Week 13 Exam 4 Flashcards
Sterilization
removal or destruction of ALL microbes on an object
-autoclave
disinfection
use of physical or chemical agents to inhibit or destroy microorganisms on surface or objects
- may or may not be free of pathogens
- bleach
decontamination/sanitization
disinfect object used by public to reduce number of pathogens
- utensils
- detergents
Antisepsis/degermation
removal of microbes by scrubbing
-surgical hand scrubs
relative resistance
primary targets are microorganisms capable of causing disease or spoilage
-not all are easy to control
Most resistant
most susceptible
-
bactericidal
cide/cidal
killing microbes
kills bacteria
static/stasis
bacteriostatic
reduction of growth
limit growth of bacteria (antibiotics)
sepsis
growth of microorganisms in the blood and other tissues
antisepsis
chemicals used on skin or tissue to inhibit or destroy microbes
antiseptics
chemical agents applied to exposed body surfaces, wounds, and surgical incisions to prevent vegetative pathogens
microbial death
permanent loss of reproductive capability, even under optimal growth conditions
death rate
death rate can be used to measure action of microbial agent
how to pick which antimicrobial to use?
5 steps
- Must be: inexpensive, fast-acting, capable of controlling growth, harmless to human/animal/surface
- site to be treated: chemicals and heat can’t be used on living subjects or fragile objects
- susceptibility of microbes
- number of microorganisms
- concentration of agent
Environmental conditions
- warm disinfectants: work better than cool, reactions are faster at higher temps
- acidic conditions: enhance antimicrobial effect of heat
- organic material: interfere with penetration of heat or chemicals
how do antimicrobials work?
- alter cell wall and membrane: damaged cell wall=osmotic stress/damaged membrane=cellular contents leak out
- damage proteins and nucleic acids: denature proteins & alter/destroy nucleic acids
physical methods of microbial control
- temp: boil, autoclave, pasteurization, incineration, ultra high temp sterilization, refrigeration freezing
- water: osmotic pressure, desiccation & lyophilization
- size: filtration
- other: radiation
microbial resistance
- bacterial endospores: exhibit greatest resistance, autoclaves usually run 121 degrees C for 15 min
- vegetative cells:
- fungi, protozoa, and worms are similar in their sensitivity to heat
- viruses are resistant to heat
Chemical methods of microbial control
- phenol & phenolics: denature proteins & disrupt cell membrane
- alcohols: intermediate level disinfectant, denature proteins, disrupt cytoplasmic membrane (H20 is required)
- halogens: Cl, I, B, Fl intermediate level, damages proteins
- oxidizing agents: ozone, peroxide, peraetic acid are high level disinfectants, kills by oxidation of microbial enzymes
- surfactants: reduce surface tension of solvents, includes soaps, detergents, disrupts cellular membranes, low level disinfectants
- heavy metals: low level bacteriostatic, denatures proteins
- enzymes: controls microbes in environment (lysosome digest peptidoglycan, prionzyme removes prions from medical instruments)
high
intermediate
low
- high level germicide: kills all pathogens including endospores
- intermediate level germicide: kills fungal spores, protozoan cysts, viruses & pathogenic bacteria
- low level germicide: kills vegetative bacteria, fungi, protozoa, some viruses
factors affecting germicidal activity
nature of the microorganisms being treated
nature of the material being treated
degree of contamination
time of exposure
strength & chemical action of the germicide (dilutions/concentrations)
2017 ban
in 2016, FDA banned 19 active ingredients in consumer products
many of the ingredients can select for resistance in microbes-proliferation of antimicrobial resistant organisms
-iodophors
-many phenols(triclosan & triclocarbon)
-some quats
soaps and detergents are sufficient for human use
biosafety levels
- BSL-1: handling microbes hat don’t cause disease in humans, precautions: hand washing w/ antibacterial soap & washing surfaces with disinfectants
- BSL-2: handling modernity hazardous agents
- BSL-3: all manipulations of microbes done in safety cabniets
- BSL-4: handling microbes that cause severe/fatal disease, lab is isolated & personnel wear protective suits
methods for evaluating disinfectants & antiseptics
- use-dilution test: metal cylinders dipped into broth cultures of bacteria, contaminated cylinder immersed into dilution of disinfectant, cylinders removed, washed, & placed into tube of medium, most effective agents entirely prevent growth at highest dilution, current standard test in US
- kelsey-sykes capacity test: bacteria are added to chemical being tested
- in-use test: swabs taken before and after application of disinfectant or antiseptic, media added to swabs, incubated for growth
