Chapter 5 & 20 Flashcards
Sterilization
Process of destroying all microorganisms or viruses within or on a product (including endospores and fungal spores); no varying degrees
Disinfection
A process that reduces the number of microorganisms or viruses within or on a product until they no longer represent a hazard
Disinfectant
A chemical agent used to disinfect inanimate objects
Antiseptic
A disinfectant that is nontoxic enough to use on human cells
Types of Disinfectants
- cide: treatments that kill
- static: treatments that inhibit rather than kill
- e.g., germicide, fungicide, viricide, bacteriostatic/fungistatic agents
Bacteriocide
Used to kill vegetative forms of bacteria, but not usually endospores
Bacteriostatic or Fungistatic Agents
A chemical or conditions that prevent the growth of these organisms, but does not kill them
Decontamination
Involves the inactivation and removal of both microbes and any toxins that may be present within or on the product
Sanitation
In the food industry, decontamination on an area or product to meet public health standards
Factors Affection Disinfectant Action
- Time of contact: death is not always instantaneous (may take hours)
- Temperature; usually work better at high temps but most are designed to work near room temp
- pH: work best at certain value (will vary)
- Number of microorganisms: greater number of cells, greater amount of time needed
- Presence of Extraneous Matter: organic matter may react and cause them to be less effective (soil, blood, pus, etc.)
- Concentration: in most cases, the more concentrated the shorter the killing time
Decimal Reduction Time (D time)
The time it takes to kill 90% of bacteria present; usually constant over time - if it takes two minutes to kill 90% of a bacteria population, then a population of 100 would be reduced to 10 in two minutes and one in four
Types of Microorganisms
- Least resistance: vegetative forms of most bacteria and viruses with membranes
- Moderate resistance: Mycobacterium tuberculosis, Staphylococcus aureus, and Pseudononas species, viruses with no membranes
- Highest resistance: bacterial endospores
Cells in the stationary growth phase are more resistant than cells that are actively growing.
Effectiveness of Destroying Microbes
- High: Kill all organisms, including endospores; surface will be sterilized
- Intermediate: Kill resistant pathogens (mycobacterium tuberculosis) and non-enveloped viruses
- Low: Kill vegetative bacteria and enveloped viruses
Antimicrobial Chemotherapy
The use of drugs to destroy or inhibit the growth of microorganisms that are causing disease
Antibiotics
A chemical produced naturally by a microorganism (usually other bacteria or molds) that have antimicrobial effects; e.g., Streptomyces griseus (soil bacteria) are used to create streptomycin
Synthetic Agents
Chemicals that have antimicrobial effects, but are produced in a laboratory (e.g., sulfa)
Antimicrobic
A word that incorporates all types of antimicrobial drugs, regardless of origin
High Selective Toxicity
An ideal characteristic of chemotherapeutic agents; the chemical is toxic to the microbe causing the disease, but much less so to the cells of the host (all chemicals are at least slightly toxic to a host - therapeutic index is used)
Therapeutic Index
Ratio of the minimum dosage that is toxic to the host to the minimum dosage that is toxic to the microbe (MIC); e.g., 500mg/hr is toxic to humans while only 50mg/hr is toxic to bacteria - the ratio is 500/50 10:1
MIC (Minimum Inhibitory Concentration)
The lowest dose that prevents the growth of a microbe
Broad Spectrum
Toxic to a wide range of different species of pathogens, usually effective against both gram+ and gram- bacteria; low TI generally
Narrow Spectrum
Toxic to only a few types of pathogens but fewer side effects; higher TI generally
Characteristics of Ideal Chemotherapeutic Agents
- High selective toxicity
- Does not induce the development of resistant strains
- Will not cause hypersensitivity to the host (creating an immune response by the host - allergic reaction)
- Does not interfere with the hosts own defense mechanisms
Targets of Antimicrobial Drugs
- Cell wall synthesis (High TI)
- DNA replication (Low TI)
- Transcription (Low TI)
- Protein Synthesis (Medium TI)
- Cell membrane function (Very low TI)
- Metabolic pathways (High TI)
Mode of Action
The adverse effect on a microorganism; how the cell is killed
Tincture
Combination of iodine with alcohol
Iodophors
Combination of iodine and detergent
Sulfonamides (synthetic)
Drugs that interfere with a unique metabolic pathway:
- Mode of Action: function as competitive inhibitors in a chemical pathway (broad spectrum)
- Toxicity: nearly harmless to humans, as folic acid is not produced in our bodies (High TI); there are some allergic reactions
- Current Effectiveness: most bacteria are resistant to the effects, as the drugs have been used extensively since the 1930s; can still be effective at high levels which can only be obtained in the urinary tract
Folic Acid
Used in many important metabolic pathways; it is a component of an enzyme that is used to synthesize certain nucleic and amino acids; humans must consume in order for metabolic reactions to occur
Penicillins and Cephalosporins
Drugs that disrupt cell wall synthesis:
- Mode of Action: Interferes with bacterial wall synthesis; cross linkages are prevented from forming in the the cell wall (in growing cells only,) creating a cell wall that is not capable of standing against the osmotic pressures generated within the cell (will lyse)
- Toxicity: very little; since humans do not have cell walls, these drugs do not cause many side effects; a portion of the population is allergic to them, and treatment may lead to death in some severe reactions; still drug of choice due to high TI
- Current Effectiveness: usually more effective against gram+ bacteria; has a hard time penetrating the outer membrane of gram- bacteria (many are narrow spectrum, some are broad)
Glycopeptides (Vancomycin)
Drugs that disrupt cell wall synthesis; must be injected because it is poorly absorbed into blood stream:
- Mode of Action: inhibits the synthesis of peptidoglycan, no cell wall constructed
- Toxicity: few; nausea, hearing loss; high TI
- Current Effectiveness: narrow spectrum; gram+ only; little resistance, but some strains of S. aureus and Enterobacteria (within the colon) are resistant
Aminoglycosides (Streptomycin, Gentamicin)
Drugs that interfere with protein synthesis:
- Mode of Action: attach to the 30S subunit of bacterial ribosomes, interfering with translation; mRNA is misread and proteins are incorrectly assembled
- Toxicity: severe, even though drug is not actively transported into eukaryotic cells; usually used in low doses and patient closely monitored for side effects, including damage to the kidneys and inner ear; low TI
- Current Effectiveness: broad spectrum, but used rarely as many bacteria are resistant; often used in conjunction with other antibiotics
Tetracycline (Tetracycline, Doxycycline, Oxytetracycline)
Drugs that interfere with protein synthesis; drug of choice to treat undiagnosed disease (secondary bacterial infections):
- Mode of Action: attach to the 30S subunit of bacterial ribosomes, preventing the attachment of tRNA; protein synthesis completely blocked
- Toxicity: severe; nausea, diarrhea, extreme sensitivity to light; also caused liver and kidney damage, staining of teeth in children of early pregnant mothers, and can lead to secondary infections; low TI
- Current Effectiveness: very broad spectrum, but resistance is more common
Secondary Infection
Infection that occurs along with or immediately following another infection, usually as a result of the first infection; antibiotics may suppress normal flora to such an extent that pathogenic organisms can easily establish themselves and cause disease; especially true with broad spectrum antibiotics
Macrolides (Erythromycin, Azithromycin)
Drugs that interfere with protein synthesis; often used when patient is allergic to penicillin:
- Mode of Action: prevents protein synthesis by binding to the 50S subunit
- Toxicity: little; gastric distress, reversible liver damage
- Current Effectiveness: narrow spectrum (gram+ and mycoplasma); gram- often resistant as cell wall is an effective barrier
Fungicides
Kill fungi; fewer drugs exist because it is harder to find unique cellular targets; generally have low TI and high toxicity; most used as topicals but a few can be taken orally or by IV; often the patient must remain in the hospital as treatment is occurring
Polyenes
Fungicide that disrupts fungal cell membranes resulting in cytoplasmic leakage (itching, gastrointestinal disturbance - kidney damage, anemia, respectively); IV drip, topical; Amphoterican B most commonly used
Flucytosine (Oral)
Fungicide that inhibits nucleic acid synthesis (rash, diarrhea, liver damage)
Antiviral Compounds
Drugs that prevent transcription and translation, or the maturation of viruses; typically have a low TI and are very toxic, with a number of side effects; no drub provides a cure but used to slow progression of the disease and treat symptoms
Acycolvir
Antiviral compound that inhibits viral DNA polymerase in the herpes virus; few side effects as the drug is only activated in cells that have the virus; either used as topical or by IV to prevent recurrent herpes out-breaks
Nucleotide Analogs (AZT, ddl, ddC)
Molecules with a similar, but not exact, molecular structure to four normal types of nucleotides; this molecule (drug) is then mistakenly incorporated into the DNA strand of growing viruses, but the strand is useless; DNA replication eventually halts
Amantadine & Rimantadine
Antiviral compounds that prevent the uncoating of the influenza virus; help alleviate symptoms; must be given in the early stages of infection
Drug Cocktails
The use of 3-4 different antiviral compounds to stop and reverse the progress of the AIDS virus; as of yet, not a cure, even though people on treatment return to normal lives and have no visible traces of the virus; if treatment ends the virus returns
Considerations for Choosing Antimicrobial Drugs When Treating Infections
- Always choose a drug with the highest TI that is effective against the specific microbe causing the infection
- Choose a drug that will not interact with any other medications/herbs that the patient is taking
- Choose a drug that can easily diffuse into the body cavities that are infected
- A mode of delivery must be determined that is most effective and most beneficial to the patient (IV drip, injection, oral)
- Kidney/Liver condition must be assessed
- If treatment is successful, then a drug or a new combination of drugs may be necessary in order to treat the disease
Antagonistic Drugs
Two drugs make each other less effective
Synergistic Drugs
Two drugs are more effective when taken together
Additive Drugs
No drug interaction; neither antagonistic or synergistic
Innate Resistance
If a bacteria naturally lacks a drug’s cell target, then it cannot be affected by the drug (e.g., Mycoplasma has no cell wall and therefore is innately resistant to penicillin)
Development of Bacterial Resistance to Antibiotics
- Innate resistance
- Bacteria acquire most resistance through mutation or genetic exchange (conjugation/R plasmid)
- Bacteria modify cellular target
- Bacteria are able to destroy or inactivate drug
- Bacteria prevent drug from entering the cytoplasm by altering membrane permeability
- If drug is an enzyme inhibitor, the bacteria can produce very large amounts of the enzyme so that the metabolic pathway is never fully inhibited
Hypersensitivities (allergies)
The body recognizes an antibiotic as a foreign substance and reacts against it; fever, rash, and anaphylactic shock, which may be life threatening
Toxicity
Drug may cause permanent damage to a patient; antibiotics that have low TIs can be especially harmful
Production of Resistant Strains
The more antibiotics are used, the better opportunity that an organism will develop resistance to it
