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Antimicrobials that inhibit microbial growth/reproduction
microbistatic, bacteriostatic, fungalstatic, etc.
Antimicrobial agent used to destory pathogenic nonsporulating bacteria or their toxins on inanimate objects. that is they are bactericidal.
germicide or microbicide
any chemical agent used to kill pathogenic organisms, some can be used (safely) on living tissue of they can be used on inanimates.
antimicrobial agent that inhibits or kills infectious microbial growth in vivo. they tend to be more bacteriostatic than bactericidal & are sufficientlt non-toxic to allow application to skin & mucous membranes.
Factors that affect Death rate
-number of microbes
-nature of microbes in the population
-temperature and PH of enviroments
-concentration or dosage of agent
-mode of action of the agent
-persence of solvents, organic matter, or inhibitors
Antimicrobial Agents' modes of action
1. the effects of agents on the cell wall
2. how agents affect the cell membrane: surfactants
3. agents affecting nucleic acid synthesis and protein synthesis
4. agents that alter protein function: denaturing
5. antimetabolites: inhibits the utilization of a metabolites necessary for growth
Methods of physical control
1. heat-moist and dry
2. cold temperatures
TDT- Thermal death time
shortest length of time required to kill all test microbes at a specified temperature
heat is applied to kill potential agents of infection and spoilage without destroying the food flavor or value (batch/flash)
Deep penetrating power that has sufficient energy to cause electrons to leave their orbit, breaks DNA; gamma rays, X-rays, cathode rays; preserving food
Little penetrating power so it must be directly exposed; UV light creates pyrimidine dimers, which interfere with replication; sterilizing air, water or surfaces
Desirable qualities of chemicals
-rapid action in low concentration
-solubility in water or alcohol, stable
-broad spectrum, low toxicity
-noncorrosive and nonstaining
-affordable and readily available
Factors that affect germicidal activity of chemicals
-nature of the material being treated
-degree of contamination
-time of exposure
-strength and chemical action of the germicide
Chlorine, hypochlorites (chlorine bleach), chloramines
-Denatuate proteins by disrupting disulfide bonds
-unstable in sunlight, inactivated by organic matter
-water, sewage, wastewater, inanimate objects
Iodine, iodophors (betadine)
-interferes with disulfide bonds of proteins
-milder medical and dental degreming agents, disinfectants, ointments
-disrupt cell walls and membranes and precipiate proteins
-low to intermediate level
-bactericidal, fungicidal, virucidal, not sporicidal
-acts as surfactants dissolving membrane lipids and coagulating proteins of vegetative bacterial cells and fungi
-produces highly reactive hydroxyl-free radicals that damage protein and DNA while also decomposing to 0(2) gas- toxic to anaerobes
-anticeptic at low concentrations; strong solutions are sporicidal
Gases and Aerosols
-strong alkylating agents
-sterilize and disinfect plastics and prepackaged devices, foods
Quaternary Ammonia compounds (quats)
-acts as surfactants that alter membrane permeability of some bacteria and fungi
-effective against some gram(+) bacteria, most viruses, fungi, and algae
-ineffective against tuberculosis bacterium, bacillus, hepatitis virus, spores and any concentration, and gram(-) bacteria
-solutions of silver and mercury kill vegetative cells in low concentrations by inactivating proteins
Merthiolate, silver, nitrate, silver
-very active against gram(+) species od bacteria and various fungi
-sometimes used for antisepsis and wound treatment
-narrow spectrum of activity
Acids and Alkalis
low level of activity
-organic-prevent spore germination and bacterial and fungal growth
-acetic-inhibits bacterial growth
-propinonic- retards molds
-lactic- prevents anaerobic bacterial growth
-benzoic and sorbic- inhibits yeast
pseudomonas sp., mycobacterium tuberculosis, staphylococcus aureus, protozean cysts
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