Podcast
Questions and Answers
What is the primary difference between disinfectants and antiseptics?
What is the primary difference between disinfectants and antiseptics?
Disinfectants kill vegetative cells on surfaces, while antiseptics kill vegetative cells on living tissue.
Why are narrow spectrum drugs considered more desirable than broad spectrum drugs?
Why are narrow spectrum drugs considered more desirable than broad spectrum drugs?
Narrow spectrum drugs specifically target pathogens and cause less harm to normal microbiota, making them preferable in treatment.
What is the significance of Streptomyces in the context of antibiotics?
What is the significance of Streptomyces in the context of antibiotics?
Streptomyces are gram-positive, saprophytic bacteria found in soil that produce natural antibiotics.
Describe the Filter Paper Disk Method and its purpose.
Describe the Filter Paper Disk Method and its purpose.
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Explain the importance of the Kirby-Bauer Method in antibiotic susceptibility testing.
Explain the importance of the Kirby-Bauer Method in antibiotic susceptibility testing.
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What does 'intrinsic resistance' mean in the context of antibiotics?
What does 'intrinsic resistance' mean in the context of antibiotics?
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What are secondary metabolites, and why are they significant?
What are secondary metabolites, and why are they significant?
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Why might a disinfectant that is effective on an agar plate fail in real-world applications?
Why might a disinfectant that is effective on an agar plate fail in real-world applications?
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What can small colonies within a zone of inhibition indicate?
What can small colonies within a zone of inhibition indicate?
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How does acquired resistance to antibiotics develop?
How does acquired resistance to antibiotics develop?
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What are the critical factors to consider when selecting a disinfectant for healthcare use?
What are the critical factors to consider when selecting a disinfectant for healthcare use?
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Why would a healthcare provider opt for a broad spectrum antibiotic over a narrow spectrum antibiotic?
Why would a healthcare provider opt for a broad spectrum antibiotic over a narrow spectrum antibiotic?
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What is the primary consequence of the misuse and overuse of antibiotics?
What is the primary consequence of the misuse and overuse of antibiotics?
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Describe the characteristics of coliform bacteria and their significance in assessing water contamination.
Describe the characteristics of coliform bacteria and their significance in assessing water contamination.
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What is the temperature and time requirement for High Temperature Short Time (HTST) pasteurization?
What is the temperature and time requirement for High Temperature Short Time (HTST) pasteurization?
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What bacterial infection is most commonly associated with contaminated poultry?
What bacterial infection is most commonly associated with contaminated poultry?
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Explain the purpose of serial dilution in determining bacterial counts in food products.
Explain the purpose of serial dilution in determining bacterial counts in food products.
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How do fungi obtain their nutrients and what are saprotrophs?
How do fungi obtain their nutrients and what are saprotrophs?
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What are hyphae in fungi and what roles do they play?
What are hyphae in fungi and what roles do they play?
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What is thermal dimorphism in fungi?
What is thermal dimorphism in fungi?
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Study Notes
Lab 8: Disinfectants and Antibiotics
- Disinfectants: Agents used to kill vegetative cells on non-living surfaces.
- Antiseptics: Agents used to kill vegetative cells on living tissues.
- Synthetic antibiotics: Laboratory-made antibiotics.
- Semi-synthetic antibiotics: Modified versions of naturally produced antibiotics.
- Narrow-spectrum drugs: Preferable, target specific pathogens with minimal harm to normal microbiota.
- Broad-spectrum drugs: Used when the infection's cause is unknown, or other antibiotics are ineffective.
- Intrinsic resistance: Natural immunity to antibiotics.
- Acquired resistance: Immunity to antibiotics due to misuse or overuse.
- Susceptibility: The state of being influenced by an agent, in this context, the effect of an antibiotic on a microbe.
- Streptomyces: Gram-positive, saprophytic bacteria (feeding on decaying matter), spore-formers, found in soil, produce secondary metabolites that benefit interacting organisms.
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Antibiotic effectiveness testing:
- Filter Paper Disk Method/Agar Disk Diffusion Assay: Measures antibiotic effectiveness by observing zones of inhibition (areas lacking bacterial growth around antibiotic disks).
- Zephiron Chloride and Vesphene: Disinfectants effective against E. coli and S. aureus.
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Antibiotic susceptibility testing:
- Kirby-Bauer Method: Uses Mueller-Hinton agar to test multiple antibiotics on bacterial growth plates, producing results showing zones of inhibition around antibiotic disks.
- Findings: Not all antibiotics are equally effective against all bacteria; the presence of small colonies within inhibition zones indicates intrinsic or acquired resistance to those particular antibiotics, and the chart values allow for interpretation of susceptibility for each antibiotic.
- Real-world limitations of antibiotic/disinfectant testing: Results from agar plate tests may vary in real-world scenarios due to environmental factors not controlled in the lab setting.
- Factors to consider when selecting disinfectant: Cost, water solubility, short exposure time, long shelf life, and non-toxicity when purchasing a disinfectant.
- Misuse and overuse of antibiotics: Misuse involves using antibiotics for viral infections; Overuse involves incorrect dosage. Both contribute to acquired resistance.
Lab 9: Fecal Contamination and Food Safety
- Fecal Contamination: Presence of coliform bacteria (such as E. coli) in food.
- Coliform bacteria: Gram-negative, non-spore-forming bacteria that ferment lactose producing acid and gas.
- Fecal coliforms: High levels found in human/animal intestines, used as indicators of fecal contamination, rarely found growing in nature.
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Milk Pasteurization: Process to reduce microbial loads in milk and other food products to safe levels.
- High Temperature Short Time (HTST) pasteurization: 15 seconds at 71.7 °C; 16-21 days.
- Low Temperature Long Time (LTLT) pasteurization: 30 minutes at 63°C; Holding method.
- Ultra High Temperature (UHT) pasteurization: Sterilizes milk; 135-150°C, immediately chilled and packaged in airtight containers. Store at 4°C to prevent bacteria multiplication.
- Chicken Contamination: Salmonella is a common foodborne illness associated with contaminated poultry.
- Fruits and Vegetables Contamination: Contamination from soil/water during growth, processing, storage and preparation.
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Determining bacterial loads in food:
- Standard Plate Count: Uses serial dilutions of food samples, plated on media, and counting colony forming units (CFU), determining the number of bacteria in the original sample (CFU/milliliter) based on dilutions.
- Serial Dilution: Creates a series of progressively diluted solutions to measure small quantities of liquid without complex calculations. Results from multiple dilutions are averaged for the final CFU/ml value.
Lab 10: Fungi
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Fungi: Heterotrophic organisms requiring organic carbon, often saprotrophic (decomposers).
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Symbiotic Relationships: Interact with other species (algae, bacteria).
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Structure: Cell walls made of chitin; multicellular (molds), unicellular (yeasts); hyphae (long branching cellular structures); mycelium (invisible mat of hyphae).
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Hyphae types: Vegetative hyphae (grow along substrate); reproductive hyphae (produce spores).
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Thermal Dimorphism: Some fungi (e.g., molds) grow at room temperature, while others (e.g., yeasts) grow at body temperature (37°C).
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Opportunistic infections: Take advantage of weak or immunocompromised individuals.
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Mold Types:
- Zygomycetes: Form zygospores (sexual reproduction), sporangiospores (asexual reproduction); e.g., Rhizopus stolonifer.
- Ascomycetes: Form ascospores (sexual reproduction), conidiospores (asexual reproduction); e.g., Penicillium notatum, Aspergillus niger.
- Basidiomycetes: Form basidiospores (sexual reproduction); e.g., Mushrooms.
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Yeast: Saccharomyces cerevisiae (budding yeast).
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Description
This quiz covers key concepts related to disinfectants, antiseptics, and antibiotics. You'll explore various types of antibiotics, including narrow-spectrum and broad-spectrum drugs, as well as resistance mechanisms like intrinsic and acquired resistance. Test your understanding of how these agents affect microbes and their applications in medicine.
