Chapter 20 & 21 Flashcards
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
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
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
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
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
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)
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
Chlorine and Iodine
- Effectiveness: intermediate
- Toxicity to humans: slightly toxic; irritating to tissues and a potential carcinogen
- Action: denatures proteins, DNA
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
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
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
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
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
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
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
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
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)
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)
Epidemiology
The study of the cause, frequency and distribution of disease
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?
Communicable Disease
An infectious disease caused by a pathogen that can be transmitted from person to person
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
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%
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