Download UV light, Antiseptics, Handwashing

Effects of Radiation on Growth
Electromagnetic radiation (EMR)
• 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 Spectrum
Ultraviolet light
• 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
• 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
• 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.
Swabbing plate for confluent growth
• 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
Experiment
• Instructor will assign organism and time
• Swab plate for confluent growth
Today’s exercise (continued)
• Label your plate to split it in half:
– Covered
– Uncovered
• Label your plate with:
Covered
Uncovered
– 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.
Evaluation of antiseptics
Exercise 10
Evaluation of Antiseptics
• 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
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.
Evaluation of antiseptics
• 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
Today’s exercise
• Inoculate the plate the same as for the UV light
experiment
• Soak a filter disk in the designated
LABEL YOUR PLATE
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
Importance of handwashing
Exercise 11
Handwashing
• Most important step to stopping the spread of
infection
Handwashing
• 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
• 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.
Normal Skin Flora
• 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
Today’s Exercise
LABEL YOUR PLATE
• 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
Washed
Unwashed
• 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