Bacteriology pyogenic infections Flashcards
pyogenic
produce pus
acute inflammatory reaction
predominantly neutrophils
cause disease as extracellular bacteria
pyogranulomatous inflammation
mixture of chronic and acute inflammation
mixture of macrophages, neutrophils, lymphocytes
granulomatous inflammation
chronic inflammation
We will classically see central necrosis surrounded by giant epithelioid cells, macrophages, lymphocytes, some granulocytes, and surrounded by a thick fibrous capsule
necrotizing inflammation
We will classically see just cellular debris, potentially a few toxic, inflammatory cells and the causative bacteria e.g., gram positive spore-forming rods
staphylococcus type of bacteria
gr + cocci
form clusters in liquid media
facultative anaerobe
opportunistic
Staphylococcus aureus
humans and other domestic species (incl. horses)
coagulase positive
staphylococcus pseudointermedius
most common pathogen in dogs
coagulase positive
coagulase test
differentiates between
weakly virulent and highly virulent staphylococci
positive are more highly virulent
where are staphylococcus normally found?
normal flora of skin
* especially near mucocutaneous junctions
* Moist areas of the body
* Distal nasal passage, external nares, near rectum
May also be found in animal products and in the environment due to contamination
* Relatively LONG LIVED in the environment (problem for control)
How do staphylococci cause disease
Staphs are GOOD pathogens (need little compromise)
Virulence factors
* Capsule or pseudocapsule (anti-phagocytic properties)
* Exotoxins – leucotoxins/hemolysins
* Intracellular survival (chronic infections)
* Biofilm formation
* Others; urease, superantigens etc
Strain variation in virulence factors & all are not constitutively expressed
capsule/pseudocapsules
- Anti-phagocytic properties
- important becuase major defence mechanism against Staphylococci is phagocytosis
- Non-pathogenic (coagulase- negative) Staphylococci are easily phagocytosed and therefore killed
endotoxins
Wide range of different exotoxins
Hemolysins/Leukotoxins are important for virulence
Cytotoxic (damage cells) and lethal
Leucotoxins also kill phagocytes – therefore help evade immune system
facultative intracellular bacteria
Allows S. aureus to (3 points):
* Evade killing by phagocytes
* Evade immune system (antibodies)
* Evade antibiotics which act extracellularly
Results in persistence of infection (chronicity) in SOME cases
not all Staphylococci have this ability (strain variation) nor can they do this all the time (genes not constitutively expressed)
What diseases do staphylococci cause (general)?
pyogenic, may be chronic (intracellular)
Staphylococci cause a WIDE RANGE of DISEASES in domestic animals
Few are pathognomic for Staphs!
they are associated with pyogenic infections
they may be associated with chronic infection
streptococci type of bacteria
Gram positive cocci that form chains
Facultatively anaerobic
pyogenic
Where are streptococci normally living?
Widely distributed in nature
Pathogenic species are most commonly found on animals and humans:
* on the mucus membranes of upper respiratory tract, lower genitourinary tract and GIT
* also on skin
Some pathogenic species may live in the environment as saprophytes
can be normal flora
hemolytic patterns
beta-hemolytic streptococci cause most of the important diseases in animals including diseases in Horses, Cattle, Dogs
α-hemolytic are also important - especially in Cattle, humans, and becoming so in dogs
non-hemolytic Streptococi are usually non-pathogenic
strangles
Streptococcus equi equi (NOT normal flora)
Cervical lymphadenitis
Major contagious disease of horse worldwide (carrier state)
What diseases does Trueperella pyogenes cause?
The most common cause of pyogenic infections in cattle!!!
Other species may also be infected e.g. pigs, ruminants, dogs, humans
Other species of bacteria may be present in lesions (mixed)
Usually initiated by trauma/viral infections
Lesions may be localised, regional or metastatic
Many different organs involved
