Please enable JavaScript.
Coggle requires JavaScript to display documents.
Control of Microbial Growth - Coggle Diagram
Control of Microbial Growth
microbial control
sterilization - destruction of all forms of microbial life, endospores
commercial sterilization - canned food
disinfection - destroy vegetative pathogens
antisepss - living tissue
determine - limited site
sanitization - safe public health, utensils
control definitions
chemotherapy - use of chem substances to treat disease
history
ehrlich (1910)- magic bullet, coined term, Salvarsan-arsenic compound against syphillis
Fleming (1928)- penicillin inhibits staphylococcus aureus growth
Florey and Chain (1940)- first clinical trials of penicillin
antimicrobial drugs - interfere with growth within host
antibiotic - produced by microbes, inhibit growth of other
disinfectants - destroy or inactivate on nonlicving surfaces
death rate
number of microbes
environment- organic debris, biofilms, medium contents
time of exposure
dies exponentially
microbial charcateristics- acid fast, endospore, game + vs gram -
action
bactericidal - directly kill, 99.9%
bacteriostatic -prevetns reproduction, kept in stationary phase
mode
alteration of membrane permeability- penicillins, polymyxin B
damage to proteins- chloramphenicol, erythromycin (translation or the ribosome
damage to nucleic acids- Quinoolones, rifampin (TB), z pack for metabolites
physical methods of control
heat
moist- autoclave, bactericidal, sterilize media, preferred
dry - bactericidal, incinerator, flaming
pasteurization - bactericidal and bacteriostatic, kill spoilage, milk, 72 degrees celsius for 15 s , kills pathogens and reduces total bacterial numbers, not sterilzed
thermoduric organisms (stereo and lactose) survive
filtration- fast, 0.2 microns, clear liquids and gasses only, HEPA 0.3 microns
low temp - bacteriostatic
listeriosis- grow at fridge temp, pregnant women- miscarriage, deli meat, blue bell ice cream
osmotic pressure - food preservation, salt or sugar or smoking, dehydration of fruit or meats
radiation
ionizing - gamma, x rat, destroy bacterial DNA, short wavelength/high energy, food, pharmacy, catheters, plastics
non-ionzing- UV, 260nm damages DNA by producing thymine dimers, not penetrate well, damaging to human
spectrum of antimicrobial activity
selective toxicity
kill microbes w/o host damage
bacteria - prokaryotes - presence/absence of cell walls, ribomes structure, metabolic pathways
viruses- within host cells, using host "machinery{
fungi/protozoans/helminths- eukaryotes, resemble human cells-fewer safe antimicrobials
penicillin- gram +
streptomycin- mycobacteria and gram -
tetra- gram - and +, chlamydias
mefloquine- malaria
niclosamide- tapeworns
viruses- acyclovir
broad spectrum
saves time w/o ID but destroys normal flora/compeittive inhibiton
opportunistic pathogens flourish
superinfection- growth of survivors
ex. Candida albicans-yeast infection, clostridium difficile
narrow spectrum
gram + - affected by penicillin G and erythromycin
gram - - affects lipopolysaccharides and porins in outer membrane
streptomycin - small, hydrophilic drugs can cross porin channels in membranes
tests to guide chemotherapy and disinfectants
diffusion method
Kirby-bauer - zone of inhibition, does it work or not, simple/inexpensive
E-test - estimates MIC only
we want to know how much, not just if it works
broth dilution tests
MIC - minimal inhibition concentration
MBC - minimal bactericidal concentration
wider zone of inhibition=more efficient disinfectant (disc diffusion method)
Antimicrobial safety
risk vs benefits (side effects)
toxic dose- Amt before undesirable effects
therapeutic dose- Amt required for desired effect, higher therapeutic dose = safer , low dose ex=chemo
resistance
enzymatic destruction (Beta lactamase)
prevention of drug penetration
alteration of drug's target site
rapid ejection of drug (efflux pump)
resistant genes on plasmids/transposons, transferred btwn bacteria
most resistant- prions, endospores
least resistant- virus w lipid envelopes, gram +
norovirus
2500 cases per year, 8/1/25-1/8/26 447 outbreaks
49% food borne illness
oyster/shrimp- can survive steamed temps up to 140
gastroenteritis - fecal/oral transmission, sheds in feces 2-3 days before illness, 2 weeks after recovery
TMT rehydration, PVT - 25T bleach/gal water, long cycle on heat