Surgical Infections Practice Questions

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

Infection. ***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.

Q: After splenectomy, the most common infection is:

Streptococcus pneumoniae. ***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.

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

Pneumococcus. ***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.

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

Ethylene oxide gas. ***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.

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

Digital nerve compression. ***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

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

Ribs. ***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.

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

Debridement & antibiotics. ***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.

Question 1

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

Accepted Answer

Infection

Answer

Contamination

Answer

Colonization

Answer

Local infection

Question 2

After splenectomy, the most common infection is:

Accepted Answer

Streptococcus pneumoniae

Answer

E. coli

Answer

Klebsiella

Answer

Haemophilus influenzae

Question 3

What is the most common infection that occurs after splenectomy?

Accepted Answer

Pneumococcus

Answer

Meningococcus

Answer

Staphylococcus

Answer

Corynebacterium

Question 4

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

Accepted Answer

Ethylene oxide gas

Answer

Absolute alcohol

Answer

Ultraviolet rays

Answer

Chlorine releasing compounds

Question 5

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

Accepted Answer

Digital nerve compression

Answer

Nail bed involvement

Answer

Median nerve involvement

Answer

A closed space infection in the distal pulp

Question 6

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

Accepted Answer

Obtain blood cultures and start broad-spectrum antibiotics immediately

Answer

Start vasopressor support as first-line treatment

Answer

Begin aggressive fluid restriction to prevent organ dysfunction

Answer

Wait for culture results before starting any treatment

Question 7

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

Accepted Answer

Ribs

Answer

Vertebrae

Answer

Hip joint

Answer

Appendix

Question 8

What is the first-line treatment for gas gangrene?

Accepted Answer

Debridement & antibiotics

Answer

Hyperbaric oxygen

Answer

Polyvalent gas gangrene antitoxin

Answer

Amputation

Surgical Infections — MCQs

Surgical Infections — MCQs

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