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Infection, Pharmacology & VTE MCQs

Practice Set 5 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 81

Topic: Infection, Pharmacology & VTE

In acute hematogenous osteomyelitis in a young child, what anatomical feature of the metaphyseal blood vessels strongly predisposes the metaphysis to bacterial seeding?

. High-velocity arterial flow
. Sluggish flow in venous capillary loops
. Abundant local macrophages
. Direct connection to the joint space in all joints
. Lack of a continuous endothelial lining

Correct Answer & Explanation

. Sluggish flow in venous capillary loops

Explanation

The metaphyseal venous sinusoids feature sluggish, turbulent blood flow and a local deficiency in phagocytic cells. This creates an ideal microenvironment for bloodborne bacteria to deposit and proliferate.

Question 82

Topic: Infection, Pharmacology & VTE

A 4-year-old boy presents with a limp and right hip pain. He is afebrile (37.2°C) but refuses to bear weight on the right leg. Laboratory tests show a WBC of 10,500/mm3 and an ESR of 22 mm/hr. What is the approximate probability of septic arthritis according to the Kocher criteria?

. 3%
. 40%
. 71%
. 93%
. 99%

Correct Answer & Explanation

. 3%

Explanation

The Kocher criteria for septic arthritis of the pediatric hip include fever > 38.5C, inability to bear weight, ESR > 40, and WBC > 12,000. Having only one positive criterion (non-weight bearing) correlates with a roughly 3% probability.

Question 83

Topic: Infection, Pharmacology & VTE

An 8-year-old girl with homozygous sickle cell disease presents with fever and severe tibial pain. Blood cultures are drawn. Empiric antibiotic therapy should ideally include robust coverage for which two most common organisms in this specific population?

. S. aureus and S. pneumoniae
. S. aureus and Salmonella species
. Group A Streptococcus and E. coli
. P. aeruginosa and S. aureus
. Kingella kingae and S. aureus

Correct Answer & Explanation

. S. aureus and Salmonella species

Explanation

While Staphylococcus aureus remains the most common overall cause of osteomyelitis in sickle cell disease, Salmonella species are disproportionately elevated in this population. Empiric therapy with a third-generation cephalosporin and an anti-staphylococcal agent is standard.

Question 84

Topic: Infection, Pharmacology & VTE
A 14-month-old child presents with acute onset of a limp and a swollen left knee. Arthrocentesis yields purulent fluid with 65,000 WBCs, but routine Gram stain and standard cultures are negative at 48 hours. Which of the following fastidious organisms is the most likely culprit?
. Neisseria gonorrhoeae
. Borrelia burgdorferi
. Kingella kingae
. Haemophilus influenzae
. Mycoplasma pneumoniae

Correct Answer & Explanation

. Kingella kingae

Explanation

Kingella kingae is a fastidious Gram-negative organism that is now a leading cause of septic arthritis and osteomyelitis in children aged 6 months to 4 years. It is notoriously difficult to culture and often requires inoculation into BACTEC blood culture bottles.

Question 85

Topic: Infection, Pharmacology & VTE

A 10-year-old girl presents with recurrent episodes of multifocal bone pain. Radiographs reveal lytic lesions with sclerotic borders in the clavicle and distal tibia. Biopsy shows sterile, non-specific inflammation. Which of the following is the most appropriate initial treatment?

. Prolonged IV antibiotics
. Surgical curettage and bone grafting
. Nonsteroidal anti-inflammatory drugs (NSAIDs)
. Intra-articular corticosteroid injections
. Radiation therapy

Correct Answer & Explanation

. Nonsteroidal anti-inflammatory drugs (NSAIDs)

Explanation

Chronic recurrent multifocal osteomyelitis (CRMO) is an autoinflammatory, non-infectious bone disease. The first-line treatment is NSAIDs, which provide significant symptomatic relief and can induce remission in most patients.

Question 86

Topic: Infection, Pharmacology & VTE

A 2-week-old neonate in the NICU is noted to have a swollen, immobile right shoulder. Ultrasound confirms an effusion, and aspiration is planned. In addition to Staphylococcus aureus, which organism is a highly prominent cause of septic arthritis specifically in this age group?

. Kingella kingae
. Streptococcus pneumoniae
. Group B Streptococcus
. Haemophilus influenzae type B
. Salmonella enteritidis

Correct Answer & Explanation

. Group B Streptococcus

Explanation

Group B Streptococcus (Streptococcus agalactiae) and Gram-negative bacilli (such as E. coli) are major causes of neonatal septic arthritis and osteomyelitis, heavily influencing the choice of empiric antibiotics in neonates.

Question 87

Topic: Infection, Pharmacology & VTE

In a 7-year-old child being treated for acute hematogenous osteomyelitis, which inflammatory marker is most useful for evaluating the response to antibiotic therapy and guiding the transition from intravenous to oral medications?

. White blood cell count (WBC)
. Erythrocyte sedimentation rate (ESR)
. C-reactive protein (CRP)
. Procalcitonin
. Serum ferritin

Correct Answer & Explanation

. C-reactive protein (CRP)

Explanation

CRP peaks within 48 hours of infection onset and drops rapidly with effective treatment, making it the most reliable dynamic marker for monitoring therapeutic response. ESR can remain elevated for weeks despite adequate treatment.

Question 88

Topic: Infection, Pharmacology & VTE

A 7-year-old boy presents with a massive knee effusion and a slight limp, but he retains full range of motion with only minimal pain. He is afebrile. Which of the following findings most strongly differentiates Lyme arthritis from pyogenic septic arthritis?

. Refusal to bear weight on the affected limb
. Peripheral WBC count > 15,000
. Knee synovial fluid WBC count > 50,000
. The disproportionate lack of severe pain with range of motion
. A markedly elevated ESR > 80 mm/hr

Correct Answer & Explanation

. The disproportionate lack of severe pain with range of motion

Explanation

Lyme arthritis classically presents with a large joint effusion but remarkably little pain on active or passive range of motion compared to the extreme pain seen in acute pyogenic septic arthritis.

Question 89

Topic: Infection, Pharmacology & VTE

A 12-year-old steps on a rusty nail that pierces his rubber-soled sneaker, subsequently developing osteomyelitis in the foot. Following surgical debridement, what is the most appropriate empiric oral antibiotic choice for the most likely organism?

. Amoxicillin-clavulanate
. Clindamycin
. Ciprofloxacin
. Linezolid
. Doxycycline

Correct Answer & Explanation

. Ciprofloxacin

Explanation

Puncture wounds occurring through rubber-soled shoes are strongly associated with Pseudomonas aeruginosa osteomyelitis. Ciprofloxacin provides excellent oral anti-pseudomonal coverage and bone penetration.

Question 90

Topic: Infection, Pharmacology & VTE
According to the Kocher criteria, which of the following is one of the independent predictors used to differentiate septic arthritis from transient synovitis of the hip in a pediatric patient?
. History of preceding upper respiratory infection
. Serum CRP > 2.0 mg/dL
. Inability to bear weight
. Presence of knee pain
. Night sweats

Correct Answer & Explanation

. Inability to bear weight

Explanation

The four classic Kocher criteria are: inability to bear weight, temperature > 38.5°C, ESR > 40 mm/hr, and WBC > 12,000 cells/mm³. While CRP is highly sensitive and used in modified criteria, inability to bear weight is one of the original four.

Question 91

Topic: Infection, Pharmacology & VTE

According to the Kocher criteria, which of the following findings is NOT one of the four classic predictors used to differentiate pediatric septic arthritis of the hip from transient synovitis?

. Inability to bear weight
. Erythrocyte sedimentation rate (ESR) > 40 mm/hr
. Fever > 38.5 degrees C
. Serum C-reactive protein (CRP) > 2.0 mg/dL
. White blood cell count > 12,000 cells/mm3

Correct Answer & Explanation

. Serum C-reactive protein (CRP) > 2.0 mg/dL

Explanation

The original Kocher criteria include: non-weight bearing, ESR > 40 mm/hr, Fever > 38.5 C, and WBC > 12,000. While CRP > 2.0 mg/dL was later identified by Caird et al. as an excellent independent predictor, it is not one of the four original Kocher criteria.

Question 92

Topic: Infection, Pharmacology & VTE

A 2-year-old boy is brought to the clinic because he refuses to bear weight on his left leg. Examination reveals minimal swelling and tenderness over the distal tibia. Initial radiographs are completely normal. What is the most appropriate next step?

. Immediate MRI of the tibia
. Aspiration of the ankle joint
. Immobilization in a long leg cast and repeat radiographs in 10-14 days
. Reassurance and immediate return to unrestricted activity
. Bone scan to rule out osteomyelitis

Correct Answer & Explanation

. Immobilization in a long leg cast and repeat radiographs in 10-14 days

Explanation

A Toddler's fracture is a nondisplaced spiral fracture of the distal tibia where initial radiographs are often normal. The standard of care is empiric immobilization and repeat imaging in 1-2 weeks.

Question 93

Topic: Infection, Pharmacology & VTE

A 2-year-old presents with a fever of 39.0°C, inability to bear weight on the right leg, an ESR of 50 mm/hr, and a serum WBC of 13,000/mm3. According to Kocher's criteria, what is the probability that this child has septic arthritis of the hip?

. 10%
. 40%
. 73%
. 93%
. 99%

Correct Answer & Explanation

. 93%

Explanation

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

Question 94

Topic: Infection, Pharmacology & VTE
A 4-year-old boy presents with right hip pain, a temperature of 38.8°C, an ESR of 50 mm/hr, and a WBC count of 14,000 cells/mm³. He refuses to bear weight. According to the Kocher criteria, what is the probability that he has septic arthritis?
. < 10%
. 30-40%
. 50-60%
. 70-80%
. > 90%

Correct Answer & Explanation

. > 90%

Explanation

The patient meets all 4 Kocher criteria (fever >38.5°C, non-weight-bearing, ESR >40, WBC >12,000). The presence of 4 criteria correlates with a 93% to 99% probability of septic arthritis.

Question 95

Topic: Infection, Pharmacology & VTE

A 4-year-old child presents with a limp, refusal to bear weight, and a temperature of 38.6°C. WBC is 13,000/mm3, and ESR is 45 mm/hr. According to the Kocher criteria, what is the probability that this child has septic arthritis of the hip?

. Less than 10%
. Approximately 40%
. Approximately 93%
. Greater than 99%
. 100%

Correct Answer & Explanation

. Approximately 93%

Explanation

The child meets 3 of the 4 Kocher criteria (fever >38.5°C, non-weight bearing, WBC >12k, ESR >40). The probability of septic arthritis with 3 positive predictors is approximately 93%.

Question 96

Topic: Infection, Pharmacology & VTE

A 5-year-old boy presents with a 2-day history of a right-sided limp and mild hip pain. He is afebrile with normal inflammatory markers. Ultrasound shows a small effusion in the right hip. He had an upper respiratory infection a week ago. What is the most appropriate management?

. Urgent joint aspiration
. Intravenous antibiotics
. Non-steroidal anti-inflammatory drugs (NSAIDs) and observation
. Hip spica casting
. Surgical irrigation and debridement

Correct Answer & Explanation

. Non-steroidal anti-inflammatory drugs (NSAIDs) and observation

Explanation

The clinical picture of mild hip pain, normal inflammatory markers, afebrile status, and recent URI strongly suggests transient synovitis. This is a self-limiting condition best treated with NSAIDs, rest, and supportive care.

Question 97

Topic: Infection, Pharmacology & VTE

A 7-year-old girl presents with torticollis and neck pain 1 week after a severe viral pharyngitis. Her head is tilted to the right and rotated to the left. Dynamic CT confirms atlantoaxial rotatory subluxation (Grisel's syndrome). What is the most appropriate initial treatment?

. Occipitocervical fusion
. Hard cervical collar alone
. Halter traction and NSAIDs/muscle relaxants
. Open reduction and internal fixation
. Translaminar screw fixation

Correct Answer & Explanation

. Halter traction and NSAIDs/muscle relaxants

Explanation

Grisel's syndrome is non-traumatic AARS secondary to retropharyngeal inflammation. Initial treatment involves soft tissue relaxation, anti-inflammatories, and halter traction, followed by cervical bracing once the subluxation is reduced.

Question 98

Topic: Infection, Pharmacology & VTE
A 4-year-old boy presents with right hip pain, refusing to bear weight. His temperature is 38.6°C, ESR is 45 mm/hr, and WBC is 10,500/mm³. Radiographs are unremarkable. According to the Kocher criteria, what is the approximate probability that this child has septic arthritis?
. < 5%
. 40%
. 71%
. 93%
. 99%

Correct Answer & Explanation

. 93%

Explanation

The Kocher criteria for septic arthritis of the hip include non-weight-bearing, temperature >38.5°C, ESR >40 mm/hr, and WBC >12,000/mm³. This patient meets three criteria, which corresponds to a 93% predicted probability of septic arthritis.

Question 99

Topic: Infection, Pharmacology & VTE

Nonselective nonsteroidal anti-inflammatory drugs (NSAIDs) have the following effect on spinal fusion:

. Increased speed of fusion
. Increased volume of fusion bone
. Decreased bleeding
. Decreased fusion rate
. Unplanned extension of fusion

Correct Answer & Explanation

. Decreased fusion rate

Explanation

Nonselective NSAIDs have been shown to decrease fusion rates in both animal models and in humans. The mechanism is most likely through an inhibition of cyclooxygenase (C OX)-1 because C OX-2 inhibitors do not show this effect.

Question 100

Topic: Infection, Pharmacology & VTE

In the evaluation of a pediatric patient with an irritable hip, which of the following is NOT one of the original Kocher criteria used to differentiate septic arthritis from transient synovitis?

. Non-weight-bearing on the affected side
. Erythrocyte sedimentation rate (ESR) greater than 40 mm/hr
. Fever greater than 38.5 degrees Celsius
. Serum C-reactive protein (CRP) greater than 20 mg/L
. White blood cell count (WBC) greater than 12,000 cells/mm3

Correct Answer & Explanation

. Serum C-reactive protein (CRP) greater than 20 mg/L

Explanation

The original four Kocher criteria are non-weight-bearing, ESR >40, fever >38.5°C, and WBC >12,000. CRP >20 mg/L was later identified as an excellent independent predictor, but it was not part of the original Kocher criteria.

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