1. Effects of Radiation on Growth

2. Radiant energy released by certain electromagnetic processes Divided into a spectrum based on wavelength – Longer wavelength: lower in energy Radio waves, microwaves, infrared – Shorter wavelength then visible light: higher energy level Ultraviolet light, X-rays, gamma radiation, cosmic rays Excite molecules to the point of disruption More destructive Electromagnetic radiation (EMR)

3. Electromagnetic Spectrum

4. Occurs in short wavelengths Most effective at 260 nm – Specific wavelength at which DNA maximally absorbs UV light Used to control the growth of microorganisms in or on materials – Used to sterilize surfaces, items that cannot be autoclaved inability to penetrate glass, plastic, or any other solid or liquid Ultraviolet light

5. Mutagen: causes mutations The absorption of UV light causes Thymine Dimers – Mutation of the DNA – Neighboring thymines in the DNA bind to each other rather then their normal partner, adenine – Bacteria have an SOS system that can go back and Repair the damaged bacteria Depends on time of exposure to UV light Ultraviolet light

6. In this lab you will compare the effects of UV light on an endospore forming bacillus (B. subtilis) and a non-endospore forming cocci (Staph aureus) Endospores are formed by some bacteria that have the ability to enter a state of “suspended animation” when conditions are unfavorable.

7. Using aseptic technique, dip a sterile swab into your bacterial culture Streak your swab straight down the middle of the plate Starting at the top, streak across your first streak to cover your plate Rotate your plate 90°, starting at the top, streak to cover your plate. Rotate your plate 45°, starting at the top, streak to cover your plate. Swab the edge of the agar Swabbing plate for confluent growth

8. Experiment Instructor will assign organism and time Swab plate for confluent growth

9. Label your plate to split it in half: – Covered – Uncovered Label your plate with: – Name of organism – Student initials – Time exposed – Date – Lab Section Bring your plate to the UV hood, remove the lid and cover the “Covered” half with an index card Expose your plate to UV light for the assigned time. Replace the lid and place in the class bin when finished. Today’s exercise (continued) Covered Uncovered

10. Evaluation of antiseptics Exercise 10

11. Antiseptics/disinfectants are chemicals agent used to control the growth of microorganisms. – Antiseptics are gentle enough to be applied to live tissue but harsh enough to inhibit microbial growth Used for washing hands, treating surface wounds, and preparing the skin for invasive procedures – Disinfectant are harsher then antiseptics and can destroy live tissue along with any microorganisms. Applied to inanimate objects (floors, counters, ect) to kill microorganisms Steriliants or sporocides : kill all microorganisms, including endospores. – Sanitizers: agents that reduce microbial numbers to a safe level but do not completely eliminate all microbes Evaluation of Antiseptics

12. Method Disk diffusion (Kirby Bauer) Kirby–Bauer antibiotic testing (KB testing or disc diffusion antibiotic sensitivity testing) is a test which uses antibiotic-impregnated wafers to test whether bacteria are affected by antibiotics. In this test, wafers containing antibiotics are placed on an agar plate where bacteria have been placed, and the plate is left to incubate. If an antibiotic stops the bacteria from growing or kills the bacteria, there will be an area around the wafer where the bacteria have not grown enough to be visible. This is called a zone of inhibition.

13. Bacteriostatic: inhibits grow but doesn’t kill microorganisms – If you remove this agent from the environment, microorganisms can begin to replicate once again Bacteriocidal: kills all bacterial cells – If you remove this agent from the environment, it will still remain sterile since the agent has killed all the cells, no cells available to replicate We will be looking at the effectiveness of 4 different antiseptics – Mouthwash – Iodine – Hydrogen Peroxide – Alcohol Evaluation of antiseptics

14. Inoculate the plate the same as for the UV light experiment Today’s exercise Soak a filter disk in the designated antiseptic. Tap to the lid to remove any excess Place the filter disk in the middle of the designated section The antiseptic will diffuse into the agar, forming a concentration gradient After the plate is incubated, we will look for zones of inhibition Zone of inhibition: area around the filter disk that is allowed no growth The bigger the zone, the more effective the antiseptic Alcohol Peroxide Mouthwash Iodine LABEL YOUR PLATE

15. Importance of handwashing Exercise 11

16. Most important step to stopping the spread of infection Handwashing

17. Improper or failure to washing hands can lead to serious increase in infections in patients – Hospital-acquired infections- nosocomial Endogenous: infection from your own skin flora Exogeneous: from surrounding areas – i.e caregiver’s hands, surgical instruments, or hospital equipment – Fomites are non-living substances capable of transmitting diseases Doorknobs, call buttons, railings, ect. Handwashing

18. Medical professionals can prevent nosocomial infections by scrubbing between contact with each patients – Scrub coming into the room, scrub coming out of the room Day Care Centers and Food preparers can easily transmit enteric bacteria to immunocompromised individuals – Wash hands before leaving bathroom or handling any type of food According to the Center of Disease Control (CDC), the estimated amount of healthcare-associated infection in Acute Care Hospitals in the USA in 2011 was 721, 800 total infections. This number includes pneumonia, GI Illnesses, UTIs, Blood Infections, surgical site infections and any other type of infection.

19. Diptheroids – Gram positive bacteria – Non-pathogenic – Example: Propionibacterium acnes Anaerobic diptheroid Lives in the hair follicles and breaks down the sebum Staphylococci – Opportunistic pathogens that can be transmitted to susceptible individuals by medical personnel and food handlers Yeasts and Fungi – Can cause opportunistic infections Hard to remove because these organisms reside in hair follicles and are entrenched in the skin Normal Skin Flora

20. Split up into Groups of 4 – Student 1: bar soap and scrub brush – Student 2: liquid soap and scrub brush – Student 3: waterless hand sanitizer – Student 4: 10% Bleach Each of you will grab 1 TSA plate – Split the plate and label as “Unwashed” and “Washed” Press your 3 central fingers gently to the agar to the “Unwashed” Side Clean your hands with the assigned cleansing solution Allow your hands to AIR-DRY Use the same 3 central fingers and press gently to the “Washed” Side Place agar plate in class bin when complete Today’s Exercise Washed Unwashed LABEL YOUR PLATE