5.2 Gram + rods Flashcards
common themes of gram positive aerobic rods; types of infection, vaccine efficacy, antimicrobial susceptibility
– Septicemic-bacteremic
– Classical vaccines effective (not for intracellulars)
– Generally susceptible to penicillin G
bacillus spp. characteristics: type, growth rate, most important species
- Widespread saprophytes (not B. anthracis!)
- Large Gram-positive rods
- Spore-forming
- Fast growing, aerobic
- Most important species: B. anthracis
- Examples of other relevant species:
– Bacillus cereus (mastitis, foodborne intoxication in humans)
what does bacillus anthracis look like under the microscope?
-encapsulated gram-positive bacilli
bacillus anthracis life cycle
- the bacteria known as Bacillus anthracis produce dormant spores (not active) that can live in the environment, like soil, for a long time, even decades
- when spores get into the body of an animal or person (a place rich with waters, sugars, and other nutrients) they can be activated and turn into active growing cells
- when they become active, the bacteria can multiply, spread out in the body, produce toxins, and cause severe illness and death
what signs will we see in the body due to bacillus anthracis?
- Overwhelming proliferation of bacteria in body = septicemia = septic shock = death
- Sudden death in ruminant and blood at body apertures
- Generalized haemorrhage, massive dark spleen, enlarged lymph nodes in ruminants
- No blood clotting
- Sometimes marked localized edema (dogs, swine)
> carcass bloated, bleeding nostrils
if you suspect an animal died of anthrax, what should you not do?
do not open the body of an animal suspected to have died of anthrax!
is anthrax common in canada? is it reportable? where can it be found in canada?
- Rare
- Anthrax is a reportable disease in Canada
- Source: spores in soil from animal dead from anthrax
- Endemic in Wood Buffalo National Park
- Sporadic along rivers in Alberta and Saskatchewan. Large outbreak in 2006 following flooding in 2005
- Few cases in bison in Saskatchewan in 2015
is immunization effective for anthrax prevention? why?
Yes! quite effective
In general , immunization is fully effective against extra-cellular (= septicemic) pathogens because “traditional” IM/SC bacterial vaccines produce excellent antibody responses
Septicemia is caused by “extra-cellular” bacteria
what bacteria do we suspect from this clinical case:
* 7 months old steer
* Fed silage in a small farm
* Acting stupid
* Drops food from mouth, tongue out, one ear drooped
* Head tilted to one side
listeria monocytogenes (in brain stem)
>listeriosis
listeria monocytogenes characteristics: physical form, environment, pathology, growth, etc.
- Gram-positive coccobacillus – rod
- Aerobic, hemolysis
- Tolerates pH as low as 5.5 (bad silage)
- Grows even (slowly) at 4°C (psychrophilic = refrigerator)
- Widespread in the environment, grass, sewage, surface water (saprophytic)
- Zoonotic: May contaminate human food (raw food, post-processing contamination) => major outbreaks
listeria monocytogenes movement strategy in the body
- adherence
- phagocytosis
- lysis of phagolysosome
- multiplication in cytoplasma
- movement and transfer to neighbouring cell (uses actin tail)
what species does listeriosis effect? what symptoms/ diseases result?
- Mainly in ruminants (but also found in other species)
- Encephalitis in ruminants: Ascending infection along trigeminal nerve (primary lesions in mouth) => microabscesses in brain stem (diagnosis)
“Circling disease”, “silage disease” - Abortion: bacteremia/septicemia, transplacental transmission to fetus→massive contamination of environment
- Mastitis, keratoconjunctivitis (rare)
- Meningitis (humans)
how can we diagnose listeriosis?
- Clinical signs
- Bacterial culture / Pathology (typical histological
lesions in encephalitis cases)
how can we treat listeriosis?
Only in early stages (cattle): Penicillin, ampicillin, tetracyclines
how can we prevent listeriosis?
- Check quality of silage
- Vaccine available but not used commonly
