Infection, Pharmacology & VTE MCQs

A periprosthetic joint infection is diagnosed in a patient 3 years after a total knee arthroplasty. Cultures isolate Staphylococcus epidermidis. This pathogen is known to form a resilient biofilm. Which of the following substances is primarily responsible for forming the glycocalyx (slime layer) in this biofilm?

In the setting of a chronic periprosthetic joint infection, organisms within a biofilm are highly resistant to systemic antibiotics. Which of the following best describes the metabolic state of bacteria in the deepest layers of a mature biofilm?

A 45-year-old immigrant presents with chronic back pain, night sweats, and progressive lower extremity weakness. MRI demonstrates destruction of two adjacent thoracic vertebral bodies with disc space preservation and a large paraspinal abscess. What is the most appropriate initial management?

A 72-year-old woman is diagnosed with an acute hematogenous staphylococcal periprosthetic joint infection of her total knee arthroplasty. She undergoes irrigation and debridement with modular exchange. Which of the following antibiotic properties makes it essential to include as part of her post-operative oral suppressive regimen?

A 14-month-old child presents with a limp and refusal to bear weight. Laboratory work reveals a normal WBC count and mildly elevated CRP. Joint aspiration yields synovial fluid with 65,000 WBCs/mm3. Routine cultures are negative at 48 hours, but PCR is positive. Which of the following is the most likely pathogen?

A 22-year-old healthy female presents with acute pain and swelling in her right knee, along with a papulovesicular rash on her trunk and tenosynovitis of her wrists. Synovial fluid aspiration of the knee yields a white blood cell count of 45,000 cells/mm3. Gram stain is negative. Which of the following is the most appropriate initial management step?

A 7-year-old boy with sickle cell disease presents with fever, leg pain, and elevated inflammatory markers. Blood cultures grow Salmonella. What is the primary pathogenic mechanism for Salmonella osteomyelitis in sickle cell patients?

A 4-year-old child presents with a 2-day history of refusal to bear weight on the left leg, fever of 39.0 C, an ESR of 55 mm/hr, and a synovial fluid WBC count of 85,000 cells/uL. Gram stain is pending. Based on current trends in community-acquired pediatric bone and joint infections, empiric antibiotic therapy must cover which of the following organisms?

A 2-year-old presents with fever, refusal to bear weight on the right leg, and elevated CRP. A joint aspiration of the knee yields a WBC count of 65,000 cells/mcL. Standard cultures are negative after 48 hours. What is the most likely fastidious organism, which is best isolated by inoculating synovial fluid into aerobic blood culture bottles?

A patient presents with a swollen, painful right knee. Aspiration reveals 80,000 WBC/mcL with 90% neutrophils. Gram stain is negative. The patient recently completed oral antibiotics for a presumed skin infection. The surgeon performs arthroscopic irrigation and debridement. Which component of the biofilm matrix is primarily responsible for protecting residual bacteria from antibiotic penetration?

A 45-year-old immigrant presents with months of insidious midthoracic back pain, low-grade fevers, and progressive lower extremity weakness. MRI demonstrates destruction of the T8 and T9 vertebral bodies with relative early sparing of the intervertebral disc, along with a large paraspinal abscess. What is the most characteristic histopathologic finding of the causative organism's infection?

A 15-year-old male presents with progressive osteolysis of his clavicle and ribs consistent with Gorham's disease. What is the most common life-threatening complication associated with this specific anatomic involvement?

A 45-year-old male presents with night sweats, fever, and thigh pain. Radiographs show a permeative diaphyseal lesion mimicking osteomyelitis.

Which MRI feature most strongly suggests a diagnosis of primary bone lymphoma over acute osteomyelitis?

During a primary TKA for a severe varus deformity, the surgeon notes the knee remains tight medially in both flexion and extension. After completely releasing the deep medial collateral ligament (MCL), what is the next most appropriate structure to release?

In a primary total knee arthroplasty for a patient with a rigid 15-degree varus deformity, what is the generally accepted initial sequence of medial soft tissue release after removal of all osteophytes?

During a primary TKA for a severe varus deformity, step-wise medial soft tissue release is necessary. After releasing the deep medial collateral ligament (MCL) and removing osteophytes, the knee remains tight in extension. Which structure should typically be released next to address this extension-predominant tightness?