38 Questions
What type of gangrene is associated with Clostridium perfringens?
Gas gangrene
What is a potential risk of using oxygen therapy to enhance antibiotic treatments?
Oxygen toxicity
What type of radiation is commonly used to sterilize packaged materials?
Ionizing radiation
What is the effect of ionizing radiation on DNA molecules?
Introduces double-stranded breaks
What is the effect of UV light on DNA replication?
Formation of thymidine dimers
What is the result of DNA polymerase encountering a thymidine dimer during DNA replication?
Random incorporation of bases
What is the ultimate effect of UV light on microbes?
Accumulation of mutations leading to cell death
What is the range of sound waves used in ultrasonic vibrations?
beyond the range of human hearing
What type of materials are commonly sterilized using ionizing radiation?
Latex and plastic items used for patient care
What is Minimum Inhibitory Concentration (MIC) compared with?
MIC's established by Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST)
What is the result of cavitation in ultrasonic vibrations?
formation of microscopic bubbles or cavities and creation of external pressures that break cells open
What is the purpose of the Phenol Coefficient method?
To measure the bactericidal activity of a chemical compound in relation to phenol
What is the primary use of ultrasonic vibrations?
as a cleaning agent
What is the name of the device used by dentists to clean teeth?
cavitron
Which bacteria are used as test organisms in the Phenol Coefficient method?
Staphylococcus aureus (gram +ve) and Salmonella enterica serovar Typhi (gram -ve)
What is the significance of a phenol coefficient of 1.0?
The chemical agent has the same level of effectiveness as phenol
What ancient people used to burn for deodorizing spaces and for sanitation?
sulphur
What was used to treat syphilis in the early days?
mercury
What is the limitation of the Phenol Coefficient method?
The conditions and organisms were arbitrarily chosen
What was used to prevent fungal growth on plants?
copper sulphate
What is the outcome of the Phenol Coefficient method?
The result provides the phenol coefficient for the test compound
What is the procedure in the Phenol Coefficient method?
The test bacterium is exposed to phenol and antimicrobial solution in water, and the concentration of phenol is compared to the concentration of the test compound
What was a valuable antiseptic in the early 1800's?
tincture of iodine
Why is it important to compare MIC with established standards?
To ensure the accuracy and reliability of antimicrobial susceptibility testing results
What is the mechanism of action of triclosan?
blocks bacterial fatty acid synthesis
What concentration of ethanol is bactericidal?
70%
What is the effect of 100% ethanol on surface proteins?
They coagulate very quickly, preventing effective penetration of ethanol into the cells.
What types of viruses are affected by alcohols?
Enveloped viruses
What is the effect of alcohols on spores?
No effect
What is the mechanism of action of halogens?
Oxidation of cellular components
What is Betadine?
Iodine complexed with an organic molecule (iodophor)
What is the use of iodine as a topical antiseptic?
Hand scrub
What is the structural characteristic of o-Phthalaldehyde that enables it to cross-link proteins and nucleic acids?
2 reactive aldehyde groups linked by an aromatic bridge
What is an advantage of using o-Phthalaldehyde over glutaraldehyde and formaldehyde?
It is less irritating to skin and nasal passages and produces minimal odor
What is the mode of action of β-Propionolactone as a disinfectant?
It binds to DNA, thereby inactivating it
What is a common application of β-Propionolactone in the medical field?
It is used as a component of vaccines to maintain sterility
What is a potential health risk associated with β-Propionolactone?
It is carcinogenic in animals and can cause permanent eye, kidney, and liver damage
What is the metabolic fate of β-Propionolactone in animals and humans?
It is quickly metabolized to lactic acid
Study Notes
Measuring Control
- Minimum Inhibitory Concentration (MIC) is compared to values established by Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST)
- Phenol Coefficient measures bactericidal activity of a chemical compound in relation to phenol
- Phenol Coefficient equals 1.0 means the chemical agent has the same level of effectiveness as phenol
Radiation
- Ionizing Radiation (e.g., X-rays, gamma rays, high-energy electron beams) damages cell components, introduces double-stranded breaks in DNA molecules, and causes mutations leading to cell death
- Ionizing Radiation is used to sterilize packaged materials, petri dishes, disposable plastic inoculating loops, gloves, intravenous tubing, and other latex and plastic items
- Non-ionizing Radiation (e.g., UV Light) causes formation of thymidine dimers, leading to mutations that accumulate and eventually kill the microbe
Sound Waves
- Ultrasonic Vibrations (Cavitation) use high-frequency sound waves to create microscopic bubbles or cavities that collapse, sending out shock waves that break open cells
- Cavitation is used for cleaning and not as a sterilizing agent
- Ultrasonic water baths are used for cleaning jewelry, coins, and teeth (by dentists)
Chemical Control Methods
- General Principles: various chemicals can be used to prevent microbial growth, with examples including resins, aromatics, iodine, and copper sulphate
- Phenolics (e.g., triclosan) block bacterial fatty acid synthesis and are used in toothpastes, soaps, cutting boards, knives, shower curtains, clothing, concrete, to make them antimicrobial
- Alcohols (e.g., ethanol, isopropanol) are bactericidal at 70% concentration, denature proteins, disrupt cell membranes, and are used as topical antiseptics, but not effective against spores
- Halogens (e.g., iodine, chlorine, fluorine) oxidize cellular components, destabilize macromolecules, and are used as topical antiseptics
- Alkylating Agents (e.g., o-phthalaldehyde, β-propionolactone) cross-link proteins and nucleic acids, inactivating them, and are used as sterilants, but can be irritating to skin and have potential health risks
This quiz assesses understanding of antimicrobial susceptibility testing, including measuring control, MIC, and comparison with established standards by CLSI and EUCAST.
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