Block 2 - Control of Microbial Growth Flashcards
When microbes are referred to as “ubiquitous”, where can they be found?
everywhere in the environment
What are microbes defined as if they are present at a given place and time and they are undesirable or unwanted?
contaminant
How many Biosafety Levels are there?
The microbes in BSL-4, are considered what?
4
highly infectious exotic microbes and toxins for hich there is no vaccine or effective treatment.
HIV is within what BioSafety Level?
BSL-2
What term means to “kill or remove the microbes”?
sterilization
True or False:
Disinfected implies that the item is sterile.
False; disinfected is NOT synonomous to sterile.
The use of chemical agents on the skin or other living tissue to eliminate or inhibit microorganisms refers to what term?
antisepsis
What is the term for the process of applying mild heat to kill, or significantly reduce the numbers of, microbes which may spoil food or beverage?
pasteurization
Define the terms thermolabile and thermostable.
thermoabile: easily altered, decomposed or destroyed by heat
thermostable: not easily altered, decomposed or destroyed by heat
True or False:
Bacterial endospores are less resistant than enveloped viruses.
False; they are more resistant.
True or False:
Regarding to microbial death, vegetative cells die more rapidly than spores.
True.
If there is damage to the microbial cell wall, what cellular processes are effected?
What is an example of something that can damage a microbial cell wall?
It blocks its synthesis, digests it, or breaks down its surface.
antibiotics / lysozyme / detergent
If there is a disruption to the cytoplasmic membrane, what cellular processes/structures are effected?
What are some examples that can cause a disruption in the cytoplasmic membrane?
The disruption causes loss of membrane integrity and selective permeability.
detergents (surfactants), heat
If the synthesis of proteins and nucleic acids are inhibited, what cellular processes are effected?
It interferes with gene translation, thus preventing protein synthesis.
If the microbial function and structure of its proteins and nucleic acids are altered, what occurs?
What substances alter the function/structure of proteins and nucleic acids?
Altered structure inactivates or denatures functions of enzymes and nucleic acids.
heat, strong organic solves, phenolics, metallic ions, antibiotics
What does the “refrigeration” of a microbe effect?
What does the “freezing” of a microbe effect?
It slows the metabolism of the microbe but does not kill them for both refigeration and freezing.
What can cause cells to lose the selective permeability of their cell membranes?
Heat
Heat can inactivate proteins and nucleic acids by doing what on the molecular level?
breaking their hydrogen bonds thus unfolding proteins and separating double-stranded nucleic acids.
Sterilization depends on:
- __________
- __________
- __________
temperature
duration of heating
humidity
What common sterilizing machine uses steam under pressure (121*C for 15 minutes)?
autoclave
Within the radiation method of physical control of microbes, there are 3 types of radiation used. What are these three types?
ionizing radiation - gamma
ionizing radiation - electron beam radiation
non-ionizing radiation - ultraviolet
Which type of radiation treatment has “low penetrating power”?
non-ionizing radiation - ultraviolet
With regard to membrane micropore filters, what is the membrane made out of?
How does this particular complex system trap microbes?
cellulose acetate and cellulose nitrate
…traps by pore size and chemical affinity to the matrix
HEPA filters have two uses described in the PDF, these two uses are:
air filters for respiratory protection
biological safety cabinet
What are the two HEPA air filters for respiratory protection?
Mask: N95, not routine surgical mask or painters mask
PAPR: Powered Air Purifying Respirator-includes HEPA filter, blower, hood
Within the methods of chemical control there are 3 levels of disinfectants.
What are the 3 levels of disinfectants?
High / Intermediate / Low-level disinfectants
Antiseptics belong to what level of disinfectant?
intermediate level disinfectants
Beta-lactam antibiotics use what type of mechanism of action?
inhibits cell wall synthesis
Penicillins and cephalosporins inhibit what bacterial cell function?
Inhibit cell wall synthesis
In regard to inhibiting the cell wall synthesis, the principle action inhibits the synthesis of what molecule of the bacteria?
peptidoglycan
What synthesis consists of about 30 enzymatic steps to synthesize long polysaccharide chains?
Peptidoglycan synthesis
What type of antibiotics act by binding to penicillin binding proteins?
beta-lactam antibiotics
What are the results of beta-lactam antibiotics binding to penicillin binding proteins?
i. Inhibition of peptidoglycan synthesis
ii. Degradation of formed cell wall through the release of autolytic enzymes
iii. Weakened cell wall loses integrity and can no longer preserve osmotic pressure. Results in cell death and increased phagocytosis.
Beta-Lactam can be used most effectively against what type of bacteria?
Gram-Positive
(due to gram negative having a different outer membrane and some degree of antibiotic prevention)
also effective against actively growing bacteria
What type of antibiotic binds onto the cross-link peptide, so that the link cannot be completed and peptidoglycan polymer cannot elongate?
Vancomycin
What type of antibiotic blocks the phospholipid carrier that helps carry subunits of peptidoglycan across membrane to cell wall?
Bacitracin
What type of antibiotic inhibits formation of mycolic acid in cell walls of mycobacterium (tuberculosis organism)?
Isoniazid (INH)
These type of antibiotics inhibits accurate translation of mRNA or polypeptide chain formation at the bacterial ribosome.
In general, these antibiotics effect what type of synthesis?
Protein synthesis
Chloramphenicol binds to what portion of the ribsome and inhibits the formation of what?
50S portion and the formation of the peptide bond
HEAT (boiling)
Describe the:
*Conditions - Uses
Disadvantages*
…of the listed physical control of microbes.
100*C for 10 min - kills vegetative
100*C for 30 min - kills resistant bacteria
boiling does not kill sports
Heat (Dry Heat)
Describe the:
Conditions
Uses
Disadvantages
…of the listed physical control of microbes.
160-180*C for 2 hours - sterilizes certain thermostable items (i.e. glassware)
Boiling & evaporation of liquids; charring of organic materials
HEAT (pressurized steam-autoclave)
Describe the:
Conditions - Uses
Disadvantages
…of the listed physical control of microbes.
121*C for 15 minutes > 15lbs pressure
- sterilizes liquids and instruments
limited volume; costly equipment; thermostable items only
Incineration
Describe the:
Conditions - Uses
Disadvantages
…of the listed physical control of microbes.
very high temperature - destruction of all microbes on hand instruments and medical waste
industrial size is expensive
Filtration (Membrane Micropore)
Describe the:
Conditions - Uses
Disadvantages
…of the listed physical control of microbes.
(bacteria common at .22um) - remove bacteria from heat-labile liquids; respiratory protection
viscous fluids clog; viruses pass through most filters
Filtration (HEPA)
Describe the:
Conditions - Uses
Disadvantages
…of the listed physical control of microbes.
very effective in removing bacteria; moderately effective in removing viruses
air only; does not remove chemicals; not 100% removal; must use additional methods for virus removal
Radiation (Gamma)
Describe the:
Conditions - Uses
Disadvantages
…of the listed physical control of microbes.
(null conditions) - sterilization of heat sensitive and bulk medical items; food preservation
danger to humans; requires special containment
Radiation (Electron Beam)
Describe the:
Conditions - Uses
Disadvantages
…of the listed physical control of microbes.
(null conditions) - decontaminate packages
direct exposure; small containers
Radiation (ultraviolet)
Describe the:
Conditions - Uses
Disadvantages
…of the listed physical control of microbes.
260 nm wavelength - decontamination of air, other gases, and surfaces
no penetration through regular glass; danger to eyes; lengthy exposure
What method removes bacteria from heat-labile liquids?
filtration (membrane micropore)
What physical method of control uses sterilization of heat sensitive and bulk medical items and food preservation?
Gamma Rays
High-level disinfectants can be what two types of
(-cidal)?
microbicidal and sporocidal
Antiseptics are a part of what level of disinfectant?
intermediate level
What is a chemical disinfectant agent and method that may be safely used on skin ad tissue?
antiseptic
What chemicals are usually (but not always) bactericidal; not sporicidal or tuberculocidal, often not fungicidal or virucidal?
low-level disinfectants
What is a chemical substance of natural, semisynthetic, or synthetic origin that inhibits or kills microbes and which can be used to treat or control infection?
antibiotics / antimicrobic agents
