PMB 313: Disinfection and Sterilization

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Questions and Answers

What significant advancement in microbiology did A. Leeuwenhoek achieve in 1676?

A. Leeuwenhoek was the first to observe and describe microbes accurately.

Describe the basic principle behind the sedimentation sampling method used for air microbiological assessment.

Sedimentation sampling relies on gravity and air currents to settle airborne microorganisms onto agar plates.

What is the primary advantage of active air sampling over passive air sampling in evaluating microbial contamination?

Active air sampling measures microbial contamination by counting CFU per cubic meter of air.

What are the key disadvantages of using the sedimentation sampling method?

The sedimentation method has long sampling times and a bias towards large particles, and it cannot measure viable particles per volume of air. Signup and view all the answers

How does the impaction method function in active air sampling for collecting bioaerosols?

The impaction method collects a known volume of air, which is directed onto a medium to capture microorganisms. Signup and view all the answers

What is the primary function of impactor methods in relation to airborne microorganisms?

Impactor methods use inertia to separate airborne microorganisms from air currents and collect them onto a surface. Signup and view all the answers

Describe how a slit sampler operates in terms of its design and particle collection efficiency.

A slit sampler has a tapered slit tube that creates a jet stream, drawing air samples through a vacuum at a constant flow rate, collecting particles onto a rotating agar plate. Signup and view all the answers

Explain the difference between single stage and multiple stage impactors in terms of particle size differentiation.

Single stage impactors do not differentiate between particle sizes, while multiple stage impactors can categorize particles into different size profiles based on their velocity. Signup and view all the answers

What role does vacuum play in the function of both slit and sieve samplers?

The vacuum creates a constant flow rate necessary for efficiently drawing air samples through the sampler and onto the collection surface. Signup and view all the answers

What type of impactor would be most appropriate for examining respirable particles of size 5 µm, and why?

A two stage impactor is most appropriate for examining respirable particles of size 5 µm due to its capability to differentiate between various particle sizes. Signup and view all the answers

Study Notes

Brief History of Air Microbiology

1676: A. Leeuwenhoek is recognized for accurately observing and describing microbes for the first time.
1884: C. Chamberland develops a bacterial filter enabling the identification of viruses.

Factors Influencing Bioaerosols

Various elements affect the presence and distribution of bioaerosols in different environments, particularly in healthcare settings.

Microbiological Assessment of Hospital and Pharmaceutical Industries

Air samplers are utilized to assess air quality in hospitals and pharmaceutical sectors.
Techniques include active air sampling and passive air sampling.

Passive Air Sampling: Sedimentation Sampling

Relies on gravity and air currents to settle airborne microorganisms onto agar plates.
Standard 90 mm plates are exposed for 15 minutes to 1 hour.
Results measured in colony-forming units (CFU) or particles per minute.
Advantages include cost-effectiveness and ease of setup; captures bioaerosols in original state.
Limitations: cannot measure viable particles per air volume, long sampling times, biased towards larger particles, low correlation with other methods.

Active Air Sampling

Measures microbial air contamination by counting CFU per cubic meter (cfu/m³) of air.
Utilizes known volumes of air, collected through various techniques that manage air currents.

Impaction Method

Common in the pharmaceutical industry; separates particles from air using inertia.
Airborne microorganisms are collected on agar or adhesive surfaces via vacuum.
Two types: slit and sieve samplers.
- Slit Samplers: Cylindrical with a tapered slit tube; maintains constant flow (28.3 L/min).
- Sieve Samplers: Use small holes for air passage; collect particles based on size through multiple stages.
Multiple stage impactors help differentiate particle sizes, useful in healthcare for respirable particles (5 µm).
Advantages: High recovery rates, minimal sampling stress, no post-collection manipulation.
Disadvantages: Bulky, expensive, require sterility until sampling, and handling can be cumbersome.

Filtration Method

Collects microorganisms onto filters connected to a vacuum source.
Filters can be sodium alginate, cellulose fiber, glass fiber, or synthetic membranes (pore sizes of 0.45 or 0.22 µm).
Gelatin membrane filters are directly placed on agar for quantification; synthetic filters need agitation in liquid.
Effective for molds or bacterial spores; vegetative cells more susceptible to damage from desiccation.
Advantages: Low cost, effective for large air volumes in short sampling times.

Impingement Method

Utilizes a liquid medium for capturing airborne microorganisms.
Air is dispersed through liquid, entrapping particles effectively.
Categorized into low and high-velocity impingers, though low-velocity impingers are less efficient for small particles.

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Description

Explore the critical concepts of air microbiology in the context of disinfection and sterilization. This quiz covers the historical milestones in microbiology, including the discoveries of A. Leeuwenhoek and C. Chamberland. Understand the factors influencing bioaerosols and the microbiological assessments in hospitals and pharmaceutical industries.