11719816
Description
Flashcards by Candice Young, updated more than 1 year ago
|
Created by Candice Young
over 6 years ago
|
|
| Question | Answer |
| Physical methods for microbial growth control | --> temperature --> temperature and pressure --> UV/etc --> filters |
| Chemical methods for microbial growth control | --> disinfectants --> antiseptics --> antibiotics |
| sterilization | REMOVAL of ALL living cells, spores, and viruses on an object the only method effective against bacterial endospores! |
| disinfection | REMOVAL of PATHOGENS from INANIMATE surfaces chemical agents: 70% EtOH, bleach, strong ionic detergents do not put any of these in our body!! |
| antiseptis | REMOVAL of PATHOGENS from surface of LIVING TISSUE (ie. skin) chemical agents: 70% EtOH wipe, hydrogen peroxide, Neosporin, iodine containing compounds |
| sanitation | REDUCING microbial population to safe levels |
| autoclave | used for heat/pressure sterilization --> steam achieves high T, rapidly kills everything --> takes about 20-40 minutes for required T to be reached by required time |
| Pasteurization | precisely controlled heat REDUCES microbial load, pathogen spread prevented --> reduced spoilage, longer shelf life --> does NOT kill all bacteria, just pathogens |
| Flash Pasteurization | liquids flowing through heat exchanger raised to 71ºC for 15 sec --> rapid cooling --> milk has refrigerated shelf life of ~2 weeks after treatment |
| Ultra-high temperature Pasteurization (UHT) | liquid is heated to 135ºC for 1-2 sec (using continuous flow heat exchangers) --> also kills endospores --> products with an unrefrigerated shelf life of 6-9 months, if unopened |
| What reduces the effectiveness of disinfectants/antiseptics? | Organic material (dirt, biofilm, etc) can bind to/react with these to reduce their effectiveness |
| Antimicrobial drugs/Antibiotics | chemicals used in humans that kill or inhibit the growth of microorganisms --> can be natural or synthetic --> must have SELECTIVE TOXICITY so the host is not harmed |
| bacteriostatic growth | growth is inhibited, but bacteria are NOT killed OD/direct visual count and viable cell count stay constant inhibitory molecules are at reversible binding equilibrium with a cellular protein, must keep agent at right concentration to constantly prevent growth!! |
| bactericidal growth | cells are killed, but not lysed OD/direct visual count constant, viable cell count decrease some irreversible damage to a protein or other component --> if agent is washed out/decreased, bacteria will still be dead |
| bacteriolytic growth | cells are killed and lysed OD/direct visual count decrease, viable cell count decrease usually do damage to the cell wall (PG) or cytoplasmic membrane --> if agent is washed out/decreased, bacteria will still be dead |
| Minimal Inhibitory Concentration (MIC) | lowest concentration of an agent that completely inhibits growth measured by a series of dilutions within culture medium, turbidity occurs in tubes with concentrations below the MIC compares the effects of different agents (as long as everything is standardized) |
| Streptomyces antibiotic production | --> production regulated by quorum sensing (G+ peptide system) --> occurs around time of sporulation, triggered by nutrient deprivation --> gives a competitive advantage against soil microbes --> resistant to own antibiotics |
| spectrum of action | tells us which bacteria are affected narrow spectrum: very specific to harming only a certain species (ie. Isoniazid) broad spectrum : affects many types of microbes (Tetracycline, Sulfonamides, Cephalosporins, Quinolones) |
| Mechanism of Action (MOA) | tells us the specific molecular target that is bound/the process that is inhibited by the drug typical targets: cell wall, cytoplasmic membrane, DNA synthesis, RNA synthesis (tx), protein synthesis (tl), metabolism |
| Examples of drugs that target well studied areas | Cell wall synthesis: penicillins Folic acid metabolism: sulfonamides Protein synthesis (30S): Tetracycline DNA gyrase: Cycloflaxin |
| Target: cell wall biosynthesis | MOA: B-lactam ring of Penicillin is suicide inhibitor of PBPs (perform transpeptidation in PG synthesis) --> BACTERIOLYTIC Spectrum: most effective agains G+ bacteria since they don't always cross OM -can have altered R groups: molecules more acid-stable, or β-lactamase resistant, or better at crossing OM of G- cells |
| how B-lactam ring binds to PBP | B-lactam ring is cysteine + valine, resembles D-ala-D-ala piece of PG --> PBP transpeptidase domain binds to this COVALENTLY, enzyme is inactivated peptide x-linking during PG synthesis blocked |
| different steps of cell wall biosynthesis to be blocked | D-Ala ligase - Cycloserine bactoprenol recycling - bacitracin transpeptidation - Penicillins, cephalosporins (D-Ala mimics) and Vancomycin (binds D-Ala-D-Ala) |
| target: DNA supercoiling/replication/integrity | MOA: Quinolones interact w/ bacterial DNA gyrase --> stabilize covalent intermediate between enzyme and DNA --> gyrase-DNA complex is roadblock for replication + creates broken ends --> irreversible damage to DNA, BACTERICIDAL Spectrum: both G+ and G- Ex: Ciprofloxacin, more soluble in fluorinated form |
| DNA gyrase | a topoisomerase II, makes ds breaks and introduces negative supercoiling found in ALL bacteria quinolone stabilizes covalent intermediate between DNA and gyrase --> blocks DNA replication |
| target: Metabolism | MOA: Growth factor analog, resembles PABA and blocks synthesis of folic acid; binds reversibly --> BACTERIOSTATIC Spectrum: G+ and G- bacteria Ex: Sulfanilamide |
| folic acid and PABA | Cells need folic acid as cofactor for single-carbon reduction rxns (used in nucleotide synthesis), and can't import it through bacterial cell membrane --> synthesize it from PABA, pteridine, and glutamic acid Sulfanilamide binds enzyme and attaches to pteridine, acts as a competitive inhibitor |
| target: protein synthesis | MOA: binds reversibly to 30S subunit of ribosome at A site --> prevents charged tRNA from entering --> BACTERIOSTATIC Spectrum: G+ and G- Ex: Tetracycline |
| Napthacene ring system and protein synthesis | Binds reversibly to 30S subunit of ribosome at the A site Tetracycline resembles this with two different R groups --> spectrum of activity (slightly diff drugs bind ribosomes of diff bacteria + diff drugs can taken up into cytoplasm of diffbacteria) |
| all steps of protein synthesis and corresponding drugs | premature peptide termination: Puromycin (mimics tRNA) peptide bond formation: Chloramphenicol (binds to 50s RNA) movement along mRNA: Erythromycin (binds to 50S rRNA) incoming tRNA: Tetracycline (binds to A site) mRNA reading accurately: Streptomycin (changes shape of 16S RNA) |
| antibiotic resistance mechanisms | 1) Slightly alter the target so that the drug no longer binds (EX: point mutation in rpsL for protein S12) 2) Modify the antibiotic so that it no longer binds the target (EX: nptI phosphorylates kanamycin, cat acetylates chloramphenicol, B-lactamases cleave B-lactam ring) 3) Pump the drug out of the cell (EX: tatA catalyzes exchange of tetracycline out for protein in) |
| Triclosan | thought to be non-specific, disrupting membrane structure/function used in toothpaste, soaps, scrubs low water solubility but can be used in high concentrations in hydrophobic substances |
| Triclosan resistance: experimental methods | perform genetic selections to identify mutant genes: make a genomic library from each resistant mutant --> select for plasmids that would confer increased resistance on WT strain |
| results of Triclosan experiments | resistant mutants had pt. mutations --> a.a. subs in FabI (carrier protein reductase ENR involved in fatty acid (FA) biosynthesis that makes new cell membranes) MOA: Triclosan binds active site of FabI --> blocks FA biosynthesis --> arrests growth at LOW concentrations (0.1-20 μg/ml) |
| Problems with Triclosan today | Triclosan is used at HIGH 2-20 mg/ml conc. in products and toothpaste + it’s a stable compound --> it’s accumulating in the environment + could disrupt the endocrine systems of fish and mammals + *some bacteria could become resistant by upregulating the expression of efflux pumps* |
| Triclosan effect on efflux pumps | efflux pumps that have relaxed specificity could help bacteria pump out OTHER antimicrobials used to treat disease --> really bad |
Want to create your own Flashcards for free with GoConqr? Learn more.