Microbiology > Staphylococci > Flashcards

Staphylococci Flashcards

(55 cards)

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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 ?

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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 ?

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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
Why is food poisoning an intoxication in staph aureus ?
- 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
What is pseudomembranous enterocolitis ?
rare complication of prolonged antibiotic therapy - cuts down intestinal normal flora - staph aureus overgrows and causes abscesses in bowels
27
What is scalded skin syndrome ?
staph secretes an exotoxin that causes the skin to peel - newborns particularly - in moist & humid areas
28
What type of environment do Staph toxins tend to like ?
anaerobic environment
29
In toxic shock syndrome what is the exotoxin secreted ?
TSST-1
30
What is a nosocomial infection ?
hospital acquired infection (within 72 hrs of admission) - MRSA (methicillin resistant staphylococcus aureus); hospital and community acquired & usually resistant to antibiotics especially penicillin
31
What is the primary cause of nosocomial diarrhea ?
Clostridium Difficile (C. Diff)
32
What is the significance of the capsule in the pathogenesis of staph aureus ?
- protects it from WBC and lets it attach to surfaces - contributes to organism pathogenicity
33
What is the significance of the cell wall in the pathogenesis of staph aureus ?
- increased amount of peptidoglycan - has protein A that binds with antibodies and interferes with phagocytosis by WBC
34
What is the function of coagulase in staph aureus ?
coagulates blood or plasma - enzyme
35
What is the function of hemolysin in staph aureus ?
lyse human and other animal RBC
36
What is the function of hyaluronidase in staph aureus ?
breaks down hyaluronic acid which binds connective fibers
37
What is the function of DNase in staph aureus ?
breaks down DNA
38
What is the function of lipase in staph aureus ?
breaks down lipids in the skin
39
What is the function of beta lactamase in staph aureus ?
breaks down penicillin's - staph are resistant to penicillin therapy
40
What are the 4 exotoxins with staph aureus ?
- 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
What does beta hemolytic mean ?
clear zone around the pathogen where the bacteria has completely destroyed the blood
42
What are some morphology of S. aureus ?
- opaque/white/yellow - medium to large - beta hemolytic
43
What happens in a catalase test ?
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
What is the importance of a coagulase test with staph ?
used to differentiate staph aureus (+) which does produce the enzyme coagulase, from S. epidermis and S. saprophyticus (-) which don't produce coagulase
45
What do the results of a coagulase test mean ?
(+): will clump (s. aureus) (-): rabbit plasmid will look milky (S. epidermis or saprophyticus)
46
What is coagulase ?
protein enzyme produced by several microorganisms that enables the conversions of fibrinogen to fibrin
47
What happens in a bound coagulase test ?
- mix loop of bacterial colony with a drop of human plasma on a slide (bound) and look for clump formation in 10 secs
48
What happens in a free coagulase test ?
- add broth with Staph to a tube containing rabbit plasma and look for solid mass in tube - (+):clumping/clotting
49
What are some characteristics of Staphylococcus intermedius ?
- infrequently seen, can be found in dog bites - beta hemolytic
50
What are some characteristics of staphylococcus epidermidis ?
- 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
What is the morphology of staphylococcus epidermidis ?
- usually white - nonhemolytic - novobiocin sensitive - round, smooth surface slightly raised, entire edge
52
What are some characteristics of staphylococcus saprophyticus ?
- can cause urinary tract infections (sexually active young females "honeymooners illness") - novobiocin resistant
53
What is the purpose of selective medium in Mannitol Salt Agar (MSA) ?
says if organism can grow in a high salt concentration
54
What is the purpose of differential medium in Mannitol Salt Agar (MSA) ?
differentiates between staphs that will ferment mannitol and those that will not
55
What are the 3 types of normal flora ?
- diphtheroids - staphylococci - yeasts
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