Chapter 7 – Microbiology – Flashcards

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which microbial structures do antimicrobial agents target?
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cell wall - prevent cell from bursting PM - permeability DNA - proteins and enzymes
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what factors determine whether an antimicrobial is effective?
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time of exposure cell wall type concentration of microbes concentration of antimicrobial temperature
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why can certain milk proudcts and fruit juices be stored as RT and not spoil?
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they go under UHT (ultra high temperature) or steam
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sterilization
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removal or destruction of all forms of microbial life heating is the most common form (dry/moist)
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commercial sterilization
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limited heat treatment used in canned food processing kills endospores of clostridium botulinum (obligate anaerobe)
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disinfection
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- destruction of vegatative (non-endospore forming) microorganisms that may be harmful - may involve chemicals, UV light, steam, boiling water includes antiseptic
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antiseptic
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a disinfectant that is used on living tissue ex. hydrogen peroxide, hand sanitizer, iodine, mouth wash, baby wipes.
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degerming
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removal of microbes from a limited region generally involves mechanical removal
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sanitization
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lower microbial counts on eating utensils high temperature washing or chemical disinfectant
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naming of treatments for microbial control
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-cide (to kill) -stat/stasis (stop/steady) limit growth - bacteriostatic
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sepsis/aseptic
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microbial contamination free of microbial contamination
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the more microbes, the _______ treatment time is required to eliminate
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longer
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enviornmental influences
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organic matter mixed with microbes lowers antimicrobial activity. ex- biofilms
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what are the factors that determine how effective an antimicrobial treatment is
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number of microbes environmental influences time of exposure microbial characteristics
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actions of microbial control agents
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target plasma membrane by damaging lipids/proteins altering permeability target proteins by breaking bond (h+ or covalent) target DNA and RNA - for DNA replication and protein synthesis
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heat resistance
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thermal death point thermal death time decimal reduction time
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thermal death point
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lowest temperature in which all microbes in a solution are killed in 10 minutes
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thermal death time
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minimal length of time for all bacteria in a solution to be killed at a given temperature
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decimal reduction time
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time in minutes in which 90% of a bacterial population will be killed at a given temperature
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physical methods of microbial growth
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(moist heat: autoclaving, pasteurization, uht) dry heat (incineration & flaming)
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moist heat
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denaturing of proteins of breaking of H bonds
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steam is how hot with how much pressure
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100C no pressure autoclaving is preferred if substance can tolerate it
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boiling
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for 10 minutes kills bacteria, viruses, and most fungi endospores and some viruses can still survive (20hours)
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autoclaving relationship
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as pressure increases, so does temperature kills all organisms and endospores in 15 minutes if its directly in contact with steam - 121C
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autoclaving cannot kill
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prions which are infectious proteins
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pasteurization
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moist heat that exposes microbes to high temperatures for a short time. still has microbes so not sterilized!
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ultra high temperature
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sterilizes allows storage of milk w/o refridgeration 140C for 4 seconds
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dry heat
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not as effective as moist direct flaming incineration - burned to ashed hot air sterilization - item is placed in oven (170C for 2 hours)
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filtration
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a physical method of microbial control used to sterilize heat sensitive materials HEPA filters remove microbes greater than 0.3 um membrane filters 0.1 um - 0.45 um
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HEPA filter
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high efficiency particular air vacuum, purifiers, operating rooms
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low temperature for microbial growth
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refrigeration- causes psychrotrophs to grow more slowly freezing- microbes are dormant, not dead & freeze thaw cycles are harmful for bacteria because ice crystals disrupt membrane structures
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high pressure: physical method for microbial control
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alters molecular structures of carbs and proteins some fruit juice endospores are resistant to this
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desiccation: physical method for microbial control
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absence of water or lyophilization no growth or reproduction can remain viable for several years
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osmotic pressure
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high salt or sugar results in a hypertonic solution decreases moisture content
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ionizing radiation
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gamma rays (from radioactive substances), xrays, high energy electrons, ebeams ionize water that form hydroxyl radicals that attack DNA.
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nonionizing radiation
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UV light which mutates DNA like hospitals and caffeteria
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microwaves
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heat kills most vegetative pathogens in moisture containing foods
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low wavelengths mean
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they are more detrimental
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3 types of radiation
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ionozing, nonionizing, microwave
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can evaluate a disinfectant by
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use dilution test
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use dilution test
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is not serial dilution use 3 types of bacteria: 2 gram negs & 1 positive metal or glass cylinders dipped in bacteria cultures are dried and placed in disinfectant for 20 minutes at 10C cylinders are transferred to sterile liquid medium, incubated, and analyzed for growth
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which gram neg bacteria is resistant to many antimicrobials?
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pseudomonas
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disk diffusion method
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inoculate an agar plate with bacteria using a cotton swab filter paper soaked with disinfectant is placed of agar check for zone around paper. larger the zone, more effective it is to disinfectant
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phenol
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used by lister in surgeries rarely used bc it irritates skin and it smells unpleasant used in throat bc local anesthetic
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phenolics
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-derivatives of phenol &chemically altered to lower irritation - target lipid membranes and affect permeability
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bisphenols
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2 phenol molecules bridged together hexachlorophene (skin infections used in nurseries) triclosan (p. aeruginosa resistant bc overuse)
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biguanides
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affect cell membranes chlorhexidine- microbial control on skin and mucous membranes, presurgical antiseptic
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halogens include
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iodine and chlorine
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iodine
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i2 - impairs protein synthesis and alters cell membranes used mainly for skin and wound disinfection tincture - solution with alcohol iodophor - combined with organic molecule (dont stain and are less irritating on skin)
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chlorine
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cl2 - germicidal activity caused by HOCl whcih diffuse easily through cell walls to inhibit enzyme function. strong oxidizing agen
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cl2 + h20 -->
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H + Cl + HOCl
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chlorine compounds
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hypochlorites - calcium and sodium chlorine dioxide - kills anthrax endospores chloramines- chlorine and ammonia
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alcohols
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kill bacteria and fungi (not endospores or nonenveloped viruses) denatures proteins, can disrupt membranes ex. ethanol (62-65%) and isopropanol
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100% alcohol is/isnt effective to kill microbes?
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no must be mixed with water to break down protein and 100% will evaporate too fast
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heavy metals
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silver: (nitrate) put in babies eyes for infection mercury, copper: inhibits green algae, zinc: rooftops/mouthwash metal ions cause protein denature oligodynamic reaction - very small amounts of heavy metals exerting antimicrobial activity
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surface active agents
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soaps and detergents - degerming used to remove debris, microbes, dead cells, oils on surface quaternary ammonium compounds
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if HOCl and quats are mixed, they form
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chlorine gas
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quaternary ammonium compounds (quats)
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most widely used surface cleaners affect PM because its positive charge cationic detergents kill gram + bacteria, fungi, amoeba, viruses dont kill endospors or mycobacteria pseudomonas is resistant
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effectiveness of some antiseptics
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soap and water aqueous zephiran 50% ethanol and 10% acetone tincture 70% ethanol and 30% water 1% iodine and 70% ethanol (tincture of iodine)
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chemical food preservatives
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SO2 - sulfur dioxide sorbic acid and sodium benzoate calcium propionate sodium nitrate and sodium nitrite
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sulfur dioxide is used in
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wine making takes a llong time
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sorbic acid and sodium benzoate is used in
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soda and prevents molds from growing in acidic foods (cheese/soft drinks)
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calcium propionate is used for what?
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fungistat which is used to stop growth in break affect mold metabolism or PM
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sodium nitrate and sodium nitrite is used for what?
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added to meat products to protect against botulism reaction in the body causes nitrosamine (reaction with amino acids) which is a carcinogen nitrate and nitrite can be converted to one another
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botulism
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causes lethargy and affects nervous system, gastrointestinal tract and it is caused by clostridium botulinum toxin
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antibiotics
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a type of disinfectant that is usally injected or injested nisin and natamycin- used in food preservation
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nisin is added to what? why?
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cheese - prevents growth of endospore forming bacteria, present naturally in dairy products
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natamycin is added to what? why?
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cheese bc it is an antifungal antibiotic
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aldehydes
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used for embalming inactive proteins by forming covalent bonds with functional groups. formaldehyde and glutaraldehyde - less irritating and more effective sterilizng agent for killing endospores but take a long time.
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gaseous chemosterilizers
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chemicals that sterilize in a closed chamber like matresses in hospitals ex. ethaline oxide/chlorine dioxide
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peroxygens
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causes molecules to get oxidized ozone (o3) hydrogen peroxide benzoyl peroxide peracetic acid
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ozone
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o3 supplements chlorine in water disinfection
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hydrogen peroxide
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disinfects inanimate objects contact lens cleaners
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benzoyl peroxide
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acne treatment
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peracetic acid
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very effective liquid chemical sterilant that does not residues so we can not be harmed. approved for washing fruits and veggies
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resistance of microbes to chemical biocides (g to l)
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prions endospores of bacteria mycobacteria cysts of protozoa vegetative protozoa gram negative fungi including most spores viruses without envelopes gram positive viruses with lipid envelopes
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