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Antimicrobial Presentation for MCB3023L

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Kaitlyn Wright

on 25 October 2012

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Transcript of Antimicrobial Presentation for MCB3023L

Groups and mechanisms Antibiotics Cell wall
Protein synthesis
Metabolic pathways
Nucleic acid synthesis
Cell membrane Antibiotics that target the cell wall Targets of Antibiotics Penicillins: contain Beta-lactam ring
Penicillin G

Mechanism: inhibit transpeptidation step in cell wall synthesis

Challenges: allergies, beta-lactamases, prone to penicillinases Cephalosporins Penicillin Protein Synthesis Bacteria, as prokaryotes, contain different ribosomes

Antibiotics target protein synthesis on the ribosome
aminoacyl-tRNA binding
peptide bond formation
translocation Aminoglycosides Bind to 30S ribosomal subunit
Cause misreading of mRNA

Ex: Streptomycin
Tetracyclines Inhibit binding of the charged tRNA to the ribosome

Can be used in people allergic to penicillin

Contain: Beta-lactam ring

Mechanism: Prevents transpeptidation

Challenges: Allergies Vancomycin *Drug of last resort*

Mechanism: inhibits transpeptidation

Used stringently Cell wall formation involves:
UDP-NAM synthesis
Pentapeptide formation
binding of NAG to NAM-pentapeptide on bactoprenol
transportation through membrane
this unit is added to growing peptidoglycan
Other cell wall synthesis inhibitors NAM-pentapeptide Transport through membrane Macrolides Contain carbon lactone rings
i.e. erythromycin, which inhibits translocation on the ribosome
Metabolic inhibitors Usually involved in synthesis of folic acid, a precursor to pyrimidines and purines

Structural analogs or enzyme inhibitors Nucleic Acid Synthesis Inhibitors Target DNA helicases, gyrases, polymerases
i.e. quinolones Targets RNA polymerases
i.e. rifampin Other types of antimicrobials Disinfectants Used on non-living surfaces to destroy microorganisms
Not effective on spores
Strong harsh chemicals, like bleach, ammonia, formaledhyde
Ozone, ethylene oxide gas
Antiseptics Used on living tissue surfaces (skin, etc)
Soap, detergent, hand sanitizer
Food preservatives
Iodine, Ag nitrate
Controlling Microbial Growth Chemically Physically Mechanically Moisture removal:
All life needs water to survive
Desiccation (Via heat or addition of sugar or salt)
Changing oxygen content
Eliminating nutrient sources
Carbon, phosphorus, etc
Using preservatives or additives (for food)
Food Additives Salt - retards bacterial growth. Not good for blood pressure.
Nitrates - can be found in some cheeses, adds flavor, maintains pink color in cured meats and prevents botulism in canned foods. Can cause adverse reactions in children, and potentially carcinogenic.
Sulfur Dioxide and Sulfites - are used as preservatives and to prevent browning in alcoholic beverages, fruit juices, soft drinks, dried fruits and vegetables. Sulfites prevent yeast growth and also retard bacterial growth in wine. Sulfites may cause asthma and hyperactivity. They also destroy vitamins.Benzoic Acid and Sodium
Benzoate - are used to preserve oyster sauce, fish sauce, ketchup, non-alcoholic beverages, fruit juices, margarine, salads, confections, baked goods, cheeses, jams and pickled products. They have also been found to cause hyperactivity. Propionic Acid and
Propionates - used in bread, chocolate products, and cheese for lasting freshness.
Sorbic Acid and Sorbates - prevent mold formation in cheese and flour confectioneries
Food Preservatives Temperature
Optimum temperature
Examples: Pasteurization (milk - 63°C for 30 minutes - batch method), boiling (water - 100oC), autoclave - sterilization (reagents – 121oC), incineration (>500oC), refrigeration (4oC), freezing (-20 to -80oC)
Normal pH, acidic/basic environment
Examples: pickles, sauerkraut
Osmotic pressure and salinity - Moisture
Isotonic, Osmosis, Plasmolysis (onion cell experiment), plasmoptysis, hypertonic, hypotonic, desiccation
Halophiles, haloduric (salt)
Examples: Drying (fruits, grains)
Radiation (UV, x-ray, gamma)
Sterilization of food
Barometric pressure
HEPA filter
High-Efficiency Particulate Air filters designed for the filtration of small particles, >99.97% of 0.3 m contaminants
Liquid filtration devices – various pore sizes (<0.2 or 0.45 m
Changing texture of surfaces
Ex: sharklet
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