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Micro > Lecture 14 > Flashcards

Lecture 14 Flashcards

1
Q

Staphylococci stain

A

GramPos

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2
Q

How does staphylococci look on a plate

A

Clusters of spheres

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3
Q

How can staphylococci live on skin?

A

Catalase + (for oxygen survival)

Can survive on NaCl

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4
Q

What are four ways to differentiate staphylococci?

A

Hemolysis pos vs neg

Coagulase pos vs neg (neg are mostly opportunists)

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5
Q

What are two coagulase- staphylococci

A

S. epidermidis

S. saprophyticus

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6
Q

What are two ways staph can cause illness?

A

Via growth

Via toxins

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7
Q

What is a more superficial manifestation of S. aureus and how does it cause illness? How does it present?

A

Via growth of bacteria
Classic lesion is a furuncle
Walled off my coagulase
Folliculitis and complication of acne are more specific examples of this!

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8
Q

What is non-bullous impetigo and what causes it?

A 
Crusted blisters
Mostly in children and teens
Infection of epidermis
Staph #1 cause
Strep group A #2
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9
Q

What is the number one cause of bacteremia and wound infections?

A

S. aureus

Realize that this bug can also release toxins and cause toxemia

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10
Q

What is a manifestation of S. aureus via exotoxin release

A

Bullous exfoliation (SSSS)
Bullous impetigo
Toxic shock syndrome
Food poisoning

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11
Q

What is bullous exfoliation (SSSS) and what causes it

A

Intraepidermal splitting and peeling
Mostly children (daycares and neonatal wards)
Good prognosis in kids, bad in adults because of bacteremia
Caused by exotoxins from S. aureus

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12
Q

What is bullous impetigo and what causes it?

A

Fluid filled blisters in epidermis
Almost always < 2 y/o
S. aureus exotoxin is only cause

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13
Q

What is toxic shock syndrome and what causes it?

A

Abrupt onset fever, skin desquamation, hypotension, multi-system involvement, DIC
Immune response to specific toxin (TSST) from S. aureus
Also a MRSA strain

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14
Q

S. aureus food poisoning manifestation

A

Violent N/V
Occasional diarrhea
No fever (onset 4 hours, gone in 24)
It is similar to B. cereus emetic variety

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15
Q

S. epidermidis coagulase status

A

Negative

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16
Q

What is a common manifestation of S. epidermidis

A

Nosocomial infection of implanted devices, peritoneal dialysis
Biofilm formation

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17
Q

What is clinical manifestation of S. saprophyticus

A

Associated with UTI in young woman (E. coli is still number one cause)

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18
Q

How is S. epidermidis often spread

A

Fomites (sheets and clothing)

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19
Q

What food is staph especially associated with and why?

A

Ham because it can live in salty conditions (also with cream and mayo)

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20
Q

Why can’t staph be eradicated?

A

It’s a native flora

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21
Q

Why is staph hard to treat?

A

It rapidly develops resistance
MDR
MRSA (mecA on SCC cassette)
Abx resistance spread through R-plasmid

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22
Q

What are the antigens on staph?

A

GramPos so no LPS
Peptidoglycan (PAMP)
Teichoic acid
PROTEIN A (binds to Fc part of antibody-resembles B cell)
Iron binding protein (scavenge Fe from heme)

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23
Q

What toxins does staph have?

A 
Coagulase-wall off infections
Hyaluronidase
Hemolysin (a-RBC & plat, b-sphingomyelin)
Leukocidin (kills WBCs)
Exfoliative toxin
TSST-superantigen-induces T cells to produce IL-1, TNF
Enterotoxins-food poisoning
Quorum sensing-biofilms
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24
Q

How do you treat MRSA?

A

Strict isolation
Chlorhexidine washes
Vanco-for severe
SxT, clinda, linezolid for moderate

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25
Q

Furuncle Tx

A

Drainage and tetracycline

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26
Q

S. saprophyticus Tx

A

Quinolones
SxT
Augmentin

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27
Q

How can you be sure to optimize Tx for staph?

A

Do a susceptibility testing

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28
Q

Streptococci and enterococci stain?

A

GramPos

29
Q

Strep and enteroc. appearance on a plate

A

Chains of spheres

30
Q

What is capsule of strep and entero

A

Polysaccharide or hyaluronic acid

31
Q

What are strep and entero classified by

A

Hemolysis (alpha, beta, or gamma-none)

Not the same as group A and B

32
Q

Which type of strep and entero are native? Which is not?

A

Alpha-native

Beta-not

33
Q

How do you determine group A-H, K-U strep infections?

A

Lancefield serotyping-specific amino acids and teichoic acid cell wall antigens

34
Q

What are strep resistant to?

A

Abx, NaCl, Bile

35
Q

What are the characteristics of group A strep?

A

Beta hemolytic

Bacitracin sensitive

36
Q

What are invasive infections Strep pyogenes can cause?

A 
Human erysipelas-dermis and SQ fat infection
Puerperal fever-Sterp inf. of uterus after delivery
Surgical sepsis
Scarlet fever
Streptococcal toxic shock-like syndrome
Necrotizing fasciitis
Pneumonia
Bacteremia
37
Q

Scarlet fever (S. pyogens) symtoms

A 
Strep bacteremia
Diffuse upper body rash
Fever
Strawberry tongue
Usually starts as pharyngitis
38
Q

How does S. pyogens cause toxic shock-like fever?

A

TSLT which is a superantigen toxin like TSST

39
Q

Does does S. pyogens cause necrotizing fasciitis

A

Deep cellulitis that spreads through SQ and fascia

40
Q

What types of local infections can S. pyogens cause?

A

Pharyngitis (can spread to OM, sinuses, meninges)
Impetigo
Post-infection sequellae (immune mimicry)

41
Q

What are symptoms of S. pygogens strep throat

A

Fever
Ant. cervical lymphadenopathy
Tonsil exudate
NO COUGH

42
Q

What are symptoms of S. pyogens impetigo

A

Crust, purulent drainage especially on face

Always non-bullous type

43
Q

What are post-infection problems from S. pyogens?

A 
Acute glomerulernephritis (blood and protein in urine, may become chronic)
Acute rheumatic fever (heart valve damage)
44
Q

What is the way strep throat is most often spread?

A

Nasal droplets

45
Q

How is s. pyogens impetigo most often spread?

A

Contact, fomites

46
Q

When is rheumatic fever like to present?

A

1-4 weeks after disseminated strep infection

Not likely from first infection

47
Q

What is strep pyogens pathogenesis

A

M-proteins (some cause secretion of heart-reactive antibodies)
Hyaluronic acid capsule (evasion)
C5a peptidase (antiphagocytic)
Strepodornase (DNAase)
Hyaluronidase
Exotoxin A,B,C-pyrogenic,associated with scarlet fever
Hemolysins

48
Q

Strep pyogens control?

A

Keep from spreading (pasteurize milk)
All Group A suscepticle to PenG
Treat ARF/AGN with anti-inflammatories

49
Q

What are characteristics of strep agalactiae

A

Beta hemolytic
CAMP+
Bacitracin resistant

50
Q

How are strep agalactiae organized?

A

Polysaccharide capsule (5 types)

51
Q

What diseases are caused by s. agalactiae? Who do they affect?

A 
Infants, immunocompromised, elderly
Neonatal sepsis and pneumonia
 (1-7 days post partum)
Neonatal meningitis 1 week old
RDS, bacteremia, soft tissue infections in eldery
52
Q

How is s. agalactiae transferred?

A

From infected mothers during delivery

53
Q

s. agalactiae treatment?

A

Screen from Group B strep before delivery

If positive cephtriaxone or amp + streptomycin

54
Q

What are the two types of Group D streps?

A

Enterococci and S. bovis

55
Q

Group D strep characteristics

A

Non hemolytic

Grow in NaCl and bile

56
Q

How does group D strep infections usually get transferred?

A

Nosocomial
Mostly from hands of hospital workers
Also from colon lesions

57
Q

Group D strep diseases

A

Bacteremia
Endocarditis
UTI (especially from caths)

58
Q

How do you treat Group D strep?

A

Very resistant
High doses of PCN and aminoglycosides
Vanc for enterococcus but becoming resistant

59
Q

Viridans streptococci characteristics

A

alpha hemolytic
Optochin resistant
Ox bile resistant

60
Q

Viridans strep infection

A

Most commonly sub-acute bacterial endocarditis especially after tooth extraction

61
Q

How does viridan strep cause endocarditis?

A

Is a normal URT flora, gets into blood after dental work

62
Q

Viridan strep treatment

A

High does of PCN or Vanc
Prophylactic Abx before dental work in some PTs
Surgical management usually better for endocarditis

63
Q

Strep pneumonia characteristics

A

alpha hemolytic
Optochin sensitive
ox bile sensitive
Diplococci with large polysaccharide capsule

64
Q

What is clinical manifestation of S. pneumonia

A

Sudden onset lobar pneumonia with fever
Sharp pain
May spread to OM (#2) or meninges (#1 for adults)

65
Q

Most common cause of CAP

A

S. pneumonia

Remember this is a native URT flora

66
Q

How does s. pneumonia survive phagocytes?

A

Living in mucous protects them

67
Q

Who is more at risk for S. pneumonia infection?

A

Alcohol or drug users because of aspiration risk

People with general debility

68
Q

S. pneumonia control

A

23-valent for adults
13 valent for kids
3rd gen cephalosporins, macrolides, quinolones

Micro (13 decks)

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