Chapter 7 Flashcards
Sepsis
Bacterial contamination
Asepsis
The absence of significant contamination Aseptic surgery techniques prevent the microbial contamination of wounds
Sterilization
Removing and destroying all microbial life
Disinfection
Destroying harmful microorganisms
Sanitization
Lowering microbial counts on eating utensils to save levels
Biocide
(Germicide) Treatments that kill microbes
Bacteriostasis
Inhibiting, not killing, microbes
Effectiveness of treatment depends on:
- Number of microbes
- Environment (organic matter, temperature, biofilms)
- Time of exposure
- Microbial characteristics
Actions of Microbial Control Agents
- Alteration of membrane permeability
- Damage to proteins (enzymes)
- Damage to nucleic acids
Physical method of sterilization
Chemical method of sterilization
Apply heat, radiation
Chemicals, disinfectants
To kill endospores
You need to apply temperatures higher than 100º C and pressure
Moist Heat Sterilization
- Autoclave: steam under pressure
- 121 ºC at 15 psi for 15 min
- Kills all microorganisms and endospores
- Steam must contact the item’s surface
- Large containers require longer sterilization times
- Test strips are used to indicate sterility
Dry Heat Sterilization
- Kills by oxidation
- Flaming (wire loop)
- Hot-air oven (powders, sharp instruments)
- 170º C for 2 hrs
Filtration
- Passage of substance through a screenlike material
- Used for heat-sensitive materials
- High-efficiency particulate air (HEPA) filters remove microbes >0.3µm
- Membrane filters removes microbes >0.22 µm
Physical Methods of Microbial Control
- Low temperature has a bacteriostatic effect
- Desiccation
- Osmotic pressure
Example of osmotic pressure for microbial control
Osmotic pressure uses salts and sugars to create hypertonic environment; causes plasmolysis
Dessication
Absence of water which prevents metabolism (microbial growth)
Examples of low temperature bacteriostatic effect methods
- Refrigeration
- Deep-freezing
- Lyphilization (freeze drying)
Name 3 methods of microbial control through radiation
- Ionizing radiation
- Nonionizing radiation (UV, 260 nm)
- Microwaves
Ionizing radiation
- X-rays, gamma rays, electron beams
- Ionizes water to create reactive hydroxyl radicals
- Damages DNA by causing lethal mutations
Nonionizing radiation
Damages DNA by creating thymine dimers
Microwaves
Kill by heat; not especially antimicrobial
Principles of Effective Disinfection
- Concentration of disinfectant
- Organic Matter
- pH
- Time
The Disk-Diffusion Method
- Evaluates efficacy of chemica agents
- Filter paper disks are soaked in a chemical and placed on a culture
- Look for zone of inhibition around disks
Phenol and Phenolics
- Injures lipids of plasma membranes, causing leakage
- E.g. mycobacteria contains lipis. Phenols are used to disinfect pus, saliva, and feces.
Biguanides
- Chlorhexidine
- Used in surgical hand scrubs
- Disrupt plasma membranes
Name two halogens
- Iodine
- Chlorine
Iodine (name 2 examples and function)
(Halogen)
- Tincture: solution in aqueous alcohol
- Iodophor: combined with organic molecules
- Impairs protein synthesis
Chlorine
- Oxidizing agents: shut down cellular enzyme systems
- Bleach: hypochlorous acid (HOCl)
- Chloramine: chlorine + ammonia
Alcohols
- Denature proteins and dissolve lipids
- No effect on endospores and nonenveloped viruses
- Ethanol and isoporpanol
- Require water
Oligodynamic action
Very small amounts exert antimicrobial activity
What percentage concentration of alcohol do you use in the lab?
60-70%
Heavy Metals and Their Compounds
- Oligodynamic action - very small amounts exert antimicrobial activity
- Acts on the sulfhydryl groups and denature proteins
- Ag, Hg, Cu, Zn
- Silver nitrate is used to prevent ophthalmia neonatorum
- Mercuric chloride prevents mildew in paint
- Copper Sulfate is an algicide
- Zinc chloride is found in mouthwash
Chemical Food Preservatives
- Sulfur dioxide prevents wine spoilage
- Nitrites and nitrates prevent endospore germination
Chemical Sterilization
- Cross-links nucleic acids and proteins
- Used for heat-sensitive material
- Ehtylene oxide
- Sterilization of disposable health care products
How does an autoclave sterilize bacteria?
By moist hear sterilization. This denaturizes the proteins. Uses 121°C and 15 lbs of pressure for 15 min. Does not work on heat sensitive microbes.
How does an oven kill bacteria?
Uses dry heat for sterilization. Requires temperature of 170°C for 2 hours. Also what flaming the wireloop involves.
How do filters kill microbes? How many types of filters are there?
Filters can sterilize heat sensitive materials such as enzymes and culture media, vaccines and antibiotics. Two types of filters:
- High-efficiency air (HEPA) filters - can remove microbes >.0.3µm (for air)
- Membrane filters: remove microbes >0.22µm
Which tool is used to kill bacteria with radiation?
X-rays. This is ionizing radiation which creates free radicals in the cell bu ionizing water to create reactive hydroxyl radicals.
Low levels of ionizing radiation are used to preserve spices, meats, and vegetables. Also used for the sterilization of medical equipmentsuch as syringes, surgical gloves.
Whihc type of radiation is used to damage the DNA of microbes? Where is it used and what is its disadvantage?
UV light;
Cafeterias, operating rooms, hospital rooms
It does not penetrate very well
Which sterilization method alters the cell membrane?
Iodine
Which sterilization method prevents the functioning of cellular enzymes?
Chlorine
Which sterilization method acts on lipid containing cellular components?
Phenol
Which sterilization methods acts on sulfhydryl groups of cellular proteins?
Heavy metals. Cu, Ag, Hg, Zn
Which of the following does not kill endospores?
Autoclave
Incineration
Pasteurization
Hot air sterilization
Pasteurization
Which of the following is most likely to be bactericidal?
Membrane filtration
Deep freezing
Lyophilization
Ionizing radiation
Ionizing radiation
What is antibiotic resistance and what measures can be taken to minimize the drug resistance?
It is when bacterias are no longer susceptible to antibiotics. Common causes of this are using outdated antibiotics, using them on innapropriate diseases(i.e. common cold), not using the medication correctly or completely, using someone else’s leftover antibiotics.
What is botulism?
Food poisoning caused by a bacterium (botulinum) growing on improperly sterilized canned meats and other preserved foods.
Why were nitrates and nitrites used in food preservation? Are they safe?
Because many people used to die of botulism from canned food. It is also used to preserve meats and the color in meat.
Nitrites and Nitrates are not entirely safe because they have cancer causing agents. FDA mandates the minimization of use of nitrates and nitrites in foods. Meat makes its own nitrates and nitrites
What are some examples of chemical methods for sterilization?
Halogens, Alcohols, Phenols, Sulfur dioxide, Ethylene oxide.
Which chemical sterilization techniques prevents endospore germination?
Use of nitrites and nitrates
Which chemical sterilization method is a gas and can be used on heat sensitive materials?
Ethylene Oxide
Which chemical sterilization technique acts on the phospholipid plasma membrane? How is it effective in this manner?
What is it used to disinfect?
Phenols; this causes leakage of the cellular contents.
Mycobacteria parce que they contain a lot of lipids in the cell wall; very good on treating pus, saliva, and feces.
Which chemical technique is effective as an antiseptic? Which one alters the cell membrane and stop protein synthesis and which one stops enzymes from functioning by oxidation?
Halogens
Iodine, Chlorine
How does iodine behave as an antiseptic?
Alters the cell membrane and stops protein synthesis
How does chlorine behave as an antiseptic?
It stops enzyme activity by oxidation
Which chemical method has no effect on endospores and non-enveloped viruses?
Alcohol
Heavy metals have bactericidal activity. How does this work?
They combine with cellular protein and cause denaturization.
What is chemotherapy?
The use of chemicals to treat a disease
What is an antibiotic?
substance produced by a microbe that inhibits another microbe
What are antimicrobial drugs?
synthetic substances that interfere with the growth of microbes
Which genus is responsible for producing most of the natural antibiotics? Where is it found?
Steptomyces - bacteria found in soil
How does penicillin work?
Prevents the synthesis of peptidoglycan
Chloramphenicol, erythromycin, steptomycin and tetracycline affect….
bacterial 70S ribosomes(protein synthesis)
What do antimicrobial peptides do?
Change membrane permeability
What do anti-fungal drugs combine with?
The membrane sterol
What do rifamycin and quinolones do?
Interfere with DNA replication and transcription
What do sulfanilamides do?
They affect the synthesis of folic acid
What are the two types of penicilins?
- Natural: extracted fro mpiniccilium cultures; narrow spectrum of activity
- Semisynthetic; contain chemically added side chains making them resistant to penicillinases
What is used for the treatment of tuberculosis and leprosy?
Isoniazid and ethambutol
How does chloramphenicol affect bacteria?
What does it suppress?
Inhibits peptide bond formation- binds to 50S subunit of the 70S ribosome
Synthesized chemically; broad spectruml can suppress bone marrow and affect blood formation?
How do sulfanomides work?
Inhibit the folic acid synthesis needed for nucleic acid and protein synthesis
competitively bond to enzyme for PABA production (folic acid precursor)
Synergism
the working together of two or more drugs, muscles, etc, to produce an effect greater than the sum of their individual effects.
Super bugs
bacteria that are resistant to large numbers of antibiotics
Resistant genes are often spread _______ among bacteria or plasmids via _______.
Horizontally; conjugation or transduction
What are two examples of polypeptide antibiotics?
Bacitracin - topical application; works aginst gram-positives
Vancomycin: gylcopeptide; last line against antibiotic-resistant MRSA
