Module 2: Control of Microbial Growth Flashcards
Define: Infectious
Microorganisms capable of causing disease (also known as pathogens or potential pathogens)
Define: Contaminant
Microbes present at a given place and time that are undesirable or unwanted. (i.e. vegetative cells, endospores, protozoan cysts, fungal hyphae, viruses, etc..)
Define: Nosocomial Infection
Infections that develop during the course of a hospital stay and not present at the time of admission.
What are Standard Precautions as per OSHA intended to limit infection in and transmission by Health-care workers?
Assume that patients are infectious and that blood and body fluids contain pathogens; use appropriate personal protective equipment, engineering controls, and work practice controls (hand washing)
What is a BSL?
Biosafety Level
Define: Biosafety Levels
Determined by degree of risk; require varying types of PPE
Define: BSL-1
Agents having no known potential for infecting healthy people.
What pre-cautions are taken in BSL-1?
Standard good laboratory technique.
Define: BSL-2
Agents most commonly encountered in clinical samples, including HIV and several more unusual pathogens (not highly transmissible by respiratory route)
What pre-cautions are taken in BSL-2?
Standard good laboratory techniques, PPE of lab coat and gloves (certain procedures), limiting access to lab, special training of personnel in handling, and performing aerosol generating procedures in Biosafety Cabinet (BSC)
Define: BSL-3
Agents include those that are more unusual or more highly transmissible such as Mycobacterium Tuberculosis, Brucella spp., infrequently encountered viruses, mould stages of fungi (highly transmissible by respiratory route)
What pre-cautions are taken in BSL-3?
Level 2 pre-cautions plus routing 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.
Define: BSL-4
Agents are certain highly infectious exotic microbes and toxins for which there is no vaccine or effective treatment.
What pre-cautions are taken in BSL-4?
Require maximum containment facilities and the highest levels of special protective equipment
Define: Sterile
Free of all microorganisms and their spores
Define: Sterilization
Use of physical procedures or chemical agents to destroy all microbial forms, including bacterial spores
Define: Disinfect/Decontaminate
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
Define: Disinfectant
Agent or method (usually chemical agent) used to carry out disinfections; normally used on inanimate objects (may burn or severely irritate skin or tissue). Varrying levels of effects (High, intermediate, low)
Define: Antisepsis
Use of chemical agents on the skin or other living tissue to eliminate or inhibit microorganisms; no sporicidal action is implied. achieved y use of antiseptic on skin
The suffix Cide or Cidal implies?
Indicates that the chemical or process is destructive to (kill) the microbe. Does not necessarily kill spores
Define: Sporicidal
Chemicals destroy spores as well as vegetative cells
The suffix Stat or Static implies?
Indicates the chemical or process of inhibiting growth multiplication of bacteria, but not killing
Define: Pasteurization
Process of applying mild heat to kill, or significantly reduce the number of, microbes which may spoil food or beverage
Define: Aseptic
Free of contaminating or infectious microorganisms; usually refers to technique
Define: Thermolabile
Easily altered, decomposed or destroyed by heat
Define: Thermostable
Not easily altered, decomposed or destroyed by heat
Give microbial resistance to killing in general sequence from most resistant to least resistant.
1- Bacterial Endospores 2- Mycobacterium 3- Protozoan Cysts 4- Non-enveloped Small Viruses 5- Vegetative Bacteria 6- Fungi 7. Enveloped Viruses
What factors contribute to effectiveness of sterilization or disinfection method/agent?
- Microbial population composition
- Microbial Death
- Population Size
- Concentration/Intensity of Antimicrobial
- Duration of Exposure
- Temperature and pH
- Presence of protective or neutralizing matter
- Physical nature of material being treated
Which Microbe is the most resistant to antimicrobial control methods?
Bacterial Endospores
Which cells are more easily destroyed, Younger cells or Mature cells?
Younger Cells
What occurs during microbial death?
Microbes are not killed instantly when exposed to lethal agents, but become dysfunctional and die over a period of time
How does population size of microbes affect the effectiveness and choice of sterilization or disinfection method or agent used?
Larger load of contaminating microbes requires a longer exposure time to destroy
Concentration/Intensity of antimicrobial affect the effectiveness and choice of sterilization or disinfection method or agent used in what way?
Typically more concentrated chemical or intense a physical agent the more rapidly microorganisms are destroyed.
Give an example where a more concentrated antimicrobial is not more effective?
70% ethanol is more effective than 95% ethanol
How does duration of exposure to antimicrobial play into the effectiveness of control of microbes?
Longer exposure to a microbicidal agent the more organisms are killed
What effect does Temperature and pH play in control of microbes?
Increase in temperature at which a chemical acts often enhances its activity. Heat kills more readily at an acid pH.
What effect does the presence of protective or neutralizing matter have on control of microbe?
Organic material protects or inactivates chemical disinfectants and/or protect from heat.
The physical nature of materials being treated play what role in control of microbes?
The material i.e. glass, metal, plastic, liquid, pores material. More dense material is easier to kill microbes on.
What modes of action are there for microbial control.
- Damage to Cell Wall
- Disrupt cytoplasmic Membrane
- Inhibit synthesis or proteins and nucleic acids
- Alter function of proteins and nucleic acids
