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What is sterilization?
the killing or removal of all viable organisms (including endospore)
What is inhibition?
Effectively limiting microbial growth
What is decontamination?
The treatment of an object to make it safe to handle
What is disinfetion?
Directly targets the removal of all pathogens, not necessarily all microorganisms
What are the physical methods of antimicrobial control?
Heat, Radiation, Filter
What are the chemical methods of antimicrobial control?
- Used on external surfaces: sterilants, disinfectants, sanitizers, antiseptics
- Used internally: antibiotics, anivirals, antifungals
What is the most widely used method of controlling microbial growth?
What do high temperatures do to macromolecules?
High temperatures denature macromolecules
What is the decimal reduction time?
Amount of time required to reduce viability tenfold is called the decimal reductio time (D)
What is the thermal death time?
Thermal death time is the time needed to jill all cells at a given temperature
What is thermal death time dependent on?
Thermal death time is dependent on the population size of the microorganism tested. Need to standardize the starting number of ells to be able to compare the sensitivity of different microorganisms
What is the autoclave?
- The autoclave is a sealed device that uses stame under pressure:
- Allows temperature of water to get above 100°C
- At 15psi, steam reach 121°C, sterilization is achieved in 10-15 min
- The object being sterilized wil reach this temperature. Not suitable for heat-sensitive object/liquid
- Not the pressure that kills things, but the high temperatures
What is pasteurization?
- Pasteurization is the process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids
- Does not kill all organisms, it is not a method of sterilization
What pathogens does pasteurization reduce significantly?
- Salmonella enterica
- E. Coli O157:H7
What is flash pasteurization?
72°C for 15 seconds
What is bulk pasteurization?
65°C for 30 mins
How is UV used for antimicrobial control?
- UV has sufficient energy to cause modifications and breaks in DNA, which inhibit replication, transcription and cause microorganism death
- UV is useful for decontamination of surfaces
- Cannot penetrate solid, opaque, or light-absorbing surfaces
What is ionizing radiation?
- Electromagnetic radiation that produce ions and other reative molecules
- Generates electrons, hydroxyl radicals, and hydride radicals
- Amount of energy required to reduce viability tenfold is analogous to D value
What are some sources of radiation?
- Cathode ray tubes (electrons)
- radioactive nuclides
What is radiation used for?
Radiation is used for sterilization in the medical field and food industry
Why is filter sterilization used?
- Filtration avoids the use of heat on sensitive liquids and gases
- Pores of filter are too small for organisms to pass through
- Pores allow liquid or gas to pass through
What are depth filters?
- Fibrous sheet or mat made from an array of fiber (paper or glass)
- Use to sterilize liquid, air
- HEPA filters
What are membrane filters?
- Function more like a sleve
- A type of membrane filter is the nucleation track (nucleopore) filter
- Filtration speed can be increased by syringe, pump, or vacuum
What are the 3 classifications of antimicrobial agents?
What is bacteriostatic?
Inhibit growth of microorganism
What is bacteriodical?
What is bacteriolytic?
Kill microorganism by inducing lysis
What is minimum inhibitory concentration (MIC)?
- The smallest amount of an agend needed to inhibit growth of a microorganism
- Varies with the organism used, inoculum size, temp, pH, etc
What is Minimym lethal concentration (MLC)?
The lowest concentration of an agent that kills a test organism
What is minimym bacteriodical concentration (MBC)?
The lowest concentration of an agent that kills a test bacterium
What is disc diffusion assay?
- Antimicrobial agent added to filter paper disc
- MIC is reached at some distance
- Zone of inhibition- area of no growth around disc
What is the zone of inhibition?
Area of no growth around disc
What are the two classifications of chemical antimicrobial agents?
- Products used to control microorganisms in commerical and industrial applications
- Products designed to prevent growht of human pathodens in inanimate environments and on external body surfaces
What are some examples of products used to control microorganisms in commerical and industrial applications?
- Chemicals in foods
- Air-conditioning cooling towers
- Textile and paper products
- Fuel tanks
What are some examples of products designed to prevent growth of human pathogens in inanimate environments and on external body surface?
What are sterilants?
- Destroy all forms of microorganism, including endospore
- COLD STERILIZATION
What are disinfectants/Sanitizers?
- Applied to nonliving obects or surface (can be toxid for animals/humans)
- Does not kill endospore
What are antiseptics?
- Applied to the surface of living tissues or skin (must not be toxic for anials/humans)
- Does not kill endospore
What are antimicrobial drugs?
- Antibiotics, antitifungals, antivirals: applied outside or inside the body of animals/humans (must not be toxic for animals/humans)
- Does not kill endospore
How do phenol/phenolics act as antimicrobial agnets?
Disinfectant/antiseptic- distrupt cytoplasmic membrane, protein denaturant (high concentration)
How do alcohols act as an antimicrobial agent?
Disinfectant/Antiseptic- Lipid solvent and protein denaturants
How do halogens act as antimicrobial agents?
Disinfectant/Antiseptic/Sterilant- Chlorine (S/D): oxidizing agent- Iodine (A): iodinate tyrosine residues in protein, oxidizing agent
How do heavy metals act as antimicrobial agents?
Disinfectant- modify proteins, interact ith RNA, DNA...severalo different mechanism
How do quaternary ammonium act as antimicrobial agent?
Interact with phospholipids of cytoplasmic membrane
How do alkylating agents act as antimicrobial agnets?
Disinfectant/Sterilant- Ethylene gas, formaldehyde, glutaraldehyde. Very toxic
How are antimicrobial drugs classified?
- Molecular structure
- Mechanism of action
- Spectrum of antimicrobial activity
What are the properties of a good antimicrobial drug?
- NO side effects, must be far more toxic for bacteria than mammalian cells
- Broad spectrum of activity to faciitate rapid medical intervention
- Appropriate bioavailability and pharmacokinetic (must reach the site of infection)
- Low cost to develop and manufacture
What is selective toxicity?
The ability to inhibit or kill a pathogen without affecting the host
What is salvarsan?
One of the first antimicrobial drugs, use to treat syphilis (treponema pallidum)
What are growth factor analogs?
- Structurally similar to growth factors but do not function in the cell
- Analogs similar to vitamins, amino acids, and other compounds
What are Sulfa drugs?
- Discovered by Gerhard Domagk in the 1930s
- Sulfanilamide is an analogue of p-aminobenzoid acid
What is isoniazid?
- A growth analog effective only against Mycobacterium
- Interferes wwith synthesis of mycolic acid
What are Nucleic acid base analogs?
- Have been formed by the addition of bromine or fluorine
- Stop DNA replication, translation
What are quiolones?
Antibacterial compounds that interfere with DNA gyrase
What are antibiotics?
Antibiotics are antimicrobial agents naturally produced by a variety of bacteria and fungi to inhibit or kill other microoranisms
How much of known antibiotics are clinically useful?
What are semisynthetic antibiotics?
Antibiotics that are modified to enhance efficacy
Why do gram-positive and gram-negative bacteria very in their sensitivity to antibiotics?
The cell wall is a major factor
What are beta-Lactam antibiotics?
- One of the most important groups of antibiotics of all time
- Include penicillins, cephalosporins, and cephamycins
- Btericidal, bacteriolytic
What are Penicillins?
- Discovered by Alexander Flemin, isolated from Penicillium chrysogenum (mold)
- Primarily effective against gram-positive bacteria
- Some synthetic forms are effetive against some gram-negatie bacteria
- Inhibit cell wall synthesis
What are cephalosporins?
- Produced by funcus Cephalosporium
- Same mode of action as the penicillins
- Commonly used to treat conorrhea (Neisseria gonorrhea)
What are Aminoglycosides?
- Kanamycin, neomycin, amikacin, streptomycin
- Target 30S subunit of ribosome, cause misreading of mRNA
What is chloramphenicol?
- Bind to 23S rRNA and block peptide elongation
What are macrolides?
- Broad-spectrum antibiotic that targets the 50S subunit of ribosome, block protein synthesis
What are tetracyclines?
- Broad-spectrum inhibition of protein synthesis, bacteriostatic
- Inhibits functioning of 30S ribosomal subunit, block protein synthesis
What is Daptomycin?
- Also produced by Streptomyces
- Used to treat gram-positive bacterial infections
- Forms pores in cytoplasmic membrane
What is Platensimycin?
- New structural calss of antibiotic
- Broad-spectrum, effective agains MRSA and vacomycin-resistant enterococci
What is antimicrobial drug resistance
The acquired ability of a microorganism to resist the effects of a chemotherapeutic agent to which it is normally sensitive
What is producer tolerance?
- Lack target sites (no peptidoglycan)
- Modify target sites
- Lack of uptake mechanism
What is resistance mechanism?
- Destroy or modify the antibiotic (beta-lactamase)
- Modify the target site
- Modify uptake mechanism
- Efflux pumps: reduce intracellular concentration
How does one acquire resistance?
- 1. Mutation of target sites
- 2. Plasmic acquisition
What predates the antibiotic era?
Evidence indicates that R plasmids predate the antibiotic era (antibiotics come from nature)
Can R plasmids be transfered between species?
R plasmids can be transferred between bacteria of the same species or related species
What is an example of a pathogen that has developed resistance to all known antimicrobial agents?
Methicillin-resistant S. Aureus (MRSA)
How can resistance be minimized?
Resistance can be minimized by using antibiotics correctly and only when needed (reduce selection)
How do antiviral drugs work?
- Most antiviral drugs also target host structures, resutling in toxicity (viruses use host cell machinery)
- Risk to the host may not justify the use of antiviral
Are antibiotics effective on viruses?
What are the most successrful and commonly used antivirals?
Most successful and commonly used antivirals are the nucleoside analgs (eg AZT): block reverse transcriptas and production of viral DNA (RNA viruses)
What are protease inhibitors?
Inhibit the processing of large viral proteins into individual components
What are fusion inhibitors?
Prevent viruses from successfully fusing with the host cell
Why do fungi pose special problems for chemotherapy?
Fungi pose special problems for chemotherapy because they are eukaryotic: much of the cellular machinery is the same as that of animals and humans
What are a few drugs that target unique metabolic processes not found in mammals?
- Ergosterol synthesis (nystatin, fluconazole)
- Cell wall synthesis (inhibitor of chitin synthesis)
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