The audio cut off with about 15-20 minutes left in the lecture. But the first part can be heard here.
- SLIDE 1
- Microbial regulation of organisms that are pathogenic
- Ancient civilizations filtered water and preserved the dead using salts and oils that microorganisms don’t like.
- Epidemic – wide spread disease in a community
- We are interested in regulating pathogens that can cause harm to human health.
- Romans figured out that burning dead bodies kept disease down. Also storage of water in copper and silver kept microbe population down.
- • Slide 2
- Decontamination methods – methods employed that will remove or destroy microorganisms on a surface (including water)
- Physical decontamination method: temp extremes and radiation. mechanical methods: filtration
- Results: sterilization or disinfection (removes all vegetative microorganism)
- Chemical methods
- liquids gases and solids
- results of method: sterilization (kills living and non-living (non-living → like endospores) organisms), disinfection (removes all vegetative microorganism) can only be applied to nonliving surfaces , antisepsis (this can be applied to our skin as it will not kill everything) is usually targeted toward specific microorganisms.
- aqueous chemical decontaminant. Mix of solid or gas with water. If you mix it with a alcohol it is called tincture.
- • Slide 3
- Bacterial endospores (very resistant)
- Two phase life cycle: vegetative (metabolically active and growing) and endospore (keeps them alive a long time and helps them survive in extreme conditions)
- Examples: Bacillus, clostridum, and thermoactinomyces
- How effective is this method of survival? → very effective, these organisms can be considered essentially immortal.
- Layers of sediment is a varve which is an annually deposited layer of sediment. Microorganims will live in these layers and then be able to come back to life once they get the appropriate nutrients.
- • Slide 4
- Antimicrobial agents (physical, mechanical, chemical) fall into two categories:
- Microbicidal agents [“cide”=to kill]
- Bacteriocide, fungacide, virucide and sporicide (could be considered a sterilant)
- Microbistatic agents [-static or –stasis=to prevent growth]
- Used on living tissue, gives our body enough time to get the immune system working
- Bacteriostatic, and fungastatic
- • Slide 5
- The mode of action of antimicrobial agents. More specific=less effective --- less specific=more effective
- Cell wall target – gram positive . . . specific.
- Cell membrane target – this is a less specific way of going about it = more effective.
- Detergents (cell membrane target) - called surfactant. A surfactant is a molecule with hydrophilic and hydrophobic ends. Phospholipids bylayer in cell membrane have a hydrophilic and hydrophobic end as well. The surfactants make their way into the phospholipids bylayer and destabilizes the cell.
- • Slide 6
- The mode of action of antimicrobial agents
- Nucleic acid and protein synthesis prevention
- UV radiation – targets pyrimidine nucleic acids (RNA, DNA). Has greatest effect on DNA. Pyrimidines includes cytosine and thymine. UV radiation “loves” these two nucleotides. For the radiation to occur the pyrimidine bases HAVE to be next to each other. Once hit with UV radiation the thymines will bond to each other – called thymine dimer. This prevents replication which brings about the death of the cell.
- Antibiotic binds to ribosome. Example: Chloramphenicol (an antibiotic) binds to ribosomes in such a way that protein synthesis is inhibited. TRNA cant add amino acids to growing protein strand. Doesn’t inhibit growth of protozoans and fungus.
- • Slide 7
- The mode of action of antimicrobial agents
- Hexokinase helps attach glucose and phosphate
- Alteration in protein conformation
- If pH is altered protein will unfold – called denaturing
- • Slide 8
- Temperature as controller
- Two physical states of heat used
- Moist heat – ex. heat created from boiling water/steam. Keeps some organisms from stabilizing, this is the best way to do mass sterilization.
- Dry heat – ex. Flames used to disinfect loops in lab.
- • Slide 9
- C. botulinum – interferes with nerve connection for muscle contraction
- Practical concerns: thermal death time (TDT)
- Food canning process
- Prevents microbial contamination including spore forming C. botulinum: botulism
- TDT for low-acid foods is 121C for 30 minutes
- • Slide 10
- Sterilization with seen under pressure
- At sea level pressure 15psi will boil water at 100C
- To kill all MOs, pressure at 30 psi and 121C (standard autoclave conditions)
- As pressure is increased temperature is increased
No comments:
Post a Comment