Effects of Radiation on Growth - PowerPoint Presentation

Slide1

Effects of Radiation on GrowthSlide2

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 disruptionMore destructive

Electromagnetic radiation (EMR)Slide3

Electromagnetic SpectrumSlide4

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 materialsUsed to sterilize surfaces, items that cannot be autoclaved inability to penetrate glass, plastic, or any other solid or liquid

Ultraviolet light Slide5

Mutagen

: causes mutations

The absorption of UV light causes

Thymine Dimers Mutation of the DNANeighboring thymines inthe 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 Slide6

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.Slide7

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 plateRotate 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 Slide8

Experiment

Instructor will assign organism and time

Swab plate for confluent growthSlide9

Label your plate to split it in half:

Covered

Uncovered

Label your plate with:Name of organismStudent initialsTime 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 Slide10

Evaluation of antiseptics

Exercise 10Slide11

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 microorganismsSteriliants 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 AntisepticsSlide12

Method

Disk diffusion (

K

irby 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.Slide13

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 cellsIf you remove this agent from the environment, it will still remain sterile since the agent has killed all the cells, no cells available to replicateWe will be looking at the effectiveness of 4 different antiseptics

Mouthwash

Iodine

Hydrogen Peroxide

Alcohol

Evaluation of antisepticsSlide14

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 PLATESlide15

Importance of handwashing

Exercise 11Slide16

Most important step to stopping the spread of infection

HandwashingSlide17

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 floraExogeneous: from surrounding areas i.e caregiver’s hands, surgical instruments, or hospital equipmentFomites are non-living substances capable of transmitting diseasesDoorknobs, call buttons, railings, ect.

Handwashing Slide18

Handwashing

Medical professionals can prevent nosocomial infections by scrubbing between contact with each patients

Scrub coming into the room, scrub coming out of the

roomDay 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. Slide19

Diptheroids

Gram positive bacteriaNon-pathogenic

Example:

Propionibacterium acnes Anaerobic diptheroidLives in the hair follicles and breaks down the sebum StaphylococciOpportunistic pathogens that can be transmitted to susceptible individuals by medical personnel and food handlers Yeasts and Fungi Can cause opportunistic infectionsHard to remove because these organisms reside in hair follicles and are entrenched in the skin

Normal Skin Flora Slide20

Split up into Groups of 4

Student 1: bar soap and scrub brushStudent 2: liquid soap and scrub brush

Student 3: waterless hand sanitizer

Student 4: 10% BleachEach of you will grab 1 TSA plateSplit the plate and label as “Unwashed” and “Washed”Press your 3 central fingers gently to the agar to the “Unwashed” SideClean your hands with the assigned cleansing solution Allow your hands to AIR-DRYUse 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