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Control of Microbial Growth - Coggle Diagram
Control of Microbial Growth
Efficacy and Microbial Action
treatments depend: # of microbes, organic debris, biofilms, medium, time of exposure, acid fact, endospore, gram.
bactericidal agent has 99.9% reduction
bacteriostatic prevents reproduction but doesn't kill. stationary phase of growth
mode of action: alteration of membrane permeability, damage to proteins and nucleic acids
microbial control
autoclave uses moist heat for sterilization. bactericidal
dry heat: flaming or incineration are bactericidal
pasteurization: heating to 72 C for 15 sec. kills pathogens but doesn't sterilize. thermoduric orgn like strep spp. and lact spp. survive and cause spoilage
filtration for clear liquid and gases. filters with 0.3 holed microns. HEPA filters
listeriosis can grow at fridge temps. causes diseases in pregnant women.
osmotic pressure: salt or sugar. meats and fruits.
ionizing radiation destroys DNA. Gamma and Xrays
non ionizing radiation: UV: damages DNA by producing thymine dimers. doesn't penetrate well
History and Safety
1910 Ehrlich coined chemotherapy against syphilis
1929 Fleming discovered penicillin. kill gram +
chemotherapy is toxicity to kill microbes without damaging the host
superinfection: pathogens flourish. can happen with broad spectrum antibiotic
narrow spectrum affect gram +
gram - cells must content with the outer membrane
tests
broth dilution test estimates MIC and MBS
Kirby Bauer test disc diffusion method: simple and inexpensive. measures zone of inhibition
therapeutic dose: amt of med to have the desired effect ^
toxic dose amount of med before undesirable effect
therapeutic index is the ratio of the toxic dose divided by the therapeutic dose. larger the index safer the med
resistance and specific agents
antibiotic resistance: enzymatic destruction, prevention of penetration of drug, alteration of drug's target site, rapid ejection via an efflux pump
resistance genes found on plasmids or transposons. transferred between bacteria
streptomyces spp. are filamentous, soil bacteria produce 50% of antibiotics
antifungal drug polyenes treat systemic fungi but are nephrotoxic.
neuraminidase inhibitors used to treat the flu include zanamivir (Relenza) and oseltamivir (Tamiflu)
zidovudine (AZT) and Acyclovir: ex of nucleoside analogs used to treat HOV and genital herpes.
triclosan works against gram + bacteria
iodine is alc based antiseptic. disinfectant
quaternary comp. like zephiran are used to treat acne
Norovirus
causes gastroenteritis and is transmitted via the fecal or oral route
can survive temp as high as 140 F
prevention: 25 TBL of bleach per gallon water