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Microbiology > Staphylococci > Flashcards

Staphylococci Flashcards

1
Q

Is staphylococcus Gram + or - ?

A

all are gram +

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2
Q

Is staphylococcus catalase + or - ?

A

all are catalase +

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3
Q

Does staphylococcus need O2 or not ?

A

can function with or without O2

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4
Q

What is the outermost layer of the skin ?

A

epidermis

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5
Q

What are some characteristics of the epidermis ?

A
  • surface layer
  • consists of dead flat cells (contain keratin, durable protein) forming a scaly layer
  • constantly sloughing/shedding off which makes it hard for bacteria to grow on it
  • takes about 1 month to regenerate
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6
Q

What is the middle layer of the skin ?

A

dermis

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7
Q

What are some characteristics of the dermis ?

A
  • supports epidermis
  • contains tiny nerves, blood vessels, and lymphatic vessel penetration
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8
Q

What is the innermost layer of the skin ?

A

subcutaneous

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9
Q

What are some characteristics of the subcutaneous layer ?

A
  • fatty layer (adipose tissue)
  • tubules of sweat glands & hair follicles that go through epidermis and dermis end in this layer
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10
Q

What is sebum ?

A

oily secretion that the sebaceous glands produce

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11
Q

What is the purpose of sebum ?

A
  • keeps hair and skin soft
  • also makes it pliable and water repellant
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12
Q

Through what layers of the skin do hair follicles go through ?

A

all of them
- can be a passageway for microorganisms to penetrate the skin and reach deeper tissues

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13
Q

What are the conditions needed for acne to develop ?

A
  • excess secretion of sebum-disorder of sebaceous glands
  • excess growth of Propionibacterium acnes
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14
Q

What is the importance of normal skin flora ?

A
  • sweat and sebaceous glands are important for the growth of the flora (supplies nutrients like water, AA, and lipids)
  • break down lipids producing fatty acid by-products (inhibit growth of potential pathogens)
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15
Q

Define normal flora ?

A

bacteria that usually is there and/or is expected

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16
Q

What are characteristics of Diphtheroids ?

A
  • Gram + rods
  • pleomorphic (change size/shape according to environment)
  • low virulence
  • Propionibacterium acnes
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17
Q

What are some general characteristics of the micrococcaceae family ?

A
  • aerobic and facultative anaerobic (with or without O2)
    • respiration and fermentation metabolism
  • gram + cocci, arranged in clumps/clusters
  • catalase +
  • found on skin and mucous membranes
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18
Q

What are some general characteristics of staphylococci ?

A
  • gram (-) in clumps/clusters
  • Catalase +
  • Aerobic or facultative anaerobes
  • fermenters of carbs
  • NaCl (salt) tolerant
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19
Q

What are the 3 skin infections caused by Staphylococcus Aureus (Staph Aureus) ?

A
  • folliculitis
  • furuncle
  • carbuncle
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20
Q

What is folliculitis ?

A

small red bumps formed at the site of the involved hair follicle
- pull hair from follicle
- usually small amount of pus and infection clears

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21
Q

What is furuncle ?

A

a boil, localized skin infection that penetrates into subcutaneous tissue

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22
Q

What is carbuncle ?

A

painful infection of skin and subcutaneous tissue that manifests as a cluster of boils
- tends to happen in areas with thicker skin like nape of skin, back or thighs
- aka. multiple furuncles grouped together

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23
Q

What is different about Hot tub folliculitis ?

A

special case of folliculitis not caused by Staph aureus
- caused by inadequate chlorine levels in hot tubs, whirlpools and pools
- caused by pseudomonas aeruginosa

24
Q

What types of infections can Staph aureus cause ?

A
  • superficial (skin)
  • wounds
  • deep infections (abscesses) and septicemia
  • pneumonia
  • food poisoning (intoxication not infection)
  • pseudomembranous enterocolitis
  • scalded skin syndrome
  • toxic shock
  • nosocomial infection
25
Q

Why is food poisoning an intoxication in staph aureus ?

A
  • staph makes an exotoxin and secretes it
  • we ingest the toxin and symptoms occur within 2 to 6 hours of ingestion of contaminated food
  • symptoms: fever, vomiting, diarrhea
  • self-limiting and generally no further treatment
26
Q

What is pseudomembranous enterocolitis ?

A

rare complication of prolonged antibiotic therapy
- cuts down intestinal normal flora
- staph aureus overgrows and causes abscesses in bowels

27
Q

What is scalded skin syndrome ?

A

staph secretes an exotoxin that causes the skin to peel
- newborns particularly
- in moist & humid areas

28
Q

What type of environment do Staph toxins tend to like ?

A

anaerobic environment

29
Q

In toxic shock syndrome what is the exotoxin secreted ?

A

TSST-1

30
Q

What is a nosocomial infection ?

A

hospital acquired infection (within 72 hrs of admission)
- MRSA (methicillin resistant staphylococcus aureus); hospital and community acquired & usually resistant to antibiotics especially penicillin

31
Q

What is the primary cause of nosocomial diarrhea ?

A

Clostridium Difficile (C. Diff)

32
Q

What is the significance of the capsule in the pathogenesis of staph aureus ?

A
  • protects it from WBC and lets it attach to surfaces
  • contributes to organism pathogenicity
33
Q

What is the significance of the cell wall in the pathogenesis of staph aureus ?

A
  • increased amount of peptidoglycan
  • has protein A that binds with antibodies and interferes with phagocytosis by WBC
34
Q

What is the function of coagulase in staph aureus ?

A

coagulates blood or plasma
- enzyme

35
Q

What is the function of hemolysin in staph aureus ?

A

lyse human and other animal RBC

36
Q

What is the function of hyaluronidase in staph aureus ?

A

breaks down hyaluronic acid which binds connective fibers

37
Q

What is the function of DNase in staph aureus ?

A

breaks down DNA

38
Q

What is the function of lipase in staph aureus ?

A

breaks down lipids in the skin

39
Q

What is the function of beta lactamase in staph aureus ?

A

breaks down penicillin’s
- staph are resistant to penicillin therapy

40
Q

What are the 4 exotoxins with staph aureus ?

A
  • exfoliatins: skin sloughing
  • leukocidins: kill WBC
  • TSST 1: from toxic shock
  • enterotoxins: act in gut and associated with staph food poisoning and pseudomembranous enterocolitis
41
Q

What does beta hemolytic mean ?

A

clear zone around the pathogen where the bacteria has completely destroyed the blood

42
Q

What are some morphology of S. aureus ?

A
  • opaque/white/yellow
  • medium to large
  • beta hemolytic
43
Q

What happens in a catalase test ?

A

want to detect the enzyme catalase using hydrogen peroxide
- Catalase +: when small amount of isolated bacteria is added to hydrogen peroxide bubbles of O2 will happen

44
Q

What is the importance of a coagulase test with staph ?

A

used to differentiate staph aureus (+) which does produce the enzyme coagulase, from S. epidermis and S. saprophyticus (-) which don’t produce coagulase

45
Q

What do the results of a coagulase test mean ?

A

(+): will clump (s. aureus)
(-): rabbit plasmid will look milky (S. epidermis or saprophyticus)

46
Q

What is coagulase ?

A

protein enzyme produced by several microorganisms that enables the conversions of fibrinogen to fibrin

47
Q

What happens in a bound coagulase test ?

A
  • mix loop of bacterial colony with a drop of human plasma on a slide (bound) and look for clump formation in 10 secs
48
Q

What happens in a free coagulase test ?

A
  • add broth with Staph to a tube containing rabbit plasma and look for solid mass in tube
  • (+):clumping/clotting
49
Q

What are some characteristics of Staphylococcus intermedius ?

A
  • infrequently seen, can be found in dog bites
  • beta hemolytic
50
Q

What are some characteristics of staphylococcus epidermidis ?

A
  • normal habitat: skin, hair follicles, and mucous membranes
  • not pathogenic often but can occasionally
  • usually result in invasion of foreign bodies
  • catheters changed every 24 hours because this staph can stick to it
  • common cause of endocarditis, CSF shunt infections
  • some strains more virulent then others
51
Q

What is the morphology of staphylococcus epidermidis ?

A
  • usually white
  • nonhemolytic
  • novobiocin sensitive
  • round, smooth surface slightly raised, entire edge
52
Q

What are some characteristics of staphylococcus saprophyticus ?

A
  • can cause urinary tract infections (sexually active young females “honeymooners illness”)
  • novobiocin resistant
53
Q

What is the purpose of selective medium in Mannitol Salt Agar (MSA) ?

A

says if organism can grow in a high salt concentration

54
Q

What is the purpose of differential medium in Mannitol Salt Agar (MSA) ?

A

differentiates between staphs that will ferment mannitol and those that will not

55
Q

What are the 3 types of normal flora ?

A
  • diphtheroids
  • staphylococci
  • yeasts

Microbiology (18 decks)

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