Surgical Infections — MCQs

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?

Q54Easy

Which of the following is responsible for crepitations in wounds?

Q55Easy

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

Q56Medium

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

Q57Easy

What is true about cellulitis of the lower limb?

Q58Easy

A carbuncle is treated by:

Q59Easy

In which condition is hyperbaric oxygen therapy useful?

Q60Easy

An antibioma is defined as:

Surgical Infections Indian Medical PG Practice Questions and MCQs

Question 51: A soldier injured in combat presents with edema, crepitus, and a brown exudate. What is the most likely diagnosis?

A. Gas gangrene (Correct Answer)
B. Crush syndrome
C. Long bone fracture
D. None of the above

Explanation: **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).

Question 52: 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?

A. Erythema
B. Leukocytosis
C. Severe pressure-like pain (Correct Answer)
D. Swelling

Explanation: **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).

Question 53: 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?

A. Amoxicillin-clavulanic acid
B. Cefepime (Correct Answer)
C. Ceftriaxone
D. Streptomycin

Explanation: ### Explanation The clinical presentation describes a classic case of **Burn Wound Sepsis** caused by ***Pseudomonas aeruginosa***. The key identifiers in the vignette are: 1. **Clinical Context:** A late-onset infection (8 days post-burn) in a major burn patient. 2. **Microbiological Clues:** Gram-negative, **oxidase-positive** bacilli that are **non-fermenters** are the hallmark laboratory characteristics of *Pseudomonas*. #### Why Cefepime is Correct *Pseudomonas aeruginosa* is notorious for its intrinsic resistance to many common antibiotics. Treatment requires an **antipseudomonal agent**. **Cefepime** is a 4th-generation cephalosporin with excellent activity against *Pseudomonas*. Other standard options include Piperacillin-Tazobactam, Ceftazidime, Carbapenems (Imipenem/Meropenem), and Aminoglycosides. #### Why Other Options are Incorrect * **Amoxicillin-clavulanic acid (Option A):** This is a beta-lactam/beta-lactamase inhibitor combination effective against many Gram-positives and some Gram-negatives, but it has **no activity** against *Pseudomonas*. * **Ceftriaxone (Option B):** While a potent 3rd-generation cephalosporin, it is famously ineffective against *Pseudomonas* ("Ceftriaxone covers everything but *Pseudomonas* and *Enterococcus*"). * **Streptomycin (Option D):** An aminoglycoside primarily used for Tuberculosis and Plague; it is not the preferred agent for pseudomonal burn infections due to high resistance rates and toxicity compared to modern alternatives like Amikacin or Cefepime. #### NEET-PG High-Yield Pearls * **Most common cause of early burn infection (<5 days):** *Staphylococcus aureus*. * **Most common cause of late burn infection (>5 days):** *Pseudomonas aeruginosa*. * **Most common cause of death in burn patients:** Septicemia/Infection. * **Identifying Pseudomonas:** Look for "fruity/grape-like odor" and "blue-green pigment" (Pyocyanin/Pyoverdin) on culture. * **Topical Agent of Choice:** Silver Sulfadiazine is standard, but **Mafenide Acetate** is preferred for deep burns/cartilage (e.g., ears) as it penetrates eschar better.

Question 54: Which of the following is responsible for crepitations in wounds?

A. Staphylococcus
B. Mycobacterium
C. Streptococcus
D. Clostridium (Correct Answer)

Explanation: **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).

Question 55: Which of the following is NOT a characteristic feature of Systemic Inflammatory Response Syndrome (SIRS)?

A. Fever
B. Leukocytosis
C. Altered mental status
D. Hypoglycemia (Correct Answer)

Explanation: **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 <36°C (Hypothermia). 2. **Heart Rate:** >90 beats per minute (Tachycardia). 3. **Respiratory Rate:** >20 breaths per minute or PaCO₂ <32 mmHg (Tachypnea). 4. **White Blood Cell Count:** >12,000/mm³, <4,000/mm³, or >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.

Question 56: What is the infection rate without antibiotic prophylaxis for clean-contaminated surgery?

A. 1-2%
B. 2-5%
C. 6-9% (Correct Answer)
D. 10-15%

Explanation: ### Explanation The classification of surgical wounds based on the degree of microbial contamination is a high-yield topic for NEET-PG. This classification predicts the risk of subsequent Surgical Site Infection (SSI). **1. Why Option C (6–9%) is Correct:** **Clean-contaminated (Class II)** surgeries involve procedures where a hollow viscus (respiratory, alimentary, genital, or urinary tract) is entered under controlled conditions without unusual contamination. Examples include elective cholecystectomy or appendectomy. * **Without antibiotic prophylaxis:** The infection rate is typically cited between **6% and 9%** (some texts range up to 10%). * **With antibiotic prophylaxis:** This rate significantly drops to approximately **2–4%**. **2. Analysis of Incorrect Options:** * **Option A (1–2%):** This represents the infection rate for **Clean (Class I)** wounds (e.g., hernia repair, thyroidectomy) where no viscous is entered and no inflammation is encountered. * **Option B (2–5%):** This is the reduced infection rate for Clean-contaminated wounds *after* the administration of prophylactic antibiotics. * **Option D (10–15%):** This range is more characteristic of **Contaminated (Class III)** wounds, which involve open accidental wounds, gross spillage from the GI tract, or acute non-purulent inflammation. **3. High-Yield Clinical Pearls for NEET-PG:** * **Dirty Wounds (Class IV):** These involve old traumatic wounds with retained devitalized tissue or existing clinical infection (e.g., perforated viscus, abscess). The infection rate is **>30%**. * **Timing of Prophylaxis:** For maximum efficacy, prophylactic antibiotics should be administered within **60 minutes before the skin incision** (except Vancomycin/Fluoroquinolones, which require 120 minutes). * **Crucial Distinction:** If an elective procedure enters the biliary or genitourinary tract and **infected** bile or urine is encountered, the wound is up-graded from Clean-contaminated to **Contaminated**.

Question 57: What is true about cellulitis of the lower limb?

A. Infection of the skin and subcutaneous tissue (Correct Answer)
B. Fever and malaise are common
C. Margins are distinct
D. All of the above

Explanation: **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.

Question 58: A carbuncle is treated by:

A. Incision and drainage (Correct Answer)
B. Cruciate incision and deroofing
C. Antibiotics alone
D. Wide excision

Explanation: **Explanation:** A **carbuncle** is a deep-seated infective gangrene of the subcutaneous tissue, most commonly caused by *Staphylococcus aureus*. It typically occurs in areas with thick, colliculated skin (like the nape of the neck or back) and is frequently associated with uncontrolled Diabetes Mellitus. **Why Option A is Correct:** The definitive treatment for a carbuncle is surgical. Once the lesion has "softened" or shows signs of suppuration, **Incision and Drainage (I&D)** is mandatory. The standard technique involves a **cruciate (cross-shaped) incision**. The four resulting triangular flaps are then lifted to excise the necrotic subcutaneous fat and debris (debridement/deroofing). This allows the pus to drain from the multiple underlying loculi (the "sieve-like" appearance) and promotes healing from the base. **Why Other Options are Incorrect:** * **Option B:** While a cruciate incision is part of the procedure, "Incision and Drainage" is the broader, standard clinical term for the surgical management of an abscess or carbuncle. In many textbooks, B and A are used interchangeably, but A is the more conventional answer for the primary mode of treatment. * **Option C:** Antibiotics alone are insufficient because the central core of a carbuncle is necrotic and avascular; drugs cannot penetrate the "slough" effectively. They are used only as an adjunct to surgery. * **Option D:** Wide excision (removing a large margin of healthy tissue) is unnecessary and leads to large, difficult-to-close defects. Management focuses on debridement of necrotic tissue, not radical excision. **NEET-PG High-Yield Pearls:** * **Commonest Site:** Nape of the neck and back. * **Predisposing Factor:** Diabetes Mellitus (always check blood sugar in a patient with a carbuncle). * **Pathology:** It is a cluster of interconnected furuncles (boils). * **Clinical Sign:** "Sieve-like" appearance with multiple openings discharging pus. * **Antibiotic of Choice:** Cloxacillin or Cephalosporins (targeting *S. aureus*).

Question 59: In which condition is hyperbaric oxygen therapy useful?

A. Tetanus
B. Gas gangrene (Correct Answer)
C. Frostbite
D. Vincent's angina

Explanation: **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 60: An antibioma is defined as:

A. An all-powerful antibiotic.
B. An antibiotic contaminant.
C. A malignant tumor caused by an antibiotic.
D. An excess mass of fibrous tissue around an abscess, persistently treated by excessive or partly sterilized antibiotic. (Correct Answer)

Explanation: **Explanation:** An **antibioma** is a clinical condition characterized by the formation of a tough, thick-walled fibrous mass around a localized infection (abscess). This occurs when an acute abscess is treated with systemic antibiotics without the mandatory surgical drainage. **1. Why the Correct Answer is Right:** The underlying medical concept is the failure of antibiotic penetration. When an abscess forms, the core is avascular (pus). If antibiotics are administered without drainage, they may sterilize the periphery and suppress the acute inflammatory symptoms (pain, fever, redness), but they cannot reach the central nidus of infection. This chronic irritation leads to the proliferation of dense **fibrous tissue**, resulting in a firm, non-tender, tumor-like mass that mimics a neoplasm. **2. Why the Other Options are Wrong:** * **Option A & B:** These are distractors. "Antibioma" is a clinical pathology term, not a description of antibiotic potency or pharmaceutical purity. * **Option C:** Despite the suffix "-oma" (often denoting a tumor), an antibioma is an inflammatory/fibrotic reaction, not a neoplastic or malignant process. **3. NEET-PG High-Yield Pearls:** * **Clinical Presentation:** It typically presents as a firm, painless, or slightly tender mass following a history of a treated infection (e.g., in the breast or gluteal region). * **Common Site:** The **breast** is the most common site (often following inadequate treatment of a breast abscess). * **Differential Diagnosis:** It is a notorious mimic of **Carcinoma Breast**. * **Management:** Antibiotics are ineffective at this stage. The definitive treatment is **surgical excision** or formal incision and drainage (I&D) with curettage of the fibrous wall. * **Golden Rule:** "Ubi pus, ibi evacua" (Where there is pus, evacuate it). Antibiotics are an adjunct to, not a replacement for, drainage.

Practice by Chapter

Surgical Site Infections

Practice Questions

Intra-abdominal Infections

Practice Questions

Soft Tissue Infections

Practice Questions

Necrotizing Soft Tissue Infections

Practice Questions

Surgical Sepsis

Practice Questions

Tetanus Prophylaxis

Practice Questions

Antimicrobial Prophylaxis

Practice Questions

Antimicrobial Therapy in Surgical Infections

Practice Questions

Surgical Drainage Procedures

Practice Questions

Infection Control in Operating Room

Practice Questions

Biofilms and Implant-Related Infections

Practice Questions

Prevention Strategies

Practice Questions

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