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Microbio Lab exam 3
| Question | Answer |
|---|---|
| antibiotics | chemical agents produced by living organisms either killing or inhibiting growth of other organisms |
| chemotherapeutic agents | antibiotics belong to this group of antimicrobial agents that affect growth. used in medicine. some made chemically (sulfa) |
| antibiotics are different from antiseptics: | antibiotics effective in very small amounts and specific for 1 group/organism |
| what a Dr needs to know | identity of infecting organism, the kind of chemotherapeutic agent to use in controlling the infection, Kirby-bauer test |
| kirby-bauer method | antibiotic sensitivity testing effectiveness of the bacteria culture by measuring zone of inhibition. The laboratory test used to determine the most effective antibiotic for a given infection |
| what can be determined about the organism in Kirby-bauer test | if its resistant, intermediate, or sensitive to the antibiotic used |
| variation in kirby-bauer test can be caused by differences in | volume of medium in dish, medium composition, etc. but all must be controlled |
| standard medium for Kirby-bauer test | mueller-hinton agar |
| standard strains to control inhibitory zone diameter in k-b test | s. aureus and E.coli |
| broth cultures used in Antimicrobial Susceptibility Testing | s. aureus, E.coli, pseudomonas aeruginosa, saccharomyces cerevisae |
| antiseptic (alcohol, hydrogen peroxide) | agents killing/inhibiting pathogen growth allowing ur body defense to finish the job. used on skin and animate (living) objects |
| disinfectants (bleach, lysol) | used only on inanimate objects killing vegetative cells not bacteria endospores |
| sanititzers | Chemical agents widely used in the food and restaurant industries. kills a predetermined # (99.99%) of vegetative cells on all cleaned surface |
| phenol coeffiecient test | compare effectiveness of disinfectants to phenol |
| use dilution test | Measures how effective a disinfectant is under actual-use conditions |
| Why is there sometimes a ring of increased growth seen at the rim of the inhibitory zone around a disinfectant, antiseptic or sanitizing agent? | some agents cause mutations/resisting colonies arise in the inhibitory zone (grow where they were supposed to die) with prolonged incubation |
| broth cultures used in Action of Disinfectants and Antiseptics | s. aureus, E. coli, Bacillus subtilis, saccharomyces cerevisiae |
| lipids | large, hydrophobic molecules that need lipase to be broken down first |
| lipase | exoenzyme that breaks down lipids so they can enter the cell |
| What are fatty acids used for in the cell? | Energy or as building blocks for biosynthesis |
| spirit blue agar tests | organisms ability to break down and use lipids, only happens if an organism makes lipase. color is caused by release of fatty acids and bacteria take up dye |
| positive lipid hydrolysis for spirit blue must also | have transparent zone around bacteria |
| which bacteria is lipid + | staphylococcus aureus |
| which bacteria is lipid - | proteus mirabilis |
| starch | polysaccharide |
| oxidase and catalase | enzymes related to an organisms ability to utilize oxygen |
| BBL dry slide | The instrument used to assess for the production of oxidase by a bacterial specimen |
| how much cells is needed in order to test for oxidase production. | a massive amount |
| oxidase | An enzyme that involves the transfer of electrons in the cytochrome chain. |
| How do you know a bacterium is oxidase-positive? | The cells turn dark purple or almost black along the streak. No change or light yellow = oxidase-negative |
| catalase | degrades hydrogen peroxide (H2O2) formed during cellular metabolism into oxygen (O2) and water (H2O). usually in aerobic organisms. |
| anaerobic | lack catalase, can't break down hydrogen peroxide, it builds up and becomes toxic for cell. |
| aerobic | use O2 as final electron and hydrogen acceptor, produce hydrogen peroxide naturally by cells metabolism and catalase breaks it down |
| what shows that catalase is present | bubbles |
| catalase postitive bacteria | staphylococcus and bacillus |
| catalase - bacteria | streptococcus and Clostridium |
| oxidase positive | pseudomonas |
| oxidase negative | E. coli |
Created by:
mahak
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