Introduction to Microbes Flashcards
What is the MALDI-TOF identification system?
- Matrix Assisted Laser Desorption/Ionisation - Time Of Flight
- Laser beam used to break up microbe into particles, particles analysed using mass spectroscopy to identify microbe
What is the coagulase test?
A test that can be used to identify Staph aureus (coagulase positive) other species of staphylococcus (coagulase negative). S. aureus produces the enzyme coagulase which causes the formation of blood clots.
Using S. aureus as an example, what is the genus and what is the species?
Staphylococcus = genus Aureus = species
What is the minimum inhibitory concentration (MIC) in microbiology?
The lowest concentration of antimicrobial drug that will inhibit the growth of the microorganism after overnight incubation.
What does MRSA stand for?
Methicillin Resistant Staphylococcus Aureus
What size is a virus? (in nm)
10-300 nm
What size is a bacterium? (in nm)
1,000 nm
What size is a red blood cell? (in nm)
7,500 nm
What does aerobic mean?
Requiring oxygen
What does capnophilic mean?
Microorganisms that are capnophilic thrive in high concentrations of carbon dioxide
What are facultative anaerobes?
A microorganism that can survive with or without oxygen
What conditions do anaerobes survive in?
Without oxygen
What does the term ‘microaerophilic’ refer to?
Microbes that are microaerophilic require only small amounts of oxygen for survival
How do bacteria reproduce?
Binary fission
What type of growth does binary fission result in?
Exponential growth
What are the 4 stages of bacterial growth?
- Lag phase
- Log phase/exponential growth
- Stationary phase
- Death/decline phase
What are pili?
Hair-like appendage on bacteria used for attachment
What is a flagellum for?
Locomotion
What type of DNA does a bacterium have?
Circular DNA
What is the capsule for on a bacterial cell?
- Enhances the bacteria’s ability to cause disease
- Protects bacteria from host’s immune system
Which shape of bacteria typically cause acute ulcerative gingivitis?
Spiral bacteria shapes
What shape are bacilli bacteria?
Rod shaped
What shape are cocci bacteria?
Round shaped
Describe the steps in a gram stain
- Stain with crystal violet
- Fix with iodine
- Add decolouriser
- Add alcohol
- Counter stain with safrinin
What colour are Gram + bacteria? (following a gram stain)
Purple
What colour are Gram - bacteria? (following a gram stain)
Pink
Why do Gram + bacteria show as purple?
Retention of the crystal violet dye due to thick peptidoglycan layer in cell wall
Which bacteria contain lipopolysaccharide (LPS) in their cell wall?
Gram -
What is LPS?
- Lipopolysaccharide
- An endotoxin
- Stimulates host’s immune system
What are the 3 main components of LPS (lipopolysaccharide)?
- O antigen
- Core
- Lipid A
What colour is prevotella intermedia following a gram stain?
Pink (gram -)
What colour is Strep. mutans following gram staining?
Purple (gram +)
What colour is Staph. aureus following gram staining?
Purple (gram +)
What colour is Clostridium difficile following gram staining?
Purple (gram +)
What colour is neisseria meningitidis following gram staining?
Pink (gram -)
What is an exotoxin?
- A toxin released by bacteria into its surroundings
- Examples include botulinum toxin (released from Clostridium botulinum) and tetanus toxin (released from Clostridium tetani)
