Week 14- controlling microbial growth Flashcards
Describe the following terms as they relate to controlling microbial growth in the environment:
pasteurization
use of heat to remove of pathogenic microorganisms in liquids
Describe the following terms as they relate to controlling microbial growth in the environment:
degerming
physical removal of microorganisms
Describe the following terms as they relate to controlling microbial growth in the environment:
sterilization
Should remove all microorganisms
like spores, endospores, cysts
Describe the following terms as they relate to controlling microbial growth in the environment:
aseptic
an environment that is completely free of microorganisms
Describe the following terms as they relate to controlling microbial growth in the environment:
antisepsis
remove all pathogenic microorganisms on human tissue
like e.coli
Describe the following terms as they relate to controlling microbial growth in the environment:
disinfection
Remove all pathogenic microorganisms on objects
like ecoli
Describe the following terms as they relate to controlling microbial growth in the environment:
sanitation
disinfectant at public health standard
What is the difference between an agent that is “cidal” versus “static” (i.e. bactericidal versus
bacteriostatic agent or fungicidal versus fungistatic
Static- will slow down mo
cidal- will kill mo
Define microbial death.
A microorganisms inability to reproduce under ideal conditions
What are the two general methods of controlling microbial growth?
Physical- heat, refrigeration/freezing, desiccation, osmotic pressure, radiation
chemical-
What specific structures/components of microbes do the modes of action of antimicrobial agents
affect?
How does the damage to each of these structures (from question above) affect the microbe adversely?
Cell wall-cells burst
cell membrane-contents leak out
viral envelope-disable attachment and prevent replication
protein-denature proteins-cause death
nucleic acids-halt protein synthesis through action on rna
Describe the main factors that need to be considered when choosing an antimicrobial agent/method and
how they affect the efficacy of an agent/method
Site
organic materials-ex-feces vomit and tissue
typically remove organic material before using antimicrobial agent
How can you adjust time to affect the effectiveness of antimicrobial methods/agents
some agents take longer times to be more effective
time needed to sterilize volume of liquid
(like 30 sec vs 5 min for a spray)
Which types of microbes are more susceptible to antimicrobial agents
enveloped virus
gram positive/gram negative
Which types of microbes are more resistant to antimicrobial agents
Bacteria endospores
cysts
protozoa
Tuberculosis
High level germicide
used on mo that are hard to kill
resistant
intermediate level germicide
used on some mo that are intermediate to kill
low level germicide
Used on Mo that are easy to kill
susceptible
How does high heat affect microbes?
denatures proteins
disrupts with structure and function of nucleic acids
What is moist heat used for and give several examples.
Used to disinfect, sanitize, sterilize, and pasteurize
Denatures proteins and destroys cytoplasmic membran
more affective then dry heat
Boiling, Autoclaving, Pasteurization, Ultrahigh-temperature sterilization
How are time and heat related when determining effectiveness of a heat method?
Typically with increased heat—time using the method can decrease
time needed to sterilize at a set temperature
When would you use dry heat?
powders or incineration of biological tissue
How do refrigeration and freezing harm microbes?
will slow down metabolism
ice crystal could form in freezing and kill
How does filtration work? What is it used for?
will filter mo because of pores-
like liquids that are heat sensitive and air quality
pores size will determine what size of mo can filter through
How does osmotic pressure work to kill microbes and what is it used for?
water follows solutes/salts
will put m.o in a hypertonic solution(more solute outside then inside) and can kill mo because water follows the salts out
How does radiation harm microbes?
damage and denature nucleic acids
What are the 2 types of radiation used?
ionizing (X-rays)
non ionizing (uv light)
Name 2 uses for radiation
sterilization of medical equipment/ preservation of food
disinfect surfaces and transparent fluids
Describe the use-dilution test
-metal cylinders are dipped into broth culture of bacteria
-Contaminated cylinder immersed into dilution of disinfectant
-Cylinders removed, washed, and placed into tube of
medium
-Most effective agents entirely prevent growth at highest dilution
Describe how resistant microbes can develop due to excessive use of antiseptics and disinfectants.
overuse of antimicrobial methods- weaker killed and stronger survive
Surfactants
Soaps and detergents. Soaps decrease surface tension and destroy cell membranes. Detergents are
positively charged organic surfactants—quaternary ammonium compounds are examples which are
antimicrobial
Oxidizing agents
high level disinfectants and antiseptics that release oxygen radicals and work well against anaerobes; includes peroxides, ozone and peracetic acid
Alcohol
Isopropanol or drinking alcohol (ethanol). Evaporate rapidly – both advantageous and disadvantageous. Can be used in tinctures (other antimicrobial agents dissolved in alcohol). Swabbing of skin with 70% ethanol prior to injection. More effective than soap
Heavy Metals
Low-level bacteriostatic and fungistatic agents, control algae in water; arsenic, zinc, mercury, silver,
and copper; silver used in creams to treat burns. Thimerosal used to preserve vaccines
Phenols
Intermediate to low level. Effective in presence of organic matter and remain active for prolonged
time. Commonly used in health care settings, labs, and homes (Pine and clove oils, Lysol, triclosan)
Halogens
Iodine tablets, iodophores (Betadine®), chlorine treatment of drinking water, bleach, chloramines in wound dressings, and bromine disinfection of hot tubs
Gaseous agents
used for sterilization in hospital settings and equipment that are heat and water sensitive but can be explosive and highly poisonous; denature proteins and DNA; ethylene oxide is commonly used—used in chambers in hospitals. Can be extremely hazardous to people using them
Aldehydes
Glutaraldehyde both disinfects (short exposure) and sterilizes (long exposure). Formalin used in embalming and disinfection of rooms and surgical or dental instruments.
