Control of Microbial Growth by Konrad T Juszkiewicz, MD, MPH Donald Burgess, Ph. D DRK Biomedical research and development LLC Almaty, October, 2013
History Humans vs. Microbes ◦ infections ◦ diseases ◦ plagues ◦ epidemics ◦ pandemics
Bubonic Plague or the Black Death Epidemic swept thru Europe in the Middle Ages (13 th and 14 th centuries) 40 million people were killed ◦ About 1/3 of the population of the continent Etiological agent: ◦ Yersinia pestis 2 Vectors ◦ Rat ◦ Flea Gram (-) rod
Yersinia pestis - Gram (-) bacillus Vectors - Rat and Flea
Bubonic Plague Infection Flea bite with Yersinia pestis Bacteria multiply in the bloodstream ◦ Bacteremia Bacteria localize in lymph nodes, especially axillary and groin areas
4. Hemorrhaging occurs in lymph nodes, resulting in “black and blue” swellings or Buboes (hence the name Bubonic Plague or Black Death)
Bubonic Plague Infection If untreated, about 50 % Mortality Rate If bacteria spread to the lungs, it becomes Pneumonic Plague and is now highly contagious (Almost a 99 % Mortality Rate)
“ I wouldn’t touch it with a 10’ pole”
Humans vs. Microbes Most of History, microbes have been winning the battle In the last 100 yrs or so the battle has swung in our favor Why? Because of our increasing knowledge of how to Control Microbial Growth
Smallpox Variola virus Eradicated in 1977 (Somalia)
Methods to Control Microbial Growth Physical Chemical
Sterilization vs. Disinfection Sterilization ◦ destroying all forms of life Disinfection ◦ destroying pathogens or unwanted organisms
Disinfectant vs. Antiseptic Disinfectant ◦ antimicrobial agent used on inanimate objects Antiseptic ◦ antimicrobial agent used on living tissue
cidal vs. static Bactericidal - kills bacteria Bacteristatic - inhibits bacterial growth Fungicidal Fungistatic Algacidal Algastatic
Factors that effect Antimicrobial Activity Temp Time Concentration of Antimicrobial agent Type of Microbe Activity of Microbe Presence of organic matter
Targets of Antimicrobial Agents 1. Cell membrane 2. Enzymes & Proteins 3. DNA & RNA
Physical Methods of Microbial Control Heat ◦ works by denaturing enzymes and proteins Thermal Death Point (TDP) ◦ lowest temp. at which all microorganism in a liquid culture are killed in 10 minutes Thermal Death Time (TDT) ◦ minimum length of time in which all microorganisms in a liquid culture are killed at a given temperature
Moist Heat Boiling Water ◦ kills vegetative bacterial cells, Fungi and many viruses ◦ not effective for endospores and some viruses ◦ Hepititis (20 min) ◦ Some spores may survive boiling water for up to 20 hrs
Moist Heat Autoclave (Steam under pressure) ◦ preferred method of sterilization ◦ Water boils at 100 C ◦ Increasing the pressure raises the Temp. ◦ 15 lbs. / per sq. inch (psi) ------> 121 C ◦ 121 C for 15 min.
Kilit Ampule Spores of Bacillus stearothermophilus Fermentable sugar p. H indicator ◦ basic - red ◦ acid - yellow
Dry Heat Direct Flaming ◦ Inoculating Loop and Needle 100% effective Incineration ◦ disposable wastes (paper cups, bags, dressings) Hot Air Sterilization ◦ Oven ( 170 C for 2 hours) ◦ used on substances that would be damaged by moist heat sterilization gauzes, dressings or powders
Filtration Removes microorganisms from solutions that might be damaged by heat ◦ ◦ culture media enzymes vaccines antibiotics
Radiation Ionizing Radiation ◦ gamma rays & x-rays penetrates most substances Used on substances that could be damaged by heat ◦ ◦ plastic petri dishes plastic syringes catheters surgical gloves
Radiation 2. Non-Ionizing Radiation ◦ UV Light does not penetrate plastic, glass or proteinaceous matter Used to reduce microbial populations ◦ hospital rooms ◦ nurseries ◦ operating rooms Thymine Dimers
Pasteurization Disinfection - not sterilization (removes unwanted organisms) Mycobacterium tuberculosis 63 C for 30 minutes 72 C for 15 seconds Thermodurics ◦ able to survive high temps. (HTST)
Methods used to control Microbial Growth 1. Heat ◦ Moist Heat Boiling Water Steam Heat (Autoclave) ◦ Dry Heat Direct Flaming Incineration Hot Air Sterilization (Oven) 2. Filtration 3. Radiation ◦ Ionizing Radiation ◦ Non-Ionizing Radiation 4. Pasteurization (Heat)
Thanks Spasiba Rakhmet Deburgess@drkbiomed. org Kjuszkiewicz@drkbiomed. org Cell. : +7 701 218 2377
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