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Bacteriology Lectures > Staph & Strep > Flashcards

Staph & Strep Flashcards

1
Q

Staph organism, growth characteristics

A

Gram positive cocci in clusters

Catalase +, salt tolerant up to 9%NaCl

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2
Q

Staph differentiation

(?)

A

Hemolysis (S. aureus)

Coagulase + S.aureus) - associated with virulence

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3
Q

Coagulase negative staph

A

CNS = S. epidermidis, S. saprophyticus

*opportunists

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4
Q

S. aureus - some presentations due mainly to ________.

What is the classic S. aureus lesion?

A

growth of bacteria

Furuncle (walled off by coagulase)

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5
Q

Staph localized to hair follicles

A

folliculitis

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6
Q

S. aureus is a frequent complication of ________ via invasion of sebacious glands.

What is the PRIMARY cause of this?

A

complication of acne

Primary cause = Propionibacterium acnes

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7
Q

_______ is the most common cause of _______, which is an infection of the superficial epidermis (most common bacterial skin disease)

Symptoms mainly due to….

A

Staph aureus causes non-bullous impetigo

*Due to immune response

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8
Q

Deep incisional staph infections often present as

A

cellulitis

(20% from staph aureus, 14% from coaulase negative staph)

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9
Q

Frequent complication of staph bacteremia

How do you detect?

How do you treat?

A

Endocarditis

Echocardiography to detect

Gentamycin to treat

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10
Q

Some staph presentations are due to bacterial growth, while others are due to _____________

A

Exotoxin release

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11
Q

Bullous exfoliation a.k.a. _________

What are the symptoms/presentation? Who is affected?

A

Staph Scalded Skin Syndrome (SSSS)

  • Intraepidermal splitting of top layers
  • Mostly in children (better prognosis than adults, who have bacteremia)
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12
Q

Bullous impetigo symptoms and who it affects

A

Fluid filled blisters within epidermis (Exfoliative toxin causes)

Almost always in kids under 2 years old

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13
Q

Toxic shock syndrome presentation

A
  • abrupt fever
  • rash with desquamation
  • hypotension
  • multisystem involvement
  • DIC
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14
Q

Toxic shock syndrome underlying pathology

A

caused by immune reaction to TSST

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15
Q

Food poisioning Sx from Staph

What particular type of cell is involved?

A

nausea, vomit, diarrhea, NO FEVER

QUICK (4-24 hours)

Treg cells involved in limiting inflammatory response?

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16
Q

Staph epidermidis associated with…

A

implanted devices (biofilm formation)

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17
Q

___ can also cause surgical implant infections, but…

A

Staph aureus

but Epidermidis doesn’t cause the diseases that S. aureus causes

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18
Q

Staph epidermidis is native flora in ___% of patients

A

100%

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19
Q

Staph saprophyticus is associated with ____ because of ________.

Most UTIs are caused by…

A

UTI because of specific adhesin for UT epithelium

UPEC E. coli

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20
Q

Menstrual TSS associated with…

A

use of retained tampons

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21
Q

Staph is difficult to treat beacuse of…

A

rapid MDR

ex. MRSA (mecA on SCC cassette)

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22
Q

Staph virulence factors (antigens)

A
  • Peptidoglycan (inflammatory PAMP)
  • Teichoic acids (check patients for alpha-TA antibodies!)
  • Protein A (binds Fc)
  • Iron-Binding Proteins
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23
Q

Other Staph virulence factors (7)

A
  • Coagulase - (wall off infctn)
  • Hyaluronidase, Staphylokinase (tissue invasion)
  • Hemolysins (Alpha toxin (RBC) and Beta Toxin (sphingomyelin), leukocidin (WBC)
  • Exfoliative toxin - SSSS, bullous impetigo
  • TSST-1 - (superantigen, induces IL-1/TNF)
  • Enterotoxin (also superantigens…food poisoning)
  • **Quorum Sensing **(turns on biofilm genes)
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24
Q

What is the big virulence factor that is associated with mrsa?

A

Panton-Valentine Leukocidin

Forms pores, causes leukopenia

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25
Q

Superantigens are located on ____ and spread via ______

A

PAI’s

transduction

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26
Q

Four control measures that have helped deal with MRSA

A

Better hand hygeine

catheter routes targeted

MRSA-specific detection and decolonization

*Isolation of carriers and Daily chlorhexadine wash

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27
Q

Recurrent furuncles from staph treated by…

A

drainage and tetracycline

(uncomplicated one may only need draining)

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28
Q

MRSA Tx

A

Bactrim, clindamycin, doy, linezolid

Severe = Vancomycin

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29
Q

Staph saprophyticus Tx

A

quinolones, bactrim, augmentin

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30
Q

Staph optomized treatment requires…

A

susceptibility testing

broth dilution, E test, or Kirby Bauer

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31
Q

Antibiotic resistance spreads via

A

R plasmids (conjugation)

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32
Q

Strep organism and appearance

A

Gram positive cocci

  • may be oval
  • in chains or pairs
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33
Q

Strep capsule

-growth characteristics/requirements

A

capsule – hyaluronic acid (group A) or polysaccharide

-fastidious growth, facultative, but prefers 5-10% CO2

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34
Q

__% of patients are carriers for beta hemolytic strep

A

10%

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35
Q

Strep classification is based on what four things?

A
  1. Hemolysis (alpha, beta, or gamma/none)
  2. Lancefield serotyping (specific amino-sugar and teichoic acid cell wall antigens)
  3. Biochemistry (AB resistance, NaCl tolerance, bile esculin)
  4. Colonization patterns (Entero, Lacto, Pneumo-cocci)
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36
Q

Strep pyogenes classification

A
  • Group A
  • Beta hemolytic
  • Bacitracin-sensitive
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37
Q

S. pyogenes causes ____ infections. Six examples?

A

Invasive infections

  1. Human erysipelas (dermis and SubQ)
  2. Puerperal fever (postpartum)
  3. Surgical sepsis
  4. Scarlet Fever (bacteremia - characteristic rash and strawberry tongue)
  5. Streptococcal toxic shock-like syndrome (TSLT superantigen)
  6. Necrotizing fasciitis (deep fascia cellulitis)
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38
Q

Scarlet fever rash appearance

Ddx from which other rash?

A

Diffuse upper body rash

Ddx from measles rash (top-down)

39
Q

Scarlet fever usually starts as…

A

Pharyngitis

40
Q

Necrotizing fasciitis may be caused by ___ or ____

A

TSST (staph) or TSLT (strep)

41
Q

Two other invasive infections from s. pyogenes

A
  1. PNA
  2. Bacteremia

*both are serious infections

42
Q

Two local infections from s. pyogenes

A

Pharyngitis (fever, anterior lymphadenopathy)

Impetigo (non-bullous)

43
Q

Two post-infection sequellae (due to ____ )

A

d/t immune mimicry (immune complexes)

Acute Rheumatic Fever - valve damage

Acute glomerulonephritis - blood/protein in urine

44
Q

Animal carriers of s. pyogenes

A

None. Only humans (10-20% carrier rate)

45
Q

Strep throat spread via ____, common during ____, and usual age of onset.

A

Spread in nasal droplets and by contact

Common in winter

Kids 6-13

46
Q

Strep impetigo most common during ____, spread by _____, and age of onset.

A
  • Common in summer
  • Spread by contact, contiguity, and fomites
  • Preschool kids
47
Q

Strep rheumatic fever occurs how long after disseminated strep infection?

Condition is more likely to be brought on by…

A

1-4 weeks

The second infection

48
Q

What are the virulence factors of Strep pyogenes?

A
  1. M protein
  2. Hyaluronic acid capsule
  3. C substance
  4. C5a peptidase
  5. streptokinase/streptodornase
  6. hyaluronidase
  7. exotoxins
  8. hemolysins
49
Q

Strep M protein is associated with…

A

thrumatic sequellae

50
Q

Strep’s Hyaluronic acid capsule function

A

mimics host, antiphagocytic

51
Q

What is C substance?

A

capsular polysaccharide

*enhances invasiveness

52
Q
  1. Streptokinase function
  2. Streptodornase function
A
  1. dissolves fibrin clots
  2. DNAse
53
Q

Strep “spreading factor”

A

hyaluronidase

54
Q

Strep. pyogenes exotoxins (types, function, and associated with…)

A

A, B, C

pyrogenic

Associated with scarlet fever, strep TSS

55
Q

S. pyogenes Hemolysins - O2 sensitivity

A

Streptolysin O = O2 sensitive

Streptolysin S = Not

56
Q

Control measures for S. pyogenes

A

pasturization of milk

isolate carriers from susceptible patients (not quarantine)

57
Q

Group A strep are sensitive to…

A

PenG

58
Q

How do you treat ARF/AGN

A

anti-inflammatory drugs and rest

59
Q

Rheumatic fever management?

A

Long term PenG prophylaxis (prevents recurrence)

60
Q

S. agalactiae classification

(group, hemolysis, cAMP, bacitracin)

A
  • Group B
  • Beta hemolytic
  • cAMP positive
  • Bacitracin-resistant
61
Q

S. agalactiae typed by…

A

its polysaccharide capsule

62
Q

Acute S. agalactiae diseases in infants and elderly

A
  1. Neonatal Sepsis (and PNA 1-7 days post-partum) – most common cause of neonatal sepsis in US
  2. Neonatal Meningitis (1 week - 3 months)
  3. Respiratory Distress Syndrome “RDS” (bacteremia, soft tissue infections)
63
Q

S. agalactiae spread when?

A

From infected mom to baby during delivery (chance of vertical transmission is 50%)

64
Q

Group B strep control

A

Screen before delivery (36 weeks)

65
Q

How to treat if there is a positive GBS screen in pregnant mom?

Do we ever use these prophylactically?

A

Intrapartum **Ceph3 **or **Ampicillin + Streptomycin **

Yes. Give prophylactically if baby is premature or if there was no GBS screening done

66
Q

Enterococci and S. bovis are ___ strep

A

Group D

67
Q

GDS hemolysis

Growth characteristics in NaCl and Bile esculin

A

non hemolytic, but sometimes alpha

Growth in 6.5% NaCl, bile-esculin growth

68
Q

GDS members

A

E. faecalis

E. faecium

Strep bovis

69
Q

GDS is a common ____ infection, which causes what conditions?

A

nosocomial infeciton

Bacteremia, endocarditis, UTI

70
Q
  • GDS transmitted mostly via…
  • What is the portal of entry?
A
  • hospital workers’ hands
  • Enter GI tract and bacteremia from colon lesions
71
Q

Big problem with Group D strep

A

MDR

72
Q

Intrinsic resistance of enterococci to ______

…but OK for ____

GDS resistant to ____ because it can steal ____ from host

A

resistant to B-lactams

OK for S. bovis

SxT resistant because it can use host’s folate

73
Q

Antibiotic Tx for GDS

Preferred Tx for S. bovis?

Tx for Enterococcus? Problems?

A
  1. GDS = High-dose Penicillin + aminoglycoside
  2. Bovis = Penicillin or ceftriaxone
  3. Enterococcus = Vancomycin (but vanR is a problem)
74
Q

80% of infective endocarditis are caused by…

A

Staph or strep infections

75
Q

Indications for antibiotic prophylaxis against endocarditis has been restricted to…

A

invasive dental procedures in patients with:

  • a prosthetic valve
  • history of endocarditis
  • unrepaired cyanotic congenital heart disease
76
Q

Viridans strep hemolysis, and growth resistances

A

alpha hemolytic

optochin resistant

ox-bile resistant

77
Q

most common viridans strep infection?

Sx?

A

sub-acute bacterial endocarditis

(especially after tooth extraction or dental surgery)

Sx = heart murmur, weakness, embolism, anemia

78
Q

VIrians strep is normal flora of

A

URT

79
Q

Viridans strep prophylaxis and Tx

A

prophylactic AB before and after oral surgery

Long term Penicillin or Vancomycin

80
Q

Better Strep viridans outcome with…

A

surgical management of endocarditis

81
Q

Pneumococci hemolysis and growth characteristics

A

alpha hemolytic

optochin sensitive

ox bile sensitive

82
Q

Pneumococci appearance and structure (capsule)

A

diplococci with large polysaccharide capsule

83
Q

Bad types of pneumococcus

A
  • 3
  • 19A
  • 23F
84
Q

Test for pneumococci

A

Quellung reaction

  1. polyvalent antiserum against capsule
  2. added to sputum
  3. if pneumococcus is present the capsule swells
  4. visualize with negative stain
85
Q

S. pneumoniae presentation

A
  • sudden onset lobar PNA
  • Fever, chills, pain, mental status change
  • HIGH leukocytes
86
Q

Patterns of PNA

A
  1. Lobar =** **(consolidation of one/more lobe, bronchi often OPEN – bronchogram Xray)
  2. BronchoPNA = peribronchial thickening, alveolar consolidation
  3. Interstitial = inflammation/edema of interstitial tissue of the lung, fibrosis
87
Q

Four routes of acquisition of pneumococcus

A

Community

Hospital

Ventilator-associated

Aspiration

88
Q

Causes of Aytpical bacterial PNA

A
  1. Mycoplasma pneumoniae
  2. Chlamydia pneumoniae + psittaci
  3. Legionella pneumophila
  4. Coxiella burnetti
  5. Bordetella pertussis
89
Q

60% of bacterial Community-acquired PNA is caused by _____

A

pneumococcal disease

90
Q

pneumococcus is the number 2 cause of _____

and the number one cause of _____

A

2 cause of Otitis Media

91
Q

Risk factors for pneumococcus infection

A

mucus accumulation

alcohol/drug use

general debility

92
Q

Pneumococcus pathogenesis based on… (3)

A

colonization of tissues

polysaccharide capsule

debilitated host

**IgA protease is of limited virulence

93
Q

Pneumococcal vax

A

23 valent capsule vaccine

PPSV23

for ADULTS (especially at-risk)

Bacteriology Lectures (14 decks)

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