lab 10 Flashcards
Understand the effects of physical and chemical agents on different types of bacteria
Highest resistance?
- Prions
- Bacterial endospores
Understand the effects of physical and chemical agents on different types of bacteria
Moderate resistance?
- protozoan cysts
- some fungal sexual spores
- naked viruses
- bacteria with more resistant vegetative cells (some gram -/+)
Understand the effects of physical and chemical agents on different types of bacteria
Least resistance?
- typical bacterial vegetative cells
- fungal spores and hyphae
- enveloped viruses
- yeast
- protozoan trophozoites
Define Sterilization
“complete removal” or destruction of all transmissible agents (microbes, spores, viruses)
name 5 ways to sterilize an inanimate object
Autoclaving (steam heat) Heat Radiation (not UV) Strong chemicals (liquids and gases) Filtration
Define Disinfection
Destruction/removal of vegetative microbes (no bacterial endospores). Used on Inanimate objects due to intensity of treatment required to be effective.
Physical agent.
Define antisepsis
Chemical applied to body surfaces to destroy or inhibit vegetative microbes. Chemical agent
Name 6 ways to Disinfect
Lysol Cidex (an aldehyde, alkylating agent) Bleach Heat UV Boiling water
Name 4 antisepsis
Alcohols (60-90%) - hand sanitizers
Hydrogen peroxide (3-6%)
Betadine (iodine compound and therefore a halogen)
Saline (>0.9%)
Define Sanitization/Degermation
destruction/physical removal of transmissible agents to safe level on inanimate/animate surfaces
- methods vary, combined physical and chemical, mechanical scrubbing, soaps, disinfection, antisepsis
- Soaps - cleansing and wetting agent that enhances the physical removal of microbes and debris but does not kill microbes
Define Microbicide
kills microbes
Define Fungicides
kills fungal hypae, spores, yeast and molds
Define Bactericeds
kills bacteria
Define Viricides
kills viruses
3 microbial control methods
Physical (boiling water, hot water, pasteurization, non ionizing and UV), Chemical (liquids) and Mechanical removal method
What does MOIST heat kill? Temp?
Vegetative cell - 80C required to kill most resistant cells
Spores/endospores - 120C required to kill most resistant spores. More resistant to heat than vegetative cells, but not invincible to heat. Resistance aided by cortex, proteins, minerals, DPA
Effects of Ultraviolet Light
Disinfectant which kills most but not all microbes.
UV mutate DNA by causing dimers to thymine and cytosine (pyrimidines)
Enzymes can sometimes repair DNA damage
Cause of skin melanomas
Common method used to disinfect equipment
What is Kirby-Bauer Susceptibility Test?
standardized test that follows a specific testing procedure to determine the susceptibility of bacteria to antimicrobial agents.
results are used to determine the correct antimicrobial agent to be prescribed to the patient
3 Kirby-Bauer Susceptibility test designation
Resistant, Intermediate, Susceptible
Define Resistant in terms of the Kirby test
organism is NOT KILLED or inhibited by the tested antimicrobial in blood or other body fluids
Define Intermediate in terms of the Kirby test
organism MAY NOT BE KILLED or inhibited by the tested antimicrobial in blood or other body fluids
Define Susceptible in terms of the Kirby test
organism is KILLED or inhibited by the tested antimicrobial in blood or other body fluids
Operating parameters for autoclave
Temp, 121.5C
Pressure, 15 psi
Time, 15-20 min
Define Penicillinase
An enzyme produced by penicillin resistant strains of bacteria to inactive penicillin
4 things that must be standardized in the Kirby Bauer sensitivity test
Mueller-Hinton agar poured at 4mm thickness
Standardized antibiotic disks are used (size of disk and concentration of chemical)
Standardized inoculum used. Compared to a McFarland standard
Incubate plates for 18-24 hours at 37C
This allows for reproducible results
Is it correct to say that dish washing sterilizes dishes?
No, its sanitizing agent only
Soaps are strong microbicides?
False
all gram negative bacteria have an outer layer of the outer membrane that consists of?
LPS, Lipid A and porin proteins
Disinfection is a cleansing process that destroys vegetative pathogens and endospores
False
Autoclaving uses steam heat as a sterilizing agent. Of the following choose which method of controlling microbes this fits
a. chemical
b. physical
c. mechanical
d. chemical and mechanical
Physical
a fungicidal agent has what effects?
destroys fungal spores, hyphea and yeast growth
Which of the following is safe to use on or near living tissue
a. antiseptic
d. disinfectant
c. aldehydes
d. ethylene oxide
Antiseptic
Starting at the core of an endospore the protective layers from the inside out?
cortex, spore coat, exosporium coat
when attempting to sterilize endospores using autoclace the temp must reach 100c at 3psi for 5 min.
False
temp 121C
15psi
15-20 min
to effectively destroy bacterial spores and endospores.
The pressure drives the steam heat into the cells and keeps water from boiling.
UV radiation is usually considered a disinfectant rather than a sterilizer. UV radiation is 99% effective in decreasing concentration of air borne microbes
True
The Kirby Bauer method determines susceptibility of organisms to antimicrobial agents. The results are compared to a standardized range for each drug and a determination is made as to whether the organism is susceptible, resistant, or intermediate to a particular drug concentration.
True
What is gram negative and what is gram positive of the following: Staphylococcus aureus Bacillus sp Escherichia coli Pseudomonas sp
Staphylococcus aureus Gram Positive
Bacillus sp Gram Positive
Esherichia coli Gram Negative
Pseudomonas sp Gram Negative
Which organisms are spore former?
Bacillus sp and C-Dif
Cell envelope structure of Gram positive, from out to in
Wall teichoic acid Lipoteichoic acid Thick Peptidoglycan Periplasmic space Cell membrane Membrane proteins
Cell envelope structure of Gram negative, from out to in
Porin proteins LPS Outer membrane layer Phospholipids Lipoproteins Thin peptidoglycan Periplasmic space Cell membrane Membrane protein
Bacterial endospores contain?
Exosporium Spore Coat Outer Membrane Cortex Intermembrane Spore Cell *highly resistance due to membranes/materials
Define Sporocide
Kills all spores
Define decontamination
The mechanical removal of most microbes
Mueller Hinton plate info
Standard medium
4mm thick agar
neutral pH
Grows most non-fastidious bacteria
What do we call a microbe that thrives in a rich carbon dioxide environments?
Capnophile- obligate anaerobes
How are Autoclaves routinely tested?
Using spore strips from Bacillus stearothermophilus - commonly used thermophile used to validate sterilization processes and the checking growth
3 forms of heat? Effects?
Dry, moist and steam
Gradual exposure to increasing temperatures may enable cells to adapt to higher “lethal” levels by producing heat shock protein in attempt to protect cell integrity
Define cidal (evaluation of chemical antimicrobial agents)
If the chemical kills the microorganism, it said to be cidal
Define static (evaluation of chemical antimicrobial agents)
If the chemical inhibits growth, it is said to be static
What does MIC stand for?
Minimum Inhibitory Concentration
Smallest concentration of drug in the series that visibly inhibits growth
What does MIC useful for?
Useful in determining the most effective dosage of a drug and in providing a comparative index against other antimicrobial.
Similarities between agar diffusion (Kirby Bauer) and tube dilution sensitivity tests
Similarities:
Both test organisms for antimicrobial susceptibility
Standardized tests
Determine the specific antimicrobial that is most effective in treating that particular strain of bacteria
Differences between agar diffusion (Kirby Bauer) and tube dilution sensitivity tests
Differences:
KB uses a Mueller-Hilton agar, MIC uses a dilution tray containing a supporting medium
MIC provides the minimum dilution of an antibiotic that would be effective in treating a specific bacterial infection, KB does not
Moist heat and dry heat differ in their modes of action as well as in their efficiency.
Moist heat operates at lower temperatures and shorter exposure time to achieve the same effectiveness as the dry heat
Kirby Bauer test infor
Agar diffusion
Measure diameter in mm around disc
If not clear enter 6mm for disk diameter
If overlap, use radius X2
