Surgical Infections Practice Questions

Q: A soldier injured in combat presents with edema, crepitus, and a brown exudate. What is the most likely diagnosis?

Gas gangrene. **Explanation:** The clinical presentation of **edema, crepitus, and a brown exudate** (often described as "dishwater" or "sweetly foul-smelling" discharge) in the context of a combat injury is the classic triad for **Gas Gangrene** (Clostridial Myonecrosis). 1. **Why Gas Gangrene is correct:** This is a life-threatening muscle infection caused primarily by *Clostridium perfringens*. In traumatic or combat wounds, anaerobic conditions allow these bacteria to proliferate. They produce alpha-toxins that cause extensive myonecrosis. The **crepitus** is a hallmark sign, resulting from gas production by the bacteria within the soft tissues. The **brown exudate** represents liquefied muscle and hemolyzed blood. 2. **Why other options are incorrect:** * **Crush Syndrome:** This involves systemic manifestations (like acute kidney injury due to myoglobinuria) following prolonged compression of muscle groups. While edema occurs, it does not typically present with crepitus or a specific brown exudate unless secondary infection sets in. * **Long bone fracture:** While common in combat, a fracture alone presents with deformity, bony crepitus (different from soft-tissue gas crepitus), and localized pain, but not the characteristic infectious exudate. **High-Yield Clinical Pearls for NEET-PG:** * **Causative Agent:** *Clostridium perfringens* (Gram-positive, spore-forming anaerobic bacilli) is the most common (80%). * **Incubation Period:** Very short, typically **12–24 hours**. * **X-ray finding:** Shows "feathery" patterns of gas in muscle planes. * **Management:** Emergency surgical debridement (fasciotomy/amputation), high-dose Penicillin G, and Hyperbaric Oxygen (HBO) therapy. * **Distinction:** Unlike necrotizing fasciitis, gas gangrene primarily involves the **muscle** (myonecrosis).

Q: Following a small-bowel resection, a 49-year-old male develops fever and anemia. The surface surrounding the surgical wound is warm to the touch and necrotizing fasciitis is suspected. What clinical manifestation would most suggest necrotizing fasciitis?

Severe pressure-like pain. **Explanation:** The diagnosis of **Necrotizing Fasciitis (NF)** is primarily clinical, and the hallmark sign is **pain out of proportion to physical findings**. While erythema and swelling may appear mild or resemble simple cellulitis, the underlying destruction of the fascia and deep tissues causes intense, severe pressure-like pain. As the infection progresses and destroys cutaneous nerves, this pain may eventually transition into anesthesia (numbness), which is also a late, specific sign. **Analysis of Options:** * **C. Severe pressure-like pain (Correct):** This is the earliest and most reliable clinical indicator. The infection spreads rapidly along the deep fascial planes, creating high-pressure inflammatory edema before significant skin changes occur. * **A. Erythema & D. Swelling:** These are common in almost all surgical site infections (SSIs) and superficial cellulitis. They lack the specificity required to differentiate NF from less severe infections. * **B. Leukocytosis:** While typically present in NF, an elevated white cell count is a non-specific systemic response to any infection, inflammation, or the stress of surgery itself. **High-Yield Clinical Pearls for NEET-PG:** * **Hard Signs of NF:** Crepitus (gas in tissues), skin necrosis/bullae, and "dishwater pus" (thin, foul-smelling discharge). * **LRINEC Score:** Used to differentiate NF from cellulitis based on laboratory markers (CRP, WBC, Hemoglobin, Sodium, Creatinine, Glucose). * **Treatment:** NF is a surgical emergency. The definitive management is **immediate and aggressive surgical debridement**, not just antibiotics. * **Type I NF:** Polymicrobial (most common); **Type II NF:** Monomicrobial (Group A Streptococcus).

Q: Which of the following is responsible for crepitations in wounds?

Clostridium. **Explanation:** The presence of **crepitations** (a crackling sensation on palpation) in a wound indicates **subcutaneous emphysema**, which is caused by gas production within the tissues. **1. Why Clostridium is correct:** *Clostridium perfringens* is the primary causative agent of **Gas Gangrene** (Clostridial Myonecrosis). As an obligate anaerobe, it utilizes carbohydrates (fermentation) in devitalized, ischemic tissue to produce gas (hydrogen and carbon dioxide). This gas tracks along muscle planes and subcutaneous tissue, manifesting clinically as crepitus. It is a surgical emergency characterized by rapid tissue destruction, "dishwater" discharge, and systemic toxemia. **2. Why the other options are incorrect:** * **Staphylococcus:** Typically causes localized pyogenic infections (abscesses) characterized by thick, creamy pus. While some strains can cause necrotizing fasciitis, they are not primary gas-producers. * **Mycobacterium:** *M. tuberculosis* causes "cold abscesses" and chronic granulomatous inflammation. These are indolent infections without gas formation. * **Streptococcus:** *Streptococcus pyogenes* is known for spreading infections like cellulitis and erysipelas via enzymes (hyaluronidase). While it can cause "Meleney’s gangrene" or necrotizing fasciitis, pure streptococcal infections are typically non-gas-forming unless a polymicrobial (Type I) infection is present. **Clinical Pearls for NEET-PG:** * **Incubation Period:** Gas gangrene has a very short incubation period (usually <24 hours). * **X-ray Finding:** "Feathering" pattern of gas in muscle fibers. * **Management:** Radical surgical debridement is the gold standard; Hyperbaric Oxygen (HBO) and high-dose Penicillin G are adjuncts. * **Non-clostridial Crepitus:** Can be seen in infections caused by *E. coli*, *Klebsiella*, or *Bacteroides* (often in diabetic foot infections).

Q: Which of the following is NOT a characteristic feature of Systemic Inflammatory Response Syndrome (SIRS)?

Hypoglycemia. **Explanation:** Systemic Inflammatory Response Syndrome (SIRS) is a clinical syndrome characterized by a robust inflammatory response to a variety of clinical insults (infectious or non-infectious). The diagnosis is based on the presence of **two or more** of the following criteria: 1. **Temperature:** >38°C (Fever) or 90 beats per minute (Tachycardia). 3. **Respiratory Rate:** >20 breaths per minute or PaCO₂ 12,000/mm³, 10% immature (band) forms (Leukocytosis/Leukopenia). **Why Hypoglycemia is the correct answer:** SIRS is a hypermetabolic state. The stress response triggers the release of counter-regulatory hormones (cortisol, catecholamines, and glucagon), which lead to gluconeogenesis and glycogenolysis. Therefore, **Hyperglycemia** is a common feature of the stress response in SIRS, not hypoglycemia. **Analysis of other options:** * **Fever (A) and Leukocytosis (B):** These are core components of the official SIRS criteria as defined by the ACCP/SCCM. * **Altered mental status (C):** While not a primary diagnostic criterion for SIRS, it is a recognized clinical feature of systemic inflammation and organ dysfunction (Sepsis-associated encephalopathy). **High-Yield Clinical Pearls for NEET-PG:** * **Sepsis vs. SIRS:** Sepsis is defined as SIRS + a documented or suspected source of infection. * **qSOFA Score:** In modern practice (Sepsis-3 guidelines), the qSOFA score (Altered mental status, Systolic BP ≤100 mmHg, and Respiratory rate ≥22/min) is used to identify patients at risk of poor outcomes outside the ICU. * **Refractory Shock:** Shock that does not respond to fluid resuscitation and requires vasopressors.

Q: What is true about cellulitis of the lower limb?

Infection of the skin and subcutaneous tissue. **Explanation:** **Cellulitis** is a common bacterial infection characterized by inflammation of the **deep dermis and subcutaneous tissues**. It is most frequently caused by *Streptococcus pyogenes* (Group A Strep) or *Staphylococcus aureus*. **Why Option A is Correct:** The fundamental pathology of cellulitis involves an acute spreading inflammation of the skin and its underlying subcutaneous fat. Unlike an abscess, it is non-circumscribed and spreads through tissue planes, often facilitated by bacterial enzymes like hyaluronidase. **Analysis of Other Options:** * **Option B (Fever and Malaise):** While systemic symptoms *can* occur, they are not universal in simple cellulitis. In many clinical scenarios, the infection remains localized with erythema, warmth, and tenderness without significant systemic upset. * **Option C (Margins):** This is a classic "distractor" for NEET-PG. **Distinct, raised margins** are the hallmark of **Erysipelas** (a more superficial infection involving the upper dermis and superficial lymphatics). In cellulitis, the margins are characteristically **ill-defined and indistinct** because the infection is deeper. * **Option D:** Since margins are not distinct, "All of the above" is incorrect. **High-Yield Clinical Pearls for NEET-PG:** * **Erysipelas vs. Cellulitis:** Erysipelas has sharp borders and involves the superficial dermis; Cellulitis has diffuse borders and involves subcutaneous tissue. * **Commonest Site:** Lower limb (often following a break in the skin or fungal infection like Tinea pedis). * **Milroy’s Disease:** Chronic lymphedema is a major predisposing factor for recurrent cellulitis. * **Treatment:** Elevation of the limb and systemic antibiotics (e.g., Flucloxacillin or Cephalosporins). If MRSA is suspected, Vancomycin or Linezolid is used.

Q: In which condition is hyperbaric oxygen therapy useful?

Gas gangrene. **Explanation:** **Gas gangrene (Clostridial Myonecrosis)** is the primary surgical indication for Hyperbaric Oxygen Therapy (HBOT). The causative organism, *Clostridium perfringens*, is a gram-positive, spore-forming **obligate anaerobe**. HBOT works by increasing the partial pressure of oxygen in tissues to levels that are directly bactericidal and bacteriostatic to Clostridia. Furthermore, high oxygen tension inhibits the production of the **alpha-toxin** (lecithinase), which is responsible for the rapid tissue destruction and systemic toxicity seen in this condition. **Analysis of Incorrect Options:** * **Tetanus:** While caused by an anaerobe (*C. tetani*), the pathology is driven by the retrograde axonal transport of **tetanospasmin** to the CNS. HBOT does not neutralize fixed toxins or reverse the clinical spasms; management focuses on wound debridement, antibiotics, and supportive care (sedation/ventilation). * **Frostbite:** The primary treatment involves rapid rewarming in water (37-39°C) and preventing secondary infection. While HBOT is sometimes studied for late-stage microvascular injury, it is not a standard or first-line indication. * **Vincent’s Angina:** This is an acute necrotizing ulcerative gingivitis caused by a symbiotic infection of fusiform bacilli and spirochetes. It is effectively managed with oral hygiene, debridement, and systemic antibiotics (Metronidazole). **High-Yield Clinical Pearls for NEET-PG:** * **HBOT Mechanism:** It delivers 100% oxygen at pressures >1 atmosphere (usually 2–3 ATA). * **Other Indications:** Carbon monoxide poisoning, Decompression sickness (Bends), Air embolism, and Chronic non-healing wounds (e.g., Diabetic foot ulcers). * **Absolute Contraindication:** Untreated pneumothorax. * **Gas Gangrene Diagnosis:** Characterized by "woody" hard muscles, crepitus (gas in tissues), and a "dishwater" discharge with a sweetish odor. X-ray shows feathery patterns of gas.

Question 1

A soldier injured in combat presents with edema, crepitus, and a brown exudate. What is the most likely diagnosis?

Accepted Answer

Gas gangrene

Answer

Crush syndrome

Answer

Long bone fracture

Answer

None of the above

Question 2

Following a small-bowel resection, a 49-year-old male develops fever and anemia. The surface surrounding the surgical wound is warm to the touch and necrotizing fasciitis is suspected. What clinical manifestation would most suggest necrotizing fasciitis?

Accepted Answer

Severe pressure-like pain

Answer

Erythema

Answer

Leukocytosis

Answer

Swelling

Question 3

A 68-year-old male patient with 3rd-degree burn wounds affecting 25% TBSA was admitted to the hospital and treated with intravenous fluids and analgesics. After 8 days of hospital admission, the patient develops fever and leukocytosis. On examination, there is erythema and swelling around the wound. Exudate from this wound is positive for gram-negative, oxidase-positive bacilli which do not ferment sugars. What is the drug of choice for this infection?

Accepted Answer

Cefepime

Answer

Amoxicillin-clavulanic acid

Answer

Ceftriaxone

Answer

Streptomycin

Question 4

Which of the following is responsible for crepitations in wounds?

Accepted Answer

Clostridium

Answer

Staphylococcus

Answer

Mycobacterium

Answer

Streptococcus

Question 5

Which of the following is NOT a characteristic feature of Systemic Inflammatory Response Syndrome (SIRS)?

Accepted Answer

Hypoglycemia

Answer

Fever

Answer

Leukocytosis

Answer

Altered mental status

Question 6

What is the infection rate without antibiotic prophylaxis for clean-contaminated surgery?

Accepted Answer

6-9%

Answer

1-2%

Answer

2-5%

Answer

10-15%

Question 7

What is true about cellulitis of the lower limb?

Accepted Answer

Infection of the skin and subcutaneous tissue

Answer

Fever and malaise are common

Answer

Margins are distinct

Answer

All of the above

Question 8

A carbuncle is treated by:

Accepted Answer

Incision and drainage

Answer

Cruciate incision and deroofing

Answer

Antibiotics alone

Answer

Wide excision

Question 9

In which condition is hyperbaric oxygen therapy useful?

Accepted Answer

Gas gangrene

Answer

Tetanus

Answer

Frostbite

Answer

Vincent's angina

Question 10

An antibioma is defined as:

Accepted Answer

An excess mass of fibrous tissue around an abscess, persistently treated by excessive or partly sterilized antibiotic.

Answer

An all-powerful antibiotic.

Answer

An antibiotic contaminant.

Answer

A malignant tumor caused by an antibiotic.

Surgical Infections — MCQs

Surgical Infections — MCQs

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