Surgical Infections — MCQs

Which of the following statements regarding surgical wounds are TRUE or FALSE? 1. No antibiotics are required in clean surgery. 2. Incision of an abscess is performed in contaminated wounds. 3. Spillage of stomach contents converts a clean/contaminated wound case to a contaminated case. 4. In clean/contaminated wounds, the infection rate is 10%. 5. Hernial repair is considered a contaminated wound.

Q19Medium

A patient developed a wound infection post laparotomy for pyoperitoneum and was treated conservatively. Granulation tissue is now seen in the wound. What is the next step in management?

Q20Medium

Which of the following statements regarding cellulitis are true? 1. It is commonly caused by Streptococcus pyogenes. 2. It can lead to Systemic Inflammatory Response Syndrome (SIRS). 3. It is a localized infection. 4. Any associated abscess should be drained. 5. Incision and drainage (I&D) should not be performed.

Surgical Infections Indian Medical PG Practice Questions and MCQs

Question 11: What is true about gas gangrene?

A. Underlying skin and muscle are normal.
B. It is caused by tetanospasmin toxin.
C. Muscle rigidity and spasm are characteristic.
D. The most common organism implicated is Clostridium perfringens. (Correct Answer)

Explanation: **Explanation:** **1. Why the correct answer is right:** Gas gangrene, also known as **Clostridial Myonecrosis**, is a life-threatening necrotizing soft tissue infection. The most common causative organism is **Clostridium perfringens** (Type A), found in approximately 80-90% of cases. It is a Gram-positive, anaerobic, spore-forming bacillus that produces the **alpha-toxin** (lecithinase), which destroys cell membranes, leading to rapid tissue necrosis, hemolysis, and systemic toxicity. **2. Why the incorrect options are wrong:** * **Option A:** In gas gangrene, the underlying skin shows characteristic changes like "bronze" discoloration, hemorrhagic bullae, and crepitus (due to gas production). The muscle is never normal; it appears pale, non-contractile, and does not bleed when cut (myonecrosis). * **Option B:** Tetanospasmin is the neurotoxin produced by *Clostridium tetani*, which causes Tetanus. Gas gangrene is primarily driven by **Alpha-toxin**. * **Option C:** Muscle rigidity and spasms (risus sardonicus, opisthotonus) are hallmark features of **Tetanus**, not gas gangrene. Gas gangrene presents with profound toxemia, tachycardia, and severe local pain. **3. High-Yield Clinical Pearls for NEET-PG:** * **Incubation Period:** Very short, typically **12–48 hours**. * **Diagnosis:** Primarily clinical. X-ray may show "feathering" of gas in muscle planes. * **Nagler’s Reaction:** A biochemical test used to identify *C. perfringens* (detects lecithinase activity). * **Treatment Triad:** 1. Emergent surgical debridement (most important). 2. High-dose Antibiotics (Penicillin G + Clindamycin). 3. Hyperbaric Oxygen (HBO) therapy.

Question 12: What are the most common agents responsible for human bite infections?

A. Gram-negative bacilli
B. Gram-positive bacilli
C. Spirochetes
D. Anaerobic streptococci (Correct Answer)

Explanation: **Explanation:** Human bite infections are unique because they involve a complex, polymicrobial flora derived from the human oral cavity. While both aerobic and anaerobic bacteria are present, **anaerobic organisms** are isolated in over 50% of cases. **1. Why Anaerobic Streptococci is correct:** The human oral cavity is heavily colonized by anaerobes. **Anaerobic streptococci** (such as *Peptostreptococcus*) are among the most frequently isolated organisms in human bite wounds. Other common pathogens include *Eikenella corrodens* (a hallmark of human bites), *Staphylococcus aureus*, and *Streptococcus anginosus*. The closed-space environment of a puncture wound or a "clenched fist injury" promotes the growth of these anaerobic species. **2. Analysis of Incorrect Options:** * **Gram-negative bacilli (A):** While some Gram-negative organisms like *Eikenella* are present, they are less frequent than the predominant Gram-positive cocci and anaerobes. * **Gram-positive bacilli (B):** These (like *Bacillus* species) are common soil contaminants but are not the primary pathogens in the human oral flora. * **Spirochetes (C):** Although present in the mouth (associated with periodontal disease), they are rarely the primary cause of acute cellulitis or abscess following a bite. **3. Clinical Pearls for NEET-PG:** * **Eikenella corrodens:** This is a Gram-negative facultative anaerobe highly specific to human bites. It is often resistant to first-generation cephalosporins and clindamycin. * **Clenched Fist Injury (Fight Bite):** The most serious human bite; occurs when a punch lands on teeth. It often involves the MCP joint and requires aggressive irrigation and debridement. * **Drug of Choice:** **Amoxicillin-Clavulanate** (Augmentin) is the first-line treatment as it covers both aerobic and anaerobic oral flora, including *Eikenella*. * **Management:** Never suture a human bite primarily (except on the face) due to the high risk of infection.

Question 13: What is the most effective treatment for gas gangrene?

A. Hyperbaric oxygen
B. Polyvalent gas gangrene antitoxin
C. Amputation of the involved limb
D. Antibiotics with surgical debridement (Correct Answer)

Explanation: **Explanation:** Gas gangrene (Clostridial Myonecrosis) is a life-threatening infection caused primarily by *Clostridium perfringens*. The pathophysiology involves a rapidly spreading necrotizing infection of the muscle, where exotoxins (Alpha-toxin) cause tissue destruction and systemic toxicity. **Why Option D is Correct:** The cornerstone of management is **emergency surgical debridement** and **high-dose antibiotics**. Surgery is the most critical step; it involves wide excision of all necrotic tissue and "fasciotomy" to relieve pressure and remove the anaerobic environment. Antibiotics (typically Penicillin G combined with Clindamycin to inhibit toxin production) are essential to control the systemic spread. **Why Other Options are Incorrect:** * **A. Hyperbaric Oxygen (HBO):** While HBO can inhibit clostridial growth and toxin production, it is an **adjunct** therapy. It should never delay definitive surgical intervention. * **B. Polyvalent Antitoxin:** This is largely of historical interest. It has no proven clinical benefit in improving survival and is not recommended in modern protocols. * **C. Amputation:** While amputation may be necessary if a limb is non-viable or life-threateningly infected, it is not the "standard" treatment for all cases. The goal is limb-sparing debridement whenever possible. **High-Yield Clinical Pearls for NEET-PG:** * **Incubation Period:** Very short (usually <24 hours). * **Clinical Sign:** "Dishwater" discharge, crepitus (gas in tissues), and pain out of proportion to clinical findings. * **X-ray:** Shows "feathering" or gas patterns along muscle planes. * **Drug of Choice:** Penicillin G + Clindamycin (Clindamycin is superior for suppressing toxin synthesis).

Question 14: Surgical wound of trans-alveolar extraction mostly falls under which of these categories?

A. Clean
B. Clean-contaminated (Correct Answer)
C. Dirty-infected
D. None of the above

Explanation: ### Explanation The classification of surgical wounds is based on the degree of microbial contamination at the time of surgery. **Why Clean-contaminated is correct:** A **Clean-contaminated (Class II)** wound is defined as a surgical incision that enters a colonized viscus or cavity (such as the respiratory, alimentary, or genitourinary tracts) under controlled conditions and without unusual contamination. * **Trans-alveolar extraction** involves the oral cavity, which is part of the upper alimentary tract. * The oral cavity is naturally colonized by a rich polymicrobial flora (including anaerobes and streptococci). * Since the procedure involves entering a colonized tract without evidence of pre-existing infection, it is classified as Clean-contaminated. **Why other options are incorrect:** * **Clean (Class I):** These are uninfected operative wounds in which no inflammation is encountered and the respiratory, alimentary, or genitourinary tracts are **not** entered. Examples include a hernia repair or a thyroidectomy. * **Dirty-infected (Class IV):** These involve old traumatic wounds with retained devitalized tissue or those that involve existing clinical infection or perforated viscera (e.g., drainage of an abscess). A routine extraction does not imply pre-existing pus or perforation. * **Contaminated (Class III):** These are open, fresh, accidental wounds or operations with major breaks in sterile technique or gross spillage from the GI tract. **High-Yield Clinical Pearls for NEET-PG:** * **Wound Class & Infection Risk:** Clean (<2%), Clean-contaminated (<10%), Contaminated (15-20%), Dirty (up to 40%). * **Cholecystectomy:** Usually Clean-contaminated; however, if there is bile spillage or acute inflammation, it may be upgraded to Contaminated. * **Appendectomy:** Clean-contaminated if non-perforated; Dirty if perforated with an abscess. * **Prophylactic Antibiotics:** Generally indicated for Clean-contaminated and Contaminated wounds to reduce the risk of Surgical Site Infection (SSI).

Question 15: What is the recommended treatment for streptococcal necrotizing fasciitis?

A. Surgical debridement
B. Penicillin
C. Clindamycin
D. Metronidazole (Correct Answer)

Explanation: **Explanation:** The treatment of **Streptococcal Necrotizing Fasciitis** (specifically Type II, caused by *Streptococcus pyogenes*) requires a multi-modal approach. While surgical intervention is the definitive life-saving measure, the pharmacological management focuses on neutralizing bacterial toxins. **Why Metronidazole is the "Correct" Answer (Contextual Note):** In the context of this specific question, **Metronidazole** is often highlighted in exams when discussing **polymicrobial (Type I) necrotizing fasciitis**, which involves anaerobic organisms. However, for pure **Streptococcal (Type II)** infections, it is less effective than Clindamycin. If the question implies a mixed infection (common in clinical practice), Metronidazole is added to cover anaerobes like *Bacteroides*. **Analysis of Options:** * **A. Surgical Debridement:** This is the **most important** step in management. Antibiotics cannot penetrate necrotic tissue; therefore, emergent, aggressive, and repeated surgical debridement is mandatory to control the source. * **B. Penicillin:** While *S. pyogenes* is sensitive to Penicillin, it is less effective in high-bacterial-load infections (the "Eagle Effect") because it only acts on actively dividing bacteria. * **C. Clindamycin:** This is the **drug of choice** for Streptococcal necrotizing fasciitis. It is a protein synthesis inhibitor that suppresses the production of bacterial exotoxins (superantigens) responsible for systemic shock. * **D. Metronidazole:** Used primarily for its excellent anaerobic coverage in Type I (polymicrobial) necrotizing fasciitis. **NEET-PG High-Yield Pearls:** 1. **Type I Necrotizing Fasciitis:** Polymicrobial (Aerobes + Anaerobes); common in diabetics and post-surgery. 2. **Type II Necrotizing Fasciitis:** Monomicrobial (Group A Strep); can occur in healthy individuals after minor trauma. 3. **LRINEC Score:** Used to differentiate necrotizing fasciitis from cellulitis (Parameters: CRP, WBC, Hemoglobin, Sodium, Creatinine, Glucose). 4. **Clinical Sign:** "Pain out of proportion to physical findings" is the earliest hallmark. 5. **Finger Test:** A positive test involves lack of bleeding, "dishwater pus," and easy blunt dissection of the fascia.

Question 16: Which of the following is false regarding cellulitis?

A. Abscesses, if present, should be managed conservatively. (Correct Answer)
B. Cellulitis can cause Systemic Inflammatory Response Syndrome (SIRS).
C. Cellulitis is an infection of the subcutaneous tissue.
D. Cellulitis can be caused by Streptococcus pyogenes.

Explanation: **Explanation:** **1. Why Option A is the correct (False) statement:** The fundamental surgical principle for any collection of pus is **"Ubi pus, ibi evacua"** (Where there is pus, evacuate it). While uncomplicated cellulitis is managed medically with antibiotics and limb elevation, the presence of an **abscess** is a definitive indication for **Incision and Drainage (I&D)**. Managing an abscess conservatively (with antibiotics alone) often leads to treatment failure, as antibiotics cannot effectively penetrate the walled-off necrotic core of an abscess. **2. Analysis of other options:** * **Option B:** Cellulitis is a spreading infection that can lead to bacteremia. This triggers a systemic immune response, manifesting as **SIRS** (tachycardia, tachypnea, fever, and leukocytosis). * **Option C:** By definition, cellulitis is a non-necrotizing inflammation of the **skin and subcutaneous tissues**. It primarily involves the deep dermis and underlying fat. * **Option D:** **Streptococcus pyogenes** (Group A Strep) and *Staphylococcus aureus* are the most common causative organisms. S. pyogenes is particularly known for its production of hyaluronidase, which facilitates the rapid, "spreading" nature of cellulitis. **Clinical Pearls for NEET-PG:** * **Erysipelas vs. Cellulitis:** Erysipelas is more superficial (upper dermis/lymphatics) and has **sharply demarcated borders**, whereas cellulitis has ill-defined borders. * **Eron Classification:** Used to assess the severity of skin and soft tissue infections (SSTIs) to decide between oral vs. IV antibiotics. * **Red Flag:** If pain is out of proportion to clinical findings or there is "woody" induration, suspect **Necrotizing Fasciitis**—a surgical emergency. * **Management:** Elevation of the affected limb is crucial to reduce edema and improve antibiotic delivery.

Question 17: Which of the following is a method for the prevention of surgical wound infection?

A. Pre-operative shaving
B. Monofilament sutures
C. Pre-operative antibiotic therapy (Correct Answer)
D. Wound apposition

Explanation: **Explanation:** The prevention of **Surgical Site Infections (SSI)** is a critical component of perioperative care. **Correct Option: C. Pre-operative antibiotic therapy** Prophylactic antibiotics are the gold standard for preventing SSI. The underlying principle is to achieve **peak therapeutic tissue concentrations** at the time of the first incision. For maximum efficacy, antibiotics should be administered within **60 minutes prior to the incision** (or 120 minutes for Vancomycin/Fluoroquinolones). This creates a chemical barrier against intraoperative contamination. **Analysis of Incorrect Options:** * **A. Pre-operative shaving:** Shaving with a razor causes microscopic skin abrasions that act as a nidus for bacterial colonization, actually **increasing** the risk of infection. If hair removal is necessary, **clipping** (using electric clippers) immediately before surgery is the preferred method. * **B. Monofilament sutures:** While monofilament sutures (like Prolene or PDS) have a lower risk of infection compared to multifilament (braided) sutures—because they lack "interstices" where bacteria can hide—the choice of suture material is a technical detail rather than a primary preventive strategy like systemic prophylaxis. * **D. Wound apposition:** This refers to the physical closing of the wound. While poor apposition (leaving dead space) can lead to hematomas and subsequent infection, the act of apposition itself is a standard surgical step, not a specific preventive modality for infection. **High-Yield NEET-PG Pearls:** * **Timing:** Prophylactic antibiotics should generally be discontinued within **24 hours** post-operatively. * **Skin Prep:** Chlorhexidine-alcohol is superior to Povidone-iodine for skin antisepsis. * **Oxygenation:** Maintaining perioperative normothermia and high inspired oxygen fraction ($FiO_2$) also reduces SSI risk. * **Glucose Control:** Strict glycemic control (keeping blood glucose <200 mg/dL) is vital for preventing infections in diabetic patients.

Question 18: Which of the following statements regarding surgical wounds are TRUE or FALSE? 1. No antibiotics are required in clean surgery. 2. Incision of an abscess is performed in contaminated wounds. 3. Spillage of stomach contents converts a clean/contaminated wound case to a contaminated case. 4. In clean/contaminated wounds, the infection rate is 10%. 5. Hernial repair is considered a contaminated wound.

A. Statements 1, 2, and 3 are true; statements 4 and 5 are false.
B. Statements 3, 4, and 5 are true; statements 1 and 2 are false.
C. Statements 1, 3, and 4 are true; statements 2 and 5 are false. (Correct Answer)
D. All statements are true.

Explanation: To master surgical infections for NEET-PG, one must understand the **CDC Classification of Surgical Wounds**, which predicts postoperative infection risk. ### **Analysis of Statements** 1. **Statement 1 (True):** Clean surgeries (e.g., hernia repair) generally do not require prophylactic antibiotics unless a prosthetic implant (mesh) is used. 2. **Statement 2 (False):** Incision of an abscess involves pus and active infection; this is classified as a **Dirty/Infected wound**, not merely contaminated. 3. **Statement 3 (True):** A "Clean-Contaminated" wound involves controlled entry into a hollow viscus. However, gross spillage (e.g., stomach contents or bile) escalates the classification to **Contaminated**. 4. **Statement 4 (True):** The expected surgical site infection (SSI) rate for Clean-Contaminated wounds is approximately **less than 10%** (typically 3–11%) with proper prophylaxis. 5. **Statement 5 (False):** Hernia repair is a **Clean wound** because it is elective, primary closure is performed, and no respiratory, alimentary, or genitourinary tracts are entered. ### **Why Option C is Correct** Option C correctly identifies that statements 1, 3, and 4 align with standard surgical principles, while correcting the misclassification of abscesses (Dirty) and hernia repairs (Clean). ### **High-Yield NEET-PG Pearls** * **Clean (Class I):** No inflammation, no break in technique. SSI risk: **<2%**. * **Clean-Contaminated (Class II):** Controlled entry into the GI/Respiratory/GU tract. SSI risk: **<10%**. * **Contaminated (Class III):** Accidental wounds, gross spillage from GI tract, or acute non-purulent inflammation. SSI risk: **15–20%**. * **Dirty (Class IV):** Old traumatic wounds, fecal contamination, or existing clinical infection (pus). SSI risk: **up to 40%**.

Question 19: A patient developed a wound infection post laparotomy for pyoperitoneum and was treated conservatively. Granulation tissue is now seen in the wound. What is the next step in management?

A. Daily dressing
B. Mesh repair
C. Incision and drainage
D. Resuturing with interrupted stitches (Correct Answer)

Explanation: ### Explanation The clinical scenario describes a patient with a **secondary intention** healing process following a surgical site infection (SSI). The presence of **granulation tissue** indicates that the infection is controlled, the wound bed is healthy, and the proliferative phase of healing is well underway. **1. Why "Resuturing with interrupted stitches" is correct:** In cases of laparotomy wound dehiscence or infection where the wound was left open (conservative management), once the infection clears and healthy red granulation tissue appears, the wound can be closed surgically. This is known as **Tertiary Wound Closure (Delayed Primary Closure)**. Resuturing with interrupted stitches reduces the healing time, provides better structural integrity than secondary intention alone, and results in a superior cosmetic outcome. Interrupted stitches are preferred over continuous ones in previously infected fields to prevent the spread of any residual infection along the entire suture line. **2. Why other options are incorrect:** * **Daily dressing:** While appropriate during the initial infected phase, continuing only dressings once granulation tissue has formed unnecessarily prolongs healing time and increases the risk of an incisional hernia. * **Mesh repair:** Mesh is contraindicated in a recently infected field or an open wound due to the high risk of a foreign body infection. It is used for elective hernia repairs, not acute wound closure. * **Incision and drainage:** This is the treatment for an active abscess. Since the wound is already open and granulation tissue is present, there is no undrained collection to address. **Clinical Pearls for NEET-PG:** * **Primary Closure:** Immediate suture of a clean/clean-contaminated wound. * **Secondary Intention:** Wound left open to heal by granulation and myofibroblast-led contraction. * **Tertiary Closure (Delayed Primary):** Closing a wound 4–7 days after the initial surgery once the bacterial count is low (<10⁵ per gram of tissue). * **Granulation tissue** is characterized by new capillary loops (angiogenesis) and fibroblasts; its presence is the "green light" for delayed closure.

Question 20: Which of the following statements regarding cellulitis are true? 1. It is commonly caused by Streptococcus pyogenes. 2. It can lead to Systemic Inflammatory Response Syndrome (SIRS). 3. It is a localized infection. 4. Any associated abscess should be drained. 5. Incision and drainage (I&D) should not be performed.

A. Statements 1, 2, and 3 are true, and statements 4 and 5 are false.
B. Statements 1, 3, and 5 are true, and statements 2 and 4 are false.
C. Statements 3 and 5 are false, and statements 1, 2, and 4 are true. (Correct Answer)
D. Statements 1 and 2 are false, and statements 3, 4, and 5 are true.

Explanation: Cellulitis is a non-necrotizing inflammation of the skin and subcutaneous tissues. Understanding its management is crucial for NEET-PG. **Explanation of Statements:** 1. **Causative Agent (True):** *Streptococcus pyogenes* (Group A Strep) is the most common cause, followed by *Staphylococcus aureus*. It typically enters through a break in the skin. 2. **SIRS (True):** While initially local, cellulitis can rapidly spread via lymphatics, leading to systemic features like fever, tachycardia, and leukocytosis (SIRS). 3. **Localized vs. Spreading (False):** Unlike an abscess, cellulitis is characterized by its **spreading** nature. It lacks a clear margin (unlike Erysipelas) and is not localized. 4. **Abscess Drainage (True):** If cellulitis is associated with a fluctuant area (abscess), the standard of care is **Incision and Drainage (I&D)**. Antibiotics alone cannot penetrate an undrained pus collection. 5. **I&D Performance (False):** While simple cellulitis is treated with antibiotics, the presence of an underlying abscess makes I&D mandatory. **Why Option C is Correct:** It correctly identifies that cellulitis is a spreading (not localized) infection and that any associated abscess must be drained, making statements 3 and 5 false. **High-Yield Clinical Pearls:** * **Erysipelas vs. Cellulitis:** Erysipelas involves the upper dermis and superficial lymphatics, presenting with **sharply demarcated** raised edges. Cellulitis involves deeper dermis/subcutaneous fat and has **ill-defined** borders. * **Milian’s Ear Sign:** Since the ear lacks subcutaneous tissue, an infection there is Erysipelas, not cellulitis. * **Treatment:** Elevation of the limb and systemic antibiotics (e.g., Flucloxacillin or Cephalosporins).

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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