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Lab Report on various disinfectants and their effectiveness.
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Name: Sara Boland
Lab Name: Disinfectant Lab
Purpose: Some microorganisms need to be controlled in order for us to maintain our current standard of living. Pathogens and microbes that spoil food are of particular concern as are microbes that deteriorate inanimate objects. One of the tools we use for controlling the spread of microorganisms are antimicrobial agents. Disinfectants are antimicrobial agents that fall into two categories: microstatic disinfects, which inhibit the growth and reproduction of microbes and microcidal disinfectants, which destroy the microbes. Specific microbes respond differently to disinfectants and this means that no single agent is effective against all microorganisms. Several factors influence how a disinfectant works. These factors include make-up of disinfectant, time of contact with microbes, pH, sensitivity of microbes, and the presence of extraneous material. There are 3 categories of disinfectant based upon how they affect the microbes. The first interferes with cell walls (phenols, alcohols, detergents), the second is interference with enzyme function (detergents, heavy metals), and the third is protein denaturation (phenols, alcohols, detergents). Knowledge of how a disinfectant works can make it easier to choose one for each specific purpose.
Materials:-4 Bottles Nutrient Agar -Sterile Petri dishes-4 Disinfectants -Forceps-Package white (control) disks -Alcohol pads-5 Packages colored disks -Hot plate
Organisms:-Bacillis cereus -Escherichia coli
Procedure:
1. Loosen caps on Agar bottles and boil until melted using a water bath. Make sure water level is well above line of Agar in bottle.2. Cool Agar to 45 degrees3. Disinfect work surface4. Shake the Bacillis cereus culture, remove cap and flame the mouth of the tube, then distribute the contents evenly between two bottles of prepared Agar5. Swirl each bottle to mix bacteria through agar and then distribute contents evenly between five Petri dishes, making sure to cover the entire bottom of dishes well. Cover immediately and let sit until Agar hardens6. Label dishes
7. Repeat steps 4, 5, and 6 with Escherichia coli.8. Incubate Petri dishes while setting up disinfectants9. Set up stations for each disinfectant with colored-paper disks, forceps, one disinfectant and three alcohol pads. Set up a control station with white-paper disks, forceps, sterile water and three alcohol pads10. Distribute one dish of E. coli and one of B. cereus to each group.11. Have each group take one station and add disks to sample.12. Incubate for 48 hours, inverted at room temperature, then refrigerated.
Results:
Paper Disks Diameter of zone of inhibition (mm)Disinfectant Color 24 Hours 48 Hours
B. cereus E. coli B. cereus E. coliWater Water