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
streptcoccus zooepidemicus
major pathogen of horses
normal flora
Streptococcus equi
only on carrier animals
causes disease in horses but less than S. zooepidemicus
S. dysgalactiae and S. agalactiae
cause mastitis in cows
S. agalactiae in carrier animals
S. dysgalactiae in normal flora
how do streptococci cause disease?
range of virulence factors that are thought to aid in the pathogenesis of disease
Primarily act by:
* Avoiding phagocytosis
* Killing phagocytes & causing inflammation
* BUT, species causing disease in animals do NOT have intracellular survival as a major host defence mechanism
How do streptococci avoid phagocytosis
M Protein
* MAJOR virulence factor of Streptococci
* Anti-phagocytic properties – both PMNs & macrophages
* Induces antibody production which are protective!!!
Capsules
* Only present on some strains and species
Killing Phagocytes
* Wide range of different exotoxins
* Hemolysins are best described
* cytotoxic for RBC, WBC and platelets
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
What kind of dz do streptococci cause?
acute, short duration
cleared with production of protective antibodies
NO intracellular survival
BUT type III sensitivity can cause chronic dz due to antibodies
strangles, mastitis, neonatal septicemia, pneumonia, endometritis, necrotising fasciitis
strangles
Streptococcus equi equi (NOT normal flora)
Cervical lymphadenitis
Major contagious disease of horse worldwide (carrier state)
mastitis
Streptococci are major cause of mastitis
Three species of importance (S. agalactiae, S. dysgalactiae, S. uberis)
S. agalactiae is contagious (carrier state)
pneumonia
streptococci zooepidemicus (horses, dogs, pigs), canis (dogs and cats), equisimilis (pigs)
lower respiratory tract infections in a variety of species
neonatal septicemia
caused by streptococci
Observed in a range of species including foals, piglets, puppies and kittens
Localization in many other body sites can occur
endometritis
Caused by Strep. equi ss zooepidemicus
Most common cause of endometritis, which is a major disease in brood mares
necrotising fasciitis
streptococci
“Flesh Eating Bacteria!!!!”
Grp G (S. canis) in dogs and cats
or Grp A (S pyogenes) in humans
how to treat streptococci
Drainage (if possible) is very important as thick walled abscesses involved
Nursing care
+/- others e.g. anti-inflammatory agents (NSAIDs)
Antibiotics
* b-hemolytic streptococci are predictably sensitive to penicillin
* Streptococci are frequently resistant to fluoroquinolones, aminoglycosides and tetracyclines
* alpha hemolytic & enterococci commonly have broader resistance to antibiotics including penicillin
antibiotics for b-hemolytic streptococci
b-hemolytic streptococci are predictably sensitive to penicillin
antibiotics for a-hemolytic streptococci
alpha hemolytic & enterococci commonly have broader resistance to antibiotics including penicillin
Trueperella pyogenes and corynebacterium type of bacteria
gr + club shaped rods
faculitative aerobic
where does Trueperella pyogenes come from
Normal flora of the mucus membranes + skin of ruminants and pigs
where does C. pseudotuberculosis come from?
Normal flora skin, mucous membranes & GIT
Also found in the environment (survives up to 8 months)
Found in lesions of infected animals which may act as primary reservoirs
where does C. renale come from?
present in the genital tract of carrier cows and bulls
Trueperella pyogenes and corynebacterium virulence factors
Exotoxins
* Pyolysin & Phospholipase D
* T. pyogenes, C. pseudotb
Pili & urease production
* C. renale & T. pyogenes (pili)
Facultative intracellular bacteria
* C. pseudotuberculosis
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
What diseases does Corynebacterium pseudotuberculosis cause?
Caseous Lymphadentis (CLA) “Cheesy Gland”
* Major (economically important) disease of sheep + goats
* Infection of superficial lymph nodes
* Usually requires a break in skin e.g. shearing, castrating,
* May disseminate (“thin ewe syndrome”)
Pigeon Breast/Pigeon Fever
* Diseases of horses, mostly in Western USA
* Thick walled, external or (more rarely) internal abscesses (more severe dz), on breasts
Ulcerative lymphangitis
* Diseases of horses (and cattle)
* Most commonly hind limbs
* Spread via lymphatics, with ulcerating lesions
C. renale causes what diseases?
Infectious Pyelonephritis
* Disease in cows (not bulls; they are carriers), occasionally other species
* Ascending infection
* Hemorrhagic cystitis, ureteritis, pyelonephritis
“Pizzle Rot” (balanoposthitis)
* Sheep (and occasionally other species) – rams and whethers
* increase protein in feed leads to increased urea in urine
* C. renale produces urease which breaks down urea to ammonia which causes irritation of skin of preputial opening and which bacteria can invade
