Podcast
Questions and Answers
Which of the following statements accurately describes sterilization methods?
Which of the following statements accurately describes sterilization methods?
- Incineration is an example of a dry heat sterilization method. (correct)
- Physical sterilization methods do not include moist heat.
- Sterilization methods are only effective on vegetative bacteria.
- All sterilization methods eliminate only viruses.
What is the purpose of using a throat swab in bacterial sample collection?
What is the purpose of using a throat swab in bacterial sample collection?
- To analyze blood for pathogens.
- To determine the presence of infections in the throat area. (correct)
- To collect a sample of cerebrospinal fluid.
- To collect nasal secretions.
Which method uses steam under pressure for sterilization?
Which method uses steam under pressure for sterilization?
- Autoclaving. (correct)
- Dry heat oven.
- Incineration.
- Hot air sterilization.
Which of the following samples would not typically be collected using a swab?
Which of the following samples would not typically be collected using a swab?
Which item is suitable for sterilization using dry heat at 160-180°C?
Which item is suitable for sterilization using dry heat at 160-180°C?
What is the primary purpose of using fractional sterilization at 100°C for 5 minutes over three consecutive days?
What is the primary purpose of using fractional sterilization at 100°C for 5 minutes over three consecutive days?
Which of the following is NOT a method of chemical sterilization mentioned?
Which of the following is NOT a method of chemical sterilization mentioned?
What is the significance of using a bacteriological filter with a pore size of 0.45 microns?
What is the significance of using a bacteriological filter with a pore size of 0.45 microns?
At what temperature and for how long is milk typically pasteurized?
At what temperature and for how long is milk typically pasteurized?
Which of the following statements about mechanical sterilization methods is correct?
Which of the following statements about mechanical sterilization methods is correct?
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Study Notes
Bacterial Sample Collection
- Bacterial sample collection depends on the infected area and type of pathogen suspected
- Common types of samples collected includes: throat swab, ear swab, nasal swab, nasal secretion, sputum, biopsy, peritoneal fluid, vaginal swab, semen/prostatic/urethral discharge, stool, urine, blood, wound swab, skin swab, cerebrospinal fluid (CSF)
- The type of sample determines the appropriate media for cultivation
Sterilization
- Sterilization is the complete eradication of all microorganisms including bacteria, spores, viruses, fungi and protozoa
- Sterilization techniques include physical and chemical methods
Physical Sterilization
- Heat:
- Dry Heat:
- Incineration: using flames to sterilize tools like loops, needles, and slides
- Hot Air: using ovens at 160-180°C for 90-120 minutes to sterilize heat-resistant materials like powders, forceps, scissors, glassware
- Moist Heat:
- Steam under Pressure: using an autoclave at 121°C and 15 psi for 15-20 minutes to sterilize media and heat-resistant materials
- Steam: using an Arnold sterilizer at 100°C for 15 minutes for three consecutive days (fractional sterilization) for sugar solutions and other materials destroyed above 100°C
- Boiling: heating items to 100°C to kill vegetative cells
- Pasteurization: heating liquid materials at 63°C for 30 minutes or 72°C for 20 minutes for milk and other protein materials
- Dry Heat:
- Radiation: using gamma, X, ultraviolet (UV), and beta rays to sterilize plastics, surgical rooms, etc.
Chemical Sterilization
- Using ethyl, methyl, and isopropyl alcohols, like 75% ethanol, for cleaning and sterilizing surfaces and hands
- Using 2-5% phenol for cleaning floors and surfaces
- Other chemicals include aldehydes, halogens, etc.
Mechanical Sterilization
- Using specific filters (bacteriological filters) like Seitz, Berkfeld, and membrane filters to sterilize heat-sensitive liquids like biological fluids (serum), enzyme solutions, vitamins, and antibiotics
- Filters have specific pores (0.45 μm) that prevent the passage of microbial cells
- The charge of the filter and the liquid's nature are essential for effective filtration
Culture Methods for Sample Collection
- Direct culture of swab samples from surfaces
- Cleaning surfaces with 75% ethanol prior to culturing
- Using nutrient agar for cultivation
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