(written by Riona Adams) Microbiology - basics Flashcards
Give 3 gram positive cocci
- ) Staphylococci
- ) Streptococci
- ) Enterococci
Give 2 gram negative cocci
- ) Neisseria
- ) Moraxella
Give 3 gram positive bacilli
- ) C. diptheriae
- ) Listeria monocytogenes
- ) Clostridia
- ) Propionibactiera
Give 5 gram negative bacilli
- ) E. coli
- ) Campylobacter
- ) Pseudomonas
- ) Salmonella
- ) Shigella
- ) Proteus
What colour does positive gram bacteria stain?
Purple
What colour does negative gram bacteria stain?
Pink
What is a gram positive anaerobic cocci?
Peptostreptococcus
What test do we do to differentiate between streptococcus and staphylococcus?
Catalase test
How does streptococcus stain in a catalase test?
Negative, no bubbles
How does staphylococcus stain in a catalase test?
Positive, bubbles
What test do we do to differentiate streptococcus?
Haemolysis on BA
What colour does beta haemolytic strep stain?
White/clearing/yellow
What colour does alpha haemolytic strep stain?
Green
Give an example of beta haemolytic strep
Antigenic group A, B, C, G
Give an example of alpha haemolytic strep
Viridans strep
What test do we do to differentiate between alpha haemolytic streps
Optochin test
What are the results of the optochin test?
Resistant or sensitive
Give an example of a sensitive alpha haemolytic strep
S. pneumoniae
What test do we do to differentiate between staphylococcus?
Coagulase
What are the results of the coagulase test?
Positive or negative
Give an example of a coagulase positive staphylococcus
S. aureus
Give an example of a coagulase negative staphyloccocus
Coagulase negative staphyloccus
Give an example of an anaerobic gram negative rod
B. fragilis
What do we do to differentiate between gram negative bacilli?
Lactose fermentation
What are lactose fermenting bacteria?
Enterobacteriaceae (coliforms)
Give an example of a lactose fermenting enterobacteriaceae
E. coli, Klebsiella
What do we do to distinguish between enterobacteriaceae? (2)
Biochemical identification and sensitivity tests
Give an example of a biochemical identification test
API strip
Give 2 examples of a non lactose fermenting bacteria
- ) Shigella
- ) Salmonella
- ) Pseudomonas
- ) Proteus
What test do we do distinguish between non lactose fermenting bacteria?
Oxidase test
What are the results of the oxidase test
Positive and negative
Give an example of an oxidase test negative bacteria
Enterobactericeae
Give an example of a non lactose fermenting enterobacteriaceae
- ) Proteus
- ) Shigella
Give an example of a oxidase test positive bacteria
Pseudomonas species
What do we do to test pseudomonas species?
Anti-pseudomonal sensitivity tests
What colour does a positive coagulase test stain?
Gold
What colour does a negative coagulase test stain?
White
What colour does non-lactose fermentation stain?
Yellow/colourless
What colour does lactose fermentation stain?
Pink
What colour does a positive oxidase test stain?
Purple
What colour does a negative oxidase test stain?
Not purple/no change
Define pathogen
An organism that causes/is capable of causing disease
Define commensal
An organism which colonises the host but causes no disease in normal circumstances
Define opportunist pathogen
A microbe that only causes disease if host defences are compromised
Define virulence/pathogenicity
The degree to which a given organism is pathogenic
Define asymptomatic carriage
When a pathogen is carried harmlessly at a tissue site where it causes no disease
Give 2 colonisation factors
-) Adhesions
-) Invasins
-) Nutrient acquisition
-) Defence
Etc
Define toxins
Effectors that are usually secreted proteins that cause damage and subversion
What are the 2 main shapes of bacteria?
Cocci (round) and bacilli (rod)
Why does a positive gram stain response occur?
Stain is able to fix to the single membrane cell wall on a gram positive bacteria
Why does a negative gram stain occur?
Stain cannot fix due to 2 membranes on gram negative bacteria
Give 2 types of bacterial toxins
- ) Endotoxin
- ) Exotoxin
Give 3 features of an exotoxin
- ) Made up of protein
- ) Specific action
- ) Labile to heat
- ) Strong antigenicity
- ) Produced by mostly gram +ve
- ) Convertible to toxoid
Give 3 features of an endotoxin
- ) Made up of lipopolysaccharide, LPS
- ) Non-specific action
- ) Stable to heat
- ) Weak antigenicity
- ) Produced by mostly gram –ve
- ) Not convertible to toxoid
What is a toxoid?
A toxin treated so that it loses its toxicity but retains its antigenicity
Give 3 ways in which bacteria can get genetic variation
- ) Mutations
- ) Swap bits of DNA with environment (via plasmids)
- ) Gene transfer
Give 3 ways in which gene transfer can occur
- ) Transformation, via plasmid
- ) Transduction, via virus
- ) Conjugation, via sex pilus
What is are plasmids?
Autonomously replicating pieces of DNA