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Control of Microbial Growth - Coggle Diagram
Control of Microbial Growth
Efficiency of Treatment depends on..
Environment (organic debris, biofilms, medium contents)
Time of exposure
Number of Microbes
Microbial characteristics- acid fast, endospore, gram positive/negative
Methods
Low temp- bacteriostatic- not used to kill- Listeria still lives in fridge temperatures
Osmotic pressure- salt or sugar with smoking to cure meats and dehydrate fruits
Filtration- filters with 0.2 microns applicable to clear liquids and gases only. HEPA filters are 0.3 microns
Radiation
Non-Ionizing- UV light- 260 nm damages DNA by producing thymine dimers- damages human tissues
Ionizing- gamma rays, x rays- short wavelengths, high energy electron beam, destroys bacterial DNA
HEAT
DRY- bactericidal- medical waste incinerator, flame, bactecinerator
MOIST- autoclave- bactericidal used to sterilize media
Pasteurization- bactericidal- mild heating (72C) for 15 seconds to kill spoilage organisms- does NOT sterilize- thermoduric organisms survive
Definitions
Antimicrobial Drugs- interfere with the growth of microbes within a host (antifungals, antivirals, antiparasitic)
SAFETY
Therapeutic Dose- amount of medication administrated to have desired effect
Therapeutic Index- toxic dose/therapeutic dose (larger=safer)
Toxic Dose- amount of medication administrated before undesirable side effects are noticed
Resistance- genes often on plasmids or transposons
Prevention of penetration of drug
Alteration of drug target site
Enzymatic Destruction (beta lactamase)
Rapid ejection of drug (efflux pump)
Antibiotic- substances produced by microbes that in small amounts inhibit the growth of other microbes
Fleming- 1928- discovers penicillin inhibited growth of staphylococcus aureus
Chemotherapy- use of chemical substances to treat a disease
Ehrlich- 1910- coined term and used salvarsan against syphilis
Disinfectant- chemical substance that destroys or inactivates microorganisms on non-living substance
Sterilization- destroying all forms of microbial life
Commercial sterilization- sufficient heat treatment to kill clostridium botulinum in canned food
Disinfection- destructive of vegetative pathogens
Antisepsis- destruction of vegetative pathogens on living tissue
Degerming- removing microbes from limited area
Sanitization- treatment intended to lower microbial counts of eating and drinking utensils to public safe levels
Actions
Bacteriostatic- prevents bacteria from reproduction but does not kill them- keeps them in stationary phase
Bactericidal- directly kills bacteria and reduces 99.9% of viable bacteria relative to initial density of bacteria over a set incubation period
Alters membrane permeability
Damages proteins
Damages nucleic acids
Spectrum
Broad Spectrum- saves time- destroys normal flora- opportunistic pathogens flourish and and superinfection may result
Narrow Spectrum
Gram positive- affected by penicillin and erythromycin
Gram negative cells- antimicrobial substances affect lipopolysaccharides and porins in outer membrane (streptomycin) (small hydrophilic drugs)
Selective Toxicity- killing microbes without damaging the host (easier in bacteria and virus but harder in fungi, protozoa, and helminths because they resemble human cells)
Testing-
Diffusion- Kirby-Bauer- disk diffusion method, zone of inhibition, simple and expensive
E- Test- estimates MIC only
Broth dilution- estimates minimal inhibitory concentration and minimal bactericidal concentration)
Types
Antifungals
Polyenes- amphotericin B- TMT of systemic fungi- nephrotoxic
Azoles- imidazole, ketoconazole, triazoles
Eukaryotic cells have less points of toxicity
Antivirals
HIV- zidovudine and tenofovir
Genital Herpes- acyclovir
Influenza- zanamivir, oseltamivir phosphate
Antibiotics
Actinomycetes- streptomyces- filamentous soil bacteria are 50% of antibiotics
Fungi- cephalosporium (cephalothin) and penicillin
Gram (+) bacilli- bacitracin + polymyxin topicals
Disinfectants
Halogens- fluorine, chlorine, iodine
Alcohol- concentration is important
Phenol- lysol, bisphenol
Quaternary Compounds- zephiran and cepacol
Norovirus- fecal/oral transmission causes gastroenteritis- survives 140F