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Flashcards in Chapter 20 & 21 Deck (37):
1

Alcohols

An exception to the concentration as these are more effective when some water is used (should be diluted to 75%); proteins dissolve in water which allows these to damage proteins:
- Effectiveness: low-intermediate
- Toxicity: varies
- Actions: disrupt cell membranes and denature cellular proteins; evaporates quickly

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Types of Alcohols

- Ethyl (ethanol, grain): non-toxic; more expensive than isopropyl
- Isopropyl (rubbing): more effective microbial agent, but more toxic to animals (vapors can damage CNS of humans)
- Neither kills endospores

3

Hydrogen Peroxide

- Effectiveness: low
- Toxicity to humans: none
- Actions: large amounts quickly overwhelm any catalase and peroxidase found within the cell; acts as a free radical which is highly toxic to living oranisms

4

Surface-Action Agents

- Effectiveness: Anionic (soaps)- essentially none; used in removing microorganisms but does not kill them; Cationic (quaternary ammonium compounds)- low effectiveness; ineffective against gram- bacteria
- Toxicity to humans: none-low
- Action: no action; disrupts cell membranes

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Heavy Metals

- Effectiveness: low
- Toxicity to humans: little on skin, but toxic if placed on wounds; topical only (used on burns)
- Action: denatures proteins
- e.g., mercury containing compounds including metaphen, silver containing compounds including silver nitrate; in the past used to prevent gonorrheal infections in the eyes of newborns, but ineffective and was irritating

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Phenol (corbolic acid) and its Derivatives

- Effectiveness: intermediate; often ineffective against non-enveloped viruses
- Toxicity to humans: very toxic to tissues; used as a topical antiseptic only (surgeon hand creams)
- Action: damage cell membranes and denature proteins
- Examples: Lysol (phenol derivative & 79% alcohol)- very effective; Chlorhexidine (hand cleanser)

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Ethylene Oxide

- Effectiveness: high
- Toxicity to humans: high; carcinogenic
- Action: denatures proteins and mutates DNA strands
- Usually in vapor form; does not require water to function well; slow acting; explosive; used extensively in hospitals when items may be damaged by heat or water

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Chlorine and Iodine

- Effectiveness: intermediate
- Toxicity to humans: slightly toxic; irritating to tissues and a potential carcinogen
- Action: denatures proteins, DNA

9

Dry Heat

Hot dry ovens or direct exposure to flame are used for this process; quickly incinerates microbes; used to sterilize glassware, powders, oils; flame of a Bunsen burner reaches 1870 degrees C

10

Incineration

- Used to completely destroy most hospital items
- Using dry heat ovens, steriliztion of all living cells and endospores would require (at minimum): 150-180 degree C heat; 2-4 hours of contact time
- Disadvantages: time, many items cannot tolerate such heat extremes

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Moist Heat

- This process would be considered boiling or steaming items
- Kills most vegetative forms of bacteria in minutes, but will not destroy endospores
- Boiling of water brings the temperature up to 100 degrees C
- Pasteurization: Flash Method- heats the fluid to 72 degrees C for 15 seconds, usually conducted as the fluid flows through pipes (very common); Holding Method- liquid heated in bulk to 63 degrees C for 30 minutes

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Disadvantages to Moist Heat

- Some viruses and bacteria can tolerate short boiling times
- Endospores can survive several hours
- Does not usually sterilize the items, but greatly reduces the number of bacteria found on or within a substance

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Moist Heat Under Pressure (the autoclave)

- Most medical and laboratory products are sterilized in this manner
- When water is present, all macromolecules are denatured at relatively low temperatures
- Complete sterilization possible (including endospores)
- Typical Criteria: 15psi (no direct role in destruction of bacteria, 121 degrees C, 15 minutes
- Disadvantages: expensive, cannot be used on something that will be ruined when it comes into contact with water at high heat

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Harvey Chemiclave

- When an alcohol/formaldehyde vapor is pressurized and heated
- Very quick turnaround time
- Used often with dental instruments
- Disadvantages: expensive, cannot be useed if articles will be damaged by chemicals, heat, or pressure

15

Non-Ionizing Radiation (UV light)

- In general, will alter the structure of DNA molecules by creating thymine dimers
- Many of these mutations can be repaired by the bacterial cell, but in high doses the DNA molecule is rendered non-functional (unable to repair all damage)
- Used as disinfection tool most often
- Often placed near air ducts in sterile areas like operating rooms
- Very good at reducing the number of living organisms (99%+)
- Very good against actively reproducing cells, but less so against endospores
- Disadvantages: readily passes through air, sightly through liquids, and much less so through solids; damaging to human tissues

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Ionizing Radiation (X-rays and Gamma Rays)

- Very high energy wavelengths
- Action: breaks linkages between adjacent nucleic acids and in the process produces free radicals
- Used in food preparation and becoming ever more popular in the hospital community
- Can penetrate fabrics, plastics, liquids, and foods
- Very good potential, just not in wide used as of yet

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Filtration

- Contain pores that range from 0.02 micrometers to 8 micrometers; the larger sized pores will catch the bacteria as it travels through, and smaller will even catch viruses but not very small toxins or viruses
- Effective in removing microorganisms from liquids and gases that are heat sensitive, but does not destroy microbes; used extensively in food processing market to being placed in air handlers in sterile environments (operating rooms)

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Modes of Action

- Cell Wall: disrupt synthesis of or digest, causing lysis
- Cell Membrane: cause leakage
- Protein and Nucleic Acid Synthesis: bind to ribosomes preventing protein synthesis; bind to DNA preventing transcription and translation; change base pair pattern of DNA
- Altering Protein Function: alter shape (denature)

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Epidemiology

The study of the cause, frequency and distribution of disease

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Epidemiology Questions

- What pathogen is responsible for the disease?
- What is the source (reservoir) of the disease?
- Who in the population is at risk?
- How is the disease spread?
- How many people have the disease?
- Geographically, where is the disease located?

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Communicable Disease

An infectious disease caused by a pathogen that can be transmitted from person to person

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Rate of Disease

Describes the proportion (percentage) of a population who have the disease; e.g., if 100 people of 1000 were infected were sick, this population would be 100/1000 or 10%; looks at the entire population, not just those exposed

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Attack Rate of Disease

Describes the proportion (percentage) of a population that develop the disease after they have been directly exposed to the pathogen; out of 1000 people, 100 drank contaminated water and 10 developed chronic diarrhea: 10/100 or 10%

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Morbidity

Describes the rate of disease along with time of the month or year; describes your chance of developing a disease at a certain time of year or a certain season

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Mortality

The proportion (percentage) of people who have contracted the pathogen and died from the disease

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Epidemic

A disease found in unusually high frequencies within a population

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Pandemic (Pan = all)

An epidemic spread across the world

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Endemic

Disease is constantly present within a given population; flu, colds never leave our population

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Chain of Infection

- Reservoir: pathogen is found in a source in which it is capable of living, growing, and spreading to other hosts (another person, other animals, the environment)
- Portal of Exit: if the pathogen is found in another human, then it must escape their reservoir through some orifice
- Mode of Transmission: a person must come in contact with the exposed material from the portal of exit
- Portal of Entry: how the organism enters the body

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Portal of Exit/Entry

- Digestive System: anus or mouth (feces, vomit)
- Urinary System: urethra (urine)
- Respiratory System: mouth, nose (mucus)
- Reproductive System: vagina, urethra (vaginal fluid, semen)
- Breaks in the skin
- Eye

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Droplet of Transmission

Inhalation of large vaporized respiratory droplets (sneeze, cough)

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Incubation Period

The length of time between exposure to the pathogen and onset of disease symptoms

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Symptomatic

Hosts that are showing symptoms of a disease; easy to identify and therefore easy to isolate to slow the transmission of the pathogen through a population

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Asymptomatic

Hosts that are not showing symptoms, but can potentially still transmit the pathogen to another host; difficult to identify hosts so easy for disease to spread through the population

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Dose

The number of pathogens a person (host) is initially exposed to; large are more likely to cause disease and will shorten the incubation time while small are less likely to cause disease and will lengthen the incubation time

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Herd Immunity

A disease has a difficult time spreading to susceptible hosts because only a few reservoirs exist

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Population Characteristics That Can Increase Susceptibility to a Disease

- Malnutrition
- Crowding
- Fatigue
- Stress
- Age
- Gender
- Genetics: blood types AB, A, B, O (from most to least) resistant to many intestinal bacteria