Prosthetic Joint Infections — MCQs
A 12 year old girl was brought with fever, malaise, and migrating polyarthritis. She had a history of recurrent throat infections in the past. Elevated erythrocyte sedimentation rate is noted. Which among the following is NOT a major Jones criteria for diagnosis of acute rheumatic fever?
A study of nosocomial infections involving urinary catheters is performed. The study shows that the longer an indwelling urinary catheter remains, the higher the rate of symptomatic urinary tract infections (UTIs). Most of these infections are bacterial. Which of the following properties of these bacteria increase the risk for nosocomial UTIs?
Which organism causes prosthetic valve endocarditis within 60 days of surgery?
A 12-year-old girl begins to limp while playing soccer. She has pain in her right leg and upper right thigh. Her temperature is 102°F. X-ray of the femur reveals that the periosteum is eroded. Assuming that this case is managed as an infectious disease, which of the following is the most likely etiologic agent?
Immediate treatment of compound fracture of tibia includes:
Bacteria most commonly involved in prosthetic valvular heart disease within 2 months of surgery is:
What is the most effective management strategy for hemarthrosis?
Antecedent diagnosis of Group A streptococcal infection in Acute rheumatic fever can be made by?
What will the aspirated synovial fluid in a case of septic arthritis typically show?
12 years male came with swelling of lower end tibia which is surrounded by rim of reactive bone. What is most likely diagnosis?
Prosthetic Joint Infections Indian Medical PG Practice Questions and MCQs
Question 1: A 12 year old girl was brought with fever, malaise, and migrating polyarthritis. She had a history of recurrent throat infections in the past. Elevated erythrocyte sedimentation rate is noted. Which among the following is NOT a major Jones criteria for diagnosis of acute rheumatic fever?
- A. Raised ESR (Correct Answer)
- B. Chorea
- C. Arthritis
- D. Carditis
Explanation: ***Raised ESR*** - **Elevated erythrocyte sedimentation rate (ESR)** is a **minor criterion** in the Jones Criteria for acute rheumatic fever, indicating inflammation but not specific enough to be a major criterion. - While it supports the diagnosis, it is a non-specific inflammatory marker rather than a distinct clinical manifestation of the disease. *Chorea* - **Sydenham's chorea** (St. Vitus' dance) is a **major manifestation** of acute rheumatic fever, characterized by involuntary, purposeless movements. - It results from central nervous system involvement and is a highly diagnostic sign, often appearing late in the disease course. *Arthritis* - **Migratory polyarthritis** is a **major criterion** for acute rheumatic fever, typically affecting large joints in a sequential pattern. - This symptom is often the presenting complaint and is highly responsive to anti-inflammatory treatment. *Carditis* - **Carditis**, involving inflammation of the heart muscle, pericardium, or endocardium, is a **major criterion** and the most serious manifestation of acute rheumatic fever. - It can lead to long-term valvular damage, particularly affecting the mitral and aortic valves.
Question 2: A study of nosocomial infections involving urinary catheters is performed. The study shows that the longer an indwelling urinary catheter remains, the higher the rate of symptomatic urinary tract infections (UTIs). Most of these infections are bacterial. Which of the following properties of these bacteria increase the risk for nosocomial UTIs?
- A. Enzyme elaboration
- B. Biofilm formation (Correct Answer)
- C. Quorum sensing
- D. Exotoxin release
Explanation: ***Biofilm formation*** - **Biofilms** are communities of bacteria encased in a self-produced extracellular polymeric substance, adhering to surfaces like indwelling catheters. - The formation of a biofilm protects bacteria from antibiotics and host immune responses, allowing them to persist and proliferate, significantly increasing the risk of **catheter-associated urinary tract infections (CAUTIs)** over time. *Enzyme elaboration* - While some bacterial enzymes (e.g., urease) can contribute to UTI pathogenesis by increasing urine pH and promoting stone formation, it is not the primary property increasing the *risk* of nosocomial UTIs related to catheter duration. - The elaboration of various enzymes is a general virulence factor but doesn't specifically explain the increased risk due to the *presence* of a foreign body like a catheter. *Quorum sensing* - **Quorum sensing** is a system of stimuli and response correlated to population density, allowing bacteria to coordinate gene expression in response to their population density. - While quorum sensing plays a role in regulating virulence factors and biofilm maturation, it is a mechanism *within* a biofilm or bacterial population rather than the direct property of bacteria that increases the basal risk of infection on a catheter. *Exotoxin release* - **Exotoxins** are proteins secreted by bacteria that can cause damage to host cells and tissues, leading to specific disease symptoms (e.g., tetanus toxin, botulinum toxin). - While some exotoxins can contribute to the severity of infections, they are not the primary reason for the increased incidence of UTIs specifically due to the presence of an indwelling catheter; the physical presence of the catheter primarily promotes bacterial adhesion and persistence via means such as biofilm formation.
Question 3: Which organism causes prosthetic valve endocarditis within 60 days of surgery?
- A. Staphylococcus aureus
- B. Staphylococcus epidermidis (Correct Answer)
- C. Fungus
- D. Streptococcus viridans
Explanation: ***Staphylococcus epidermidis*** - This organism is the **most common cause of early prosthetic valve endocarditis (within 60 days of surgery)**, accounting for 30-40% of cases. - As a coagulase-negative Staphylococcus, *S. epidermidis* commonly colonizes the skin and can be introduced during the surgical procedure. - It produces **biofilms**, which allow it to adhere to prosthetic surfaces and resist antibiotic treatment. *Staphylococcus aureus* - *Staphylococcus aureus* is the **second most common cause of early prosthetic valve endocarditis** (20-25% of cases) and can cause both early and late infections. - It typically presents with a more **fulminant, aggressive course** compared to *S. epidermidis*. - While both staphylococcal species cause early PVE, *S. epidermidis* remains more frequent. *Fungus* - **Fungal endocarditis** on prosthetic valves (typically *Candida* species) accounts for 5-10% of early PVE cases. - More commonly seen in immunocompromised patients, those with prolonged antibiotic use, or after complicated cardiac surgery. - Its incidence is significantly lower than staphylococcal causes in the early post-operative period. *Streptococcus viridans* - *Streptococcus viridans* is the **most common cause of native valve endocarditis**, particularly in patients with pre-existing valvular heart disease. - It typically causes a **subacute presentation** and is more associated with **late prosthetic valve endocarditis** (>60 days post-surgery), not early PVE. - Rarely implicated in early prosthetic valve infections.
Question 4: A 12-year-old girl begins to limp while playing soccer. She has pain in her right leg and upper right thigh. Her temperature is 102°F. X-ray of the femur reveals that the periosteum is eroded. Assuming that this case is managed as an infectious disease, which of the following is the most likely etiologic agent?
- A. Salmonella enteritidis
- B. Staphylococcus saprophyticus
- C. Listeria monocytogenes
- D. Staphylococcus aureus (Correct Answer)
Explanation: ***Staphylococcus aureus*** - *S. aureus* is the most common cause of **osteomyelitis** in children, accounting for the symptoms of bone pain, limp, fever, and periosteal erosion. - The organism frequently gains access to bone via **hematogenous spread** from a superficial infection or direct inoculation through trauma. *Salmonella enteritidis* - While *Salmonella* can cause osteomyelitis, especially in patients with **sickle cell disease**, there is no indication of this predisposing factor in the girl's history. - *Salmonella* osteomyelitis is less common than that caused by *S. aureus* in the general pediatric population. *Staphylococcus saprophyticus* - *S. saprophyticus* is primarily associated with **urinary tract infections (UTIs)**, particularly in young, sexually active females. - It is an uncommon cause of osteomyelitis and typically not the primary pathogen in bone infections. *Listeria monocytogenes* - *Listeria monocytogenes* is known to cause severe infections in **immunocompromised individuals**, neonates, and pregnant women. - While it can cause osteomyelitis, it is a rare cause in an otherwise healthy 12-year-old and would usually be associated with specific risk factors.
Question 5: Immediate treatment of compound fracture of tibia includes:
- A. Antibiotics and debridement only
- B. Debridement and splinting only
- C. Antibiotics, debridement, and splinting (Correct Answer)
- D. Debridement, splinting, and blood transfusion
Explanation: ***Antibiotics, debridement, and splinting*** - **Antibiotics** are crucial to prevent infection in **compound (open) fractures** due to communication with the external environment. - **Debridement** removes contaminated and devitalized tissue, while **splinting** stabilizes the fracture and minimizes further soft tissue damage. *Antibiotics and debridement only* - While antibiotics and debridement are essential, **splinting** is also critical for immobilizing the fracture and preventing further injury. - Without stabilization, the fracture site can move, causing additional soft tissue damage and increasing the risk of infection and delayed healing. *Debridement and splinting only* - This option overlooks the critical need for **antibiotics** in compound fractures, which are at high risk of infection due to the exposure of bone and tissue to bacteria. - Infection can lead to serious complications such as **osteomyelitis**, significantly impacting recovery and patient outcomes. *Debridement, splinting, and blood transfusion* - While debridement and splinting are correct, a **blood transfusion** is generally not an immediate routine treatment for all compound tibial fractures unless there is significant hemorrhage leading to hypovolemic shock. - The primary immediate concerns are infection prevention and stabilization, not typically massive blood loss requiring transfusion in every case.
Question 6: Bacteria most commonly involved in prosthetic valvular heart disease within 2 months of surgery is:
- A. Staphylococcus epidermidis (Correct Answer)
- B. Streptococcus viridans
- C. Enterococci
- D. Hemophilus
Explanation: ***Staphylococcus epidermidis*** - This coagulase-negative staphylococcus is a common cause of **early-onset prosthetic valve endocarditis (PVE)**, occurring within 2 months of surgery. - It is a normal skin flora, and infections are often related to **intraoperative contamination** during valve replacement surgery. *Streptococcus viridans* - This group of streptococci is a leading cause of **late-onset PVE** and **native valve endocarditis (NVE)**, often following dental procedures. - Infections typically occur more than 2 months post-surgery, differentiating it from early-onset cases. *Enterococci* - Enterococci can cause both **NVE** and **PVE**, but they are more commonly associated with infections in patients with **nosocomial acquisition** or those undergoing genitourinary or gastrointestinal procedures. - While they can occur post-surgery, they are not the most common causative agent within the first 2 months compared to *Staphylococcus epidermidis*. *Hemophilus* - *Haemophilus species* are considered part of the **HACEK group** (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella), which are known for causing **culture-negative endocarditis**. - While they can cause endocarditis, they are rare causes of early-onset PVE and are more associated with subacute or chronic forms of endocarditis.
Question 7: What is the most effective management strategy for hemarthrosis?
- A. Immobilization with a P.O.P. cast
- B. Application of a compression bandage
- C. Needle aspiration to remove excess blood (Correct Answer)
- D. All of the options
Explanation: ***Needle aspiration to remove excess blood*** - **Aspirating the blood** from the joint effectively reduces intra-articular pressure, pain, and inflammation. - This procedure also helps prevent **synovial hypertrophy** and **cartilage damage** caused by the presence of blood in the joint. *Application of a compression bandage* - While helpful for reducing swelling and providing support, a **compression bandage alone** does not remove the accumulated blood. - It may alleviate some discomfort but does not address the underlying issue of **intra-articular blood accumulation**. *Immobilization with a P.O.P. cast* - **Immobilization** can help rest the joint and reduce pain, but it does not remove the blood from the joint space. - Prolonged immobilization can lead to **joint stiffness** and **muscle atrophy**, which are undesirable outcomes. *All of the options* - While compression and immobilization can be supportive measures, they are not the **most effective primary strategy** for managing hemarthrosis. - The direct removal of blood via **aspiration** is crucial for alleviating pressure and preventing long-term joint damage.
Question 8: Antecedent diagnosis of Group A streptococcal infection in Acute rheumatic fever can be made by?
- A. ASO (Correct Answer)
- B. ESR elevation
- C. Low C3 levels
- D. CRP
Explanation: ***ASO*** - ASO (Antistreptolysin O) titer measures antibodies to **Streptolysin O**, a toxin produced by Group A Streptococcus (GAS), indicating a recent GAS infection. - An elevated or rising ASO titer is a key diagnostic criterion for confirming a preceding GAS infection in the context of **Acute Rheumatic Fever (ARF)** [1]. *ESR elevation* - **Erythrocyte Sedimentation Rate (ESR)** is a non-specific marker of inflammation and will be elevated in ARF, but it does not confirm a preceding GAS infection [2]. - Many inflammatory conditions can cause ESR elevation, hence it's not specific for antecedent streptococcal infection. *Low C3 levels* - **Low C3 levels** are typically associated with complement consumption in diseases like systemic lupus erythematosus or post-streptococcal glomerulonephritis, not directly with ARF. - While post-streptococcal glomerulonephritis can follow a GAS infection, ARF does not primarily involve significant C3 depression as a diagnostic feature. *CRP* - **C-reactive protein (CRP)** is another non-specific acute-phase reactant that is elevated during inflammation, including ARF [2]. - Like ESR, elevated CRP indicates inflammation but does not specifically confirm an antecedent **Group A streptococcal infection**.
Question 9: What will the aspirated synovial fluid in a case of septic arthritis typically show?
- A. Clear and straw-colored fluid
- B. Low viscosity fluid
- C. Cloudy or purulent fluid
- D. Markedly increased polymorphonuclear leukocytes (Correct Answer)
Explanation: ***Markedly increased polymorphonuclear leukocytes*** - **Septic arthritis** is characterized by an acute infection within the joint, leading to a profound inflammatory response with a significant influx of **neutrophils** (polymorphonuclear leukocytes) into the synovial fluid. - A synovial leukocyte count greater than **50,000 cells/mm³** with over **75% neutrophils** is highly suggestive of septic arthritis. *Clear and straw-colored fluid* - This description typically corresponds to **normal synovial fluid** or fluid from a mild **non-inflammatory condition**, which is not consistent with bacterial infection. - Normal synovial fluid is usually **transparent**, indicating the absence of significant cellular debris or inflammatory cells. *Low viscosity fluid* - While septic synovial fluid can have reduced viscosity due to the breakdown of **hyaluronic acid** by bacterial enzymes and inflammatory mediators, this characteristic alone is not the most definitive diagnostic feature. - Reduced viscosity is also observed in other inflammatory conditions, making it less specific than direct cellular analysis for diagnosing infection. *Cloudy or purulent fluid* - The presence of **cloudy** or **purulent (pus-like)** fluid *is* often seen in septic arthritis, reflecting the high cell count and protein content. - However, this is a **gross visual observation**, and a more precise and diagnostic indicator is the microscopic finding of markedly increased **polymorphonuclear leukocytes**.
Question 10: 12 years male came with swelling of lower end tibia which is surrounded by rim of reactive bone. What is most likely diagnosis?
- A. GCT
- B. Hyper PTH
- C. Brodie's Abscess (Correct Answer)
- D. Osteomyelitis
Explanation: ***Brodie's Abscess*** - A **Brodie's abscess** is a subacute or chronic osteomyelitis characterized by a localized bone abscess, typically with a surrounding **sclerotic rim of reactive bone**. - It often occurs in the **metaphysis of long bones** (like the lower end of the tibia) in children and adolescents, presenting with localized pain and swelling. *GCT* - **Giant cell tumor (GCT)** typically occurs in **skeletally mature adults** (20-40 years old) and is a lytic lesion often found in the **epiphysis** of long bones, rarely with a distinct sclerotic rim. - GCTs are generally more aggressive and demonstrate a **soap-bubble appearance** with cortical expansion rather than a thick reactive bone rim. *Hyper PTH* - **Hyperparathyroidism** causes bone changes such as **osteopenia**, **subperiosteal bone resorption**, especially in the phalanges, and **brown tumors** (lytic lesions). - It does not typically present as a localized lesion with a **sclerotic rim of reactive bone** in a child. *Osteomyelitis* - While chronic osteomyelitis can involve local bone destruction and reactive bone formation, a **Brodie's abscess** is a specific, well-circumscribed form of **subacute osteomyelitis**. - Acute osteomyelitis presents with more diffuse systemic symptoms (fever, malaise) and less defined reactive bone in its early stages compared to the distinct **sclerotic rim** seen in a Brodie's abscess.
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