Antimicrobial Prophylaxis — MCQs
In postoperative intensive care unit, five patients developed postoperative wound infection on the same day. The best method to prevent cross infection occurring in other patients in the same ward is to:
A patient with grossly contaminated wound presents 12 hours after an accident. His wound should be managed by -
When do we have to start antibiotics to prevent post-operative infection?
What is the drug that can be used for rheumatic fever prophylaxis in a patient with a history of allergy to Penicillin?
Preferred time for prophylactic antibiotic administration for surgery?
Which of the following is true regarding prophylactic antibiotic use in surgical practice?
Which of the following is an example of a clean surgery?
What is the optimal timing for administering antibiotic prophylaxis before surgery?
Best skin disinfectant for central line insertion is?
Dapsone is NOT used in:
Antimicrobial Prophylaxis Indian Medical PG Practice Questions and MCQs
Question 1: In postoperative intensive care unit, five patients developed postoperative wound infection on the same day. The best method to prevent cross infection occurring in other patients in the same ward is to:
- A. Practice proper hand washing (Correct Answer)
- B. Disinfect the ward with sodium hypochlorite
- C. Fumigate the ward
- D. Give antibiotics to all other patients in the ward
Explanation: ***Correct: Practice proper hand washing*** - **Proper hand hygiene** is the **single most effective method** for preventing the transmission of **healthcare-associated infections (HAIs)**, including surgical site infections - It physically removes or inactivates **transient microorganisms** from the hands of healthcare workers, thereby stopping their spread between patients - This is the **gold standard** recommended by **WHO, CDC**, and all major infection control guidelines for preventing **cross-infection** in healthcare settings *Incorrect: Disinfect the ward with sodium hypochlorite* - While disinfection with **sodium hypochlorite** is important for **environmental cleaning**, it is **less effective than hand hygiene** in preventing direct patient-to-patient transmission - Environmental disinfection alone **cannot interrupt the main routes of transmission**, which often involve **direct contact** or contaminated hands of healthcare personnel - This is a **secondary measure**, not the primary prevention strategy *Incorrect: Fumigate the ward* - **Fumigation** is typically used for **terminal disinfection** in specific situations, such as after highly contagious outbreaks, and is **not a routine** or primary method for preventing cross-infection in an active ward - Its effectiveness in preventing day-to-day cross-infection is **limited compared to immediate infection control practices** like hand hygiene - This practice is largely **outdated** in modern infection control protocols *Incorrect: Give antibiotics to all other patients in the ward* - **Prophylactic antibiotic use** in all other patients is **discouraged** due to the risk of **antimicrobial resistance (AMR)** and potential adverse effects - It does **not address the source of infection** or the transmission pathways, and can lead to wider public health issues - This is an **inappropriate primary prevention strategy** that violates antimicrobial stewardship principles
Question 2: A patient with grossly contaminated wound presents 12 hours after an accident. His wound should be managed by -
- A. Thorough cleaning with debridement of all dead and devitalised tissue without primary closure (Correct Answer)
- B. Primary closure over a drain
- C. Covering the defect with split skin graft after cleaning
- D. Thorough cleaning and primary repair
Explanation: ***Thorough cleaning with debridement of all dead and devitalised tissue without primary closure*** - For a **grossly contaminated wound** presenting 12 hours after injury, thorough **wound lavage** and **debridement** of all non-viable tissue are crucial to reduce bacterial load. - **Delayed primary closure** or **secondary intention healing** is preferred over primary closure in such cases to prevent infection spread. *Primary closure over a drain* - **Primary closure** of a grossly contaminated wound significantly increases the risk of **wound infection**, even with a drain. - Drains may help with fluid collection but do not sufficiently mitigate the risk of infection in a dirty wound. *Covering the defect with split skin graft after cleaning* - Applying a **skin graft** to a potentially infected wound is contraindicated as it will likely fail due to the **bacterial burden**. - Grafting is typically performed on clean, well-vascularized wound beds. *Thorough cleaning and primary repair* - While **thorough cleaning** is essential, **primary repair** (closure) of a grossly contaminated wound is associated with a high risk of **surgical site infection**. - **Delayed closure** allows for observation and further debridement if necessary.
Question 3: When do we have to start antibiotics to prevent post-operative infection?
- A. 1 week before surgery
- B. 2 days before surgery
- C. After surgery
- D. 30-60 minutes before incision (up to 24 hours post-op) (Correct Answer)
Explanation: ***30-60 minutes before incision (up to 24 hours post-op)*** - Surgical antibiotic prophylaxis (SAP) should be administered **30-60 minutes before surgical incision** to ensure adequate tissue and serum concentrations at the time of incision. - This timing allows optimal drug distribution to surgical tissues, which is crucial for preventing surgical site infections (SSIs). - For most clean and clean-contaminated surgeries, prophylaxis should be limited to a **single dose** or continued for **maximum 24 hours post-operatively** as per WHO and CDC guidelines. - Prolonged post-operative antibiotics beyond 24 hours do **not** reduce infection rates and increase the risk of **antibiotic resistance** and **adverse effects**. *1 week before surgery* - Administering antibiotics this far in advance is **unnecessary** and **ineffective** for surgical prophylaxis. - It increases the risk of **antibiotic resistance** and does not guarantee adequate drug levels at the time of incision. - Pre-operative antibiotic use should be avoided unless treating an active infection. *2 days before surgery* - This timeframe is too early to achieve prophylactic benefit during the surgical procedure. - Prolonged pre-operative use promotes **bacterial resistance** without providing additional protection. - Drug levels will not be optimal at the time of incision due to metabolism and excretion. *After surgery* - Starting antibiotics **after surgical incision** is **too late** for prophylaxis as contamination has already occurred. - Post-operative initiation is considered **therapeutic treatment** for established infection, not prevention. - The critical window for prophylaxis is the period from skin incision to wound closure.
Question 4: What is the drug that can be used for rheumatic fever prophylaxis in a patient with a history of allergy to Penicillin?
- A. Erythromycin (Correct Answer)
- B. Amoxicillin
- C. Streptomycin
- D. Sulfasalazine
Explanation: ***Erythromycin*** - **Erythromycin** is a macrolide antibiotic that is a suitable alternative for **rheumatic fever prophylaxis** in patients with a documented allergy to penicillin. - It effectively covers *Streptococcus pyogenes*, the causative agent of group A streptococcal (GAS) pharyngitis that precedes rheumatic fever. *Amoxicillin* - **Amoxicillin** is a penicillin-class antibiotic and would be contraindicated in a patient with a **penicillin allergy**, as it carries a high risk of cross-reactivity and allergic reaction. - Using amoxicillin in this scenario could lead to severe hypersensitivity reactions, compromising patient safety. *Streptomycin* - **Streptomycin** is an aminoglycoside antibiotic primarily used for infections like **tuberculosis** and severe bacterial endocarditis. - It is not indicated for the treatment of *Streptococcus pyogenes* infections or for **rheumatic fever prophylaxis**. *Sulfasalazine* - **Sulfasalazine** is an anti-inflammatory and immunomodulatory drug primarily used in the management of **inflammatory bowel disease** and **rheumatoid arthritis**. - It has no antimicrobial activity against *Streptococcus pyogenes* and is therefore not used for **rheumatic fever prophylaxis**.
Question 5: Preferred time for prophylactic antibiotic administration for surgery?
- A. 1 day before surgery
- B. At the time of induction of anaesthesia (Correct Answer)
- C. I.V. during surgery
- D. I.M. 6 hrs before surgery
Explanation: ***At the time of induction of anaesthesia*** - This timing ensures that a **therapeutic concentration** of the antibiotic is present in the tissues at the time of the initial surgical incision, when the risk of bacterial contamination is highest. - Administering the antibiotic too early or too late can reduce its effectiveness in preventing **surgical site infections (SSIs)**. *1 day before surgery* - Administering antibiotics a day before surgery would lead to the drug being **metabolized and eliminated** from the body before the surgical incision is made, rendering it ineffective for prophylaxis. - This timing also increases the risk of **antibiotic resistance** development without providing adequate protection against SSIs. *I.V. during surgery* - Administering the antibiotic intravenously during surgery means that the drug will not have reached sufficient **tissue concentrations** at the crucial moment of the initial incision. - The protective effect is largely dependent on adequate tissue levels **prior to contamination**, which would not be achieved by administration only during the procedure. *I.M. 6 hrs before surgery* - While closer to the optimal timing than 1 day before, administering intramuscularly 6 hours prior may result in **suboptimal drug levels** at the time of incision, especially for drugs with shorter half-lives. - Intramuscular administration can also have variable absorption rates compared to intravenous, potentially delaying peak tissue concentration and reducing reliability for **prophylactic efficacy**.
Question 6: Which of the following is true regarding prophylactic antibiotic use in surgical practice?
- A. is given orally
- B. continued for a minimum of 7 days
- C. first dose is given before induction of anesthesia (Correct Answer)
- D. depends on individual preference
Explanation: ***First dose is given before induction of anesthesia*** - **Prophylactic antibiotics** are most effective when present in adequate concentrations in tissue **before the surgical incision** is made - Administering the first dose **within 60 minutes before incision** (typically before induction of anesthesia) ensures optimal tissue levels at the time of potential bacterial contamination - This timing is a **key principle** of effective surgical antibiotic prophylaxis *Is given orally* - Surgical prophylaxis requires **intravenous administration** for rapid and reliable tissue levels - IV route ensures predictable bioavailability and adequate drug concentration at the surgical site - Oral route may be used in specific outpatient scenarios but is **not standard** for surgical prophylaxis *Continued for a minimum of 7 days* - Prophylactic antibiotics are given for **short duration**: typically a **single dose** or continued for less than 24 hours post-operatively - Extended courses (≥7 days) are reserved for **treating established infections**, not prophylaxis - Prolonged use increases risk of **antibiotic resistance**, adverse effects, and *Clostridioides difficile* infection *Depends on individual preference* - Prophylactic antibiotic use follows **evidence-based guidelines** and institutional protocols, not individual preference - Guidelines consider surgery type, patient risk factors, local **antibiogram data**, and established efficacy - Standardized protocols improve outcomes and reduce surgical site infections
Question 7: Which of the following is an example of a clean surgery?
- A. Hernia surgery (Correct Answer)
- B. Cholecystectomy
- C. Rectal surgery
- D. Gastric surgery
Explanation: ***Hernia surgery*** - **Clean surgeries** involve no entry into hollow viscera (e.g., gastrointestinal, genitourinary, or respiratory tract) and are characterized by **no inflammation** or infection. Hernia repair typically fits this description. - The risk of **surgical site infection** (SSI) is usually less than 2% in clean cases, making it a benchmark for surgical infection control. *Gastric surgery* - This involves entry into the **gastrointestinal tract**, which is considered a **contaminated** or **clean-contaminated** procedure due to the presence of bacteria. - The risk of infection is higher than in clean surgeries, often requiring prophylactic antibiotics. *Cholecystectomy* - This procedure involves the **gallbladder**, which is part of the biliary system, often considered a **clean-contaminated** wound if bile spills or if there's no evidence of active infection. - If performed for **acute cholecystitis** (inflammation/infection), it would be classified as **contaminated** or **dirty**. *Rectal surgery* - This involves the **rectum**, which is part of the lower **gastrointestinal tract** and contains a high bacterial load. - Procedures involving the rectum are classified as **contaminated** or **dirty** due to the high risk of bacterial contamination.
Question 8: What is the optimal timing for administering antibiotic prophylaxis before surgery?
- A. Immediately before induction of anesthesia
- B. 30-60 minutes before incision (Correct Answer)
- C. 2-3 hours before surgery
- D. Immediately after surgery
Explanation: ***30-60 minutes before incision*** - This is the **optimal timing** recommended by WHO, CDC, and major surgical guidelines for most commonly used prophylactic antibiotics (cefazolin, cefuroxime). - Ensures **peak tissue and serum concentrations** are achieved at the time of incision, providing maximum protection against surgical site infections. - Based on **pharmacokinetic principles**: the antibiotic must be present at bactericidal concentrations in tissues when bacterial contamination occurs. - Studies show this timing significantly reduces surgical site infection rates compared to other timings. *Immediately before induction of anesthesia* - While acceptable in some protocols, this may be too early if there is a delay between induction and incision. - Could result in **declining antibiotic levels** by the time the incision is made, especially for antibiotics with shorter half-lives. *2-3 hours before surgery* - This is **too early** for most antibiotics. - Tissue levels may have already **declined below therapeutic concentrations** by the time of incision. - Does not provide adequate protection during the critical period of bacterial contamination. *Immediately after surgery* - This is **treatment, not prophylaxis**. - Offers **no preventive benefit** against intraoperative contamination. - By this time, bacteria introduced during surgery have already adhered to tissues and begun forming biofilms.
Question 9: Best skin disinfectant for central line insertion is?
- A. Povidone iodine
- B. Cetrimide
- C. Alcohol
- D. Chlorhexidine (Correct Answer)
Explanation: ***Chlorhexidine*** - **Chlorhexidine gluconate** with alcohol is highly recommended for **skin antisepsis** prior to central venous catheter insertion due to its rapid and persistent antimicrobial activity. - It effectively reduces the risk of **catheter-related bloodstream infections (CRBSIs)** by targeting a broad spectrum of bacteria. *Povidone iodine* - While effective, **povidone iodine** has a slower onset of action and is less persistent compared to chlorhexidine, making it less ideal for this specific procedure. - Its efficacy can be reduced in the presence of organic material, and it may cause **skin irritation** in some patients. *Cetrimide* - **Cetrimide** is a cationic surfactant with antiseptic properties but is generally considered less potent and less widely recommended than chlorhexidine for surgical skin preparation. - It is more commonly found in preparations for cleaning wounds rather than for **major invasive procedures** like central line insertion. *Alcohol* - **Alcohol** provides rapid antisepsis and has a broad spectrum of activity, but its effect is not persistent and it is volatile, leading to quick evaporation. - Its efficacy is enhanced when combined with other agents, such as chlorhexidine, rather than being used alone for **central line insertion**.
Question 10: Dapsone is NOT used in:
- A. Dermatitis herpetiformis
- B. Alopecia areata (Correct Answer)
- C. Pneumocystis jirovecii pneumonia prophylaxis
- D. Leprosy
Explanation: ***Alopecia areata*** - **Dapsone** is an **antibiotic** with anti-inflammatory and immunomodulatory properties and is not indicated for the treatment of **alopecia areata**. - Treatment for **alopecia areata** typically involves **corticosteroids** (topical, intralesional, or systemic) or other immunosuppressants. *Dermatitis herpetiformis* - **Dapsone** is the **first-line treatment** for **dermatitis herpetiformis** due to its rapid antipruritic effect, often providing relief within 24-48 hours. - It works by reducing the inflammation and formation of the characteristic **subepidermal blisters** seen in this condition. *Pneumocystis jirovecii pneumonia prophylaxis* - **Dapsone** is an effective **alternative agent** for prophylaxis against **Pneumocystis jirovecii pneumonia (PCP)**, especially in patients who cannot tolerate trimethoprim-sulfamethoxazole. - It is often used in combination with **pyrimethamine** for toxoplasmosis prophylaxis in HIV-infected patients. *Leprosy* - **Dapsone** is a crucial component of **multidrug therapy (MDT)** for both paucibacillary and multibacillary forms of **leprosy**. - It acts as a **bacteriostatic agent** against Mycobacterium leprae and has been a cornerstone of leprosy treatment for decades.
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