Staphylococcus Flashcards
What are the 6 major characteristics of species in the genus Staphylococcus?
- G+ cocci arranged in grape-like clusters
- facultative anaerobe
- non-motile (non-flagellated)
- non-spore forming
- catalase positive (can break down and detoxify H2O2)
- grow on media containing high salt
What are the 2 widely used culture media for Staphylococcus?
- Mannitol salt agar containing high salt concentrations (6.5-10%)
- Blood agar
What 4 Gram-positive bacteria are able to grow on Mannitol salt agar? What 2 bacteria are selected against?
- Staphylococcus
- Enterococcus
- Listeria
- Micrococcaceae
- Gram-negative bacteria
- Streptococcus
What 2 species of Staphylococcus can be differentiated on Mannitol salt agar?
- S. aureus is able to ferment the mannitol, which causes the agar to change from a red to yellow color
- S. epidermidis is not able to ferment mannitol, so there is no color change
Staphylococcus on purple agar base:
What is the purpose of blood agar in Staphylococcus identification? What 3 classifications can be made?
differentiates between the type of hemolysis toxin produced
- α = incomplete hemolysis, gree
- β = complete hemolysis, clear
- γ = no hemolysis, no change in media
What causes β-hemolyzing Staphylococcus to turn blood agar yellow? Give an example of a β-hemolyzing and and γ-hemolyzing Staphylococcus species.
the presence/production of the golden-colored carotenoid, staphyloxanthin (antioxidant)
β = S. aureus
γ = S. epidermidis
What 3 ways should Staphylococcus infections be diagnosed?
- Gram stain: shape/stain color
- biochemical tests: hemolysis, catalase, coagulase
- molecular biology: PCR of nuc gene
How should Staphylococcus test in catalase tests?
positive - they have catalase that is able to break down H2O2
What tests aid in genus identification of Staphylococcus? Species/pathogenicity?
- Gram stain
- catalase test
- coagulase test
- blood agar growth
Coagulase test:
Which strains of Staphylococcus are most pathogenic? Why?
coagulase-positive, especially those with β-hemolysis
can clot hosts serum and lyse RBCs
(S. aureus, S. schleiferi, S. pseudointermedius, S. delphini)
Staphylococcus can be found in the normal microflora of many species. When do they become dangerous?
OPPORTUNISTIC PATHOGEN - if the host is in unfavorable circumstances causing stress or depression of the immune system, the bacteria is able to cause disease
In what 2 places are Staphylococcus normally found in animals?
- skin
- tubular orifices (nasal cavity, buccal cavity, nasopharynx, mammary glands, groin)
What are the 3 major risk factors of Staphylococcal diseases?
- linked to parasitic (tick, sarcoptic mange, lice), fungi (Mycotoxin), and viral (Parvovirus, Poxvirus) infections
- shearing sheep/grooming damages skin and can disrupt the normal barriers that keep Staphylococcus out
- nutritional imbalances, like zinc and vitamin deficiencies
What are the 3 broad virulence factors for pathogenicity in Staphylococcus?
- body structures for adhesion and binding
- enzymes
- toxins
What are the 4 body structures for adhesion and binding in Staphylococcus?
- cell wall - bacterial viability, homeostasis, protection from attack by host lysozyme
- protein A - binds Fc of IgG to block immune response and opsonization
- binding or clamping factors - attachment to host proteins
- capsule (slime layer) - useful for adhesion, preventing chemotaxis, and inhibiting phagocytosis by polymorphonuclear leukocytes
What 7 enzymes are present in Staphylococcus to increase their virulence?
- hyaluronidase - breaks down connective tissue between adjacent cells to let the bacteria dig deeper between cells
- catalase - protects against host reactive oxygen species
- coagulase - clots blood to hide in it
- staphylokinase - lyses clots to come out and disperse itself
- lipase - digests lipids, allowing it to colonize skin surface and sebaceous glands
- protease - destroys tissue proteins
- β-lactamase - inactivates β-lactams to survive treatment
What 5 toxins contribute to Staphylococcus virulence?
- hemolysin - destroys RBCs, neutrophils, macrophages, and platelets
- cytolytic toxins (leukocidin) - destroy cell membranes of host cells (leukocytes)
- exfoliative toxin - separates skin layers, resulting in impetigo and peeling
- toxic shock syndrome (TSS) toxin - causes shock and superantigens (mass T cell activation)
- enterotoxins - cause food poisoning by stimulating gut motility and superantigens
What are the 6 steps in Staphylococcal pathogenesis?
- entry of 100s of Staphylococci by breaching body barriers
- adhesion and attachment on the host cell surface or to a matrix between each cell
- biofilm formation on the host cell surface for persistence
- advance into intracellular invasion, multiplication, and persistence within host cells
- elicit inflammation, abscess formation, necrosis, and bacterial encapsulation
- bacteria will either hide in dormant small colony variants (SCVs) or the abscess containing them will mature, rupture, and cause bacterial spread
What does abscess rupture tend to lead to? What organs are most affected?
bacteremia, followed by diverse organ infection
those with high cardiac output - endocardium, lung, meninges, liver, kidney, uterus, bones, joints
Metastasis of Staphylococcus in the blood is dependent on what 2 things?
- serotype of Staphylococcus
- immune status
What are 4 coagulase-positive species of Staphylococcus? 3 coagulase-negative?
- S. aureus —> mammals and birds
- S. hyicus —> pigs
- S. pseudointermedius —> pigs
- S. schleiferi —> pets
- S. chromogenes —> mammals
- S. felis —> pets
- S. epidermidis —> humans
How does S. epidermidis cause foot odor in humans?
isovaleric acid production following degradation of leucine in sweat by bacterial leucine dehydrogenase
Staphylococcus advances from what 4 directions? What systemic and life-threatening infections can it cause? How does it cause life-threatening toxicosis?
- cutaneus pus/anscess
- ear
- mammary glands
- urogenital system
bacteremia/septicemia, endocarditis, metritis, pneumonia, osteomyelitis, meningitis
releases diverse toxins that can cause shock
How does S. aureus infection begin? What does it progress into?
abscesses, dermatitis, mastitis
septicemia, endocarditis, meningitis, osteroarthritis
How does S. aureus affect multiple species? Cattle? Sheep? Goats? Pigs? Horses? Poultry? Dogs and cats?
MULTI = abscess, septicemia, surgical lesion infection
CATTLE = mastitis, teat base pustules, impetigo, gangrenous teat
SHEEP = mastitis, tick pyemia, dermatitis of torn skin, periorbital dermatitis
GOAT = subacute/peracute mastitis, dermatitis
PIGS = mastitis, impetigo, endometritis
HORSES = mastitis, botrymocosis of spermatic cord after castration
POULTRY = septicemia, bumble foot, artritis
DOGS and CATS = supperative lesions
Staphylococcus skin peeling:
caused by exfoliative toxins
Pig Staphylococcus skin infection:
Dog Staphylococcus ear infection:
How do Staphylococcal infections typically present in humans? What species typically causes human infection?
scalded skin diseases, where skin layers slough off and exudative epidermitis is common
- presence of fluid-filled blisters that are easily broken
- exfoliation due to the breakdown of desmosomes by exfoliative exotoxins
S. aureus
What are the most common signs of Staphylococcal disease in pigs? What 2 species can cause them?
- greasy pig disease (exudative epidermitis)
- excess sebaceous secretion
- exfoliation
- poly-limb lameness (polyarthritis)
- metritis
- vaginitis
- S. hyicus
- S. chromogenes (sometimes
What are the most common dermal signs of Staphylococcal disease in dogs and cats? What 3 species cause this?
- pyoderma
- erythema
- pustule, papule, crust, scaling
- allopecia
- epidermal collarettes
- S. pseudointermedius
- S. aureus (less common)
- S. schleiferi (less common)
What is the major differences in dermal signs of Staphylococcal disease in dogs and cats?
DOGS: most common areas affected are the axillae, groin, ventral neck and abdomen, and interdigital spaces
CATS: tend to present with multiple crusted papules (miliary dermatitis) or erosive plaques on the face, neck, and ventrum
What are other non-dermal signs of Staphylococcal disease in dogs and cats? What 2 species cause this? What is the difference in otic signs between dogs and cats?
- otitis externa
- pyoderma
- pyometra
- S. pseudointermedius
- S. aureus
DOGS = S. schlefieri
CATS = S. felis
What are the most common signs of Staphylococcal disease in ruminants? What species cause this?
- mastitis
- udder ulceration (impetigo)
- gangrenous masitis
S. aureus - subclinical mastitis
S. chromogenes
What is the most costly disease is cattle cause by Staphyloccocus?
mastitis —> loss of $2 billion each year in the USA
What is a common cause of the systemic spread of Staphylococcus in sheep? What age is most susceptible? What species causes this?
tick pyemia - Staph released from an abscess
lambs 2-5 weeks infested with Ixodes ricinus
S. aureus
What are major signs of Staphylococcal disease in horses? When are scrotal infections common? What species causes this?
- mastitis
- skin botryomycosis
- nodules on lips, limbs, and scrotum
- multifocal/widespread papules/pustules
after castration
S. aureus
What are common signs of Staphylococcal disease in poultry? What species causes this?
- bumblefoot: pyogranulomatous process of subcutaneous tissue on foot and joints
- arthritis, septicemia in turkeys
- omphalitis: yolk sac infection
- wing rot or gangrenous dermatitis
S. aureus
Why is treatment and control of Staphyloccoal disease difficult?
Staphylococcus consists of multi-drug resistant species
(S. aureus - ESKAPE)
What 2 antimicrobials is S. aureus known globally for acquiring resistance?
- Methicillin
- Vanomycin
What are 4 practices that can be done to control Staphyloccocus infection?
overall improvement to hygiene and wellbeing
- improve immunity, feeding, and hygiene of each animal and its house/barn
- tick control in lambs by using pour-ons or dipping in acaricide
- proper cleaning of wounds and surgical openings
- careful shearing and grooming
What are 5 specific practices for controlling and preventing Staphylococcus in dairy animals?
- good hygiene at milking time (single-use paper towels, gloves, teat dip after milking in iodine)
- dry cow therapy
- separate infected/positive cows
- cull cows if they remain clinical or have chronic masitits
- prevent reinfection into the herd using a quarantine period and culture testing for new cows
