Lecture 14 Flashcards by Carter Duggan

Staphylococci stain

GramPos

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How does staphylococci look on a plate

Clusters of spheres

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How can staphylococci live on skin?

Catalase + (for oxygen survival)

Can survive on NaCl

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What are four ways to differentiate staphylococci?

Hemolysis pos vs neg

Coagulase pos vs neg (neg are mostly opportunists)

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What are two coagulase- staphylococci

S. epidermidis

S. saprophyticus

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What are two ways staph can cause illness?

Via growth

Via toxins

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

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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What is non-bullous impetigo and what causes it?

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

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

S. aureus

Realize that this bug can also release toxins and cause toxemia

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What is a manifestation of S. aureus via exotoxin release

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

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What is bullous exfoliation (SSSS) and what causes it

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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What is bullous impetigo and what causes it?

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

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What is toxic shock syndrome and what causes it?

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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S. aureus food poisoning manifestation

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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S. epidermidis coagulase status

Negative

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What is a common manifestation of S. epidermidis

Nosocomial infection of implanted devices, peritoneal dialysis
Biofilm formation

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What is clinical manifestation of S. saprophyticus

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

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How is S. epidermidis often spread

Fomites (sheets and clothing)

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What food is staph especially associated with and why?

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

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Why can’t staph be eradicated?

It’s a native flora

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Why is staph hard to treat?

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

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What are the antigens on staph?

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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What toxins does staph have?

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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How do you treat MRSA?

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

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Furuncle Tx

Drainage and tetracycline

S. saprophyticus Tx

Quinolones SxT Augmentin

How can you be sure to optimize Tx for staph?

Do a susceptibility testing

Streptococci and enterococci stain?

GramPos

Strep and enteroc. appearance on a plate

Chains of spheres

What is capsule of strep and entero

Polysaccharide or hyaluronic acid

What are strep and entero classified by

Hemolysis (alpha, beta, or gamma-none) | Not the same as group A and B

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

Alpha-native | Beta-not

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

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

What are strep resistant to?

Abx, NaCl, Bile

What are the characteristics of group A strep?

Beta hemolytic | Bacitracin sensitive

What are invasive infections Strep pyogenes can cause?

``` 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 ```

Scarlet fever (S. pyogens) symtoms

``` Strep bacteremia Diffuse upper body rash Fever Strawberry tongue Usually starts as pharyngitis ```

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

TSLT which is a superantigen toxin like TSST

Does does S. pyogens cause necrotizing fasciitis

Deep cellulitis that spreads through SQ and fascia

What types of local infections can S. pyogens cause?

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

What are symptoms of S. pygogens strep throat

Fever Ant. cervical lymphadenopathy Tonsil exudate NO COUGH

What are symptoms of S. pyogens impetigo

Crust, purulent drainage especially on face | Always non-bullous type

What are post-infection problems from S. pyogens?

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

What is the way strep throat is most often spread?

Nasal droplets

How is s. pyogens impetigo most often spread?

Contact, fomites

When is rheumatic fever like to present?

1-4 weeks after disseminated strep infection | Not likely from first infection

What is strep pyogens pathogenesis

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

Strep pyogens control?

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

What are characteristics of strep agalactiae

Beta hemolytic CAMP+ Bacitracin resistant

How are strep agalactiae organized?

Polysaccharide capsule (5 types)

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

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

How is s. agalactiae transferred?

From infected mothers during delivery

s. agalactiae treatment?

Screen from Group B strep before delivery | If positive cephtriaxone or amp + streptomycin

What are the two types of Group D streps?

Enterococci and S. bovis

Group D strep characteristics

Non hemolytic | Grow in NaCl and bile

How does group D strep infections usually get transferred?

Nosocomial Mostly from hands of hospital workers Also from colon lesions

Group D strep diseases

Bacteremia Endocarditis UTI (especially from caths)

How do you treat Group D strep?

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

Viridans streptococci characteristics

alpha hemolytic Optochin resistant Ox bile resistant

Viridans strep infection

Most commonly sub-acute bacterial endocarditis especially after tooth extraction

How does viridan strep cause endocarditis?

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

Viridan strep treatment

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

Strep pneumonia characteristics

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

What is clinical manifestation of S. pneumonia

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

Most common cause of CAP

S. pneumonia | Remember this is a native URT flora

How does s. pneumonia survive phagocytes?

Living in mucous protects them

Who is more at risk for S. pneumonia infection?

Alcohol or drug users because of aspiration risk | People with general debility

S. pneumonia control

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