Important Definitions Flashcards
What is spontaneous generation?
False hypothesis that living
organisms can originate from non-living matter
What are Koch’s Postulates?
A sequence of experimental steps to relate a specific microbe to a specific disease
What is genetic engineering?
Use of microorganisms as molecular tools for the artificial manipulation of genes in cells
What is gene therapy?
A technique whereby an absent or faulty gene is replaced by a working gene
What are chemoorganotrophs?
Organisms that obtain their energy from organic compounds
What are aerobes?
Chemoorganotrophs that can extract energy from compounds in the presence of oxygen
What are anaerobes?
Chemoorganotrophs that can extract energy from compounds in the absence of oxygen
What are chemolithotrophs?
organisms that can trap the energy available in inorganic compounds
What are phototrophs?
organisms that can contain pigments that allow them to use light as an energy source- cells are coloured
What are heterotrophs?
Organisms requiring one or more organic compounds as their carbon source
What are autotrophs?
CO2 is the carbon source
What are growth factors?
Essential compounds that the organism is unable to synthesize from available nutrients
What are extremophiles?
Organisms that inhabit extreme environments
What are mesophiles?
organisms with an temperature range of
15-400C with an optimum of 370C
What are thermophiles?
organisms with an optimum temperature
between about 40C and 70C
What are hyperthermophiles?
organisms with an optimum
temperature of ≥80C and a max. as high as 115C
What are psychrophiles?
these cold-loving organisms are defined
by their ability to grow at 0–300C
What are obligate aerobes?
They require O2 for growth
What are obligate anaerobes?
They do not need or use O2 for growth
O2 is toxic - either kills or inhibits
What are facultative anaerobes?
Organisms that can switch between aerobic and anaerobic types of metabolism
Fermentation/anaerobic respiration or aerobic respiration
What are acidophiles?
Organisms which grow at an optimum pH well below neutrality
What are neutrophiles?
Organisms which grow best at neutral pH
What are alkaliphiles?
Organisms which grow best under alkaline conditions
What is general purpose media?
Supports the growth of many different species of microbes
What is enriched mmedia?
Media fortified with yeast extracts, or protein
infusions - useful in growing fastidious organisms
Addition of special nutrients, promotes the growth of any
bacteria that may be present
What is selective media?
encourage the growth of one organism whilst
suppressing the growth of another
What is differential media?
Differentiate
target organisms from a mixed culture
What is chemotaxis?
Response to a chemical gradient of attractant or repellent molecules in the environment
What are pili?
Pili are thin filamentous protein structures, that
extend from the surface of the bacterial cell
What is conjugation?
Conjugation is the transfer of genetic material
between bacteria through direct cell-to-cell contact
What is a glycocalyx?
a viscous covering of fibres outside of the cell wall
What is a capsule?
A glycocalyx that appears as an extensive,
tightly bound accumulation of gelatinous material
adhering to the cell wall,
What is a slime layer?
A glycocalyx that appears unorganised and more loosely attached
What is a biofilm?
A common secreted adhesive matrix
What are moulds?
Multinucleated filamentous fungi composed of threadlike strands of cells
What are dermatophytes?
A group of moulds that cause superficial mycoses of the hair, skin and nails e.g. ringworm and athlete’s foot
What are yeasts?
Unicellular fungi
What are helminths?
Multicellular animals
What are commensals?
The non-pathogenic bacteria that grow on the skin and in the mucous membranes (collectively the microbiome)
What is competitive inhibition?
The inhibited access of potential pathogens to nutrients and binding sites
What is microbiota dysbiosis?
Disturbing the gut causes disease such as coeliac
What are the stages of bacterial pathogenesis?
Exposure/entry Adherence and local invasion Colonisation Invasion and growth Evasion of the Host Immune Defenses
What are degradative enzymes?
Enzymes that degrade components of the extracellular matrix providing bacteria with easier access to host cell surfaces
What are cytolytic toxins?
Toxins that degrade integrity of cytoplasmic membranes causing cell lysis
What are AB toxins?
Toxins consisting of two units
What are superantigen toxins?
Toxins that over stimulate the immune system causing extensive inflammation and tissue damage
What is innate immunity?
Nonspecific host defence mechanisms directed against a broad variety of pathogens
What is adaptive immunity?
Specific host defences directed against individual species of pathogens
What are antibodies?
Proteins found in blood or other bodily fluids used to identify and neutralize foreign objects, such as bacteria and viruses
What is antigen switching?
The process by which pathogens can periodically change their surface antigens to prevent host antibody mediated activity e.g. Salmonella
What is a compromised host?
One or more defence mechanisms are inactive
How does infection spread?
6
Pathogen source
Reservoir of infection
Portal of exit
Mode of transmission
Portal of entry
Susceptible host
What is a health care associated infection?
2
An infection contracted while a person is in a health-care facility
An infection that first appears 48 hours or more after hospital admission
What are standard precautions?
Work practices that provide a basic level of infection control for the care of all patients/clients
What are transmission based precautions?
Work practices that are used in addition to standard precautions when a patient is known to have/be colonised with a transmissible agent
What is surveillance?
Work practices that allow investigation of chain of infection and monitoring of infection control practices
What are the WHO My 5 Moments for Hand Hygiene?
Before touching patient
Before clean/aseptic procedure
After body fluid exposure risk
After touching a patient
After touching patient surroundings
What are the three microbial growth measures in the environment?
What are the three main ways of controlling microbes in the environment?
Decontamination
Disinfection
Sterilization
What is decontamination?
treatment that renders an object or
inanimate surface safe for use or disposal
What is disinfection?
destruction of vegetative organisms which
might cause disease (or in the context of food industries,
which might cause spoilage) - does not necessarily kill
spores
What is sterilzation?
the killing or removal of all viable
organisms- implies the destruction of all microorganisms
including endospores
What are the two microbial growth measures in the human host?
Antibiotic/antiviral/antifungal treatment
Vaccines
What measure is used in physical methods of controlling microbes in the environment?
Sterilization
i.e. sterilization is used to physically remove microbes
What measure is used in chemical methods of controlling microbes in the environment?
Disinfection
i.e. disinfectants are used in chemical methods of removing microbes
What are the methods of sterilization used in a microbiology lab?
Red heat
Dry heat
Moist heat
Filtration
What are the methods of sterilization used in a healthcare environment?
Moist heat
Radiation
Incineration
What is a hot air oven?
A thermostatically controlled oven, fitted with a fan to ensure even temperature in all parts of the load
Use of moist heat in micro lab?
2
Autoclave used to:
Safe discard of specimens and biohazardous waste
Sterilisation of culture media, reagents and equipment before use
Use of moist heat in healthcare?
Autoclave used to sterilise medical devices
What is an autoclave?
It applies steam heat under pressure at temperature above the boiling point of water and can thus kill both vegetative cells and endospores
What is incineration?
A high-temperature dry oxidation process that reduces waste to inorganic matter
What is filter sterilization?
Involves the physical removal of microorganisms from air or liquids
Radiation makes use of what means to remove microbes?
Decontamination or sterilization
What are disinfectants?
Chemicals used to kill microbes but not necessarily their endospores on inanimate objects or surfaces
List the limitations of disinfectants.
6
Must be made up fresh daily
Must be made up at correct concentration
May be corrosive to skin
Activity is reduced in presence of large numbers of organisms e.g. biofilms
Inactivated by blood and plastics
Susceptibility of pathogen to disinfectant vaires
What are cidal agents?
Antibiotics used to kill organisms
bacteriocidal, fungicidal, viricidal
What are static agents?
2
Antibiotics that do not kill but only inhibit growth
bacteriostatic, fungiastatic, viristatic agents
What are broad spectrum antibiotics?
Antibiotics that act on both gram pos and neg bacteria
What are narrow spectrum antibiotics?
Antibiotics that act on a single group of organisms
What are the five main targets antibiotics have in bacteria?
Cell wall
Protein synthesis
Nucleic acid synthesis
Cytoplasmic membrane
Folic acid synthesis
What is a vaccine?
A preparation which is used to improve immunity to a particular infection - prevent infection
