Miscellaneous Gram Negative Bacteria Flashcards
(36 cards)
List two properties/characteristics of Gram Negative endotoxins
- Heat stable
- Lipid A of GN wall
- Not antigenic
- Activates coagulation, complement, fibrinolysis
- Not secreted - released when cells disrupted
- Less potent than exotoxins
Which genera from the family of Enterobacteriaceae are always motile?
Proteus sp.
Providencia sp.
Morganella morganii
What genera of Enterobacteriaceae would you expect to isolate if an unknown organism was TDA positive?
Proteus sp.
Providencia sp.
Morganella morganii
How would you know if unknown organism was a member of the Enterobacteriaceae family and not a member of the Pseudomonas, Vibrio or Aeromonas? (hint: rapid test)
Conducting an oxidase test will show rapid distinction between these species because the Enterobacteriaceae family are negative oxidase and pseudomonas, vibrio and Aeromonas are all positive oxidase.
Where is Pseudomonas aeruginosa normally found?
In the environment (i.e. soil, plants, water supplies)
Where are O and H antigens located?
O antigen is located on the cell wall (lipopolysaccharide) on the organism and H antigen is located on the flagellum.
How could you tell if an organism growing on a culture plate is encapsulated?
The growth will have a mucoid texture/look
Where are the members of the genera Haemophilus, Neisseria and Moraxella found as normal flora?
Normal flora of the URT
What type of infections are Haemophilus and Moraxella usually associated with?
Respiratory Tract infections
Which species of Haemophilus requires both X and V factors but can grow readily on blood agar?
Haemophilus haemolyticus
Why are CHOC plates always incubated in CO2?
This agar is used to encourage the growth of more fastidious species such as Haemophilus and Neisseria which are both capnophiles therefore they require high a CO2 environment to grow.
Name two pigments produced by Pseudomonas aeruginosa and identify which one is fluorescent under UV light?
Green pyocyanin and Yellow pyoverdin (fluorescein)
Compare the infectious dose required for human cholera, salmonellosis and shigellosis. Where are these organisms acquired from? (i.e. what is there usual/natural reservoir?
Cholera - Infective dose 10^10 orgs/ml - natural reservoir are contaminated water supplies, fish/shellfish from contaminated water supplies, contaminated foods and asymptomatic carriers.
Salmonellosis - Infective dose >10^5 orgs/ml - natural reservoir are animals such as poultry, cows, pigs, sheep, pets, birds and reptiles.
Shigellosis - Low infectious dose of 10-100 organisms - Associated only with humans.
What would the presence of GNID indicate if seen in a throat swab?
Possible Neisseria gonorrhoeae infection
What primary test results would you expect for a member of the Enterobacteriaceae?
- Gram stain - Gram Neg Bacillus
- non-fastidious
- Catalase pos
- Oxidase neg
- OF - Fermentative
- Facultative anaerobes
- All motile genera have peritrichous flagella
- Grey, moist, shiny looking colonies on BA (slightly more opaque centre than edge)
- Usually non-haemolytic
How could you rapidly differentiate between the three swarming strains of Proteus sp.? What would be the results for each?
Conduct an Indole and Maltose test to differentiate between them.
- P. vulgaris - Indole pos and Maltose pos
- P. mirabilis - Indole neg and maltose neg
- P. penneri - Indole neg and maltose pos
List 4 characteristic laboratory features of Pseudomonas aeruginosa.
GNB Non-fastidious Obligate aerobe motile oxidase pos OF: oxidative Distinct colony morphology: flat. matt colonies, uneven periphery, sheild shaped colonies.
If you had mucoid LF/LLF growing on CLED or MAC, how could you differentiate this as either an Enterobacter sp. or Klebsiella sp. without setting up overnight tests?
check the consistency of the colony. If it’s sticky then it’s most likely Klebsiella.
When performing an Indole Spot test what culture plates do we and don’t we take colonies from?
Use BA
Don’t use colonies from CLED or MAC
What indole reaction will you get from E. coli?
Indole pos
The family Enterobacteriaceae what are the overt pathogen that we consider significant (hint: they are NOT considered NF)
- Salmonella
- Shigella
- Yersinia
- Diarrhoea producing strains of E. coli.
The most common isolates in the clinical lab are from what family of bacteria?
Enterobacteriaceae
What are the common genera of Enterobacteriaceae? (not the clinically significant overt pathogens)
- Escherichia
- Citrobacter
- Klebsiella
- Proteus
- Providencia
- Morganella
- Serratia
- Enterobacter
What are the non-motile genera of Enterobacteriaceae
- Klebsiella
- Shigella
- Yersinia
