Chapter 9 : Controlling microbial growth Flashcards
1
Q
Sterile/ Sterilization
A
-kill all things
2
Q
Aseptic/asespsis
A
-kill the ones that are pathogenic, but not all of them
3
Q
Disinfectants/disinfection
A
-used on hard surfaces
4
Q
Antiseptic/antisepsis
A
-used on skin to sterilize
5
Q
degerming
A
-physical removal of microbes
ex: hand washing
6
Q
Sanitization
A
-lowering the number of germs to a safe level. safe level depends on location Would be used in healthcare setting, food places, grocery stores
7
Q
Difference between pasteurization and sterilization
A
-sterilization seeks to eliminate all microorganisms and spores, while in pasteurization is killing pathogens and spoilage microbes for safe consumption
8
Q
static or stasis
A
-to stop growth
9
Q
cide or cidal
A
-to kill
10
Q
Decimal reduction time (D)
A
-the time it takes to reduce the population by 90%
-number of living organisms on the x axis
-Time (min) on the y axis
-microbes die at a constant rate
11
Q
What does a decimal reduction time with a steep slope mean?
A
Less than a minute
12
Q
What does a decimal reduction time with a gradual slope mean?
A
-more than a minute
13
Q
What are the two modes of action antimicrobial agents fall into
A
- alteration of cell walls or cell membranes
2.Interference with proteins and nucleic acids
14
Q
Alteration of cell wall or cell membrane
A
-cell walls help maintain integrity of cell so when disrupted they are more susceptible to osmotic forces
-the membrane selectively controls passage of chemicals into and out of the cell
15
Q
Viral envelope
A
-is responsible for attachment of the virus to the targeted cell therefore damage to the envelope interrupts viral replication rendering them avirulent
*handwashing can render them gone
16
Q
Non-enveloped virus
A
-these viruses have a greater tolerance to harsh conditions
17
Q
Interference with proteins and nucleic acids
A
-protein, DNA, RNA integrity/function depends on their 3-Dimensional shape
-heat or certain chemicals, or heat denaturing of nucleic acid
18
Q
dentaure
A
-to change shape
19
Q
Chemicals, radiation, or heat denaturing of nucleic acid and proteins result in?
A
- generating fatal mutations
- halting protein synthesis (through denaturing RNA/DNA)
20
Q
An ideal antimicrobial agent would be?
A
-one that is inexpensive, fast acting, stable for storage and would control all microbial growth while being harmless to humans, animals, and objects
21
Q
Is there an ideal agent
A
No
22
Q
What are the factors to be considered when selecting an agent
A
- nature of the site to be treated
- Harsh chemicals, and extreme heat cannot be used on animals, humans, or fragile objects
- degree of susceptibility of microbes
- relevant environmental conditions and their effects on the agent
23
Q
Susceptibility of microbes
A
most resistant: prions (infectious proteins)
Bacterial endospores
least resistant: enveloped viruses
most gram positive bacteria
24
Q
Germicides
A
-are classified as high, intermediate, or low level, based on how well they work on medical instruments that can’t be heat sterilized
25
high level germicides
-germicides are needed on implants, cardiac catheters, heart and lung machines
-kill all pathogens including endospores
26
Intermediate level germicides
-germicides used on instruments that contact the mucous membrane, kill fungal spores, protozoan cysts, viruses, and pathogenic bacteria but not endospores
27
low level germicides
-kill vegetative cells and some viruses for skin contact applications such as electrodes
28
Biosafety level 1
handling pathogens that do not cause disease in healthy humans (e.coli)
29
biosafety level 2
handling moderately hazardous agents (MRSA, e.coli strain 0157-H7)
30
biosafety level 3
handling virulent or harmful microbes in safety cabinets
31
biosafety level 4
handling microbes that cause most severe or fatal diseases (Ebolavirus)
32
Physical methods of microbial growth control
1. extreme temperatures
2. desiccation
3. filtration
4. osmotic pressure
5. radiation
33
Thermal death point
-the lowest temperature that kills all cells in a volume of broth in 10 minutes
34
thermal death time
the time needed to sterilize a set volume of liquid at a set temperature
35
moist heat
-used to disinfect, sanitize, or sterilize
-more effective than dry heat
36
why is moist heat more effective than dry heat
-water has a high capacity for heat
37
Methods of microbial control using moist heat
1. boiling
2. autoclaving
3. pasteurization
4. ultrahigh temperature sterilization
38
Boiling
-this kills all vegetative cells of bacteria and fungi, protozoan, trophozoites, and most viruses within 10 minutes at sea level
-but resistant forms like endospores or resistant protozoan forms, cyst and some viruses can survive boiling temp
-boiling time is critical and depends on elevation
39
how do we raise the boiling temperature of water above 100C
-use pressure
-ex: autoclave
40
Relationship between boiling temperature and pressure
-as pressure increases and boiling point temperature increases
41
Autoclaving
-pressure applied to boiling water prevents steam from escaping therefore boiling temperature increases as temperature increases
- conditions in autoclave are 121 C at 15 psi for 15 min
42
Verifying media sterlization
1. after autoclaving, flexible vial is squeezed to break ampule and release medium onto spore strip
2. yellow medium means spores are viable and autoclaved objects are not sterile
3. red medium means spores were killed, autoclaved objects are sterile
43
Pasteurization
is used for dairy products, wine, beer, fruit juices
-thermodures and thermophiles survive but they do not cause spoilage and not pathogenic
44
List three milk pasteurization protocols
1. batch method
2. flash pasteurization
3. ultrahigh temperature pasteurization
45
Batch method
30 minutes 63 C
46
Flash pasteurization
15 seconds at 72 C
47
ultrahigh temperature pasteurization
1 sec at 134 C (this temp may affect taste)
48
Why is dry heat used?
-used for material like powders, oils, and some metals
-cannot use autoclave b/c they introduces moisture
49
Dry heat
-requires heat at a much higher temperature for longer time
-to sterilize with dry heat at 121C it would take 16 hours
-usually use temperatures of 160-171
49
Incineration
-the ultimate means of sterilization
ex: bacinerator or Bunsen burner
50
What does refrigeration, freezing, and drying do?
-decreases microbial metabolism, growth and reproduction but not always cidal (kills)
-chemical reactions are slowed down at low temperatures and if frozen, liquid water is not available for metabolism
-refrigeration halts most growth of pathogens
-slow freezing is more effective than quick freezing if you want to kill organisms but organisms vary in susceptibility
-drying inhibits growth due to removal of water but is microbiostatic
51
Lyophilization
-used for long term preservation of microbial cultures
-precents the formation of damaging ice crystals
52
Microbiostatic
-microbial like statis (halts growth)
53
osmotic pressure
-high concentrations of salt or sugar in foods to inhibit growth
-fungi have greater ability than bacteria to survive this environment
54
Radiation
-short wavelength= more energy = greater penetration
55
electron beams
very effective at surface killing but do not penetrate well
56
gamma rays
-penetrate much farther than electron beams but require hours to kill microbes
-used to sterilize spices, meats, fruits, medical and dental supplies
-also kills larva and eggs, minimize spoilage
57
Non-ionizing radiation
-excites electrons causing them to make new covalent bond so it can affect the 3-D- structure of proteins and nucleic acids
-UV light can cause pyrimidine dimers in DNA
58
UV light
-does not penetrate well but is ok for disinfecting or, transparent fluids, and surfaces
-air ducts can include banks of UV light to purify air in HVAC systems
-some cities use UV light to process drinking water or sewage therefore reducing amount of chlorine drunken
59
chemical methods of microbial growth control
-their effects vary with temperature, length of exposure, and amount of organic matter
-also varies with pH, concentration, and age of chemical
-more effective against enveloped viruses and vegetative cells of bacteria, fungi, and protozoa
60
Two modes of action for chemical methods of microbial growth control
1. denature proteins/nucleic acids or disrupt cell membranes as heat does
2. oxidation reactions
61
denature
change shape
62
folded protein
-functional
63
unfolded protein
-not functional
64
oxidation
-lose electrons (cells that are oxidized are permanently damaged)
65
Phenol and phenolics
-intermediate to low level disinfectants
-effective in presence of organic matter and they remain active for prolonged time (long half life)
-commonly used in health care settings, labs, and homes
-ex: lysol)
-pine and clove oils are natural phenolics
-phenolics have a bad smell and possible side effects in high doses over long time
66
What does lysol do?
-destroys the cell membrane and denature proteins
67
Alcohol
-intermediate level disinfectant
-evaporate rapidly, both good and bad b/c wont cause damage to skin but stays on long enough to kill microbes. Bad b/c does not stay on surface long enough (bad disinfectant)
ex: swabbing of skin or surfaces with 70% ethanol prior to injection
-alcohols typically antiseptic
68
Halogens
-intermediate-level disinfectant
-believed to damage enzymes via oxidation
ex: iodine tablets, idophors (betadine), chlorine, or diluted bleach
-chloramine and idophors release slowly
-halogens steal electrons from chemicals (not true oxidizing agent)
69
Oxidizing agent
-peroxide, ozone, and peracetic acid kill by oxidation of microbial agents
-steal lots of electrons
-good for killing microbes
70
Hydrogen peroxide
-can disinfect and sterilize surfaces of objects but...
-humans contain an enzyme called catalase which neutralizes these and produce bubbles on tissue so not a good choice for open wounds or puncture
-can be used as an antiseptic or disinfectant
71
ozone
treatment of drinking water
-ex: hot tubs
72
peracetic acid
-an effective sporocide used to sterilize equipment
-expensive and toxic for humans
73
sporicide
-kills everything
-even endospores
74
Surfactant
-surface active chemicals that reduce surface tension of solvents and make them more effective at dissolving solutes and degerming
75
soaps and detergents
-soaps have hydrophilic and hydrophobic ends, good at degerming agents but not naturally antimicrobial
-soaps that are antimicrobial or antibacterial have an antimicrobial agent added to the soap
76
degerming
physically remove
77
quats
-ammonium cations with hydrogens replaced by hydrocarbons, which disrupt cell membranes, they are harmless and tasteless to us in low concentrations
-not often used and good for bacteria only
-long molecules that poke a hole (disrupt membrane)
78
low level bacteriostatic and fungistatic agent examples
-heavy metals (arsenic, zinc, mercury, copper, silver)
79
1% silver nitrate
-used to be applied to all newborns eyes to prevent blindness caused by N. gonorrhoeae but newer less irritating agents replace it
-also sterilize burn victims
80
silver
-still used in some burn creams or catheters
81
thimerosal
to preserve vaccines but it is not used as much any more b/c heavy metal content
-mercury is in it
82
Copper
-controls algal growth in reservoirs, fish tanks, swimming pools, and water storage tanks, interferes with chlorophyll and stops photosynthesis
83
Aldehydes
-contains a terminal carbonyl group
-messes up the bonds of other molecules
84
formalin
- is 37% formaldehyde solution used in embalming and disinfection of rooms and instruments
-stops all chemical reactions and stops microbe from breaking down tissue
85
gluteraldehyde
-sometimes is used to disinfect medical/surgical instruments
86
Gaseous agents
-high level agents used for sterilizing heat/moisture sensitive material
-ethylene oxide (most common), propylene oxide and beta-propiolactone need to be in close chambers to sterilize
-used in hospitals and dental offices on material heat sensitive
87
What are drawbacks of gaseous agents
-they are often highly explosive, extremely poisonous, and are potentially carcinogenic
88
Enzymes
-new emerging field using microbial enzymes to sterilize or disinfect
89
lysozyme
-most commonly used
-also used in cheese to control microbial growth
90
prionzyme
-binds to prions and cause them to breakdown
91
prions
misfolded proteins
-indestructible
-can come in contact with any molecule and cause them to change shape
92
True antibiotic
-antibiotic produced by an organism
93
semisynthetic antibiotic
-antibiotic produced by an organism and modified in a research lab to work better
94
synthetic antibiotic
completely produced in a lab
95
antibiotic
-used for treatment of diseases or in research not often in environmental conditions
-some are used for antimicrobial control outside the body such as chloramphenicol in research or food production like nisin and natamycin`
96
Phenol coefficient
-evaluates the efficacy of disinfectants and antiseptics by determining the ratio of agents ability to control microbes compared to that of phenol
Phenol = 1 means more powerful
phenol less than 1 means less powerful
-method has been replaced by newer methods
97
use dilution test protocol
-test chemical efficiency
-metal or porcelain cylinders are dipped in broth cultures of bacteria and dried. then immersed in disinfectant for 10 minutes. Cylinders are then removed and rinsed with sterile water and placed in tubes of growth media for 48 hours
-the most effective agent entirely prevents growth at the highest dilution
-currently the standard in US
-use this to find best concentration to use
98
what test does Europe used for use-dilution
Kelsey-Sykes capacity method
-add bacteria to disinfectant then transfer to fresh broth
99
In-use dilution test
-applies evaluation to a real time application
-swabs taken from objects before and after application of disinfectant or antiseptic
-swabs are inoculated into growth medium and incubated
-medium monitored for growth
-this provides an accurate determination of proper strength and application procedure for each specific situation
100
Are antibacterial soaps good to use all the time?
- no b/c over time the bacteria can build resistance
101
When do you need to use antibacterial soap?
no, soap only needs to physically remove germs but people with equipment such as ports in their body need this soap
