Surgical Infections — MCQs

Surgical Infections Indian Medical PG Practice Questions and MCQs

Question 171: What is the term for bacteria that are actively dividing and have invaded the wound surface in the context of surgical site infection?

A. Contamination
B. Colonization
C. Local infection
D. Infection (Correct Answer)

Explanation: ***Infection*** - This term precisely describes bacteria that are **actively dividing** and have **invaded the host tissue**, causing a clinical infection with tissue damage and host immune response. - In surgical site infections, this represents the stage where microorganisms have overcome host defenses and are causing disease. - This is the standard terminology used in surgical literature to describe the progression from contamination to active disease. *Contamination* - **Contamination** refers to the presence of microorganisms on a surface or in a wound without active proliferation or host response. - It's an early stage where bacteria are present but not yet multiplying or causing disease. *Colonization* - **Colonization** indicates that microorganisms are replicating on the host surface or in a wound without tissue invasion or causing an immune response. - Unlike infection, colonization does not involve invasion of tissue or clinical signs of disease. *Local infection* - While this describes an infection confined to a particular anatomical area, it is a descriptor of the **location** rather than the **process** described in the question. - The question asks specifically about the term for dividing and invading bacteria, which is simply "infection" - the word "local" adds information about location but doesn't define the fundamental process.

Question 172: After splenectomy, the most common infection is:

A. E. coli
B. Klebsiella
C. Streptococcus pneumoniae (Correct Answer)
D. Haemophilus influenzae

Explanation: ***Streptococcus pneumoniae*** - The **spleen** is crucial for filtering encapsulated bacteria and producing opsonizing antibodies, making individuals **asplenic** or functionally asplenic highly susceptible to infections by **encapsulated organisms**. - *S. pneumoniae* is the most common cause of **overwhelming post-splenectomy infection (OPSI)**, leading to rapid onset **sepsis** and high mortality. *E. coli* - While *E. coli* is a common cause of infections, particularly **gram-negative sepsis** or **urinary tract infections**, it is not an encapsulated bacterium and thus not the primary opportunistic pathogen post-splenectomy. - The spleen's role in clearing *E. coli* is less central compared to encapsulated organisms. *Klebsiella* - *Klebsiella* species are also encapsulated bacteria, but *S. pneumoniae* is statistically the most frequently implicated organism in OPSI. - While *Klebsiella* can cause severe infections, particularly **pneumonia** and **bacteremia**, it is less common than *S. pneumoniae* in the context of post-splenectomy sepsis. *Haemophilus influenzae* - **Encapsulated strains of *Haemophilus influenzae***, particularly type B (Hib), can cause severe infections in asplenic patients, including **meningitis** and **epiglottitis**. - However, with widespread Hib vaccination, its incidence has significantly decreased, and *Streptococcus pneumoniae* remains the most prevalent cause of OPSI.

Question 173: What is the most common infection that occurs after splenectomy?

A. Pneumococcus (Correct Answer)
B. Meningococcus
C. Staphylococcus
D. Corynebacterium

Explanation: ***Pneumococcus*** - Patients who have undergone a splenectomy are at significantly increased risk of developing **overwhelming post-splenectomy infection (OPSI)**, with *Streptococcus pneumoniae* (Pneumococcus) being the most common causative organism. - The spleen plays a crucial role in clearing **encapsulated bacteria**, and its absence leaves the individual vulnerable to these infections. *Meningococcus* - While *Neisseria meningitidis* (Meningococcus) is also an encapsulated bacterium and can cause severe infections in asplenic patients, it is **less common** than Pneumococcus as the primary cause of OPSI. - Vaccination against Meningococcus is recommended for splenectomized patients, but *Pneumococcus* remains the leading concern. *Staphylococcus* - *Staphylococcus* species, such as *Staphylococcus aureus*, are common causes of various infections but are generally **not encapsulated bacteria** in the same way *Streptococcus pneumoniae* is. - The spleen's primary role in clearing encapsulated organisms means that *Staphylococcus* infections are **not the most common or characteristic** post-splenectomy infection. *Corynebacterium* - *Corynebacterium* species are typically associated with infections like **diphtheria** or **opportunistic infections** in immunocompromised individuals. - They are **not encapsulated bacteria** and do not represent the most common encapsulated bacterial infection seen after splenectomy.

Question 174: Heat-labile instruments for use in surgical procedures can be best sterilized by what method?

A. Absolute alcohol
B. Ultraviolet rays
C. Chlorine releasing compounds
D. Ethylene oxide gas (Correct Answer)

Explanation: ***Ethylene oxide gas*** - **Ethylene oxide** is a highly effective **sterilizing agent** that can penetrate packaging and is suitable for **heat-sensitive materials** due to its low-temperature application. - It works by **alkylating microbial proteins and nucleic acids**, leading to the death of all microorganisms, including **spores**. *Absolute alcohol* - While **alcohol** is an effective **disinfectant**, it is not a reliable sterilant as it does not consistently kill **bacterial spores**. - Its efficacy as a disinfectant is also limited by its **rapid evaporation** and inability to penetrate organic matter effectively. *Ultraviolet rays* - **UV radiation** is a surface disinfectant and is not suitable for sterilizing surgical instruments as it has **poor penetration** capabilities and cannot sterilize shadowed or covered areas. - It primarily works by damaging the **DNA of microorganisms**, making it effective for air and surface disinfection but not for complex instruments. *Chlorine-releasing compounds* - **Chlorine compounds** are potent disinfectants, but they are often **corrosive to metals** and can damage delicate surgical instruments upon prolonged exposure. - While effective at killing many microorganisms, they are also **not reliably sporicidal** at concentrations safe for instrument sterilization and may leave residues.

Question 175: The intense pain associated with a felon occurs due to compression of which nerve in the finger?

A. Digital nerve compression (Correct Answer)
B. Nail bed involvement
C. Median nerve involvement
D. A closed space infection in the distal pulp

Explanation: ***Digital nerve compression*** - A felon is a **closed-space infection** of the **distal pulp space** of the fingertip - The pulp is divided into compartments by **vertical fibrous septa** extending from periosteum to skin - As infection and pus accumulate in this tight, non-distensible compartment, **pressure increases dramatically** - The **digital nerves** (proper digital nerves) running through the pulp space are compressed by this increased pressure, causing **intense throbbing pain** - This is the direct anatomical cause of the characteristic severe pain of a felon *Median nerve involvement* - The median nerve does **not directly enter the finger** - It gives off **digital branches** (common and proper digital nerves) that supply specific fingers - A felon can occur in **any finger**, including those supplied by ulnar nerve branches (little finger, ulnar half of ring finger) - Therefore, attributing the pain specifically to "median nerve" is anatomically inaccurate *Nail bed involvement* - This describes **paronychia**, an infection of the **nail fold**, not the pulp space - Paronychia is a different clinical entity with different anatomy and treatment - While painful, it does not involve the closed compartment pressure dynamics of a felon *A closed space infection in the distal pulp* - This correctly describes the **pathophysiology** of a felon - However, this is the **underlying cause** rather than the direct mechanism of pain - The pain specifically results from **nerve compression secondary** to this closed-space infection - The question asks what causes the pain, and the answer is the nerve compression itself

Question 176: In a patient with suspected sepsis, which of the following is the MOST appropriate initial intervention?

A. Start vasopressor support as first-line treatment
B. Obtain blood cultures and start broad-spectrum antibiotics immediately (Correct Answer)
C. Begin aggressive fluid restriction to prevent organ dysfunction
D. Wait for culture results before starting any treatment

Explanation: ***Obtain blood cultures and start broad-spectrum antibiotics immediately*** - This is the **most appropriate initial intervention** following the **Surviving Sepsis Campaign Hour-1 Bundle** - Blood cultures should be obtained **before** antibiotics when possible, but antibiotic administration should not be delayed beyond 1 hour of sepsis recognition - **Early antibiotic therapy** (within 1 hour) significantly reduces mortality in sepsis - Broad-spectrum coverage is initiated empirically, then narrowed based on culture results and clinical response *Begin aggressive fluid restriction to prevent organ dysfunction* - This is **completely contraindicated** in sepsis management - Sepsis causes **vasodilation and capillary leak** leading to relative hypovolemia - The Surviving Sepsis Campaign recommends **aggressive fluid resuscitation** with 30 mL/kg crystalloid bolus within 3 hours - Fluid restriction would worsen **tissue hypoperfusion** and organ dysfunction *Start vasopressor support as first-line treatment* - Vasopressors are **second-line** therapy in sepsis - They should only be initiated when **fluid resuscitation alone** is insufficient to maintain MAP ≥65 mmHg - Starting vasopressors before adequate fluid resuscitation can worsen tissue perfusion *Wait for culture results before starting any treatment* - Sepsis is a **medical emergency** where every hour of delayed antibiotic therapy increases mortality by approximately 7-8% - Treatment must be initiated **immediately** based on clinical suspicion - Cultures are obtained to guide **de-escalation** of therapy, not to delay initiation

Question 177: Infection of all the following structures can be a cause of psoas abscess, except:

A. Vertebrae
B. Hip joint
C. Appendix
D. Ribs (Correct Answer)

Explanation: ***Ribs*** - Infections of the ribs are typically confined to the **thoracic cage** and are less likely to directly spread to the **psoas muscle**, which lies deep within the abdomen and pelvis. - While severe rib infections might lead to systemic sepsis, direct extension to form a psoas abscess is anatomically improbable due to the **diaphragm** and intervening structures. *Vertebrae* - **Vertebral osteomyelitis** (especially of the lumbar spine) is a common cause of psoas abscess due to the close anatomical proximity of the psoas muscle to the vertebral bodies. - Infection can spread directly from the infected bone into the overlying psoas sheath. *Appendix* - **Retrocecal appendicitis**, particularly if perforated, can lead to direct extension of infection into the right iliac fossa and then into the right psoas sheath due to its anatomical location. - An inflamed or ruptured appendix can cause a **perforated appendicitis** and subsequent inflammatory response in adjacent structures. *Hip joint* - **Septic arthritis of the hip joint** can spread to the psoas muscle because the psoas tendon crosses anteriorly to the hip joint capsule, allowing for contiguous spread of infection. - Inflammatory fluid or pus from an infected hip can track along the fascial planes into the psoas sheath.

Question 178: What is the first-line treatment for gas gangrene?

A. Debridement & antibiotics (Correct Answer)
B. Hyperbaric oxygen
C. Polyvalent gas gangrene antitoxin
D. Amputation

Explanation: ***Debridement & antibiotics*** - **Aggressive surgical debridement** to remove necrotic tissue and reduce bacterial load is the most critical initial step. - **Broad-spectrum antibiotics**, particularly penicillin G, are essential to target the causative *Clostridium perfringens* and prevent systemic spread. *Hyperbaric oxygen* - While **hyperbaric oxygen therapy** can be a useful adjunct by inhibiting bacterial growth and toxin production in anaerobic environments, it is not the *first-line* or sole treatment. - It should be used in conjunction with debridement and antibiotics, not as a standalone initial therapy. *Polyvalent gas gangrene antitoxin* - **Antitoxins** are generally not recommended due to their limited efficacy and potential for severe allergic reactions. - The primary treatment focuses on removing the source of infection and killing the bacteria, not neutralizing toxins alone. *Amputation* - **Amputation** is a drastic measure typically reserved for cases where the limb is irreversibly damaged, infection is uncontrollable by other means, or there is a threat to life. - It is not the initial treatment but may be necessary in advanced or complicated cases.

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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