Sterilization and Disinfection Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Sterilization and Disinfection. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Sterilization and Disinfection Indian Medical PG Question 1: What is the best way to control the MRSA infection in the ward?
- A. Fumigation of ward frequently
- B. Washing hand before and after attending patients (Correct Answer)
- C. Wearing masks during invasive procedures in ICU
- D. Vancomycin given empirically to all the patients
Sterilization and Disinfection Explanation: **Washing hand before and after attending patients**
- **Hand hygiene** is the single most effective measure in preventing the transmission of **healthcare-associated infections**, including **MRSA**.
- **Healthcare workers' hands** are the primary vehicle for spreading pathogens from one patient to another.
*Fumigation of ward frequently*
- **Fumigation** is generally not recommended for routine infection control and has limited efficacy against resistant organisms like **MRSA** in this context.
- It does not address the primary mode of transmission, which is direct contact via **contaminated hands** or surfaces.
*Wearing masks during invasive procedures in ICU is important.*
- While important for preventing infections during **invasive procedures** and protecting against **aerosolized pathogens**, masks are not the primary strategy for controlling the spread of **MRSA** in routine ward settings.
- **MRSA transmission** is predominantly contact-based, not airborne.
*Vancomycin given empirically to all the patients*
- **Empirical broad-spectrum antibiotic use** for all patients is a significant driver of **antibiotic resistance**, including **MRSA**.
- It should be reserved for patients with suspected or confirmed **MRSA infections** based on clinical criteria and culture results, not as a general preventive measure.
Sterilization and Disinfection Indian Medical PG Question 2: All are methods of sterilization except.
- A. Filtration
- B. Heat
- C. Gases
- D. Sunlight (Correct Answer)
Sterilization and Disinfection Explanation: ***Sunlight***
- While sunlight has some **disinfectant** properties due to its **UV radiation**, it is not considered a reliable method of **sterilization** because it cannot kill all forms of microbial life, including bacterial spores.
- Sterilization requires the **complete elimination of all viable microorganisms**, which sunlight cannot consistently achieve.
*Gases*
- Certain gases, such as **ethylene oxide** and **hydrogen peroxide vapor**, are effective **sterilizing agents** used for heat-sensitive materials and medical devices.
- These gases penetrate packaging and kill microorganisms by **alkylating proteins** and **nucleic acids**.
*Filtration*
- **Filtration** is a method of **sterilization** for liquids and gases that cannot withstand heat, by physically removing microorganisms.
- Filters with very small pore sizes (e.g., **0.22 micrometers**) can retain bacteria and fungi, even though they do not kill them.
*Heat*
- **Heat** is one of the most common and effective methods of sterilization, used in various forms like **dry heat** (e.g., sterilization ovens) and **moist heat** (e.g., autoclaving).
- **Autoclaving** with **saturated steam under pressure** is particularly effective as it rapidly coagulates and denatures microbial proteins.
Sterilization and Disinfection Indian Medical PG Question 3: Sterilization accuracy is assessed by using:
- A. Clostridium botulinum
- B. Geobacillus stearothermophilus (Correct Answer)
- C. Staphylococcus aureus
- D. Clostridium perfringens
Sterilization and Disinfection Explanation: ***Geobacillus stearothermophilus***
- This organism forms **highly resistant spores** and is used as a **biological indicator** to validate steam sterilization processes.
- The presence or absence of growth after sterilization indicates whether critical parameters like temperature, pressure, and time were met.
*Clostridium perfringens*
- This bacterium is a common cause of **gas gangrene** and food poisoning, forming spores, but it is not typically used for sterilization validation.
- Its spores are **not considered as resistant** to heat as those of *Geobacillus stearothermophilus*.
*Staphylococcus aureus*
- This is a well-known human pathogen causing a variety of infections and is **not a spore-forming bacterium**.
- Therefore, it is **not suitable for assessing sterilization efficacy** against highly resistant microbial forms.
*Clostridium botulinum*
- This is a spore-forming bacterium known for producing a potent **neurotoxin** and is a concern in food preservation.
- While spore-forming, its spores are **less heat-resistant** than *Geobacillus stearothermophilus* and it is not the standard biological indicator.
Sterilization and Disinfection Indian Medical PG Question 4: Fibreoptic scopes are sterilized by
- A. Ethylene oxide
- B. Glutaraldehyde (Correct Answer)
- C. Alcohol
- D. Autoclaving
Sterilization and Disinfection Explanation: ***Glutaraldehyde***
- **Glutaraldehyde** is the most commonly used agent for **high-level disinfection** of heat-sensitive endoscopes and fibreoptic equipment in clinical practice.
- It effectively kills bacteria, viruses, fungi, and most spores through **alkylation** of proteins and nucleic acids.
- While technically providing high-level disinfection rather than true sterilization, it is the **standard method** for processing flexible endoscopes between procedures.
- **Advantages:** Liquid-based, relatively quick (20-45 minutes), compatible with delicate instruments, and does not require special equipment.
*Ethylene oxide*
- **Ethylene oxide** (EtO) can achieve true sterilization of heat-sensitive instruments and is sometimes used for rigid endoscopes requiring sterility.
- However, it is **not practical for routine flexible endoscope processing** due to: lengthy cycle times (12-24 hours including aeration), need for specialized equipment, toxic residue concerns, and cost.
- Glutaraldehyde remains preferred for **routine clinical use** of flexible fibreoptic scopes.
*Alcohol*
- **Alcohol** (ethanol, isopropanol) is an intermediate-level disinfectant effective against many bacteria and viruses.
- It is **not sporicidal** and cannot achieve high-level disinfection or sterilization.
- Used only for surface disinfection and preliminary cleaning, not as the primary disinfection method for endoscopes.
*Autoclaving*
- **Autoclaving** uses high-pressure steam (121°C or 134°C) for sterilization and is highly effective.
- **Not suitable for flexible fibreoptic scopes** as the high heat would **damage** the delicate optical fibers, lenses, and plastic components.
- May be used for some heat-resistant rigid endoscopic instruments.
Sterilization and Disinfection Indian Medical PG Question 5: Diagnosis of C. difficile infection is made by which of the following methods?
- A. Stool microscopy for pseudomembranes
- B. Culture
- C. Toxin gene detection by polymerase chain reaction (PCR) (Correct Answer)
- D. Enzyme-linked immunosorbent assay (ELISA)
Sterilization and Disinfection Explanation: ***Toxin gene detection by polymerase chain reaction (PCR)***
- **PCR for toxin genes (tcdA and tcdB)** is the most sensitive and specific method for diagnosing **Clostridioides difficile infection (CDI)**, directly detecting the genetic material responsible for the pathology.
- This method is superior because it identifies the presence of toxigenic C. difficile, which is crucial for determining clinical significance and guiding treatment.
*Stool microscopy for pseudomembranes*
- While **pseudomembranes** are a hallmark of severe CDI, their detection requires **endoscopy** and is not a direct diagnostic test for the pathogen itself.
- Furthermore, their absence does not rule out CDI, as pseudomembranes may not form in all cases, especially milder ones.
*Culture*
- **Culture for C. difficile** can identify the presence of the organism, but it does not differentiate between toxigenic and non-toxigenic strains.
- Many individuals can be **colonized with non-toxigenic C. difficile** without having an active infection, leading to false positives if culture alone is used for diagnosis.
*Enzyme - linked immunosorbent assay (ELISA)*
- ELISA tests primarily detect **C. difficile toxins A and B** or **glutamate dehydrogenase (GDH)** antigen in stool.
- While rapid, ELISA for toxins A/B has **lower sensitivity** than PCR, potentially missing cases, and GDH detection alone only indicates the presence of C. difficile (toxigenic or non-toxigenic), requiring further toxin testing for confirmation.
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