microbiology Flashcards
describe the steps involved in a gram stain reaction
- make film
- flood with crystal violet (blue)
- all cells will take up this dye^
- flood with Lugoi’s iodine
- all stains go blue-black
- de-colourise with acetone
- gram +ve retain dye, gram -ve are de-colourised
- counterstain with a red dye
- gram +ve appear blue-black, gram -ve appear red
are exotoxins gram positive or negative?
Gram positive
are endotoxins gram positive or negative?
gram-negative bacteria produce endotoxins
What is a pathogen?
Organism capable of invading the body and causing disease
What is a commensalism?
An organism which is part of the normal flora
What is pathogenicity?
The ability to cause disease
What is the lifecycle of a parasite?
- parasite
- enters/ attaches to host
- multiplication in host
- causes harm
- release from host
- transmission
What is colonisation?
Microbes find a new host and start to multiply (no harm done)
Exogenous vs endogenous infection
Endogenous is if the source of the microbe is the patients own flora
Parts of a prokaryotic cell
How do bacteria attach?
Pili
What’s an example of an encapsulated infection?
Meningitis (can be caused by streptococcus)
What is the function of the capsule in a bacteria cell?
- protection from immune invasion
Exotoxin vs endotoxin
- exotoxins are produced inside gram POSITIVE bacteria
- endotoxins are produced on the outside of gram NEGATIVE bacteria
What is mycology?
Study of fungi
What organelles do prokaryotes and eukaryotes have in common?
- cell membrane
- DNA
- ribosomes
What is an example of non-selective agar plate?
Blood agar
What is an example of a selective agar plate?
Mannitol salt agar
What does aerobic mean?
With oxygen
What does capnophilic mean?
With carbon dioxide
What does facultative mean?
With and without oxygen
What does microaerophilic mean?
Require small amounts of oxygen
What does anaerobic mean?
Without oxygen
Gram stain reaction steps…
- make a film
- crystal violet and iodine (all cells dyed)
- acetone (gram positive cells retain dye (blue/black) and gram negative are decolourised)
- red dye (gram positive are blue black and gram negative are red)
What type of bacteria is lipopolysaccharide?
Gram negative endotoxin
What shape is cocci bacteria?
Round
What shape is bacilli bacteria?
Rod (rice)
What is an example of a gram positive cocci bacteria?
Streptococcus mutants
Staphylococcus aureus
What does streptococcus mutants cause?
Gingivitis
What an example of gram negative bacilli?
Prevotella intermedia
What can stapholococcus aureus cause?
Angular chellitis
What is an example of gram negative cocci bacteria?
Neissera meningitidis
What is an example of gram positive bacilli?
Clostridium tetanii
What does staphylos mean?
Grapes
What causes MRSA?
Stapholococcus aureus
What are common healthcare infections?
C. Dificile and MRSA
What causes C. difficile?
Antibiotics
What is infection ?
Invasion of the body by pathogenic microbes and the reaction of the tissues
Chain of infection…
- infectious agent
- reservoir
- portal of exit
- mode of transmission
- portal of entry
- susceptible host
What is an infectious agent?
Microorganism which has the ability to cause disease
What is the reservoir in the chain of infection?
Where the microorganisms can live and thrive eg a person or object
What is the portal of exit in the chain of infection?
The way the microorganism leaves the reservoir eg sneezing
What is the mode of transmission in the infection cycle?
How a microorganism is transmitted from one person to another eg via hands
What is the portal of entry in the chain of infection?
How the infection enters another individual eg breathed in
What is the susceptible host in the chain of infection ?
The person vulnerable to infection
What does transient bacteria mean?
Bacteria not normally found in the body
What is an example of commensal bacteria?
S epidermidis
How would you take a sample of angular cheilitis?
Take a damp swab
What does coagulate mean?
Clumping
What are koch’s postulates germ theory of disease?
- microbe must be present in every case of the disease
- microbe must be isolated from the diseased host and growth in pure culture
- disease must be reproduced
- microbe must be recovered from an experimentally infected host
Describe the structure of a virus…
Lipid membrane (sometimes)
Protein capsule
DNA/RNA
What are the stages of viral replication?
- attachment
- penetration
- uncoating
- synthesis
- assembly
- release
What type of virus are influenza viruses?
RNA viruses
What should be used to treat patients with a transmittable disease?
Treat every patient the same- SICPs, standard infection control procedures
What organelles do prions lack?
DNA/RNA
When is the transmission of respiratory viruses more common?
- closed setting
- close contact
- crowding
What causes candidiasis?
Candida albicans (fungi)
What are the ways to control the hazards in the environment?
- elimination
- substitution
- engineering controls
- administrative controls
- PPE
What are the stages in biofilm development?
- adhesion
- colonisation
- accumulation
- complex community
- dispersal
What are the benefits of bacteria being in a biofilm?
- protective environment
- coordinated cellular events
- labour division
- less energy used
- survival in numbers
What is a biofilm?
Matrix enclosed bacterial or fungal populations adherent to each other and/or to surfaces/interfaces
Where does stapolococcus commonly live?
Nose
What are the three factors involved in biofilm development?
- microorganism
- conditioning film
- surface
What is the glycocalyx?
- surrounds the bacteria cell membrane
- extra cellular matrix
- maintains a hydrated environment
- protective barrier
What is dental plaque?
A diverse microbial community (mainly bacteria) found on the tooth surface embedded in a matrix of polymers of bacterial/salivary origin
What is the main aetiologies agent associated with caries and periodontal diseases?
Dental plaque
What is an example of an endodontic infection?
Root canal
What is an example of a biofilm in the oral cavity?
Plaque
What are the stages in caries progression?
- adhesion
- survival and growth
- biofilm formation
- complex plaque
- acid
- caries
