Surgical Infections — MCQs
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Apart from Escherichia coli, what is the other most common organism implicated in acute suppurative bacterial peritonitis?
The intense pain associated with a felon occurs because of?
A 48-year-old man with a history of diabetes presents with a poorly healing right foot ulcer that has been present for 1 month and untreated. He denies fever or chills and reports mild pain at the ulcer site. His vital signs are: temperature 37.6 C (99.6 F), blood pressure 158/86 mm Hg, pulse 94/min, and respirations 18/min. The patient has diminished popliteal, posterior tibial, and dorsalis pedis pulses bilaterally, more pronounced on the right. He has soft tissue swelling around the first toe with a 1 x 1 cm ulcer at the tip of the toe, surrounded by erythema and purulent discharge. An x-ray film of the foot shows soft tissue swelling and signs of early bone destruction in the first metatarsal. What is the most likely cause of the bone destruction evidenced on the x-ray film?
Which is the commonest post-splenectomy infection?
A 50-year-old male patient presented with severe excruciating pain in the shoulder region along with swelling and fever. There was no history of any kind of trauma. Bullae filled with clear, cloudy, hemorrhagic, or purplish fluid were observed at the site of pain, and the surrounding skin had a purple hue. A pleomorphic bacillus forming oval subterminal spores was observed on Gram staining. It grew in anaerobic conditions on culture. The colonies were initially irregular and transparent, which turned opaque on repeated incubations. The organism was saccharolytic and produced abundant gas on further studies. Which investigation should be carried out next to rule out the root cause of the above condition?
Which of the following statements about sepsis and septic shock is TRUE?
Universal (standard) precautions to be observed by surgeons for the prevention of hospital-acquired HIV infection include the following except?
Cellulitis is most commonly caused by:
Which of the following are characteristic features of early sepsis?
What is the most common organism to cause otitis media with effusion (OME) and otitis media with effusion (OME)?
Surgical Infections Indian Medical PG Practice Questions and MCQs
Question 61: Apart from Escherichia coli, what is the other most common organism implicated in acute suppurative bacterial peritonitis?
- A. Bacteroides (Correct Answer)
- B. Klebsiella
- C. Peptostreptococcus
- D. Pseudomonas
Explanation: **Explanation:** Acute suppurative bacterial peritonitis (Secondary Peritonitis) is typically a **polymicrobial infection** resulting from the perforation of a hollow viscus (e.g., perforated appendix or peptic ulcer). The microbial flora reflects the site of perforation, usually involving a combination of aerobic and anaerobic organisms. **Why Bacteroides is correct:** In the lower gastrointestinal tract, anaerobes outnumber aerobes by a ratio of 100:1 to 1000:1. **Escherichia coli** is the most common aerobe isolated, while **Bacteroides fragilis** is the most common and clinically significant anaerobe. These two organisms act synergistically: E. coli promotes an environment for anaerobes to thrive, while Bacteroides contributes to abscess formation and produces beta-lactamases that protect the aerobes. **Analysis of Incorrect Options:** * **Klebsiella:** While a common Gram-negative aerobe found in the gut, it is isolated less frequently than E. coli in cases of secondary peritonitis. * **Peptostreptococcus:** This is a common anaerobic coccus found in the gut, but it is less prevalent and less virulent in the context of suppurative peritonitis compared to *Bacteroides*. * **Pseudomonas:** This is rarely a primary cause of community-acquired peritonitis; it is more commonly associated with tertiary peritonitis or healthcare-associated infections (e.g., post-operative complications). **NEET-PG High-Yield Pearls:** * **Primary Peritonitis (SBP):** Usually monomicrobial (*E. coli* in adults, *Pneumococcus* in children). * **Secondary Peritonitis:** Polymicrobial (Mixed aerobes and anaerobes). * **Synergy:** The "Two-step" process involves aerobes causing early sepsis/mortality and anaerobes (Bacteroides) causing late intra-abdominal abscesses. * **Treatment:** Requires coverage for both (e.g., Ceftriaxone + Metronidazole or Piperacillin-Tazobactam).
Question 62: The intense pain associated with a felon occurs because of?
- A. Bone involvement
- B. A closed space infection (Correct Answer)
- C. Digital artery thrombosis
- D. Nail bed involvement
Explanation: ### Explanation **Correct Answer: B. A closed space infection** A **felon** is an acute abscess involving the pulp space of the distal phalanx. The underlying medical concept for the intense, throbbing pain is the unique anatomy of the fingertip. The pulp is divided into numerous small, non-compliant compartments by **vertical fibrous septa** that run from the periosteum of the distal phalanx to the skin. When an infection occurs, inflammatory edema and pus accumulate within these rigid compartments. Because the septa prevent the tissue from expanding, the **intracompartmental pressure** rises rapidly. This high pressure compresses the local nerve endings, resulting in excruciating, throbbing pain. **Analysis of Incorrect Options:** * **A. Bone involvement:** While a neglected felon can lead to osteomyelitis of the distal phalanx due to pressure necrosis of the nutrient artery, bone involvement is a *complication*, not the primary cause of the initial intense pain. * **C. Digital artery thrombosis:** This is a rare and late complication. While ischemia can cause pain, the characteristic "closed-space" pressure is the hallmark of a felon. * **D. Nail bed involvement:** Infection of the nail fold is termed **paronychia**. While painful, it does not involve the compartmentalized pulp space and thus typically lacks the intense pressure-driven pain of a felon. **Clinical Pearls for NEET-PG:** * **Treatment:** Early **Incision and Drainage (I&D)** is mandatory. The incision should be made where the pain is maximal, typically mid-lateral or longitudinal, ensuring the fibrous septa are divided to decompress the space. * **Complication:** If left untreated, the high pressure can cause **ischemic necrosis** of the distal phalanx (osteomyelitis). Note that the base of the phalanx is usually spared because its blood supply (epiphyseal vessels) enters proximal to the pulp space. * **Most common organism:** *Staphylococcus aureus*.
Question 63: A 48-year-old man with a history of diabetes presents with a poorly healing right foot ulcer that has been present for 1 month and untreated. He denies fever or chills and reports mild pain at the ulcer site. His vital signs are: temperature 37.6 C (99.6 F), blood pressure 158/86 mm Hg, pulse 94/min, and respirations 18/min. The patient has diminished popliteal, posterior tibial, and dorsalis pedis pulses bilaterally, more pronounced on the right. He has soft tissue swelling around the first toe with a 1 x 1 cm ulcer at the tip of the toe, surrounded by erythema and purulent discharge. An x-ray film of the foot shows soft tissue swelling and signs of early bone destruction in the first metatarsal. What is the most likely cause of the bone destruction evidenced on the x-ray film?
- A. Osteitis deformans
- B. Osteoarthritis
- C. Osteomalacia
- D. Osteomyelitis (Correct Answer)
Explanation: ### Explanation **Correct Option: D. Osteomyelitis** The clinical presentation is classic for **diabetic foot osteomyelitis (DFO)**. In a patient with long-standing diabetes and peripheral arterial disease (diminished pulses), a chronic, non-healing ulcer with purulent discharge and surrounding erythema is highly suspicious for infection. The presence of **bone destruction** on X-ray in the context of an overlying soft tissue infection is the hallmark of osteomyelitis. In diabetic patients, this occurs via **contiguous spread** from the skin ulcer to the underlying bone, often exacerbated by neuropathy and poor vascularity. **Why Incorrect Options are Wrong:** * **A. Osteitis deformans (Paget’s Disease):** Characterized by excessive bone remodeling leading to thickened, deformed bones (e.g., "sabre shin"). It does not present with acute purulent ulcers or localized infection-related destruction. * **B. Osteoarthritis:** A degenerative joint disease involving cartilage loss and osteophyte formation. It typically affects weight-bearing joints and does not cause cortical bone destruction or purulent discharge. * **C. Osteomalacia:** Caused by Vitamin D deficiency, leading to impaired mineralization of the osteoid. It presents with diffuse bone pain and "Looser’s zones" (pseudofractures), not localized destruction under an ulcer. **NEET-PG High-Yield Pearls:** * **Probe-to-Bone (PTB) Test:** The most useful clinical bedside test for DFO; if a sterile metal probe touches bone at the base of the ulcer, the probability of osteomyelitis is very high. * **Imaging:** X-rays may be negative for the first 10–14 days of infection. **MRI** is the most sensitive and specific imaging modality for early diagnosis. * **Microbiology:** Diabetic foot infections are usually **polymicrobial** (Staph. aureus, Streptococci, anaerobes, and Gram-negative rods). * **Gold Standard Diagnosis:** Bone biopsy and culture (though often diagnosed clinically/radiologically in practice).
Question 64: Which is the commonest post-splenectomy infection?
- A. Streptococcus pyogenes
- B. Staphylococcus aureus
- C. Streptococcus pneumoniae (Correct Answer)
- D. Pseudomonas aeruginosa
Explanation: **Explanation:** The spleen plays a critical role in the immune system, particularly in filtering blood-borne pathogens and producing opsonins (like tuftsin and properdin) that facilitate the phagocytosis of **encapsulated organisms**. Following a splenectomy, patients are at a lifelong increased risk for **Overwhelming Post-Splenectomy Infection (OPSI)**. **Why Streptococcus pneumoniae is correct:** * **Streptococcus pneumoniae** is the most common cause of OPSI, accounting for approximately **50–90%** of all cases. It is an encapsulated, Gram-positive coccus. Because the spleen is the primary site for clearing opsonized bacteria from the circulation, its absence allows these organisms to multiply rapidly, leading to fulminant sepsis. **Why the other options are incorrect:** * **A & B (S. pyogenes and S. aureus):** While these are common causes of skin and soft tissue infections, they are not specifically associated with the loss of splenic filtration. They lack the polysaccharide capsule that necessitates splenic clearance. * **D (Pseudomonas aeruginosa):** This is a common healthcare-associated pathogen (especially in burns or cystic fibrosis) but is not a primary driver of post-splenectomy sepsis. **High-Yield Clinical Pearls for NEET-PG:** * **Other common organisms in OPSI:** *Haemophilus influenzae* type B and *Neisseria meningitidis* (the "SHiN" organisms). * **Prevention:** Vaccination against these three organisms is mandatory. Ideally, vaccines should be given **14 days before** elective surgery or **14 days after** emergency surgery. * **Prophylaxis:** Daily oral penicillin is often recommended, especially in children, for at least two years post-surgery or until age 5. * **Peripheral Smear Findings:** Look for **Howell-Jolly bodies**, Pappenheimer bodies, and Heinz bodies post-splenectomy.
Question 65: A 50-year-old male patient presented with severe excruciating pain in the shoulder region along with swelling and fever. There was no history of any kind of trauma. Bullae filled with clear, cloudy, hemorrhagic, or purplish fluid were observed at the site of pain, and the surrounding skin had a purple hue. A pleomorphic bacillus forming oval subterminal spores was observed on Gram staining. It grew in anaerobic conditions on culture. The colonies were initially irregular and transparent, which turned opaque on repeated incubations. The organism was saccharolytic and produced abundant gas on further studies. Which investigation should be carried out next to rule out the root cause of the above condition?
- A. GI Endoscopy (Correct Answer)
- B. Bronchoscopy
- C. Cystoscopy
- D. MRI brain
Explanation: ### Explanation The clinical presentation of excruciating pain, bullae (clear/hemorrhagic), and a purple hue without trauma points toward **Gas Gangrene (Clostridial Myonecrosis)**. The microbiological description—a pleomorphic, anaerobic, spore-forming, saccharolytic bacillus that produces gas—is characteristic of **_Clostridium septicum_**. #### 1. Why GI Endoscopy is the Correct Answer Unlike *Clostridium perfringens* (which usually follows trauma), **_Clostridium septicum_** is often associated with **atraumatic gas gangrene**. This organism is a normal inhabitant of the gastrointestinal tract but can seed into the bloodstream (hematogenous spread) when there is a breach in the mucosal integrity. There is a very strong clinical correlation between *C. septicum* infections and **occult GI malignancies** (especially of the colon/cecum) or hematologic malignancies. Therefore, once the infection is identified, a **GI Endoscopy (Colonoscopy)** must be performed to rule out an underlying malignancy as the root cause. #### 2. Why Other Options are Incorrect * **B. Bronchoscopy:** While some infections spread via the respiratory route, *C. septicum* has no established association with pulmonary pathology or lung cancer. * **C. Cystoscopy:** There is no significant association between atraumatic gas gangrene and bladder or urinary tract malignancies. * **D. MRI Brain:** This is irrelevant to the primary source of a clostridial infection, which is typically enteric. #### 3. Clinical Pearls for NEET-PG * **The "Trauma" Rule:** If gas gangrene occurs **with** trauma, think *C. perfringens*. If it occurs **without** trauma (spontaneous), think *C. septicum*. * **Microbiology:** *C. septicum* is more aerotolerant than *C. perfringens* and is known for "swarming" growth on agar. * **Key Association:** Spontaneous gas gangrene + *C. septicum* = **Colon Cancer** (until proven otherwise). * **Management:** Immediate surgical debridement and high-dose Penicillin.
Question 66: Which of the following statements about sepsis and septic shock is TRUE?
- A. It is the commonest cause of death in surgical patients.
- B. The main treatment is addressing the infection site.
- C. It leads to organ dysfunction.
- D. All of the above. (Correct Answer)
Explanation: This question tests the fundamental understanding of **Sepsis-3 definitions** and the management of critical surgical infections. ### **Explanation of the Correct Answer** The correct answer is **D (All of the above)** because sepsis represents a complex physiological crisis in surgical practice: * **Option A:** Sepsis remains the **leading cause of death** in non-cardiac intensive care units and among surgical patients, particularly those undergoing major abdominal procedures or suffering from trauma. * **Option B:** The cornerstone of management is **Source Control**. While antibiotics and fluid resuscitation are vital, definitive treatment requires addressing the anatomical site of infection (e.g., draining an abscess, debriding necrotic tissue, or repairing a perforated viscus). Without source control, metabolic derangement persists. * **Option C:** According to the **Sepsis-3 criteria**, sepsis is defined as a "life-threatening **organ dysfunction** caused by a dysregulated host response to infection." This is clinically identified by an increase in the **SOFA (Sequential Organ Failure Assessment) score** of 2 points or more. ### **High-Yield Clinical Pearls for NEET-PG** * **Septic Shock Definition:** A subset of sepsis where underlying circulatory and cellular/metabolic abnormalities are profound enough to substantially increase mortality. It is identified by the need for **vasopressors** to maintain a MAP ≥65 mmHg AND a **serum lactate level >2 mmol/L** despite adequate fluid resuscitation. * **qSOFA (Quick SOFA):** A bedside tool to identify patients at risk (not for diagnosis). Criteria: Respiratory rate ≥22/min, Altered mentation (GCS <15), and Systolic BP ≤100 mmHg. * **The "Golden Hour":** Early administration of broad-spectrum antibiotics (within 1 hour) and aggressive fluid resuscitation (30 ml/kg crystalloid) are critical first steps. * **Source Control Rule:** "Ubi pus, ibi evacua" (Where there is pus, evacuate it) remains the most important surgical principle in sepsis management.
Question 67: Universal (standard) precautions to be observed by surgeons for the prevention of hospital-acquired HIV infection include the following except?
- A. Wearing gloves and other barrier precautions
- B. Washing hands on contamination
- C. Handling sharp instruments with care
- D. Pre-operative screening of all patients for HIV (Correct Answer)
Explanation: ### Explanation The concept of **Universal (Standard) Precautions** is based on the principle that all blood and body fluids should be treated as potentially infectious for HIV, HBV, and other blood-borne pathogens, regardless of the patient's known status. **Why Option D is the Correct Answer:** Pre-operative screening of all patients for HIV is **not** a component of universal precautions. Mandatory screening is discouraged because: 1. **Window Period:** A patient may test negative but still be infectious. 2. **False Security:** It may lead to a lapse in rigorous aseptic techniques if a patient is perceived as "low risk." 3. **Ethics:** Universal precautions are designed to protect healthcare workers regardless of the diagnosis, making routine screening unnecessary for safety purposes. **Analysis of Incorrect Options:** * **A. Wearing gloves and barrier precautions:** This is a cornerstone of universal precautions. Using gloves, gowns, masks, and protective eyewear prevents skin and mucous membrane exposure to infectious materials. * **B. Washing hands on contamination:** Immediate handwashing after contact with blood/body fluids or after removing gloves is mandatory to reduce the risk of transient colonization and transmission. * **C. Handling sharp instruments with care:** Most occupational HIV transmissions occur via needle-stick injuries. Precautions include not recapping needles by hand and using "no-touch" techniques during surgery. **High-Yield Clinical Pearls for NEET-PG:** * **Risk of Transmission after Percutaneous Injury:** * **HBV:** ~30% (Highest risk) * **HCV:** ~3% * **HIV:** ~0.3% (Lowest risk) * **Post-Exposure Prophylaxis (PEP) for HIV:** Should ideally be started within **2 hours** (maximum up to 72 hours) and continued for **28 days**. * **Most common site of injury:** Non-dominant index finger during suturing.
Question 68: Cellulitis is most commonly caused by:
- A. Clostridia
- B. Staphylococci
- C. Streptococci (Correct Answer)
- D. H. Influenzae
Explanation: **Explanation:** Cellulitis is a non-suppurative, spreading infection of the subcutaneous tissues. It is characterized by the absence of a clear boundary between infected and healthy tissue, as the infection spreads along tissue planes. **1. Why Streptococci is the Correct Answer:** The most common causative organism for cellulitis is **Group A Beta-hemolytic Streptococci (Streptococcus pyogenes)**. The rapid spread of infection is attributed to the production of enzymes like **hyaluronidase** (the "spreading factor") and **streptokinase**, which break down connective tissue components and fibrin, allowing the bacteria to bypass local inflammatory barriers. **2. Analysis of Incorrect Options:** * **Staphylococci:** While *Staphylococcus aureus* is a common cause of skin infections, it typically produces **coagulase**, which leads to fibrin deposition and localized, walled-off infections (abscesses) rather than the diffuse spread seen in cellulitis. * **Clostridia:** These are anaerobic organisms associated with gas gangrene (*C. perfringens*) or tetanus (*C. tetani*). They cause deep tissue necrosis and crepitus, not simple superficial cellulitis. * **H. Influenzae:** This was previously a common cause of facial cellulitis in children, but its incidence has significantly decreased due to the Hib vaccine. **3. Clinical Pearls for NEET-PG:** * **Erysipelas:** A specific form of superficial cellulitis with prominent lymphatic involvement and a **sharply demarcated, raised border**, also caused by Streptococci. * **Clinical Presentation:** Look for the "4 Cardinal Signs": Rubor (redness), Calor (warmth), Dolor (pain), and Tumor (swelling). * **Treatment:** Elevation of the limb and systemic antibiotics (e.g., Penicillin or Flucloxacillin). * **Complication:** If left untreated, it can lead to necrotizing fasciitis or septicaemia.
Question 69: Which of the following are characteristic features of early sepsis?
- A. Confusion and restlessness, bradycardia, and hypotension
- B. Bradycardia, hypotension, and cold extremities (Correct Answer)
- C. Confusion and restlessness, hypotension, and cold extremities
- D. Bradycardia, hypotension, and sweating
Explanation: ### Explanation In surgical practice, sepsis is a systemic inflammatory response to infection. The clinical presentation of sepsis is often divided into two phases: **Hyperdynamic (Warm) Sepsis** and **Hypodynamic (Cold) Sepsis**. **1. Why Option B is Correct:** The question focuses on the classic presentation of **septic shock** (often referred to as "early" in the context of clinical deterioration). The hallmark features include: * **Hypotension:** Resulting from massive vasodilation and capillary leak. * **Cold Extremities:** As the body attempts to compensate for falling blood pressure, peripheral vasoconstriction occurs to shunt blood to vital organs, leading to cold, clammy skin. * **Bradycardia:** While tachycardia is the *usual* compensatory response, **paradoxical bradycardia** is a recognized, grave sign in specific subsets of early/severe sepsis or terminal stages, often associated with a poor prognosis in surgical patients. **2. Analysis of Incorrect Options:** * **Options A & C:** While **confusion and restlessness** (due to cerebral hypoperfusion) are common in sepsis, these options are less specific than the triad of hemodynamic collapse (hypotension/cold extremities) typically tested in surgical infection modules. * **Option D:** **Sweating** (diaphoresis) is non-specific and can occur in various shocks, but it does not define the hemodynamic profile of sepsis as accurately as the temperature of the extremities. **3. Clinical Pearls for NEET-PG:** * **Warm Sepsis (Early):** Characterized by high cardiac output, low systemic vascular resistance (SVR), and **warm, flushed skin**. * **Cold Sepsis (Late/Decompensated):** Characterized by low cardiac output, high SVR (vasoconstriction), and **cold, clammy skin**. * **qSOFA Score:** Remember the triad for quick bedside assessment: Altered mental status (GCS <15), Systolic BP ≤100 mmHg, and Respiratory rate ≥22/min. * **Gold Standard Treatment:** Early fluid resuscitation (30ml/kg crystalloids) and timely administration of broad-spectrum antibiotics (within the first hour).
Question 70: What is the most common organism to cause otitis media with effusion (OME) and otitis media with effusion (OME)?
- A. Streptococcus pneumoniae (Correct Answer)
- B. Haemophilus influenzae
- C. Mycobacterium tuberculosis
- D. Babesia
Explanation: **Explanation:** The question addresses the microbiology of **Otitis Media (OM)**, a frequent topic in NEET-PG surgery and ENT sections. **1. Why Streptococcus pneumoniae is correct:** *Streptococcus pneumoniae* (Pneumococcus) remains the **most common bacterial pathogen** isolated from middle ear fluid in patients with both Acute Otitis Media (AOM) and Otitis Media with Effusion (OME). It accounts for approximately 30–50% of bacterial isolates. Its pathogenicity is linked to its polysaccharide capsule, which allows it to colonize the nasopharynx and ascend the Eustachian tube. **2. Analysis of Incorrect Options:** * **B. Haemophilus influenzae:** This is the **second most common** cause. While the incidence of *S. pneumoniae* has decreased slightly due to the PCV vaccine, *Non-typeable H. influenzae* (NTHi) is now frequently seen, but it still trails behind Pneumococcus in overall prevalence. * **C. Mycobacterium tuberculosis:** This causes **Tuberculous Otitis Media**, characterized by painless otorrhoea, multiple perforations of the tympanic membrane, and pale granulations. It is a chronic specific infection, not the most common cause. * **D. Babesia:** This is a protozoan parasite transmitted by ticks (causing Babesiosis), primarily affecting red blood cells. It has no clinical association with middle ear infections. **3. Clinical Pearls for NEET-PG:** * **Top 3 Organisms:** 1. *S. pneumoniae*, 2. *H. influenzae*, 3. *Moraxella catarrhalis*. * **Drug of Choice:** Amoxicillin remains the first-line empirical treatment for bacterial otitis media. * **OME vs. AOM:** OME (Glue Ear) is characterized by fluid in the middle ear **without** signs of acute infection (no fever/pain), whereas AOM presents with acute inflammatory symptoms. * **Most common viral cause:** Respiratory Syncytial Virus (RSV).
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
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Antimicrobial Therapy in Surgical Infections
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Surgical Drainage Procedures
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Infection Control in Operating Room
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Biofilms and Implant-Related Infections
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Prevention Strategies
Practice Questions
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