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Chemical method of control which dislodges bacteria from hands; reduce surface tension of solvents to make them more effective at dissolving solutes
Surfactants
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Chemical method of control which is colorless, tasteless, harmless to humans, and antimicrobial & used in medical settings
Quats = quaternary ammonia compound
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How are heavy metals antimicrobial?
Metal ions alter 3-D shape of protein so no longer functions
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What is used on babies to prevent blindness caused by N. gonorrhoeae?
1% silver nitrate
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What metal inhibits algal growth by interfering w/chlorophyll, so it's used in fish & water storage tanks?
Copper
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3 basic principles of antimicrobial therapy
- 1. Selective toxicity
- 2. Reach site of infection at inhibitory concentrations
- 3. Penetrate & bind to target
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Exploiting differences in structure & metabolism of pathogens and host cells
Selective toxicity
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5 modes of action of antimicrobials- what is inhibited or damaged in microbial cell
- 1. Synthesis of cell wall
- 2. Synthesis of proteins
- 3. Synthesis of nucleic acids
- 4. Damage cell membrane
- 5. Structural Analogues
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Example of disruption of cytoplasmic membrane
Amphotericin B (polyene) attaches to ergosterol in fungal membranes which makes the cell wall leaky
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Drug which disrupts cytoplasmic membranes of Gram-negatives; toxic to human kidneys so given as last resort
Polymyxin
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Drug which binds to particular enzyme involved in a bacterial metoblic pathway
Trimethoprim
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2 drugs which target viral metabolism
Amantadine & rimantadine
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Example of a structural analog- Growth factor analog structurally related to PABA which inhibits microbial growth by inhibiting folate synthesis
Sulfanilamide
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Why are drugs that inhibit bacterial nucleic acid synthesis toxic to human cells also?
Only slight differences b/w prok & euk DNA
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_____ and _____ (2 drugs) act against prok DNA gyrase
Quinolones, fluoroquinolones
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Drug binds to and inhibits action of RNA polymerase during transcription
Rifampin
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General term for drugs that prevent attachment by peptide in viruses
attachment antagonists
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What are the 2 general HIV drugs used
- Reverse Transcriptase Inhibitors: prevents RT enzyme from turning RNA into DNA; ex: AZT
- Protease Inhibitors: protease cuts DNA, so this is inhibited
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Lowest concentration of a substance that inhibits growth of a test organism
Minimum inhibitory concentration (MIC)
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Test which uses antibiotic-impregnated wafers to test whether particular bacteria are susceptible to specific antibiotics
Kirby-Bauer
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3 main categories of side effects
- Toxicity
- Allergies
- Disruption of normal microbiota
-
Organs that are especially susceptible to toxicity
- Liver: maintains amt of chemicals in body & removes them
- Kidneys: excrete these chemicals
- Also, nerves
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Resistance by bacteria is acquired 2 ways:
- New mutations of genes
- Exchange of R-plamids
-
Multiple resistance is caused by:
exchange of R-plasmids
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Bacteria that are resistant to many drugs
Superbugs
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When bacteria is resistant to one drug, as well as all other drugs that are in the same family
Cross resistance
-
Spread of resistant bacteria throughout the community, outside of hospital setting
Community transfer
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2 diseases that are most problematic b/c of microbial resistance
-
When 2 drugs work in combination & complement each other
Synergism
-
Ways to reduce resistant microbes (2)
- Maintain intake of drug long enough for microbe to be killed off completely, not just until symptoms go away
- Limit use of antimicrobials
-
Cellular mechanisms of antibacterial resistance (3)
- Altered target: target site or enzyme become altered
- Altered uptake: can increase impermeability of cell wall by losing porins, or by pumping drugs out of cell (efflux)
- Drug inactivation: producing enzymes which inactivate antibacterial
-
2 major types of antifungals
-
Antifungal which inhibits cell mem synthesis by blocking biosynthesis of ergosterol
Azoles
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Antifungal which affects function of cell membrane by binding to sterols in it, which causes leakage of cellular compenents & cell death
Polyenes (Amphotericin B)
-
Who produces antibiotics in nature (antagonism)
(3)
- Streptomyces: bacteria
- Bacillus: bacteria
- Penicillium: fungi
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