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Bacteriology > staphylococcus > Flashcards

staphylococcus Flashcards

1
Q

what si the most common and most important staph?

A

staphylococcus aureus

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2
Q

what is the metabolism of staph?

A

facultative anaerobes

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3
Q

is staph catalase positive or negative?

A

catalse positive

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4
Q

S. aureus grows in what environment

A

high salt conc

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5
Q

what does S. aureus ferment?

A

mannitol

-mannitol salt agar

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6
Q

describe the hemolysis of S. aureus

A

double zone hemolysis

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7
Q

what does coagulase do?

A

converts fibrinogen to fibrin

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8
Q

does s. aureus produce coagulase?

A

yes

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9
Q

what does CNS mean?

A

staph aureus coagulase negative

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10
Q

what staphylococcal diseases occur in humans

A
  • skin/soft tissue infections
  • food poisoning
  • MRSA
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11
Q

what does MRSA stand for?

A

methicillin resistant staphylococcus aureus

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12
Q

is MRSA zoonotic?

A

yes

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13
Q

what does S aureus cause in cows?

A

mastitis

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14
Q

what does S. aureus cause in chickens and turkeys?

A

-skin and joint infections

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15
Q

what does s aureus cause in pigs

A

septicemia (rarely)

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16
Q

what does S. aureus cause in horses

A

dermatitis and celllitis

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17
Q

what does S. pseudointermedius cause in dogs

A
  • pyoderma

- otits externa

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18
Q

what does S. hyicus cause in pigs

A

-exfoliative epidermitis (greasy pig disease

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19
Q

what are the best sites to take samples from for S aureus?

A

the nostrils

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20
Q

what is protein A

A

a surface protein that binds to Fc region of TgG molecules, which disrupts opsonization and phagocytosis

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21
Q

what are caspsular polysaccharides

A
  • 11 serologically distinct capsule type in s aureus of humans and cattle
  • interfere with host defense mechanisms by inhiiting attachment of antibiodies, induce the relase of cytokines
  • mediate binding to epithelial and endothelial cells
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22
Q

what do peptidoglycan and lipoteichoic acid do?`

A

stimulate cytokine release

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23
Q

what do ahesins do

A

surface proteins that promote attachment to host proteins

  • fibronectin-binding protein
  • collagen-binding protein
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24
Q

what are teh exoenzymes

A

coagulase
lipase
hylauronidase
protease

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25
Q

what is coagulase

A
  • exoenzyme

- converts fibrinogen to fibrin

26
Q

what is lipase

A
  • exoenzyme

- hydrolyzes lipid molecules that the host produces in response to infections

27
Q

what is hyaluronidase

A

-digests hyaluronic acid present in connective tisure and promtoes spread of the infection

28
Q

what is protease

A

=-exoenzyme

  • obtain amino acids as nutrient
  • cleave and inactivate antibodies, antimicrobial peptides (defensins)
  • contribute to tissue proein destruction and enhance invasiveness
  • best described enzyme is serine protease
29
Q

what us toxic shock syndrome toxin

A
  • exotoxin

- superantigen activity

30
Q

do all strains of S. aureus produce exotoxins?

A

no

31
Q

what do enterotoxins do?

A
  • responsible for food borne infections
  • nine types of enterotoxins and 9 enterotoxin-like toxins
  • may have superantigen activity
  • toxins are produces by bacteria in contaminated food
32
Q

how do you get sick from enterotoxins

A
  • they resist proteases, heat stable and not inactivated by cooking (the bacteria get killed from cooking but not the toxin)
  • toxin is ingested with the food and in the stomach the toxin stimulates vagus nerve endings to induce vomiting and abdominal pain
33
Q

what are exfoliative or epidermolytic toxins?

A

produces by S. aureus: ETA and ETB

-repsonisble for a variety of skin diseases in humans

34
Q

what are hemolysins?

A
  • protein toxins that lyse RBCs

- produced by S. saureus and S pseudointermedius

35
Q

S aureus produces what 4 hemolysins?

A

-alpha, beta, gamma and delta hemolysins

36
Q

what is alpha hemolysins

A
  • membrane-damaging (pore-forming) toxin
  • produced a zone of COMPLETE hemolysis surrounding the colony
  • binding of thetoxin to platelets and monocutes results in the relase of cytokines triggering production of inflammatory mediators
  • responsible for the symptom of septic shokc that occur during severe S aureus infcetions
37
Q

what is beta hemolysins

A
  • a sphingomyelinase, which damages membranes rich in sphingomyelin lipid
  • responsible for INCOMPLETE hemolysis of ruminant erythrocytes
  • aka hot-cold hemolysins, refrigeration enhances hemolysis
38
Q

what is double zone hemolysis

A

alpha and beta hemolysins are responsible for double zone hemolysis

39
Q

do all S aureus strains produce leukotoxin?

A

no

40
Q

what is gamma hemolysin aka?

A

leukotoxin

41
Q

what is significant abot leukotoxin?

A

pore-forming toxin and the genes are located on a prophage

42
Q

what is delta hemolysin

A
  • delta toxin is a small peptide

- direct/indirect effects on neutrphils, hence a pro-inflammatory toxin

43
Q

what is beta-lactamase?

A

hydrolyzes beta lactam ring of penicillines and cephalosporins

44
Q

what is penicillin-binding protein 2a

A 
conferes resistance to penicillins and cephalosporins-class of antibiotics
-carried by MRSA
45
Q

what is the pathogenic mehcanism of S aureus

A
  • pyogenic or supportive lesions
  • injury to skin or immune suppression if a predisposing factor
  • virulence factors to promote tissue colonization (protein A and ahesions)
  • immune evasion (capsular polysaccharide, teichoic acid, protein A, catalse, coagulase),
  • spread (hyaluronidase, lipase, protease)
  • tissue destruction (toxins)
46
Q

what is folluculitis?

A

infection of the hair follicle

47
Q

what is furuncle

A

a boil, localized anscess surrounded by a zone of inflammation

48
Q

what is a carbuncle

A

enlarged infected area

49
Q

what staphylococcal diseases occur in humans?

A
  • impetigo

- scaled skin syndrome

50
Q

what is the route of infection for bovine mastitis?

A

though the teat

51
Q

how can you diagnose bovine mastitis?

A
  • double zone on blood agar
  • biochemical tests
  • increased somatic cell count because of increased leukocytes
52
Q

how do you treat bovine mastitis

A
  • intramammary administration of antibiotics (e.g. ceftiofur)
  • dry cow therapy
53
Q

what is dry cow therapy

A

administration of antibiotics a the beginning of the dry period is often used to treat or prevent staphylococcal mastitis

54
Q

what are staphylocccal diseases in poultry

A
  • dermatitis, osteomylelitis, arthritis, synovitis

- lameness due to infection

55
Q

what is bumblefoot

A

localized lesion on the foot resulting from penetration by foreign object and subsequent infection by S. aureus and other bacteria

56
Q

what is exudative dermatitis?

A
  • caused by S. hyicus that produces exfoliative toxin
  • organisms are normally present on the skin
  • can penetrate the skin, however a breach of the epidermis is the most common predisposing factor
57
Q

how do you treat exudative dermatitis?

A
  • antibiotics in early stages are effective
  • eg. ceftiofur
  • severely infected animals do not repsond
58
Q

what causes pyoderma in dogs?

A

S. pseudointermedius

59
Q

what is pyoderma

A
  • dermatitis and folliculitis
  • lesions start as papular eruptions progressing into pustules and small intradermal abscesses
  • deep skin lesions (furuncles) may rupture to become fistulous tracts with pus
60
Q

are MRSA more virulent than other strains?

A

no, but they are more difficult to treat with standard antibiotics and thus more dangerous

61
Q

what are MRSA resistant to ?

A

beta-lactam antibiotics and penicillins, and the cephalosporins

62
Q

MRSA’s resistance is conferred by a gene called..

A

mecA

Bacteriology (17 decks)

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