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
“The” opportunist pathogen of cattle (sheep and swine too):
Trueperella pyogenes
Trueperella pyogenes morphology, growth patten, air status, blood interaction
-pleomorphic gram positive rods
-slow growing (48h), facultatively anaerobic
-hemolytic
what is a pleomorphic bacteria?
Pleomorphic bacteria exhibit a variety of morphological types, some of which are identical to other bacteria.
what kind of infections does truperella pyogenes cause? where is it found? where does it multiply? how does it interact with other bacteria?
- Purulent infections (often chronic)
- Normal inhabitant of exposed mucosa and skin of ruminants, pigs
» most important opportunistic pathogen of cattle - Survives in the environment, multiplies in host
- Tendency to cause bacteremia (spread through
the blood) - Often mixed infection with anaerobic organisms
(Fusobacterium necrophorum) - Creates anaerobic conditions for the others
what are specific disease processes that we see associated with T. pyogenes infections?
- Purulent wounds
- Abscesses (Bacteremia)
- Mastitis
- Endocarditis (Bacteremia)
- Arthritis (Bacteremia)
- Metritis
- Abortion (Bacteremia)
- Chronic pneumonia (secondary bacterial pneumonia)
- Footrot, foot wounds
how can we diagnose Truperella pyogenes?
- Smear of purulent material
- Culture
how can we treat truperella pyogenes? what do we have to keep in mind?
- Good susceptibility in vitro, but poor in vivo response because of capsulation of abascesses and antibiotic-binding proteins in pus
prevention strategies for truperella pyogenes?
- Avoid primary cause/lesion
- No efficient vaccine
what are the physical characteristics of genus Actinomyces? where is it found and what type of infections is it associated with? what do its colonies look like?
- Branching filaments
- Mouth flora animals (endogenous infection)
- Cause chronic infections associated with mouth, bites
- Micro-colonies, surrounded by calcified macrophages (“Sulphur granule”)
what are the physical characteristics of genus Actinomyces? where is it found and what type of infections is it associated with? what do its colonies look like?
- Branching filaments
- Mouth flora animals (endogenous infection)
- Cause chronic infections associated with mouth, bites
- Micro-colonies, surrounded by calcified macrophages (“Sulphur granule”)
what does a sulfur granule associated with genus Actinomyces look like?
Bacteria in the middle of the lesion with calcified macrophages at the periphery
what disease does genus Actinomyces commonly cause in cows?
A. bovis: “Lumpy jaw” cattle, chronic suppurative osteomyelitis of mandible, associated with teething or trauma
what disease does genus actinomyces commonly cause in humans and dogs?
A. viscosus: periodontal disease humans, pneumonia in dogs, abscess under the skin of dogs, associated with foreign bodies, dog bites
how do we diagnose actinomyces?
Straightforward, Gram stain
how can we treat actinomyces?
Problematic since chronic. Often surgery plus prolonged antimicrobial therapy (does not restore normal bone structure)
