 1261

Topic: Infection, Pharmacology & VTE

A 9-year-old African American boy with homozygous sickle cell disease (HbSS) presents with a 4-day history of fever, chills, and severe pain in his right thigh. Blood cultures and a subperiosteal aspirate grow a non-lactose fermenting, Gram-negative motile bacillus that produces hydrogen sulfide. Which of the following pathophysiological mechanisms best explains this patient's unique susceptibility to this specific organism?

. Impaired splenic macrophage function and reticuloendothelial blockade
. Deficiency in the terminal complement cascade (C5-C9)
. Defective neutrophil oxidative burst
. Absence of secretory IgA in the gastrointestinal tract
. T-cell lymphopenia due to chronic hemolysis

Correct Answer & Explanation

. Impaired splenic macrophage function and reticuloendothelial blockade

Explanation

Correct Answer: A (Impaired splenic macrophage function and reticuloendothelial blockade)The organism described isSalmonellaspecies, which is uniquely a common cause of osteomyelitis in patients with sickle cell disease (thoughS. aureusremains the most common overall). Patients with sickle cell disease experience recurrent vaso-occlusive crises, leading to microinfarctions of the spleen and eventual autosplenectomy by early childhood. This loss of splenic function severely impairs the reticuloendothelial system's ability to clear encapsulated organisms and intravascular bacteria. Furthermore, microinfarctions in the bowel wall allowSalmonellato translocate into the bloodstream, where the defective splenic macrophages fail to clear the bacteremia, allowing the bacteria to seed areas of ischemic bone.

Question 1262

Topic: Infection, Pharmacology & VTE

A 65-year-old male undergoes total knee arthroplasty. On postoperative day 2, he develops acute shortness of breath, pleuritic chest pain, and hypoxemia. What is the most likely diagnosis?

. Pneumonia
. Acute myocardial infarction
. Pulmonary embolism
. Fat embolism syndrome
. Atelectasis

Correct Answer & Explanation

. Pulmonary embolism

Explanation

Acute shortness of breath, pleuritic chest pain, and hypoxemia occurring post-total knee arthroplasty are classic symptoms of a pulmonary embolism (PE). Deep vein thrombosis (DVT) and subsequent PE are serious and relatively common complications of major orthopedic surgery. While atelectasis is common post-operatively, it usually presents with more subtle symptoms. Pneumonia and myocardial infarction are possibilities but less likely to manifest with pleuritic pain so acutely after TKA. Fat embolism syndrome usually occurs earlier (within 24-48 hours), often after long bone fractures, and includes petechial rash and neurological changes, which are not mentioned here.

Question 1263

Topic: Infection, Pharmacology & VTE

A 50-year-old male with a history of chronic alcoholism presents with pain and swelling in his left great toe. On examination, the joint is warm, erythematous, and exquisitely tender to touch. Serum uric acid level is elevated. What is the most appropriate acute management?

. Initiate allopurinol immediately.
. Prescribe indomethacin or colchicine.
. Aspirate the joint and inject corticosteroids.
. Start long-term urate-lowering therapy.
. Refer for surgical fusion of the MTP joint.

Correct Answer & Explanation

. Prescribe indomethacin or colchicine.

Explanation

The presentation is classic for an acute gouty arthritis attack (podagra). The most appropriate acute management is to prescribe non-steroidal anti-inflammatory drugs (NSAIDs) like indomethacin, or colchicine. Oral corticosteroids can also be used if NSAIDs are contraindicated or ineffective. Allopurinol is a urate-lowering therapy and should not be initiated during an acute attack, as it can worsen symptoms by mobilizing uric acid crystals; it is for long-term management once the acute attack has subsided. Joint aspiration and corticosteroid injection are options if only one or two joints are involved and diagnosis is confirmed. Surgical fusion is for end-stage arthritis, not acute management.

Question 1264

Topic: Infection, Pharmacology & VTE

What is the most common causative organism for septic arthritis in a healthy adult?

. Staphylococcus aureus
. Streptococcus pyogenes
. Neisseria gonorrhoeae
. Escherichia coli
. Pseudomonas aeruginosa

Correct Answer & Explanation

. Staphylococcus aureus

Explanation

Staphylococcus aureus is the most common causative organism for septic arthritis in healthy adults, accounting for over 80% of cases. Streptococcus pyogenes is also a significant pathogen but less common than S. aureus. Neisseria gonorrhoeae is a common cause in young, sexually active individuals but not the overall most common. E. coli and Pseudomonas aeruginosa are typically seen in immunocompromised patients, those with urinary tract infections, or intravenous drug users.

Question 1265

Topic: Infection, Pharmacology & VTE

A 4-year-old child presents with a high fever, refusal to bear weight, and exquisite pain on passive range of motion of the right hip. Laboratory tests show elevated white blood cell count, ESR, and CRP. Plain radiographs of the hip are normal. What is the most appropriate immediate diagnostic and therapeutic step?

. Administer oral antibiotics and observe.
. Obtain an MRI of the hip.
. Perform a CT scan of the hip.
. Aspirate the hip joint.
. Prescribe NSAIDs and bed rest for transient synovitis.

Correct Answer & Explanation

. Aspirate the hip joint.

Explanation

The clinical presentation (fever, refusal to bear weight, exquisite pain on passive hip ROM, elevated inflammatory markers, normal radiographs) is highly suggestive of septic arthritis of the hip, an orthopedic emergency in children. The most appropriate immediate step is to aspirate the hip joint. This allows for definitive diagnosis (cell count, Gram stain, culture) and therapeutic decompression of the joint. Delay in diagnosis and treatment can lead to rapid cartilage destruction and long-term joint damage. Oral antibiotics are inadequate. MRI and CT can confirm effusions but aspiration is critical for diagnosis and treatment. NSAIDs and bed rest are for transient synovitis, which has lower inflammatory markers and less severe pain on ROM.

Question 1266

Topic: Infection, Pharmacology & VTE

A 3-year-old boy presents with a limp and refusal to bear weight on the right leg. He is afebrile but has limited internal rotation. An AP pelvis radiograph is shown. The right teardrop distance measures 11 mm, while the left measures 8 mm. What is the most definitive next step in management to determine the etiology?

. MRI of the pelvis with contrast
. Ultrasound-guided hip aspiration
. Technetium Tc 99m bone scan
. Closed reduction and spica casting
. Intravenous antibiotics and observation

Correct Answer & Explanation

. Ultrasound-guided hip aspiration

Explanation

Correct Answer: BThe widened teardrop distance (a difference of >2 mm compared to the contralateral side) indicates a significant joint effusion. In a child presenting with refusal to bear weight and limited motion, septic arthritis must be urgently ruled out. Hip aspiration is the most definitive test to differentiate septic arthritis from transient synovitis by obtaining fluid for cell count, Gram stain, and culture.

Question 1267

Topic: Infection, Pharmacology & VTE

A 5-year-old child presents with a severe limp. Radiographs reveal complete resorption of the right femoral head and neck with a high-riding trochanter (Choi type IV) as a sequela of neonatal MRSA septic arthritis. Which salvage procedure provides the most stable fulcrum for ambulation and equalizes leg length?

. Total hip arthroplasty
. Pelvic support osteotomy (Ilizarov technique)
. Trochanteric arthroplasty
. Shelf osteotomy
. Chiari osteotomy

Correct Answer & Explanation

. Pelvic support osteotomy (Ilizarov technique)

Explanation

A pelvic support osteotomy utilizes a proximal femoral valgus-extension osteotomy to abut the pelvis (creating a fulcrum) combined with distal femoral lengthening. It is a highly effective salvage for unsalvageable post-infectious hip defects in children.

Question 1268

Topic: Infection, Pharmacology & VTE

A 35-year-old female on chronic corticosteroids for SLE presents with groin pain. MRI reveals bilateral femoral head avascular necrosis (Ficat Stage II). What is the primary rationale for performing a core decompression?

. To replace necrotic bone with vascularized fibula
. To decrease intraosseous pressure and promote revascularization
. To prevent DVT
. To reshape the femoral head
. To delay the onset of hip dysplasia

Correct Answer & Explanation

. To decrease intraosseous pressure and promote revascularization

Explanation

Core decompression aims to reduce the elevated intraosseous pressure in the femoral head caused by venous stasis and edema. This provides a channel for neoangiogenesis and potentially halts disease progression in pre-collapse stages (Ficat I and II).

Question 1269

Topic: Infection, Pharmacology & VTE
A 4-year-old boy presents with a limp, right hip pain, a temperature of 38.6°C (101.5°F), and refusal to bear weight. His laboratory values show WBC 14,000/mm³, ESR 45 mm/hr, and CRP 25 mg/L. According to Kocher's criteria, what is the approximate probability of this child having septic arthritis?
. 3%
. 40%
. 73%
. 93%
. 99%

Correct Answer & Explanation

. 99%

Explanation

Kocher's criteria include non-weight bearing, fever >38.5°C, ESR >40 mm/hr, and WBC >12,000/mm³. The presence of all four predictors yields an approximately 99% probability of septic arthritis.

Question 1270

Topic: Infection, Pharmacology & VTE

A 30-year-old construction worker presents with chronic low back pain and radicular symptoms to his right leg. He has undergone 3 months of physical therapy, NSAIDs, and activity modification without significant relief. MRI shows a contained L4-L5 disc protrusion without significant migration, impinging the L5 nerve root. Neurological exam reveals mild weakness in right great toe extension (4/5) but no bladder/bowel dysfunction. What is the most appropriate next step?

. Continue conservative management for another 3 months
. Urgent microdiscectomy
. Transforaminal epidural steroid injection
. Lumbar fusion surgery
. Psychological counseling

Correct Answer & Explanation

. Transforaminal epidural steroid injection

Explanation

Given the failure of 3 months of conservative management for persistent radicular pain due to a disc protrusion and mild, non-progressive motor weakness, a transforaminal epidural steroid injection is a reasonable next step. It can provide significant pain relief by delivering anti-inflammatory medication directly to the affected nerve root. Surgical intervention (microdiscectomy) is typically considered for intractable pain after a trial of epidural injections, or for progressive neurological deficits. Lumbar fusion is overly aggressive for this presentation. Continuing conservative management foranother3 months without any specific escalation may be prolonged, and psychological counseling is not the primary intervention for this specific clinical picture, although it can be part of a multidisciplinary approach for chronic pain.

Question 1271

Topic: Infection, Pharmacology & VTE

When treating a staphylococcal periprosthetic joint infection (PJI) with implant retention (DAIR), which of the following antibiotic agents is essential for penetrating the established bacterial biofilm?

. Cefazolin
. Vancomycin
. Rifampin
. Gentamicin
. Linezolid

Correct Answer & Explanation

. Rifampin

Explanation

Rifampin is highly active against stationary-phase staphylococci embedded within biofilms. It is a critical component of combination oral antibiotic therapy following DAIR for staphylococcal PJI.

Question 1272

Topic: Infection, Pharmacology & VTE

A 50-year-old chronic alcoholic presents with a painless, swollen, and deformed midfoot. Radiographs show tarsometatarsal destruction, fragmentation, and subluxation. What is the primary underlying etiology of this condition?

. Direct alcohol toxicity to articular cartilage
. Alcoholic peripheral neuropathy leading to loss of protective sensation
. Malnutrition-induced osteomalacia
. Chronic hematogenous osteomyelitis
. Alcoholic myopathy causing muscular imbalance

Correct Answer & Explanation

. Alcoholic peripheral neuropathy leading to loss of protective sensation

Explanation

This is a classic presentation of Charcot neuroarthropathy. Chronic alcohol abuse causes toxic and nutritional peripheral neuropathy, leading to absent protective sensation, repetitive microtrauma, and severe joint destruction.

Question 1273

Topic: Infection, Pharmacology & VTE

A patient develops a deep periprosthetic infection 4 weeks after a total knee arthroplasty, caused by a virulent strain of Staphylococcus aureus as seen in similar iatrogenic hardware infections.

Which essential component of the biofilm matrix is primarily responsible for adhering the bacteria to the implant and protecting them from systemic antibiotics?

. Peptidoglycan cell wall
. Lipopolysaccharide (LPS) endotoxin
. Polysaccharide intercellular adhesin (PIA)
. Hyaluronic acid capsule
. Mycolic acid

Correct Answer & Explanation

. Polysaccharide intercellular adhesin (PIA)

Explanation

Biofilm formation in staphylococcal implant infections relies heavily on the production of polysaccharide intercellular adhesin (PIA), which is synthesized by the ica operon. This extracellular polymeric substance securely anchors bacteria to the prosthesis and severely limits antibiotic penetration.

Question 1274

Topic: Infection, Pharmacology & VTE

Which of the following organisms is most notorious for causing chronic, indolent periprosthetic joint infections due to its robust ability to produce a polysaccharide intercellular adhesin (PIA) that forms a resilient protective biofilm?

. Streptococcus pyogenes
. Neisseria gonorrhoeae
. Staphylococcus epidermidis
. Pseudomonas aeruginosa
. Clostridium perfringens

Correct Answer & Explanation

. Staphylococcus epidermidis

Explanation

Staphylococcus epidermidis (a coagulase-negative staphylococcus) is highly associated with chronic, low-grade PJIs. Its pathogenicity relies heavily on its ability to secrete PIA and form a dense glycocalyx/biofilm on metallic and polymeric implants, shielding it from antibiotics and host defenses.

Question 1275

Topic: Infection, Pharmacology & VTE

A 52-year-old man with poorly controlled type 2 diabetes presents with a 3-week history of purulent drainage from a plantar ulcer under the first metatarsal head. The ulcer measures 2 cm in diameter. A sterile blunt probe is easily advanced through the ulcer until it strikes a hard, gritty surface. Which of the following statements regarding this clinical finding is most accurate?

. It has a high negative predictive value for osteomyelitis.
. It is highly predictive of osteomyelitis, and empiric antibiotics should be started immediately without further imaging.
. It has a high positive predictive value for osteomyelitis in the setting of a clinically infected ulcer.
. It indicates the need for immediate major lower extremity amputation.
. It is only useful if accompanied by systemic signs of infection such as fever and leukocytosis.

Correct Answer & Explanation

. It has a high positive predictive value for osteomyelitis in the setting of a clinically infected ulcer.

Explanation

Correct Answer: It has a high positive predictive value for osteomyelitis in the setting of a clinically infected ulcer.The probe-to-bone (PTB) test is a valuable clinical tool in the evaluation of diabetic foot ulcers. In the setting of a clinically infected ulcer, a positive PTB test (palpating a hard, gritty surface with a sterile blunt probe) has a high positive predictive value (up to 89%) for underlying osteomyelitis. While a negative test does not completely rule out osteomyelitis (it has a lower negative predictive value), a positive test in a high-prevalence population strongly supports the diagnosis and guides further management, including advanced imaging (MRI) and bone biopsy for culture.

Question 1276

Topic: Infection, Pharmacology & VTE

A 55-year-old diabetic patient is admitted with a severe, limb-threatening diabetic foot infection and suspected osteomyelitis of the great toe. He has not received any recent antibiotics. Deep tissue cultures and a bone biopsy are obtained. Which of the following best describes the most likely microbiological profile and appropriate initial empiric antibiotic therapy?

. Monomicrobial Staphylococcus aureus; treat with narrow-spectrum oral cephalosporin.
. Polymicrobial including aerobic Gram-positive cocci, Gram-negative bacilli, and anaerobes; treat with broad-spectrum intravenous antibiotics.
. Monomicrobial Pseudomonas aeruginosa; treat with oral ciprofloxacin.
. Polymicrobial with a predominance of fungal organisms; treat with intravenous fluconazole.
. Monomicrobial Streptococcus pyogenes; treat with intravenous penicillin.

Correct Answer & Explanation

. Polymicrobial including aerobic Gram-positive cocci, Gram-negative bacilli, and anaerobes; treat with broad-spectrum intravenous antibiotics.

Explanation

Correct Answer: Polymicrobial including aerobic Gram-positive cocci, Gram-negative bacilli, and anaerobes; treat with broad-spectrum intravenous antibiotics.Severe, limb-threatening diabetic foot infections, especially those with suspected osteomyelitis or deep tissue involvement, are typically polymicrobial. The microbiological profile often includes aerobic Gram-positive cocci (e.g., Staphylococcus aureus, Streptococcus species), Gram-negative bacilli (e.g., Enterobacteriaceae, and Pseudomonas in chronic/macerated wounds), and obligate anaerobes (e.g., Bacteroides, Peptostreptococcus). Therefore, initial empiric therapy should consist of broad-spectrum intravenous antibiotics covering these organisms until culture results and sensitivities are available to narrow the therapy.

Question 1277

Topic: Infection, Pharmacology & VTE

A 52-year-old man with poorly controlled diabetes presents with a 3-week history of a purulent ulcer on the plantar aspect of his right great toe. The ulcer measures 2 cm in diameter. A sterile metal probe easily reaches the bone at the base of the ulcer. What is the positive predictive value of this "probe-to-bone" test for diagnosing underlying osteomyelitis in this clinical setting?

. Less than 20%
. 30-40%
. 50-60%
. 85-90%
. 100%

Correct Answer & Explanation

. 85-90%

Explanation

Correct Answer: DThe "probe-to-bone" test is a highly useful clinical tool for evaluating diabetic foot ulcers. In a high-prevalence population (such as a patient with a chronic, clinically infected, purulent ulcer), a positive probe-to-bone test has a high positive predictive value (PPV) of approximately 85% to 90% for underlying osteomyelitis. While it does not replace advanced imaging or bone biopsy for definitive diagnosis, it strongly guides initial empiric management and surgical planning.

Question 1278

Topic: Infection, Pharmacology & VTE

A 52-year-old diabetic man requires surgical debridement and partial ray amputation for a chronic, limb-threatening diabetic foot infection with osteomyelitis. He has a history of multiple recent hospitalizations and antibiotic courses. Which of the following best describes the most likely microbiological profile of his deep bone cultures?

. Monomicrobial Staphylococcus aureus
. Monomicrobial Pseudomonas aeruginosa
. Polymicrobial including Gram-positive, Gram-negative, and anaerobic organisms
. Monomicrobial Streptococcus pyogenes
. Fungal infection primarily with Candida species

Correct Answer & Explanation

. Polymicrobial including Gram-positive, Gram-negative, and anaerobic organisms

Explanation

Correct Answer: CWhile acute, mild diabetic foot infections in antibiotic-naive patients are often monomicrobial (typically Staphylococcus aureus or Streptococcus species), chronic, severe, or limb-threatening infections—especially in patients with a history of recent hospitalization or antibiotic use—are overwhelmingly polymicrobial. These infections typically involve a mix of aerobic Gram-positive cocci, Gram-negative bacilli, and obligate anaerobes. Empiric antibiotic therapy for such severe infections must be broad-spectrum until definitive deep tissue or bone cultures guide targeted therapy.

Question 1279

Topic: Infection, Pharmacology & VTE

A 52-year-old man with poorly controlled diabetes mellitus presents with a 3-week history of purulent drainage from a medial right great toe ulcer. Radiographs show soft tissue swelling and periosteal reaction at the proximal phalanx. Which of the following clinical findings is most highly predictive of underlying osteomyelitis in this patient?

. Erythema extending 2 cm beyond the ulcer margin
. A palpable bounding dorsalis pedis pulse
. Ability to palpate hard, gritty bone with a sterile blunt probe
. An elevated erythrocyte sedimentation rate (ESR) greater than 30 mm/hr
. Presence of a foul-smelling polymicrobial discharge

Correct Answer & Explanation

. Ability to palpate hard, gritty bone with a sterile blunt probe

Explanation

Correct Answer: CThe "probe-to-bone" test is a highly specific and predictive clinical examination maneuver for diagnosing underlying osteomyelitis in the setting of a diabetic foot ulcer. If a sterile blunt probe can be advanced through the ulcer to palpate hard, gritty bone, the test is positive. Studies have shown that a positive probe-to-bone test in a high-prevalence population (such as a diabetic patient with a chronic, deep, draining ulcer) has a positive predictive value of nearly 90% for osteomyelitis. While elevated inflammatory markers (ESR, CRP) and radiographic changes can support the diagnosis, the clinical probe-to-bone test is the most direct and reliable bedside indicator.

Question 1280

Topic: Infection, Pharmacology & VTE

A 52-year-old man with poorly controlled type 2 diabetes presents with a 3-week history of purulent drainage from a medial right great toe ulcer. Examination reveals a 2 cm ulcer with visible bone at the base. What is the most appropriate initial diagnostic step to confirm the presence of osteomyelitis?

. Three-phase technetium bone scan
. Probe-to-bone test
. Positron emission tomography (PET) scan
. Superficial wound swab for aerobic and anaerobic cultures
. Serum inflammatory markers (ESR and CRP)

Correct Answer & Explanation

. Probe-to-bone test

Explanation

Correct Answer: BIn a patient with a diabetic foot ulcer, the probe-to-bone test is a highly specific, cost-effective, and reliable initial clinical test for diagnosing underlying osteomyelitis. If a sterile blunt probe can be advanced through the ulcer to touch hard, gritty bone, the test is positive and highly predictive of osteomyelitis. While MRI is the most sensitive and specific advanced imaging modality for osteomyelitis, the probe-to-bone test is the best initial bedside diagnostic step. Superficial wound swabs are not reliable for identifying the causative organism of osteomyelitis; deep tissue or bone biopsy cultures are required. Bone scans lack specificity in the setting of neuropathic arthropathy or active soft tissue infection.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page