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Flashcards in Chapter 26 Deck (61)

What is sterilization

The killing or removal of ALL viable organisms


What is inhibition

Effectively limiting/inhibiting microbial growth. Ex. dehydration, refrigeration, freezing, etc


What is decontamination

Treatment of objects, surfaces, etc to make them clean and safe to handle


What is disinfection

Removal of all active pathogens, but not necessarily all microorganisms and not spores (dormant and not active)


What is widely used for killing microbes and why

Heat - high temperatures denatures macromolecules and DNA, which kills microbes


What is the decimal reduction time

The amount of time required to reduce viability tenfold, is determine in relation to the temperature and growth conditions


What can survive heat

Endospores and other types of spores can survive heat treatment that would normally kill vegetative cells


What is an autoclave

A device that uses steam under presure to produce 121C at 15 PSI, allows the termpature of water to get above 100C without evaporating


What are autoclaves used for

Used to sterilize both liquids and dry items


How long does it take to sterilize small volumes

About 15 minutes, it takes larger volumes more time because it takes longer to heat up large amounts


What is pasteurization

Precisely controlled heat and time to reduce the microbial load in heat-sensitive liquids, such as milk. It kills all pathogens in the product but does NOT kill all the normal microorganisms. It avoids the altering of product quality


What is used in radiation sterilization

Microwaves, UV, X-rays, gamma rays, and electrons can kill microbes. Exposing microbes to high enough energy can damage them to death


What is UV useful for

UV is useful for decontamination of surfaces because it can't penetrate solid, opaque, or light-absorbing material


What is ionizing radiation

High energy electromagnetic radiation that produce ions and other reactive molecules that damage cell components, some microorganisms can be more resistant to this than others


What is filter filtration

Filtration avoids the use of heat on sensitive liquids and gases. The pores of filter are too small for organisms to pass through


What are depth filters

HEPA filters


What are membrane filters

Function more like a seive


What are the 3 possible antimicrobial agents

Bacteriostatic, bacteriocidal, and bacteriolytic


What is bacteriostatic

After adding the agent, the number of cells and number of viable cells have stopped increasing and is leveling off. They are still alive just not growing anymore


What is bacteriocidal

The cells are killed after the agent is added and the number of viable cells decrease while the number of cells stops increasing


What is bacteriolytic

An agent that will cause the cells to break apart (penicillin) as the cells grow. The cells will burst leading to the decline of the number of cells as well as the number of viable cells


What is minimum inhibitory concentration

MIC - is the smallest amount of an agent needed to inhibit growth of a microorganisms. It varies with the organism and its numbers as well as the abiotic factors such as temp, pH, and medium


Describe a disc diffusion assay

A antimicrobial agent is added to filter paper disc, which is then placed on a petri plate inoculated with a lawn of the test bacteria. The MIC is reached at some distance from the disc


What is the zone of inhibition

The area of no growth of the test bacteria around the disc, this zone can be measured and compared. Larger zone of inhibition means its more effective


Describe the antibiotic dilution series

Useful for determining the MIC. Have a set of tubes with broth that bacteria can grow in. Perform a series of serial dilutions of the antibiotic and putting dilutions in the broth. The first tube to show no microbial growth is most likely the dlution of MIC


What are the two categories of chemical antimicrobial agents

Products used to control microorganisms in industrial applications and products designed to prevent growth of human pathogens in inanimate environments and body surfaces


What are sterilants

Kills all microbes


What are disinfectants

Kills most microbes but not all and not spores


What are sanitizers

Reduce microbe levels considered safe


What are antiseptics

Kill or inhibit microbes without harming the host


What are important antiseptics

Alcohol, Phenol-containing compounds, Cationic detergents, Hydrogen peroxide, and Octenidine


What does penicillin affect

Cell wall synthesis


What is cirpoflaxin affect

DNA gyrase, is important because bacteria have it but humans don't


What is erythromycin affect

Ribosomal 50s subunit


What do tetracyclines and streptomycins affect

Ribosomal 30s subunit


What is selective toxicity

The ability to inhibit or kill a pathogen without affecting the host


What are growth factor analogs

Are structurally similar to growth factors but are not functional. Can disrupt cell metabolism


What are antibiotics

Naturally produced antimicrobial agents but less than 1% of antibiotics are clinically useful


What are semisynthetic antibiotics

Antibiotics that have been modified


What is the broad spectrum of antibiotics

Different bacteria vary in their sensitivity to antibiotics


What are B-lactam antibiotics

They consist of over half of all antibiotics used worldwide. Includes penicillins and cephalosporins


What is penicillin

Produced by fungi. Is primarily effective against G+ bacteria. It targets cell wall syntehsis by inhibiting transpeptidation by biding to transpeptidase enzymes


What are aminoglycosides

They contain amino sugars bonded by glycosidic linkages


What are some examples of (streptomyces) aminoglycosides. Streptomyces makes several antibiotics

Kanamycin, neomycin, and streptomycin


What do aminoglycosides target in bacteria

They target the 30s ribosomal subunit to inhibit protein synthesis


Why are they aminoglycosides no longer used today

Neurotxicity and nephrotoxicity


What are macrolides

Broad-spectrum of antibiotic that targets the 50s ribosomal subunit of ribosome Ex. Erythromycin


What are tetracyclines

Broad-spectrum inhibitom of protein synthesis by inhibiting the function of 30s ribosomal subunit of ribosome


What is antimicrobial drug resistance

The acquired ability to resist the effects of a chemotherapeutic agent, can result from the mutation of bacterial gene


What is an example of a mutation that could lead to antimicrobial drug resistance

A mutation that encodes for the ribosomal protein that alters the antibiotic binding site without altering the protein's function. Can also result from acquiring a foreign gene


What are the 6 reasons that microorganisms can be resistant to certain antibiotics

1. WT lacks target that the antibiotic inhibits
2. WT is impermeable to antibiotic
3. Evolve change in the target of the antibiotic (mutation to produce resistance)
4. Evolve a resistant biochemical pathway (bypass targeted pathway
5. Acquired gene to inactivate or degrade the antibiotic
6. Acquire gene to pump out the antibiotic


Describe antibiotic inactivation by modification or cleavage

Antibiotics can have certain functional groups attacked that render it inactive


Where are drug-resistance genes located

On the R plasmid or sometimes on transposon that jumped into the R plasmid


Where do R plasmids originate

R plasmids predate the human use of antibiotics, originally evolved in soil bacteria and were used as a defense against bacteria and fungi that produce antibiotics


What happens when antibiotics are overused

The wide-spread use of antibiotics selects for the evolution and spread of R plasmids.


How do you minimize resistance to antibiotics in bacteria

By using antibiotics correctly and only when needed


What can happen to the R plasmid over time in a population

Resistance to an antibiotic can be lost in a population if the antibiotic is not used for several years, carrying an unnecessary plasmid or gene is a burden and selected against


What is bacteriophage therapy

The use of bacteriophage to kill pathogenic bacteria


What are sulfa drugs

Inhibit synthesis of folic acid


What are nucleic acid base analogs

Formed by addition of bromine or fluorine, block nucleic acid synthesis


What are quinolones

Interfere with DNA gyrase. Ex. ciproflaxin