unit 6 quiz Flashcards
sterilization is
the complete removal or killing of all vegetative cells, endospores, and viruses from the targeted item or environment
aseptic technique
combination of protocols used to collectively maintain sterility in clinical procedures or in a microbiology laboratory
commercial sterilization
process used to destroy common pathogens responsible for food poisoning
disinfection is
the inactivation of most microbes on an inanimate surface
antiseptics
chemicals that lead to the inactivation of most microbes on living skin or tissues
sanitization is
the cleaning of inanimate objects to remove enough microbes to achieve levels deemed safe for public health
degerming is
the process where microbial numbers are significantly reduced by gently scrubbing living tissues
the type of microbial control that can kill would have the suffix
cide
the type of microbial control that only inhibits microbial growth would have the suffix
static
describe the factors that can affect the effectiveness of a particular antimicrobial agent
amount of time needed for the agent to be in contact with the item, concentration of the agent needed, other conditions that may limit contact of the agent with the item
physical methods
can non-specifically kill cells by disrupting membranes or by damaging cellular proteins/nucleic acids
chemical methods
can work non-specifically, or specifically to kill cells; chemical safety is important when using with humans and the environment
disc-diffusion assay is used to
assess the relative effectiveness of a chemical-based antimicrobial agent
what situations would require sterilization cleaning
microbiology lab: equipment used, media
hospital: items in contact with susceptible people
moist heat (autoclave)
combines steam & heat, useful in laboratories to sterilize anything that can get wet (media, agar, glassware, final disposal of waste
dry heat (direct flaming or oven)
useful to sterilize anything can be heated (inoculation loop)
slow freezing
forms ice crystals which can damage proteins, useful only to control eukaryotic parasites
ionizing radiation (gamma or x rays)
limited use due to effects on humans, can penetrate through tissue, paper, and plastic
what is ionizing radiation used for
tissues for transplantation, materials made of paper/plastic, food
non-ionizing radiation (UV rays)
only sterilizes the surface
used for: purify water, germicidal lamps
filtration
a liquid or gas is passed through a filter with pores that physically remove microbes from passing through
filtration is used for
solutions that cannot be heated (contains vitamines or antibiotics); air/water filters
alkylating agents
main chemical capable of sterilization, but is carcinogenic
2 types of alkylating agents
2% glutaraldehyde (liquid) & ethylene oxide (gas)
alkylating agents used for
surgical equipment, hospital surfaces
ethylene oxide is a gas and can be used for heat-sensitive items or for items that getting wet would make it impractical
disinfection is used for
prevention of disease: after an outbreak, typical hospital cleaning, deeper household cleaning
phenol and phenolics
effective against gram-positive bacteria and yeast, not effective against gram-negative bacteria, viruses and endospores
examples of phenols
disinfectant: house cleaning = lysol
antiseptic: toothpastes, anti-bacterial soaps = triclosan
heavy metals
effective against all cells (and also toxic to humans; not effective against endospores
examples of heavy metals
disinfectant: products (clothing) embedded with silver, zinc, copper
antiseptic: silver nitrate (eyes), mouthwash containing zinc
halogens - iodophors
effective against all cells (but not endospores)
examples: disinfectant: water purification
antiseptic: hand scrub prior to surgery, or cleaning of skin wounds (betadine)
halogens - chlorine
effective against all cells (but typically not endospores)
disinfectant: water purification (pools); surface cleaning
bleach: this chemical is an exception and is capable of removing endospores
alcohol (in a solution with water)
effective against bacteria, fungi, enveloped viruses, not effective against non-enveloped viruses; also induces formation of endospores
examples: 70-90% ethanol - used to clean surfaces and for skin surfaces
surfactants - QUATS
effective against bacteria, fungi, enveloped viruses. Not effective against non-enveloped viruses and endospores
disinfectant: housecleaning - lysol
antiseptic: mouthwash
peroxygens
effective against all cells (but not endospores)
higher concentrations are needed against endospores, viruses, and bacteria that have catalase
disinfectant: hydrogen peroxide in liquid and gas forms to clean hospitals
antiseptic: acne medication, toothpaste
what situations would require sanitization level of cleaning
general cleaning
pasteurization application
increase shelf-life of food items such as dairy products, alcohol, juices
refrigeration (bacteriostatic only) application
short-term storage of food items or bacterial cultures
lyophilization (bacteriostatic only) application
freeze-drying (rapid freezing combined with desiccation)
long term storage of bacterial cultures, long term preservation of food
osmotic pressure (high concentration of sugar or salt) applications
salted foods, honeys, jams
surfactants - soaps
mechanical removal of microbes through emulsification of oils and microbes into small drops, and then rinsed away
- does not contain any other antimicrobial agent
antimicrobial drugs are
chemicals used to treat diseases
narrow-spectrum antibiotics
target only specific subsets of pathogens (penicillin)
use if the causative pathogen has been identified & minimizes damage to normal flora
broad-spectrum antibiotics
target a wide variety of pathogens (tetracycline)
broad-spectrum is used if
- treatment needs to start right away
- mixed infection with multiple causative pathogens
- prevention of infection of invasive surgical procedures
- failure in treatment by a narrow-spectrum antibiotic
risks for broad-spectrum include
- normal flora can be targeted which can increase the risk of developing an opportunistic infection (yeast)
- contributes to antibiotic resistance
inhibitors of cell wall synthesis
major mode of action for bacterial antibiotics
prevent the formation of cell wall, making more susceptible to lysis, less side effects for humans (penicillin)
inhibitors of membrane function
major modes of action for bacterial antibiotics
has detergent - like properties and can disrupt outer and plasma membranes, can be toxic to humans if ingested, so used only in the form of topical creams (polymyxin)
inhibitors of protein biosynthesis
targets the ribosomes, preventing protein synthesis, less side effects as prokaryotic ribosomes are different from eukaryotic ribosomes (tetracycline)
inhibitors of nucleic acid synthesis
interfere with DNA replication or blocks RNA polymerase, typically has more side effects so used in combination with other antibiotics (rifampin, which blocks RNA polymerase)
inhibitors of metabolic pathways
act as antimetabolites and competes with regular substrates for the same enzyme, leading to loss of function, side effects depends on the actual antibiotic (sulfonamides, blocks the synthesis of folic acid)
kirby bauer technique
used to determine the effectiveness of an antibiotic; similar to the disc diffusion assay where a more effective antibiotic would exhibit a larger zone of inhibition
explain the difficulty in development of drugs to target fungal, protozoan and helminthic infections
these infections are caused by pathogens that are also eukaryotic, meaning that they are more similar to human cells
as result, it is difficult to develop drugs that would only target these pathogens
antifungal drugs
(miconazole)
disrupts the synthesis of ergosterols, which is the predominant sterol used in fungal plasma membranes
antiprotozoan drug
(atovaquone)
affects the electron transport chain, mainly used to treat malaria
antihelminthic drug
(ivermectin)
binds to chloride channels, which disrupts neuronal transmission
first mechanism through which bacteria can resist drugs
- efflux
- bacterium contains pumps that can transport the drug out of the cell
- found in both gram-negative and gram-positive bacteria
second mechanism through which bacteria can resist drugs
- drug modification or inactivation
- chemically modify or degrade the antibiotic inactive
- found in both gram-negative and gram-positive bacteria
third mechanism through which bacteria can resist drugs
- prevention of cellular uptake
- smaller pores of gram-negative bacteria prevent the antibiotic from entering the cell
fourth mechanism through which bacteria can resist drugs
- target modification
- through mutations, the drug targets change over time due to antibiotic selection
- e.g. the ribosomes in tetracycline-resistant bacteria have been modified through mutations over time to remain functional, but not affected by tetracycline
- found in both gram-negative and gram-positive
describe how antimicrobial drug resistance is a result of antimicrobial drug usage
due to genetic variation, there will be some cells that are resistant to drugs
as antimicrobial drugs are used
susceptible cells are killed, and resistant cells will survive
over time, the proportion of drug-resistant cells will increase
3 steps of how antimicrobial resistance is result from drugs
- normal microbes keeps opportunistic pathogens in check
- broad-spectrum antibiotics kill nonresistant cells
- drug-resistant pathogens proliferate and can cause a superinfection
viruses are obligate intracellular pathogens that
uses host cell machinery to replicate
current antiviral drugs
neuraminidase inhibitors: target influenza viruses (prevent release of virus from host cell)
HIV infection: reverse transcriptase inhibitors, protease inhibitors prevent processing and maturation of HIV virions, integrase inhibitors prevent the formation of the provirus
describe phage therapy
the collection and growth of bacteriophages that target the pathogens
recent trials include
administering phage therapy through IV application
advantages to phage therapy
will only target bacteria, specificity of bacteriophages means that normal flora is unaffected, bacteriophages are also capable of evolution, along with bacteria
