Microbial Growth Control Flashcards
The ___ may be vegetative cells, endospores, protozoan cysts, fungal hyphae, viruses, etc.; and each type poses different degrees of difficulty for dealing with them
contaminant, microbes present at a given place and time that are undesirable or unwanted
infections that develop during the course of a hospital stay and not present at the time of admission. Limit such infections by adhering to good infection control practices
Nosocomial infection (Hospital Acquired Infection)
Nosocomial infection produce a more ____ microbe
robust
AND patients are at a lowered immune state
Examples of levels of control of contamination
Normal household conditions
General medical conditions
Strict transmission control conditions
assume that patients are infectious and that blood and body fluids contain pathogens; use appropriate personal protective equipment (PPE), engineering controls, and work practice controls such as handwashing
Standard Precautions (Universal)
agents having no known potential for infecting health people. Precautions include standard good laboratory technique. Applies to teaching laboratories in a high school or college beginning level general microbiology course
BSL 1
agents most commonly encountered in clinical samples, including HIV and several more unusual pathogens (i.e. not highly transmissible by respiratory route). Safety procedures and precautions include standard good laboratory techniques plus PPE of lab coat and gloves (for certain procedures), limiting access to the laboratory, special training of personnel in handling pathogenic agents, and performing aerosol-generating procedures in a Biosafety Cabinet (BSC).
BSL 2
agents include those that are more unusual or more highly transmissible such as Mycobacterium tuberculosis, Brucella spp., infrequently encountered viruses, mould stages of fungi (i.e. highly transmissible by respiratory route). Precautions include Level 2 precautions plus routine use of a BSC, wearing of a HEPA-filter mask, special laboratory design and engineering features that contain potentially dangerous material by control of air movement
BSL 3
agents are certain highly infectious exotic microbes and toxins for which there is no vaccine or effective treatment and that require the maximum containment facilities and the highest levels of special protective equipment
BSL 4
free of all microorganisms and their spores; i.e. microbes have been destroyed or removed
Sterile
Terms like “partially sterile” or “somewhat sterile” are ___ ; an item is either sterile or it is not.
nonsense
BSAT
Biological Select Agents & Toxins
Special security, storage, and transport for “Select Agent”
use of physical procedures or chemical agents to destroy all microbial forms, including bacterial spores (kill or remove the microbes).
Sterilization
use of physical procedures or chemical agents to destroy, inhibit, neutralize, or remove at least most (but not necessarily all) potentially infectious microorganisms on an object or surface.
Disinfect / Decontaminate
Very few viable remaining microbes, low risk of transmission
Does not imply “sterility”.
Disinfect / Decontaminate
agent or method (usually a chemical agent) used to carry out disinfection; normally used on inanimate objects (may burn or severely irritate skin or tissue). Agents have varying levels of effect (high, intermediate, low).
Disinfectant
Sterility can still have _____ from microbes
remnants of DNA
use of chemical agents on the skin or other living tissue to eliminate or inhibit microorganisms; no sporicidal action is implied.
Antisepsis
chemicals destroy spores as well as vegetative cells
Sporicidal
Suffix that indicates the chemical or process of inhibiting (prevent) growth or multiplication of bacteria, but not killing
-stat, -static
process of applying mild heat to kill, or significantly reduce the numbers of, microbes which may spoil food or beverage.
Pasteurization
easily altered, decomposed or destroyed by heat
thermolabile
Not easily altered, decomposed, or destroyed by heat
thermostable
suffix that indicates that the chemical or process is destructive to (kills) the microbe (e.g. bacteria, fungi, viruses), although it does not necessarily kill spores
-cide, -cidal
Overall degree of microbial resistance to killing (general sequence from most resistant to least resistant):
(1) Bacterial endospores
(2) Mycobacterium (TB)
(3) Protozoan cysts
Below are equalish:
(4) Non-enveloped small viruses
(5) Vegetative bacteria
(6) Fungi
(7) Enveloped viruses
______ are much more resistant to antimicrobial control methods than all other microbial forms.
Bacterial endospores
____ die more rapidly than spores.
Vegetative cells
Microbes are not killed instantly when exposed to lethal agents but become _____
dysfunctional and die over a period of time
_____ are more resistant than enveloped virures because phospholipids are easily dissolved by organic solvents – rendering them without any attachment structures
Enveloped viruses
Factors affecting the effectiveness and choice of sterilization
- Microbial population composition
- Microbial death (time)
- Population size
- Concentration/Intensity of antimicrobial
- Duration of exposure
- Temperature and pH
- Presence of protective or neutralizing matter
- Physical nature of materials being treated;
Some agents are more effective at lower concentrations; e.g. ____
70% ethanol is more effective than 95% ethanol.
However, usually, more concentrated means more effective
High temperatures can inactivate ____ or denature molecules
enzymes
Strong acid can directly kill microbes; ___ may enable chemical disinfectants to inactivate microbes faster
weak acid
_____ protects or inactivates chemical disinfectants. ____ can protect microorganisms from heating and chemical disinfectants.
Organic matter (both blanks)
At higher altitudes or extreme cold temperatures, sterilization can take ____
longer
Modes of Action of Microbial Control Methods
- Damage to cell wall
- Disrupt cytoplasmic membrane
- Inhibit synthesis of proteins and nucleic acids
- Alter function of proteins & nucleic acids
Cell Wall Damage Examples
Abx, lysozomes, detergents
Disrupt cytoplasmic memrane examples
(alter membrane integrity or selective permeability)
detergents (surfactants), heat
Inhibit synthesis of proteins and nucleic acids (explain and examples)
Interference with gene translation, thus preventing protein synthesis
(ex: abx, radiation, formaldehyde)
Alter function of proteins & nucleic acids (explain and examples)
Alter bonds that determine secondary and tertiary structure. Altered structure inactivates or denatures functions of enzymes and nucleic acids
(heat, strong organic solvents, phenolics, metallic ions, antibiotics)
slows metabolism of microbes, but does not kill most microbes
Refrigeration
____ kills cells by disrupting cell membrane functions, denaturing proteins, and inactivating nucleic acids
Heat
