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68 Cards in this Set
- Front
- Back
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What do antibiotics have in common?
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1. Usually selective
2. Targets something a mircobe has that the host cell does not have 3. Produced by bacteria and molds 4. Primarily target bacteria 5. Broad spectrum (target a wide variety of bacteria) 6. Low toxicity index 7. High therapuetic index 8. Microbes tend to become resistant to all antibiotics |
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Disease and scientific name of C diff
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Clostridium difficile
Disease: Antibiotic associated colitis, pseudomembranous colitis Scientific name: Clostridium difficile |
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Classification of C diff
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Domain: Bacteria
Division: Firmicute Genus: Clostridium Species: difficile |
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Cell structure and morphology of C diff
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Cell type: Prokarya
Shape: Bacillus Arrangement: Solitary and chain Glycocalyx: Capsule Cell wall: Gram positive Chemical composition: peptidoglycan 1 periplasmic space Appendages: Motile- Peritrichious (Bacilli with many flagella all over their surface) Fimbria Organelles: Cell membrane, Plasmids, Endospores, 70s ribosomes, Nucleoid Nucleoid- Chromosome number and shape: 1 circular chromosome |
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Reproduction of C diff
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Bianary fusion
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Metabolism of C diff
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Nutritional type: Chemoheterotroph
Carbon source: Organic compounds Energy source: Organic compounds |
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Physical requirements of C diff
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Temperature: Mesophile
Oxygen: Obligate anaerobe pH: Neutrophile |
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Nutritional requirements for bacterial growth
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A source of energy (light or chemicals)
A source of carbon (CO2 or organic molecules) A source of nitrogen (nitrate via salt for amino acids =purines and pyrimidines -A-G, C-T) A source of sulfur (for some amino acids and coenzymes) Vitamins (or coenzymes) A source of phosphorous (phosphates) (for ATP and nucleic acids) Minerals (e.g. Na, Ca, include trace element metals for cofactors e.g. zinc, Cu) Water (to keep molecules in solution, hydrolysis) |
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Photoautotroph (phototroph)
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Source of carbon: acquires carbon source from carbon dioxide
Source of energy: Light Examples of organisms: Plants/algae, cyanobacteria, prochlorophytes, green and purple sulfur bacteria |
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Photoheterotroph
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Source of carbon: Acquires carbon source from organic compounds
Source of energy: Light Examples of organisms: Archea, green and purple non-sulfur bacteria |
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Obligate aerobes
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O2 MUST be present
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Obligate anaerobes
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Cannot live in the presence of O2
No superoxide dismutase or catalase |
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Microaerobes
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Can tolerate a small amount of O2
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Facultative anaerobes
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Can live with or without O2
Pasteur point-Oxygen level at which an organism switches from aerobic to anaerobic metabolism |
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**Pasteur point
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Oxygen level at which an organism switches from aerobic to anaerobic metabolism
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Neutrophile
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Optimum pH is between 6.5 and 7.5, most organisms
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Acidophiles
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Optimum pH is near 3
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Alkalinophile
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Optimum pH is near 12
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Halophiles
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Requires an environment with high concentrations of salt to stabilize membranes
Don’t dehydrate- have concentrate compatible solutes that don’t interfere with their metabolism e.g. K+ and amino acids Some have water binding proteins |
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Mesophiles
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Temp range: 10* --> 47*
Optimum: 37* Responsible for human disease causing microbes (because its optimum is human body temp) |
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Psychrophile
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Temp range: 0*--> 20*
Optimum: 15* Responsible for refrigerator spoilage and plant disease |
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Thermophile
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Temp range: >45* <80*
Few human diseases, compost piles |
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Hyperthermophile
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Temp range: >80*
Includes extremophiles (<0*C) Extreme temperatures affect bacterial enzymes and structural proteins (Archea have proteins that can survive these extremes) |
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Psychrotolerant
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Temp range: 20* --> 40*
A mesophile that can grow at 0*, disease and spoilage |
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Media type- Synthetic
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Chemically defined
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Media type- Non-synthetic
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Not chemically defined
Infusions and extracts Provide nutritional and physical requirements of common bacteria |
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Media type- Enriched
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Provides additional (additives) and or conditions (to promote growth) for fastidious bacteria
e.g. TSA and blood agar |
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Media type-Selective
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Prevents growth of one type of bacteria without inhibiting the growth of another
e.g. EMB, Columbia CNA, SM 110(only one that is only selective) and mannitol salt agars |
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Media type-Differential
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The way the organism grows on or its effects of a media helps tell the bacteria apart
Forms halo around bacteria colonies or turns bacteria different colors e.g. EMB, blood agar, ChromAgar (only differential), MSA, Columbia CNA |
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Media type- Liquid
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Good for propagating large numbers of organisms as well as for testing
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Media type- solid
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Shows surface growth patterns; convenient for “pure culturing” organisms
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Salvarsan
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Developed to treat trypanosomes, causative agent of African sleeping sickness
Ultimately used to treat SYPHILIS |
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Alexander Fleming
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Discovered penicillin (the first antibiotic)
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Ernst Chain and Howard Florey
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Isolated and purified penicillin
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Types of selective agents -Synthetic drugs
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Types of selective agents- Antibiotics
Produced by living cells |
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Turbidity Method
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NOT produced by living cells, produced in a laboratory
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Method of determining bacterial growth
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Increased cloudiness that parallels the increase in population (mass)
An estimate of population growth Includes living and dead cells Most convenient technique (Benefit- HIGH CONVENIENCE) Low sensitivity |
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Plate count (3.14)
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Method of determining bacterial growth
1 ml of bacteria is transferred to an agar tube and a plate pour is generated (May include serial dilution of the bacterial) Determines living cells only (not accurate if bacteria clump) High sensitivity (Benefit- HIGH SENSITIVITY) Medium convenience (about 1 day) |
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Generation time
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The time it takes to double the number of viable cells
Temperature correlates to Generation Time in bacteria: At optimum temperature enzymes are most efficient, bacterial cells are able to multiply in the least amount of time. Escherichia, Staphyloccocus, & Salmonella generation time is about 20 minutes |
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What is Thermal Death Point? (TDP)
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A measure of the lowest temperature at which microbes are killed in a 10 minute period of time
(Based on a 24 hour culture in neutral pH) |
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What is Thermal Death Time? (TDT)
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Shortest time it takes to kill all microbes at a given temperature
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Phenol coefficient
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Dilution of Phenolic that kills test bacteria in 10 min/ Dilution of Phenol that has same effect
1:1000 dilution of Phenolic coefficient/ 1:100 dilution of Phenol 1000/100=10 Phenolic is better if Phenol coefficient is over 1 *The numerical expression of the effectiveness of a disinfectant when the disinfectant is compared with phenol |
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Sensitivity testing
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Sensitivity disk: Look for a clear area around paper disks soaked in a given agent- where bacterial growth has been inhibited
Can help determines the effectiveness of an antibiotic or any agent claiming to reduce or inhibit bacteria Staphylococcus aureus is the usual tested organism Can’t tell if the organisms are dead or alive Various agents diffuse through agar at different rates |
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Dilution test
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Can help determines the effectiveness of an antibiotic or any agent claiming to reduce or inhibit bacteria
Bacteria are added to tubes with different dilutions of a chemical agent and then incubated This method can be used to identify agents that prevent growth at the greatest dilution Used in pasteurization to determine the level of contamination, to get the numbers down so that when it comes time to count there is a reasonable number MIC and MBC are part of dilution test |
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Sterilization
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The elimination of all microbes
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Disinfectant
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Used to reduce the number of microbes on INANIMATE objects
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Antiseptic
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Used to reduce the number of microbes on ANIMATE objects
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Beta hemolysis
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Have enzymes that break down red blood cells and hemoglobin (cause clear halo where red blood cells are destroyed)
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Alpha hemolysis
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Have enzymes that break down red blood cells and hemoglobin (causes greenish tint halo from the pigment biliverdin, a product of hemoglobin hydrolysis)
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Why can disinfectants and antiseptics be used internally?
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They are not selective so they can harm our cells
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When is a chemical agent considered selective
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When the agent can attack bacteria without causing damage to our cells
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Are antibiotics typically selective or non selective?
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Selective
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What organism do antibiotics primarily target?
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Bacteria
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What was the first antibiotic discovered?
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Penicillin
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Who discovered this antibiotic?
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Alexander Fleming
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Why do we do antimicrobic sensitivity testing?
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To reduce the risk of resistance, to find which antibiotic is most effective against specific bacteria
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Decontaminate
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Sterilize PLUS removes microbial toxins
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Dry heat
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Sterilizes (oven, incineration)
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Moist heat: Boiling
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Sterilizes if spores are not present (if spores are present= Tyndallization)
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Tyndallization
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The intermittent boiling and cooling to kill endospores
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Moist heat: Autoclave
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Results in temperatures above boiling, good penetration, the most practical and dependable (pressure cooker)
Replaced tyndallization- more effective Most practical in a laboratory situation |
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Moist heat: Pasteurization
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Does NOT sterilize, eliminates pathogens from food products (beverages)
Media that are high concentrated or contain fats and sweeteners require higher temperatures (skim milk vs. cream) Controlled, intermittent heat below boiling |
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Bactericide
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Inhibits bacteria
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Bactericide
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Kills bacteria
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Viricide
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Kills viruses
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Fungicide
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Kills fungi
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Germicide
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Kills microbes
All inclusive (broad) |
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Sporicide
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Destroys bacterial or fungal spores
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