Lecture 7 - Control of Microbial Growth Flashcards
Asepsis
refers to the absence of significant contamination
Sepsis
refers to significant contamination
Who introduced antisepsis techniques into medical practice by having doctors wash hands with Calcium Hypochloride.
Ignaz Semmelweis
Why were so many women dying after childbirth in Semmelweis’s maternity ward?
The medical students were not washing their hands between doing vaginal exams on dead patients and doing vaginal exams on women in labor.
Known as “The Savior of the Mothers”
Ignaz Semmelweis
Phenol AKA
Carboxylic Acid
Introduced the use of phenol in surgeries
Joseph Lister
Sterilization
killing all forms of microbes on non-living objects
Antisepsis Techniques
killing microbes (including potential pathogens) on living tissues
Disinfections
destroying mirobes (not including endospores) on non-living surfaces
Using an alcohol wipe to remove microbes from a small area of skin is referred to as ______.
Degerming
Washing hands with soap is an example of _______.
Degerming
Why does soap work to remove germs?
soap is made of amphipathic molecules with a polar and non-polar side allowing it to bind to both the water and the oils so germs stuck in the oil can be lifted and washed away
nosocomial infections
infections aquired at a hospital or during healthcare treatment
What microbe is a common cause of nosocomial infections?
Pseudomonas aeruginosa
Is Pseudomonas aeruginosa Hemolytic?
Yes, it is beta-hemolytic and will completely destroy RBCs
RBC
Red Blood Cells
WBC
White Blood Cells
Is Pseudomonas aeruginosa Gram Positive or Negative?
Gram-Negative
Why is Pseudomonas aeruginosa so difficult to destroy?
It has magnesium in the outer membrane which aids in very strong bonds between the lipopolysaccharide molecules making it resistant to penetration by antiseptic compounds
Name a few things that are effective in destroying Pseudomonas
- Acids
- Glutaraldehyde
- Silver
- Strong Phenolic Disinfectants
-static / -stasis
stop/stand still
3 Main Targets of Microbial Control Agents
- Plasma Membrane
- Intracellular Proteins (i.e. enzymes)
- Nucleic Acids (i.e. DNA/RNA)
-cide
to kill
3 Main Methods of Damaging Microbes
- Heat
- Chemicals
- Radiation
Factors Affecting the Rate of Microbial Death
- Number of Microbes
- Presence of Organic Debris
- pH
- Temp
- Nature of Suspending Medium
- Time of Exposure
- Characteristics of the Microbe Being Attacked
Desiccation
creating a hypertonic environment to dehydrate cells
Is desication effective against endospores?
No
Is desiccation effective against viruses?
No
Is desiccation effective against most bacteria?
Yes
Why are low temps effective against microbes?
It decreases the metabolic rate against most microbes so they cannot grow or produce toxins easily
Thermal Death Point
the lowest temperature at which all microbes in a suspension can be killed in 10 minutes
Thermal Death Time
the minimum length of time it would take to kill all bacteria in a liquid culture at a certain temp
Dismal Retention Time
the length of time it will take to kill 90% of microbes in a suspension at a given temp
How long should something boil to kill most of the microbes?
10 minutes
How resistant are endospores to boiling?
It depends on the type of endospore, but some Hepatitis endospores can survive 30 minutes of boiling and other endospores can survive almsot a full day of boiling
Autoclaving
a true and effective sterilization method
uses moist heat at 121 C at 15 psi for 15 minutes to sterilize metal and glass
prion
infectious misfolded proteins
Can prions survive autoclaving?
Yes, some prions can survive autoclaving
Pastuerization
uses heat to destroy pathogens and reduce the number of microbes that can spoil food
Does pasturization change the nutritional composition of milk?
No
HTST
High Temperature, Short Time
HTST Pasturization AKA
Flash Pasturization
UHT
Ultra High Temperature
How long does it take to treat milk using HTST Pasteurization vs UHT Sterilization?
HTST takes 15 seconds whereas UHT takes 4 seconds
What method of treatment has Gossner’s Milk undergone in order to be stored unrefridgerated on the shelf?
UHT Sterilization
Can UHT Sterilization kill endospores?
Yes
Three Methods of Dry-Heat Sterilization
Open Flame
Heated Incinerator
Hot Air Oven
Which method of serilization is faster? Moist Heat or Dry Heat?
Moist Heat
Two Methods Used to Sterilize Substances That Cannot Be Treated With Heat
Membrane Filtration
High Pressure
Radiation (ionizing or nonionizing)
What two microbes could potentially survive membrane filtration and why?
Spirochaetes (may be able to wiggle their way throught holes in the filter)
Mycoplasma does not have a cell wall and may be able to distort its shape enough to fit through the holes in the filter.
Two Types of Radiation
Ionizing Radiation
Nonionizing Radiation
Ionizing Radiation
uses gamma rays, xrays or high-energy electron beams to penetrate cells and break apart water molecules into free radicals that can destroy DNA molecules
Non-Ionizing Radiation
uses UV light to create thymine dimers in the DNA which prevents DNA replication and transcription
Which type of radiation penetrates deeper? Ionizing or Nonionizing?
Ionizing
Why are microwave ovens beneficial in killing pathogens?
it generates heat which can denature proteins in microbes
What method was used to sterilize catheters and prevent UTIs in catheterized patients?
High-Intensity Narrow-Spectrum (HINS) Light
Two Methods Used to Evaluate a Disinfectant
- Use-Dilution Test
- Disk-Diffusion Method
Expalin How the Disk-Diffusion Method Works to Evaluate a Disinfectant
small paper disks soaked in disinfectant are placed on an agar plate covered in microbial growth then the zones of inhibition where microbes have been prevented from growing are evaluated
Phenol works by ____.
Damaging Plasma Membranes
Name 4 Halogens
Fluorine
Chlorine
Bromine
Iodine
Iodine and Iodophors works as an antiseptic by
inhibiting protein synthesis and altering cell membranes
Chlorine works as an antiseptic by
penetraiting cell walls and inhibit cellular enzymes
What dilution of bleach is recomended?
1 part chloride to 4 parts water
What percent of rubbing alcohol is most effective againt microbes?
70%
Why is 100% ethanol ineffective against microbes?
it evaporates too quickly and doesn’t have sufficient time to destroy microbes
How does rubbing alcohol work against microbes?
It denatures proteins and dissolves lipids/disrupts plasma membranes
Oligodynamic Action
only a small amount is required in order to be effective
Heavy Metals are effective against microbes by
denaturing proteins
Examples of Heavy Metal Compounds Used to Combat Microbes
Silver Nitrate
Silver Sulfadiazene
Surfacine
Silver Sulfadiazene is often applied topically to treat ____.
Burns
Copper Sulfate is commonly used to disinfect _____.
water
Zinc Chloride is often used in which two hygiene items?
Anti-Dandruff Shampoo & Mouthwash
Used often as a Disinfectant during Embalming
Quaternary Ammonium Compounds
Used to Treat Cold Sores
Quaternary Ammonium Compounds
Common Chemical Food Preservatives
Sulfur Dioxide
Sodium Benzoate
Sorbic Acid
Calcium Propionate
Nitrates and Nitrites
Why are Aldehydes Effective Antimicrobials?
they cross-link proteins inside of a cell making them unable to function properly
Used to Preserve Cadavers
Formalin
Cidex (2% Glutaraldehyde)
a liquid sterilant and can kill endospores
Explain How Ethylene Oxide Gas Works Against Microbes
it cross-links proteins inside of a cell making them unable to function properly
Two Methods often used to Sterilize Laparoscopes
Plasmas and Supercritical Fluids
Often Used in Water Purification Systems
Ozone
Why is Peroxide Ineffective for Cleaning Wounds?
our cells contain catalase which turns the H2O2 into water and oxygen gas
Name the 4 Microbes that are Most Restistant to Chemical Biocides
Prions
Endospores
Mycobacterium (waxy cell walls)
Cysts of Protozoa
Which is more reistant to chemical biocides? Gram Negative or Gram Positive Bacteria?
Gram-Negative
TSE
Transmissible Spongiform Encephalopathies
Bovine Spongiform Encephalopathy AKA
Mad Cow Disease
Name Two Common Prion Diseases
Mad Cow Dieseas
Creutzfeld-Jakob Disease
How is Mad Cow Disease Transmitted?
- eating contaminated meat
- genetic defect
- transplant of infected organs
