Thẻ ghi nhớ: 2003MSC EOT General Chapters

Sterilization

Treatment of an object to ensure destruction of all living microbes, spores, and viruses

Microbicidals

Agents that kill microbes; also called germicidals.

Bactericidals

Agents that specifically target and kill bacteria.

Fungicidals

Agents that specifically target and kill fungi.

Commercial sterilization

The process of killing all pathogens in a product, particularly in the food supply

reduces the numbers of pathogens or discourages their growth

Sanitization

Bacteriostatics

Agents that discourage the growth of bacterial species.

Microbiostatic

Agents, such as disinfectants and antiseptics, that inhibit growth of all microbes.

Fungistatics

Agents that discourage the growth of fungal species.

Microbial growth control agents

exert their effect by targeting either cellular structures or interfering with metabolic activities

The bacterial cell envelope

A variety of agents target the cell wall; a damaged or broken structure leads to cell lysis (e.g. Phospholipids and cell membrane proteins)

Proteins and DNA

Denaturation of proteins, especially enzymes, inhibit cell function; disruption of DNA function inhibits cell growth and division

Elevated temperature is a common physical control method

At temperatures above the growth range: Proteins and nucleic acids are destroyed and Water is removed.

thermal death time/ Death point

•Each microbial species has a thermal death time for a given temperature.

Dry heat

inceration uses directr flame, hot air ovens do not penetrate easily but long term exposure can be used to sterilise, 160ºC for 2 hours will sterilize most objects.

Moist heat exposure

is faster and effective at lower tempuratures then dry heat, It kills microbes by denaturing their proteins.

Moist heat procedures

boiling water doesn't kill all spores or inactivate viruses.

Pressurized steam is used in autoclave as it is more dependable

Autoclave procedures

Pressure of 15 psi at 121ºC for 15-30 minutes, depending on the object being sterilized, will kill bacteria.

Used in hospitals to sterilize linens and tools.

Used in the lab to sterilize liquids and glassware.

Pasteurization

is moist heat sterilization. reduces bacterial populations in food and drink. Three methods: Holding/batch method, Flash pasteurization, Ultra-high-temperature sterilization.

Cold tempurature control methods

cold tempuratures slow microbial growth, 5ºC retards metabolic activity not kill them. freezing below 0ºC inhibits metabolism and growth can kill with ice crystals penetrating cells.

filtration membrane

traps microorganisms, organisms above a certain size threshold are trapped in the pores, can be used for liquid or air (HEPA filter)

ultraviolet light Irradiation control

exposure causes thymine molecules to link together in DNA, produces errors in protein synthesis and impairment of chromosome replication

ionizing irradiation control

x-rays and gamma rays force electrons out of microbial molecules, affects cell metabolism and physiology. can be used on food

Lyophilization food preservation

freeze drying is food frozen with liquid nitrogen then subjected to a vacuum pump to draw off water.

drying food preservation

desiccation, removes the water necessary for microbes

Salting Food Preservation

causes water to diffuse out of organisms by osmosis, causing dehydration and death, good for high sugar but susceptible to fungal contamination

Chemical control

medicinal chemicals came widespread in 1800's rarely achieve sterilization but do disinfect

Antiseptics chemical control

used to destroy pathogens on living tissue, critical to surgical settings, preventing contamination

Disinfectants chemical control

used on inanimate objects to reduce or eliminate pathogens

Degerming chemical control

mechanically removing organisms from an object's surface

chemical agents considerations

•Microbial susceptibility.

•Temperature and pH.

•Concentration.

•Environment.

•Endospore formers.

Phenol coefficient

indicates disinfecting ability compared to that of phenol under identical conditions. number higher than 1 is more effective lower is less effective

use-dilution test

Chemical agents of various dilutions are exposed to a test microbe for 10 minutes and placed in growth medium to see which dilutions are clear of growth

In-use test

Swabs are taken of a test surface before and after cleaning with a chemical agent. Growth is checked after incubation.

Disk diffusion method

Examines the effect of different chemical agents against a specific bacterium; plates are checked for zones of inhibition where bacteria have been eliminated

Halogen chemical agents

chlorine keeps bacterial populations low in water, iodine is used to disinfect wounds, water and restaurant equipment.

Penol chemical control

denature proteins it Is expensive, Is caustic, Has a pungent odor.

Derivatives have, Greater germicidal activity, Lower toxicity than phenol.

Bisphenols are combinations of two phenol molecules.

Heavy metal microbial control

interfere with microbial metabolism, Mercury, copper, and silver are reactive with proteins, They disrupt cellular metabolism by inactivating enzymes and denaturing structural proteins, resulting in the death of microbes.

Alcohol microbial control

denature proteins and disrupt membranes, Effective against vegetative cells but not spores, Membrane disruption is caused by lipid dissolution, is used in many hand sanitizers.

Soap microbial control

remove microbes by emulsifying and solubilizing particles on the skin.

Detergents microbial control

are surfactants, They also cause cytoplasm leakage from microbial membranes, Quaternary ammonium compounds react with cell membranes and destroy some bacteria and viruses.

Hydrogen peroxide microbial control

damages cellular components, Catalase in wounded tissue transforms it to oxygen and water, The oxygen is effective against anaerobic bacteria.

sterilizing gas microbial control

are used on heat-sensitive plastics.

Ethylene oxide is used as the chemical counterpart to heat- and pressure-based autoclaves

Sterilizing gasses of microbial control

Aldehydes: Cause cross-linking that inactivates proteins and nucleic acids.

Ethylene oxide: Effective but carcinogenic and explosive gas.

Chlorine dioxide: A nontoxic and noncarcinogenic gas

History of chemotherapy

originated with Paul Ehrlich. Ehrlich and Sahachiro Hata discovered the effectiveness of arsphenamine (Salvarsan) against the syphilis spirochete Treponema pallidum

Penicillin history

Alexander fleming's observation ushered in antibiotics era.

Antibiotics deriving

1940 waksman, synthetics drugs antimicrobials that are lab made.

semisynthetic drugs antimicrobials that are chemically modified natural drug

Antimicrobial factors

therapeutic success includes dosing, elective toxicity says drug harms pathogen but not host.

toxic dose causes harm to host, therapeutic dose eliminated pathogen in host, togther form therapeutic window.

Antimicrobial spectrum

range of pathogens drugs work on, broad-spectrum affect many taxonomic groups, narrow-spectrum only affect a few pathogens

Antibiotics description

•are secondary metabolites, or chemical compounds not directly used by the organism for growth and reproduction. usually in the secondary phase to compete for limited resources, kill competitors as a selective advantage

Synthetic antibacterial agents

Primarily Inhibit DNA Synthesis and Cell Wall Formation, sulfonamides target specific metabolic reactions, they are broad spectrum and bacteriostatic

Sulfonamides description

out-compete essential folic acid components for binding sites in a bacterial enzyme, They prevent nucleic acid synthesis and DNA replication

Quinolones description

block DNA synthesis in bacteria by inhibiting an enzyme needed for the process, They work on gram-positive and gram-negative bacteria, Fluoroquinolones, including ciprofloxacin, are used to treat UTIs, gonorrhea, chlamydia, and GI infections.

Penicillin description

are in the beta-lactam group because they include a beta-lactam ring with a variable side group, They are active against many gram-positive and some gram-negative bacteria, They interfere with cell wall synthesis in rapidly growing cells, causing the cell to burst.

penicillin production

are produced by the fungus pencillium notatum

Penicillin resistance

is when beta-lactamases is produced, that inactivates penicillian, co drugs such as beta-lactamase inhibitors have been developed and othe semisynthetic penicillins

glycopeptide antibiotics

inhibit bacterial cell wall synthesis, Vancomycin, Effective against gram-positive bacteria such as staphylococci, Side effects include damage to the ears and kidneys, Used as a last resort, especially to treat MRSA.

Polypeptide antibiotics

have unacceptable internal therapeutic window. used topically instead, bacitracin interferes with transport cell wall precursors through the membrane. polymyxins increase membrane permeability of gram-negative rods

Antibiotics affect on translation

many antibiotics cause this affect, aminoglycosides attach to bacterial ribosomes blocking transcription, by binding to 30S subunit, where as chloramphenicol binds to 50S subunit

Tetracycline

broad-spectrum antibiotics that target the attachment of tRNA to the 30S subunit. They can destroy intestinal microbiota and cause staining of the teeth and stunted bones, have a benzene ring, is used for infections of gram-negative bacteria, including syphilis, gonorrhea, and pneumococcal pneumonia

antibiotics inhibiting nucleic acid synthesis

rifampin interferes with RNA synthesis by binding to bacterial RNA polymerase

tube dilution method antibiotic assays

•Uses a series of tubes with different concentrations of an antibiotic to determine the lowest concentration of the antibiotic that is effective.

-Minimum inhibitory concentration (MIC).

Etest antibiotic assays

Determines MIC using an antibiotic-infused strip placed on an agar plate.

Disk diffusion method antibiotic assays

Involves different antibiotics diffusing from paper disks on a bacterial confluent growth

antiviral drugs

interfere with viral replicatrion, via stopping attachemnt/penetration, genome replication, assembly/release

antifungal drugs

fungal pathogen metabolism simular to human cells, mild to serve toxic affect on patient

antiprotozoal agents

aim to eradicate the parasite

Aminoquinolines

•Antimalarial drugs that accumulate in parasitized red blood cells and interfere with the parasite's ability to break down and digest hemoglobin.

artemisinin

Destroys malarial parasites by releasing free radicals in red blood cells

antihelminthic agents

target nondiving helminths.

paraziquantel; membrane permeability

membendazole; inhibits nutrient uptake

avermectins; affect nervous system

antibiotic resistance development

resistance can delevop through spontaneous mutations, horizontal gene transfer e.g. transformation, transduction and conjugation

antibiotic resistance proctection

resistance is usually Antibiotic hydrolysis, Antibiotic modification, Membrane modification/efflux, Target modification, Metabolic pathway alteration.

What is the virosphere?

Collective term for all viruses.

Where are viruses found?

Everywhere, including Cave of Crystals, freshwater lake in Antarctica, and the open ocean.

What is the role of viruses in evolution?

They are a major driving force for the evolution of other organisms.

Who discovered viruses?

Mayer, Ivanowsky, and Beijerinck.

What did Reed study?

Yellow fever and its viral disease agent.

What did Twort and d'Herelle study?

Bacteriophages.

What did Woodruff and Goodpasture develop?

Culture technique for acellular viruses using chicken eggs.

What is the study of viruses called?

Virology.

What is the nature of viruses?

Nonliving agents of disease and acellular parasites.

What is the structural organization of viruses?

Simple.

What are viruses?

Tiny infectious agents that are obligate intracellular parasites.

What do viruses lack?

Machinery for generating energy and large molecules.

What do viruses need to replicate?

A host cell.

What is the size relationship between cells and viruses?

Viruses are smaller than cells.

What is the viral replication cycle?

The process of viral replication.

What are the two types of genomes found in viral genomes?

DNA or RNA

What is the protein coat of a virus called?

Capsid

What are the spikes on some viruses used for?

To attach to and penetrate the host cell

What are naked viruses composed of?

Nucleocapsid (capsid with enclosed genome)

What are enveloped viruses?

Viruses surrounded by an envelope

What is a completely assembled, infectious virus outside its host cell called?

Virion

How can viruses be grouped based on their shape?

Rod or filament shape (helical symmetry), capsid with 20 triangular sides (isocahedral symmetry), or complex symmetry

What is the term for the organisms that a virus can infect?

Host range

What does tissue tropism refer to?

The ability of a virus to infect certain cell or tissue types within the host

What does a virus need to invade a host cell?

A specific receptor

What is the International Committee on Taxonomy of Viruses (ICTV) responsible for?

Developing a classification system for viruses

What are DNA viruses?

Viruses with single- or double-stranded DNA genomes that are replicated in host cell DNA

What are RNA viruses?

Viruses with single- or double-stranded RNA genomes.