Flashcards in Chapter 7 - Control of Microbial Growth Deck (55):
removal of all microbial life (includes endospores!)
killing C. botulinum endospores before being placed on grocery shelves
removal of vegetative/non-endospore forming pathogens
destruction of vegetative pathogens or living tissue
removal of microbes from a limited area (usually skin)
lowers the microbial count on eating and drinking utensils
Mycobacteria have what kind of cell wall?
waxy and lipid
What part of the protozoa are resistant to chemical disinfection?
Gram ____ bacteria are more resistant.
_____ are resistant to normal autoclaving and disinfection.
What are 5 factors that influence the effectiveness of antimicrobials?
1) number of microbes
2) certain characteristics
3) environmental conditions
4) time of exposure
5) action of antimicrobial
What are 2 actions of antimicrobials?
1) changing of the permeability of the plasma membrane
2) damaging the protein/nucleic acid
More resistant microbes include
prions, endospores, mycobacteria, cysts of protozoa, vegetative protozoa
Less resistant microbes include
viruses with lipid envelopes, gram-positive bacteria, viruses without envelopes, fungi, gram-negative bacteria
sterilization using moist heat (higher than boiling point) in the form of steam by autoclaving at 121 degrees at 15 psi for 15 minutes
*preferred form of sterilization, its moist heat denatures proteins
sterilization that kills most vegetative pathogens, viruses, and fungi along with their spores (most of the time)
Direct Flaming and Incinerators
sterilization by dry heat which kills by oxidation (inoculating loop)
sterilization by dry heat which sterilized metal, glass, and plastic items (heat-sensitive items)
sterilization of culture media (virology), vaccines, IVs/antibiotics, solutions, and hospital equipment
sterilization by separating bacteria from suspending liquids
HEPA (high efficiency particulate air)
sterilization used for airborne microbes such as in the mycobateriology lab, burn unit, operating room, and rooms of AIDs patients
sterilization that destructs DNA by means of x-rays. gamma rays, and electron beams
sterilization that damages DNA by means of UV rays
sterilization that disrupts the of metabolism by removing water from microbes (used for food preservation)
sterilization that alters the molecular structure of proteins and carbohydrates but preserves nutrient values (used for fruit juices)
sterilization that uses plasmolysis for food preservation
sterilization that causes metabolic inhibition used to control molds and some bacteria in food
Nitrates/Nitrites (meat products)
sterilization that inhibits certain iron-containing enzymes of anaerobes that prevents the growth of C. botulinum
sterilization that decreases chemical reactions
sterilization that decreases chemical reactions (-50 - -95 degrees C)
sterilization that decreases chemical reactions that leaves a poweder-like residue for preservation
denatures proteins by using high heat for a short amount of time (reduces spoilage) (doesn't sterilize)
Soap and Water
mechanical removal of microbes through scrubbing
Cationic Detergents (Quats)
antiseptics for utensils that inhibit enzymes, denature proteins, and disrupt plasma membranes (most effective against gram positives)
degerming (antiseptic) or disinfecting (thermometers) that denatures proteins and disrupts plasma proteins (not effective again endospores)
oxidizing agents such as tincture and iodophors that inhibit protein function
skin disinfectants (surgical hand scrubbing) that disrupt plasma membranes
disinfectants such as lysol and amply used on inert surfaces to denature enzymes and disrupt plasma membranes
disinfectant hand soaps and antiseptics (hexachlorophene) that might disrupt plasma membranes
gluteraldehydes and formaldehyde disinfect medical equipment by denaturing proteins
antiseptics such as copper sulfate and silver nitrate that denature entire proteins
disinfectants and antiseptics that act as oxidizing agents to clean contaminated surfaces
How does the filter paper disk diffusion method work?
1) paper disk soaked w/ disinfectant
2) place disk on inoculated agar plate
3) disinfectant diffuses out of disk into agar during incubation
4) clear zone of inhabitation indicates effectiveness of disinfectant
*larger the zone, the more sensitive the microbe is
All the following achieve sterilization EXCEPT:
What is the mode of action for phenols?
a. dissolve lipids
b. denature proteins
c. oxidizing agents
d. disruption of the plasma membrane
e. both b and d
E) both B and D
If a microbiologist wants to use a gas to sterilize hospital items, which of the following methods is appropriate?
b. ethylene oxide
e. all of the above
B) ethylene oxide
The term disinfection refers to:
a. removal of all forms of microbial life
b. lowering microbial counts on eating and drinking utensils
c. destruction of vegetative pathogens on living tissue
d. removal of microbes from a limited area, such as skin
e. destruction of vegetative pathogens on inert surfaces.
E) destruction of vegetative pathogens on inert surfaces
Which of these is most resistant to chemical antimicrobials?
c. gram-negative bacteria
e. enveloped viruses
Which method is preferred for sterilizing heat-labile culture media?
b. hot air oven
B) hot air oven
Which of these factors influences the effectiveness of antimicrobial treatments?
a. microbial load
b. microbes in surface biofilms
c. presence of feces in the material
d. exposure time
e. all of the above
E) all of the above
used on live surfaces