Exam 3 Flashcards
What agents do microbial control methods consist of? Function?
Physical and chemical agents that prevent the spread of infectious agents, retard spoilage, and they keep commercial products safe.
Why must microbial control methods be adjusted to fit individual situations?
The population of microbes that cause spoilage or infection varies widely in species composition, resistance, and harmfulness.
What agent destroys all viable organisms, including viruses?
Sterilization
What agents reduce the numbers of viable microbes to a specified level?
Antisepsis, disinfection, and sanitization
What ability do antimicrobial agents have?
To destroy or inhibit microbial growth.
What do microbicidal agents cause?
Microbial death
Define -cidal
Sporicides, bactericides, fungicides, virucides
What are microbistatic agents?
Inhibitors that slow microbial growth
Define antiseptic agent
Applied to living tissue to destroy or inhibit microbial growth.
Define disinfectant agent
Used on inanimate objects to destroy vegetative pathogens but not bacterial endospores.
Define sanitization
Reduces microbial numbers on inanimate objects to safe levels by physical or chemical means.
Define degermation
The process of mechanically removing microbes from the skin.
Define microbial death
The permanent loss of reproductive capability in microorganisms.
What specific cell sites do antimicrobial agents attack in order to cause microbial death or damage?
The cell wall
The cell membrane
Biosynthesis pathways for DNA or RNA
Protein (enzyme) function
What are the physical methods of microbial control?
Heat
Cold
Radiation
Drying
Filtration
How is heat used in microbial control?
In combination with water (moist heat)
Dry heat (oven, flames)
Define Thermal Death Time (TDT)
The shortest length of time required to kill all microbes at a specific temperature.
Define Thermal Death Point (TDP)
The lowest temperature at which all microbes are killed in a specified length of time. (10 minutes)
Define Autoclaving
The process by which steam is heated under pressure to sterilize a wide range of materials in a comparatively short time. It is effective for most materials except water-resistant substances such as oils, waxes, and powders.
Boiling water and pasteurization of beverages ______ but do not _____ materials.
disinfect, sterilize
Describe dry heat
Microbicidal under specified times and temperatures. It is used when total destruction of microbes and materials is desired.
Describe chilling, freezing, and desiccation
Microbistatic not microbicidal. They are not considered true methods of disinfection because they are not consistent in their effectiveness.
Describe Radiation
Composed of high energy electromagnetic rays and are highly microbicidal.
Irradiation with ionizing radiation (cold sterilization) by gamma rays and X rays damages ____?
DNA and cell organelles by producing disruptive ions.
Define Ultraviolet Light
Has limited penetrating ability. It is restricted to disinfecting air and certain liquids and solids.
Describe Sterilization by Filtration
Removes microbes from heat-sensitive liquids and circulating air. The pore size of the filter determines what kinds of microbes are removed.
How are chemical agents of microbial control classified?
Physical state and chemical nature
Describe Chemical Agents
Can be either microbicidal or microbistatic. Also classified as -high,-medium,-low level germicides.
What are the factors that determine the effectiveness of a chemical agent?
The type and numbers of microbes involved, the material involved, the strength of the agent, the exposure time.
Describe Halogens
Microbicidal and microbistatic
Chlorine compounds: disinfect water, food, and industrial equipment.
Iodine: used as either free iodine or iodophor to disinfect water and equipment.
Iodophors: also used as antiseptic agents.
Describe Phenols
Strongly microbicidal agents.
Used in heneral disinfection.
Milder phenol compounds, the bisphenols, are also used as antiseptics.
Describe Alcohols
Dissolve membrane lipids and destroy cell proteins.
Their action depends on their concentration.
Generally only microbistatic
Describe Hydrogen Peroxide
Versatile microbicide that can be used as an antiseptic for wounds and a disinfectant for utensils.
A high concentration is an effective sporicide
Describe Aldehydes
Potent sterilizing agents and high-level disinfectants that irreversibly disrupt microbial enzymes.
What two gaseous sterilants work by alkylating protein and DNA?
Ethylene oxide
Chlorine dioxide
What are the two types of surfactants and what do they do?
Detergents and soaps
They reduce cell membrane surface tension, causing membrane rupture.
What are Cationic Detergents?
low-level germicides limited by the amount of organic matter present and the microbial load.
What products have limited applications as antiseptics and preservatives?
Heavy metals: Silver and Mercury
Define Antimicrobial Chemotherapy
Involves the use of drugs to control infection on or in the body.
Define Antimicrobial Drugs
Are produced either synthetically or from natural sources. They inhibit or destroy microbial growth in the infected host.
Define Antibiotics
The subset of antimicrobials that are produced by the natural metabolic processes of microorganisms.
What is the primary sources of most antibiotics?
Bacteria and Fungi
What are the three factors of Antimicrobial Therapy?
The microbe’s sensitivity
The drug’s toxicity
The health of the patient.
Antimicrobial drugs mode of action ( 5 categories)?
They inhibit or kill by acting on cell walls, cell membranes, DNA and RNA function, protein synthesis, or metabolic enzymes.
Drugs should be?
Selectively toxic to microbes and not cause disruptions in the host.
How many major drug families are antimicrobials classified into?
20
How are antimicrobial drugs classified?
By their range of effectiveness against many types of microbes.
Narrow-spectrum antimicrobials are effective against a limited group of microbe.
A limited amount of antimicrobials are effective against?
Protozoa
Helminthes
Fungi
Viruses
Blocks cell wall synthesis?
Penicillin’s
Cephalosporins
bacitracin
Vancomycin
Cycloserines
Blocks protein synthesis in prokaryotes?
Aminoglycosides
Effective against a broad range of microorganism and block steps in the synthesis of nucleic acids?
Sulfonamides
Trimethoprim
Isoniazid
Nitrofurantoin
fluoroquinolones
Fungal antimicrobials that are used for systemic and superficial infections?
Macrolide polyenes
Griseofulvin
Azoles
Flucytosine
Antifungal Drugs?
Most are selective for cell membranes. causing lysis of the fungus, but their action on membranes makes them potentially toxic.
Why are their fewer antiparasitic drugs than antibacterial drugs?
Parasites are eukaryotes like their human hosts and they have several life stages, some of which can be resistant to the drugs.
Describe Anthelminthic Drugs
Immobilize or disintegrate infesting helminths or inhibit their metabolism in some manner.
Describe Antiviral Drugs
Interfere with viral replication by blocking viral entry into cells, blocking the replication process, or preventing the assembly of viral subunits into complete virons.
Describe Antiviral Agents
They inactivate the replication process when incorporated into viral nucleic acids.
Describe Interferon
Effective in vivo against certain viral infections.
Commercial interferon is mainly restricted to certain cancers and hepatitis B and C.
When are microorganisms are termed drug resistant ?
They are no longer inhibited by an antimicrobial to which they were previously sensitive.
Define Drug Resistance
Genetic; microbes acquire gens that code for methods of inactivating or escaping the antimicrobial or acquire mutations that affect the drug’s impact. Resistance is selected by environments where antimicrobial’s are present in high concentrations, such as hospitals.
Microbial Drug Resistance
Develops through the selection of preexisting random mutations and through acquisition of resistance genes from other microorganisms.
Varieties of microbial drug resistance
Drug inactivation
Decreased drug uptake
Decreased drug receptor sites
Modification of metabolic pathways formerly attacked by the drug.
Widespread indiscriminate use of antimicrobials has resulted in?
An explosion of microorganisms resistant to all common drugs.
Side effects of antimocrobials?
Toxicity to organs
Allergic reaction
Problems resulting from suppression or alteration of resident microbes.
Toxicity might be?
Mild and short-lived or severe and very damaging.
What can drugs stimulate?
An overreaction by the immune system that causes various allergic symptoms.
Antimicrobials that destroy most but not all normal residents allow?
The unaffected survivors to overgrow, causing a superinfection.
Considerations for choosing an effective antimicrobial?
Nature of the infecting microbe
The microbes sensitivity to available drugs
The overall medical status of the infected host.
The Kirby-Bauer Test
Identifies antimicrobials that are effective against specific infectious bacterial isolate.
The Minimum Inhibitory Concentration (MIC)
Identifies the smallest effective dose of an antimicrobial toxic to the infecting microbe.
The Therapeutic Index
Ratio of the amount of drug toxic to the infected host and the MIC. The smaller the ratio, the greater the potential toxic host-drug reactions.
Compromised effectiveness of Antimicrobial Drugs?
Innapropriate prescription
Use of broad-spectrum instead of narrow.
Use of higher-cost drugs.
Sale of over the counter antimicrobials in other countries
Lack of sufficient testing before prescription.
Humans are in contact with microbes from ?
The moment of birth onward.
Infection?
Condition in which contaminating microorganisms overcome host defenses, multiply, and cause disease, damaging tissues and organs.
Resident or Normal Bacteria include?
Bacteria
Fungi
Protozoa
Viruses
Inhabitants of the alimentary canal?
Mouth
Large intestine
Rectum
Residents of the respiratory tract?
The nasal cavity to the lower pharynx.
Microbiota of genitourinary tract?
Restricted to the urethral opening in males and the urethra and vagina in females.
