Celine - Gram Negative Rods - Pasteurella, Bordetella, Brucella Flashcards
Write about Pasteurella
(6)
Colonise mammals both domestic and feral
Normal nasopharyngeal flora for cats and dogs
Most human disease associated with some form of animal contact most commonly dog bites or cat scratches - zoonosis
Six species
P. multocida most commonly infects humans
Isolated from 50% of dog bites and 75% cat scratches
What three syndromes are associated with Pasteurella
Skin and soft tissue infections localised swelling and cellulitis following dog bite/cat scratch
Chronic pulmonary disease in lung dysfunction patients
Systemic infection in immunocompromised host
What virulence factors are associated with Pasteurella
Capsule
Endotoxin
What does diagnosis of pasteurella depend on
Clinical appearance
History of animal contact
Results of culture
What clinical specimen is seen in Pasteurella
Usually pus from skin/tissue infection
Write about the isolation of Pasteurella
(3)
Not fastidious
Grows on blood agar, incubated at 37 degrees in air over night
But fails to grow on MacConkey - good clue
Write about the colonial morphology of Pasteurella
(4)
1 mm white/grey wet colonies
Gram-negative coccobacilli old cultures bipolar ‘safety pin’ staining
Oxidase positive
Catalase positive
What confirmatory tests are carried out for P. multocida
Biochemical tests
- Fermentation - peptone water ‘sugars’ - glucose, maltose, sucrose
Indole production
Ornithine decarboxylase test
Write about the fermentation of peptone waters for Pasteurella
Fermentates glucose and sucrose
i.e. yellow colour after addition of Phenol Red indicator
Write about indole production by Pasteurella
(5)
Peptone media is a source of the amino acid trytophan
Hydrolysis of trytophan, leads to accumulation of indole
Add Kovacs reagent
Cherry red colour on surface is positive
Red colour seen in pasteurella
Write about Ornithine decarboxylase test for Pasteurella
Decarboxylase broth contains nutrients, dextrose, pH indicator (purple) plus a single amino acid e.g. ornithine, lysine
Carboxylase breaks down ornithine - alkaline by-products-pH drop-indicator- purple colour change
Control tube - only dextrose ferments dextrose - pH decrease = yellow colour
P.multicoda positive for ornithine decarboxylase
Write about Bordetella
(4)
Gram negative, small rod/ovoid pairs
Boretella pertussis
Bordetella parapertussis
Bordetella bronchiseptica
Write about Bordetella pertussis
Exclusively human pathogen
Infects ciliated bronchial epithelial cells
Induces excess mucous secretion -> whooping cough
Highly contagious disease
Significant morbidity and mortality worlwide where vaccination unavailable
Worldwide deaths > 300,000/ year
In Ireland pertussis vaccine offered to all children as part of the routine immunisation programme since 1952
In absence of active immunisation -> disease dangerous in young child
Write about Pertussis epidemiology
(5)
Over time significant decrease in infection since vaccine introduction in 1952
Marked increase in pertussis since 2011/2012 predominantly affecting infants incidence highest children < 1 year
Similar increase in other countries - waning immunity in mothers contributory factor
Booster introduced in 2012 for health care workers and pregnant women
Cases begining to decrease again
Write about whooping cough
(4)
3 phases: Catarrhal, paroxysmal, convalescence
CNS dysfunction in around 10% cases
Infection not as dangerous in older children and adults
Adolescents/adults reservoir for infection for young children
