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Bacteriology > Staphylococcus > Flashcards

Staphylococcus Flashcards

1
Q

Staphylococcus characteristics

A

-gram positive
-cocci (clusters of grapes)
-aerobic or facultatively anaerobic
-can be coagulase positive or negative (will appear as zone clearing on dish OR clots in tubes)
-colonies are generally creamy/white on blood agar

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2
Q

Staphylococcus biocontainment

A

level 2

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3
Q

Staphylococcus aureus characteristics

A

Blood agar:
-creamy white colonies
-hemolytic (beta-hemolysis)

CHROMagar:
-pink/purple colonies

Mannitol salt agar:
-yellow colonies

-coagulase occurs

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4
Q

Staphylococcus epidermidis characteristics

A

Blood agar:
-not hemolytic (no zone clearing)
-white colonies

Mannitol salt agar:
-does not ferment mannitol so not yellow!

-no coagulase occurs in tests

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5
Q

Staphylococcus pseudintermedius characteristics

A

Blood agar:
-beta hemolysis occurs (double zones)
-white/grey (often more than S. aureus)

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6
Q

Natural host or habitat

A

-part of normal microbiota (skin, mucous membranes, pharynx, intestinal tract)

-different species specific to different hosts (S. aureus colonize 30% people; S. pseudintermedius colonize 90% of dogs)

-environmental contamination may play role in hospital environments

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7
Q

Taxonomy of Staphylococcus genus

A

-64 species
-based on coagulase, hemolysis, hyaluronidase acetoin

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8
Q

What species is coagulase variable?

A

Staphylococcus schleiferi
>has two subspecies (schleiferi and coagulans)
need biochemical tests to differentiate

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9
Q

What differentiates with negative hemolysis (when coagulase positive)?

A

Staphylococcus hyicus

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10
Q

What differentiates with Hyaluronidase acetoin?

A

Positive: S. aureus

Negative: S intermedius group

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11
Q

Virulence factors of staphylococcus

A

-toxic shock syndrome toxin= superantigen
-enterotoxins= food poisoning
-exfoliates- skin damage (Scalded skin)
-leucocidins (ex. Panton-Valentine Leucocidin PVL; destruction of WBCs)
-MSCRAMM (facilitate adherence to host tissues and structures like fibronectin, fibrinogen, elastin, cellular lipids)
-Catalase (resists hydrogen peroxide)
-Hyaluronidase (degradation enzyme which facilitates spread to contiguous tissues)

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12
Q

Clinical significance of S aureus

A
  1. cattle, sheep, goats, pigs, horses- Mastitis
  2. Poultry- bumblefoot
  3. dogs and cats- opportunistic and skin infections
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13
Q

Clinical significance of S. pseudintermedius

A
  1. Dogs and cats- opportunistic and skin infections
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14
Q

Clinical significance of S schleiferi

A

Dogs- opportunistic and skin infections

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15
Q

Clinical significance of S hyicus

A

Pigs- exudative epidermitis (greasy pig)

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16
Q

Clinical significance of S chromogenes

A

Cattle, sheep, goats- Mastitis

17
Q

Mastitis in cows

A

-udder of colonized cow is main reservoir
-Adheres to and invades mammary epithelium, and can form small colony variants and L-forms (metabolically inactive mutant strains that are difficult to treat)

18
Q

Staphylococcus aureus mastitis disease categories

A
  1. Peracute- rapidly progressive clinical disease

2.Subclinical- no clinical signs, decreased production

19
Q

Staphylococcus aureus as mastitis- role in economics

A

-chronic subclinical disease can lead to reduced production and sporadic clinical disease

20
Q

How to go about a herd with S. aureus/mastitis?

A

-improved hygiene (disinfection of equipment; not milking affected quarter)
-cull carrier cows
-intra-mammary antibiotics (be careful of MRSA…avoid beta-lactams

21
Q

Staphylococcus aureus/bumblefoot in poultry

A

-infections of many sites (bones, tendon sheaths, joints)
-associated with green-liver osteomyelitis complex
-morbidity and mortality usually low (affects individuals not flocks)

22
Q

How to go about bumblefoot cases?

A

-likely opportunistic, common colonzer; not contagious
-good management practices (remove sharp objects, ensure good litter quality, control other diseases)
-vaccines not effective
-treatment based on susceptibility test results

23
Q

Staphylococcus pseudintermedius in dogs

A

-90% healthy dogs are colonized
-causes wide array of infections:
>pyoderma and otitis externa- often secondary to disease (atopica dermatitis, allergy, endocrinopathy)
>surgical site infections
>orthopedic implants
>necrotizing fasciitis
>nosocomial infections

24
Q

Staphylococcus hyicus in pigs

A

-Exudative epidermitis (greasy pig disease)- dark brown crusty lesions
-acute or peracute, sporadic within herd
-seen in suckling and newly weaned piglets when:
>mixing litters
>animals fight
>teeth unclipped
>rough bedding
-affected animals can have high mortality rate (up to 70%)
-early antimicrobial treatment may be effective

25
Q

Staphylococcus chromogenes in cattle, sheep, goats, pigs

A

-coagulase negative
-mastitis in cattle, sheep, goats
-greasy pig syndrome in pigs

26
Q

Collecting specimens for mastitis

A

-clean outside of teat before collection, or use milk from bulk tank immediately after milking

27
Q

Collecting specimens for dermatitis/superficial infections

A

-use swabs to collect pus or exudates

28
Q

Collecting specimens of urine

A

cystocentesis collected urine preferable to free catch

29
Q

collecting specimens for systemic infections in chickens

A

-test yolk sacs, joints, and stab swabs of internal organs

30
Q

Staphylococcus transport

A

-tough genus;no special transport needed
-do not freeze most samples; can freeze milk since it is cryoprotective

31
Q

Lab ID of staphylococcus

A

-easily grown using standard culture (blood agar)
-easily identifies major species by MALDI-TOF or biochemicals
-Need to request selective culture for Methicillin resistance

32
Q

Zoonotic/interspecies transmission

A
  1. Staphylococcus aureus has broad host range
    -Livestock associated MRSA common in pigs and cattle and found in humans
    - strain common in chickens (ST5)
    -horses have own population
    -dogs and cats have S aureus that they probably got form people
  2. Rise of staphylococcus pseudintermedius in people, likely got from dogs
33
Q

Treatment options for staphylococcus

A

-must be guided by susceptibility testing

-resistance is emerging and unpredictable

-Be aware of intrinsic polymyxin resistance and methicillin resistance

-can use locally administered therapy (Burrows solution for canine otitis or shampoos for pyoderma; intramammary prep for mastitis)

34
Q

Nosocomial

A

acquired from hospital

35
Q

Superantigen

A

antigen which is capable of stimulating a much larger number of T-cells than an ordinary antigen, resulting in an exaggerated response

36
Q

Peracute vs acute vs subacute vs chronic

A

Peracute- Fastest

Acute- sudden onset, sharp rise

Subacute- between acute and chronic

Chronic- continuing, constant, long term

37
Q

Subclinical

A

-not clinically apparent (doesn’t appear sick)
-may be disease with mild, less obvious effects… BUT NOT asymptomatic

38
Q
A

Bacteriology (20 decks)

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