Staphylococcus Flashcards
what are the general characteristics of all staphylococcus?
gram-positive cocci
catalase positive
where are commensal staphylococcus found?
skin and mucous membrane
How do opportunistic staphylococcus cause infection?
pyogenic infection by damage to skin or MM, immunocompromised patients
what are tests that can be used to differentiate between staphylococcus species?
coagulase
colony color
hemolysis
what is a positive and negative result of coagulase test indicative of with staphylococcus?
positive - pathogenic strains
negative - non-pathogenic strains
What is a staphylococcus species that causes hemolysis indicate?
causes disease
what are virulence factors present with staphylococcus?
adhesins
protein A
toxins
invasins
urease ( S. pesudintermedius)
what are adhesins?
facilitate bacterial attachment to host tissues
what is protein A?
virulence factor that interferes with opsonization and phagocytosis
what does alpha-toxin (alpha-hemolysin) do?
complete lysis of RBCs
spasm of smooth muscle
what does beta-toxin (beta-hemolysin) do?
incomplete/partial lysis of RBC
what does gamma-toxin (leucocidin) do?
cytolytic destruction of leukocytes
what enterotoxins do staph produce? what does it lead to?
enterotoxin A-E and G-J, SEA-SEJ, superantigen
food poisoning
which bacteria secrete toxins and which release?
secrete - exotoxins
release - endotoxins
what is a superantigen?
binds non-specifically to MHC-II and T cell receptor, leads to massive T cell activation
what is TSST-I?
toxic shock syndrom toxin - I
toxic shock when released into blood
superantigen
what is an exofoliative toxin?
proteases that exfoliate onto skin
what staphylococcus cases exudative epidermitis in pigs? what does this?
S. hyicus
exfoliative toxins
what are invasins?
enzymes that contribute to tissue destruction
what are some invasins that staph produce? what do they do
staphylokinase - break down blood clot
hyuluronidase - depolymerizes hyaluronic acid (CT)
capsule - protects bacterial cells from phagocytosis
what does S. pseudointermedius urease do?
raise pH of urine
possible formation urinary stones - urolithiasis
what is the causative agent of mastitis in cattle?
staphylococcus aureus
where is the main source of infection with mastitis?
udder
what virulence factors contribute to mastitis?
adhesins, invasins, capsule, leukocidin, hemolysins, exotoxins
toxins cause tissue damae
What are the two clinical manifestations of mastitis?
acute and peracute
chronic/subclinical
How does acute and peracute mastitis present?
acute swelling of udder, peracute gangrenous (venous thrombosis > tissue necrosis), quarter sore and swollen, fever anorexia, lameness
what is the most common mastitis in cattle?
chronic/subclinical
How does chronic mastitis present in cattle?
elevated somatic cell counts, duct blockage and atrophy, limited antibiotic access (hard to treat), damage to udder and drop in milk yield, majority of cases become low grade or subclinical
How do you monitor/test for mastitis in cattle?
CMT - california mastitis test
what does CMT measure?
somatic cells in milk
How do you orient yourself when doing a CMT?
stand on right side of cow
what is a positive culture for mastitis?
> 400,000 cells/mL
How can mastitis be prevented?
milking equipment - maintenance
hygienic procedures
eliminate fly-breeding sites
culling (extended time, additional health problems)
what is the vaccine on the market that can prevent mastitis?
Lysigin
what is the causative agent of exudative epidermitis in pigs?
Staphylococcus hyicus
what age of pigs is exudative epidermitis seen mostly in?
3 months of age
what is the contagion level of exudative epidermitis?
highly contagious
what is the pathogenesis of exudative epidermitis?
enter skin through minor abrasions or bite wound
same virulence factors as S. aureus except non-hemolytic
exfoliative toxins
what are the clinical manifestations of exudative epidermitis in pigs?
excessive sebaceous secretion
exfoliation and exudation on skin
greasy exudate - ‘greasy pig disease’
which age of pigs has a lower mortality?
adult
How do you diagnose exudative epidermitis in pigs?
clinical presentation
culture and antibiotic sensitivity
How do you treat exudative epidermitis in pigs?
early systemic antibiotics - amoxicillin, fluroquinolone, ceftiofur, lincomycin
How do you control exudative epidermitis from spreading to other pigs?
strict isolation of affected pigs
what is the causative agent of pyoderma in cats and dogs?
S. pseudintermedius
what are the two types of pyoderma?
superficial - epidermis and hair follicles
deep dermis - furunculosis (boils)
what are the virulence factors of S. pseudintermedium?
same as S. aureus
adhesins most important
How does pyoderma present in dogs?
multifocal areas - alopecia, folllicular papules/pustules, crusts
what is the causative agent of this dog disease?
S. pseuintermedius
what is the causative agent of this pig disease?
S. hyicus
what is the causative agent of this cow disease?
S. aureus
How does pyoderma present in cats?
alopecia, ulceration, hemorrhagic crust, draining tracts
what is the causative agent of this cat disease?
S. pseudintermedius
what is MRSA?
methicillin-resistant S. aureus
what is MRSP?
methicillin-resistant S. pseudintermedium
How do you treat pyoderma?
antibiotics, medicated shampoos
How do you diagnose a staph infection?
isolation/culture - standard
microscopy - gram + staphlycoccus
what agar is selecting for gram negative species?
MacConkey
What agar selects for Staphylococcus species?
mannitol salt agar
What should you do for owners who have pets carrying MRSA?
tell them to wash their hand thoroughly
no broken skin around pet
