CPA #15 Questions Flashcards
explain: hygiene hypothesis
exposure to everything can reduce infections; fewer childhood illnesses and increased personal hygiene have reduced children’s exposure to microbes so that when they do, the immune system overreacts and causes allergies
what infectious agent does sterilization not apply to?
prions; standard sterilization techniques do not destroy them
is commercially canned food free of microbes?
no; the commercial sterilization technique does not kill hyperthermophilic microbes because they do not cause disease and do not cause food to spoil at normal temp
define: degerming
removal of microbes from a surface by scrubbing, such as when you wash your hands; the action of scrubbing is more important than the chemicals
define: -stasis/-static
chemical agent that inhibits microbial growth/metabolism, but does not kill them
define: -cide/-cidal
refer to agents that destroy or permanently inactivate microbe
what are the two categories of antimicrobials?
- those that disrupt the integrity of cells by adversely altering their cell walls or cytoplasmic membranes
- those that interrupt cellular metabolism and reproduction by interfering with the structures of proteins and nucleic acids
what are the 3 characteristics of ideal antimicrobials?
inexpensive, fast-acting, stable during storage
what are the 3 factors when selecting a microbial control method?
- relative susceptibility of microbes
- environmental conditions
- site to be treated
define: high-level germicide
kill all pathogens (excluding prions), including bacterial endospores; healthcare professionals use them to sterilize invasive instruments
define: intermediate-level germicide
kill fungal spores, protozoan cysts, viruses, and pathogenic bacteria, but not endospores
define: low-level germicides
eliminate vegetative bacteria, fungi, protozoa, and some viruses; used to disinfect items that contact only the skin of patients (furniture, electrodes)
what agency established the biosafety levels?
Center for Disease Control and Prevention (CDC)
define: biosafety level-I (BSL-I)
suitible for handling microbes, such as E. coli, not known to cause disease in healthy humans; precautions are minimal; include hand-washing with antibacterial soap and disinfecting surfaces
define: BSL-II
designed for handling moderately hazardous agents, such as hepatitis and influenza viruses, methicillin-resistant S. aureus; precautions taken with contaminated sharps and aerosol producing procedures
define: BSL-III
all manipulations be done inside safety cabinets with HEPA filters; TB, yellow fever, Rocky Mountain Spotted Fever, anthrax
define: BSL-IV
“space suits”; separate buildings for testing; fatal diseases; ebola, smallpox, lassa fever viruses
why is heat used for microbial control?
high temps denature proteins, interfere with integrity of cytoplasmic membrane/cell walls, and disrupt the function of nucleic acids
define: moist heat
commonly used to disinfect, sanitize, sterilize, pasteurize; more effective than dry heat because water is a better conductor of heat than air
define: autoclave
pressure chamber; pipes introduce and evacuate steam; valves remove air and control pressure
define: pasteurization
thermoduric and thermophilic prokaryotes survive; combination of time and temperature, varies by product;
how is cold used to control microbial growth?
halts/slows down growth for mesophiles
does freezing eliminate bacteria?
no, because it just slows down the metabolism, does nothing to inactivate the pathogen
define: desiccation
aka drying; preserves foods such as fruits, beans, grains, etc; inhibits growth because metabolism requires liquid water
define: lyophilization
combines freezing and drying; preserves microbes for many years; liquid nitrogen or frozen carbon dioxide; vacuum removes frozen water; prevents the formation of large, damaging ice crystals
passage of fluid through a sieve to trap microbes and separate them from the fluid; used to sterilize heat-sensitive materials
Filtration
how do hypertonic solutions inhibit microbe growth?
high concentrations of salt/sugar in foods; osmotic pressure (area of high conc. to an area of low conc.); removal of water inhibits cellular metabolism
define: ionizing radiation
electron beams, gamma rays, some x-rays; wavelength shorter than 1 nm; they have sufficient energy to eject electrons from atoms, creating ions; ions disrupt hydrogen bonds, oxidize double covalent bonds, and create highly reactive hydroxyl groups; these ions denature other molecules, particularly DNA, causing fatal mutations and death
define: nonionizing radiation
electromagnetic radiation with a wavelength greater than 1 nm; does not have enough energy to force electrons out of orbit and cause new covalent bonds effecting 3D shape; UV, visible light, infrared radiation, radio waves
dips several metal cylinders into broth cultures and briefly dries them at 37C; immerses each container into different dilution of the disinfectant; after 10 minutes, each cylinder is removed, rinsed, and placed into a sterile medium for 48 hours
use-dilution
add a suspension of bacterium to a suitable concentration of the chemical being tested; at predetermined times, samples are moved into a growth medium containing disinfectant deactivator; after 48 hours, turbidity in medium determines effectiveness of treatment and bacteria survival
kelsey-sykes capacity test
time consuming and realistic; swabs are taken from actual objects before and after a disinfectant treatment; swabs are inoculated into appropriate growth media
in-use test
explain Paul Ehrlich
arsenic compounds to fight syphyllis; chemotherapy
explain Alexander Fleming
penicillin
explain Gerhard Domagk
sulfanilamide; treats wide array of bacterial infections
define: selective toxicity
effective microbial agent must be more toxic to a pathogen than to the pathogen host
