Chapter 7 - Microbiology

25 July 2022
4.7 (114 reviews)
76 test answers

Unlock all answers in this set

Unlock answers (72)
question
which microbial structures do antimicrobial agents target?
answer
cell wall - prevent cell from bursting PM - permeability DNA - proteins and enzymes
question
what factors determine whether an antimicrobial is effective?
answer
time of exposure cell wall type concentration of microbes concentration of antimicrobial temperature
question
why can certain milk proudcts and fruit juices be stored as RT and not spoil?
answer
they go under UHT (ultra high temperature) or steam
question
sterilization
answer
removal or destruction of all forms of microbial life heating is the most common form (dry/moist)
question
commercial sterilization
answer
limited heat treatment used in canned food processing kills endospores of clostridium botulinum (obligate anaerobe)
question
disinfection
answer
- destruction of vegatative (non-endospore forming) microorganisms that may be harmful - may involve chemicals, UV light, steam, boiling water includes antiseptic
question
antiseptic
answer
a disinfectant that is used on living tissue ex. hydrogen peroxide, hand sanitizer, iodine, mouth wash, baby wipes.
question
degerming
answer
removal of microbes from a limited region generally involves mechanical removal
question
sanitization
answer
lower microbial counts on eating utensils high temperature washing or chemical disinfectant
question
naming of treatments for microbial control
answer
-cide (to kill) -stat/stasis (stop/steady) limit growth - bacteriostatic
question
sepsis/aseptic
answer
microbial contamination free of microbial contamination
question
the more microbes, the _______ treatment time is required to eliminate
answer
longer
question
enviornmental influences
answer
organic matter mixed with microbes lowers antimicrobial activity. ex- biofilms
question
what are the factors that determine how effective an antimicrobial treatment is
answer
number of microbes environmental influences time of exposure microbial characteristics
question
actions of microbial control agents
answer
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
question
heat resistance
answer
thermal death point thermal death time decimal reduction time
question
thermal death point
answer
lowest temperature in which all microbes in a solution are killed in 10 minutes
question
thermal death time
answer
minimal length of time for all bacteria in a solution to be killed at a given temperature
question
decimal reduction time
answer
time in minutes in which 90% of a bacterial population will be killed at a given temperature
question
physical methods of microbial growth
answer
(moist heat: autoclaving, pasteurization, uht) dry heat (incineration & flaming)
question
moist heat
answer
denaturing of proteins of breaking of H bonds
question
steam is how hot with how much pressure
answer
100C no pressure autoclaving is preferred if substance can tolerate it
question
boiling
answer
for 10 minutes kills bacteria, viruses, and most fungi endospores and some viruses can still survive (20hours)
question
autoclaving relationship
answer
as pressure increases, so does temperature kills all organisms and endospores in 15 minutes if its directly in contact with steam - 121C
question
autoclaving cannot kill
answer
prions which are infectious proteins
question
pasteurization
answer
moist heat that exposes microbes to high temperatures for a short time. still has microbes so not sterilized!
question
ultra high temperature
answer
sterilizes allows storage of milk w/o refridgeration 140C for 4 seconds
question
dry heat
answer
not as effective as moist direct flaming incineration - burned to ashed hot air sterilization - item is placed in oven (170C for 2 hours)
question
filtration
answer
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
question
HEPA filter
answer
high efficiency particular air vacuum, purifiers, operating rooms
question
low temperature for microbial growth
answer
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
question
high pressure: physical method for microbial control
answer
alters molecular structures of carbs and proteins some fruit juice endospores are resistant to this
question
desiccation: physical method for microbial control
answer
absence of water or lyophilization no growth or reproduction can remain viable for several years
question
osmotic pressure
answer
high salt or sugar results in a hypertonic solution decreases moisture content
question
ionizing radiation
answer
gamma rays (from radioactive substances), xrays, high energy electrons, ebeams ionize water that form hydroxyl radicals that attack DNA.
question
nonionizing radiation
answer
UV light which mutates DNA like hospitals and caffeteria
question
microwaves
answer
heat kills most vegetative pathogens in moisture containing foods
question
low wavelengths mean
answer
they are more detrimental
question
3 types of radiation
answer
ionozing, nonionizing, microwave
question
can evaluate a disinfectant by
answer
use dilution test
question
use dilution test
answer
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
question
which gram neg bacteria is resistant to many antimicrobials?
answer
pseudomonas
question
disk diffusion method
answer
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
question
phenol
answer
used by lister in surgeries rarely used bc it irritates skin and it smells unpleasant used in throat bc local anesthetic
question
phenolics
answer
-derivatives of phenol &chemically altered to lower irritation - target lipid membranes and affect permeability
question
bisphenols
answer
2 phenol molecules bridged together hexachlorophene (skin infections used in nurseries) triclosan (p. aeruginosa resistant bc overuse)
question
biguanides
answer
affect cell membranes chlorhexidine- microbial control on skin and mucous membranes, presurgical antiseptic
question
halogens include
answer
iodine and chlorine
question
iodine
answer
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)
question
chlorine
answer
cl2 - germicidal activity caused by HOCl whcih diffuse easily through cell walls to inhibit enzyme function. strong oxidizing agen
question
cl2 + h20 -->
answer
H + Cl + HOCl
question
chlorine compounds
answer
hypochlorites - calcium and sodium chlorine dioxide - kills anthrax endospores chloramines- chlorine and ammonia
question
alcohols
answer
kill bacteria and fungi (not endospores or nonenveloped viruses) denatures proteins, can disrupt membranes ex. ethanol (62-65%) and isopropanol
question
100% alcohol is/isnt effective to kill microbes?
answer
no must be mixed with water to break down protein and 100% will evaporate too fast
question
heavy metals
answer
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
question
surface active agents
answer
soaps and detergents - degerming used to remove debris, microbes, dead cells, oils on surface quaternary ammonium compounds
question
if HOCl and quats are mixed, they form
answer
chlorine gas
question
quaternary ammonium compounds (quats)
answer
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
question
effectiveness of some antiseptics
answer
soap and water aqueous zephiran 50% ethanol and 10% acetone tincture 70% ethanol and 30% water 1% iodine and 70% ethanol (tincture of iodine)
question
chemical food preservatives
answer
SO2 - sulfur dioxide sorbic acid and sodium benzoate calcium propionate sodium nitrate and sodium nitrite
question
sulfur dioxide is used in
answer
wine making takes a llong time
question
sorbic acid and sodium benzoate is used in
answer
soda and prevents molds from growing in acidic foods (cheese/soft drinks)
question
calcium propionate is used for what?
answer
fungistat which is used to stop growth in break affect mold metabolism or PM
question
sodium nitrate and sodium nitrite is used for what?
answer
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
question
botulism
answer
causes lethargy and affects nervous system, gastrointestinal tract and it is caused by clostridium botulinum toxin
question
antibiotics
answer
a type of disinfectant that is usally injected or injested nisin and natamycin- used in food preservation
question
nisin is added to what? why?
answer
cheese - prevents growth of endospore forming bacteria, present naturally in dairy products
question
natamycin is added to what? why?
answer
cheese bc it is an antifungal antibiotic
question
aldehydes
answer
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.
question
gaseous chemosterilizers
answer
chemicals that sterilize in a closed chamber like matresses in hospitals ex. ethaline oxide/chlorine dioxide
question
peroxygens
answer
causes molecules to get oxidized ozone (o3) hydrogen peroxide benzoyl peroxide peracetic acid
question
ozone
answer
o3 supplements chlorine in water disinfection
question
hydrogen peroxide
answer
disinfects inanimate objects contact lens cleaners
question
benzoyl peroxide
answer
acne treatment
question
peracetic acid
answer
very effective liquid chemical sterilant that does not residues so we can not be harmed. approved for washing fruits and veggies
question
resistance of microbes to chemical biocides (g to l)
answer
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