Bacteremia on management of SSTI Flashcards by Pierre Wadeie

What is an example of bacteremia for each
Transient
Intermittent
Persistent/sustained

Transient
- tooth brushing, biopsy
- quickly cleared

Intermittent (spurts of bacteria into blood)
- Abscess
- UTI, pneumonia, SSTI

Persistent/sustained
- Endocarditis
- infected thrombi’s
- infected mesh wiring

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How do we collect blood cultures?
How many bottles?
From where do we collect?

2 sets (4 bottles total) (1 for aerobic, other for anaerobic)

Each set collected from different access point (central line, PICC, dialysis, Venipuncture/peripheral, etc..) - to reduce chance of contamination

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Which are more common in collecting cultures, false negatives of positive

False positive

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What are reasons for false negatives in culture (3)

Drawn after antimicrobials started
Inadequate volume of blood collected
Slow-growing pathogen (eg. anaerobes)

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What are reasons for false positives in culture (2)

bad hand hygiene
Collected from colonized venous catheter

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Blood culture incubation time? What takes longer?
How to assess the culture?

Incubate for 5 days
- Fastidious organisms take longer

CO2 detected with a light sensor, will only be detectable once enough bacteria is making CO2

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When do most organisms show growth?
How long do you wait until the results are likely negative?

Most will show growth in 48 hours
If nothing in >72 hours - most likely negative

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What does a short time to positivity indicate about bacteria

The higher the bacterial load

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What bugs are gram-positive cocci clusters

Staphylococcus auerus

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What bugs are gram-positive cocci pairs

streptococcus pneumoniae

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What bugs are gram-positive cocci chains (2)

Streptococcus pyogenes
Streptococcus pneumoniae

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What bugs are gram-negative cocci

N. Gonorrhea

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What bugs are gram-negative bacilli non-lactose fermenter oxidase positive

Pseudomonas spp

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What do you do if there is no clinical evidence of infection? Especially if (3)

Consider contamination
- Time to positivity TTP is 72hrs+
- only one site positive
- Growth is common skin contaminant

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Which bugs are common skin contaminant (5)

Most bacillus spp
Corynebacterium
Propionibacterium acnes
Coagulase-negative staphylococci

**Staph aureus should never be ruled out

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What is an endovascular infection? Give examples (2)

bacteria getting stuck to components of the vasculature like a prosthetic valve/vascular stent
causing
- endocarditis
- septic thrombophlebitis

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When would you suspect an endovascular infection

Persistent bacteremia despite 72 hours of appropriate therapy

What is an extravascular infection? aka seeding. Give examples of what it can cause (4)

bacteria getting stuck to things OUTISDE the vasculature like bones, joints, brain

Can cause
- Psoas (infection in muscle)
- Osteomyelitis (infection in bones esp. if fractured, hip replacement)
- Pulmonary (infection in the lung)
- Cerebral septic emboli (infection in the brain)

When do we suspect an extravascular infection

organ-specific symptoms present OR still febrile despite 72 hours of appropriate therapy

T/F seeding (extravscular metastic infection) is more common in GAS vs staph aueus

False
- seeding is more common in staph aureus

T/F it is common to see seeding in gram neg bacteria

False

What pathogens are more likely to cause bloodstream infections or endocarditis

Staph aureus, Candida spp
Streptococcus
Other gram-positives
Other gram-negatives

Which bug is the most common cause of bacteremia but risk of endocarditis is low (not sticky) (2)

S. pneumonia
S. pyogenes

Which bug is the least common cause of bacteremia but risk of endocarditis is high (very sticky)

S. mutans

What do you do if a culture is positive for staph aureus?

Always look for seeding/metastatic infection (extravascular infection)

What to do if a patient has an endovascular or metastic infection due to SSTI

Drives therapy - eg. prolonged duration - additional interventions

For patients with hospitalized SSTI do we perform a blood culture or not? What do the results look like?

Yes perform blood culture - likely negative result but could be positive

What bugs do we empirically treat for while waiting for blood culture?

Group A strep GAS Staph aureus - Add on MRSA if pt has active MRSA risk factors

What abx do you give while patient is hospitalized and bacteremia is suspected as you wait for blood culture? What if MRSA is a concern?

Oral therapy if option has high bioavailability (FQs, linezolid, Septra) MRSA concern: IV Beta-lactam Cefazolin or Cloxacillin

What case of hospitilization would absolutley require a blood culutre

Abscess - due to risk of S. aureus bacteremia

What if the culture results at 48-72 hours is negative: Positive:

Negative: transition to ORAL beta-lactam (duration: 5 to 7 to 10 days) Positive: may need to continue IV

Which bug do we not need to confirm clearance with repeat blood culture in bacteremia

Group A strep Streptococcal bacteremia

What does the balance trial say for duration of therapy for SSTI with GAS bacteremia? Bottom line?

Extend SSTI treatment to 7 days, no need for 14 days Bottom line: - Treat cellulitis for 5 days. If streptococcal bacteremia due to cellulitis. Use a 7 day duration

What is the treatment and duration for SSTI with staph. Aureus MSSA bacteremia.

Cloxacillin or cefazolin for 14 days min. If life threatening beta-lactam allergy - vancomycin (however inferior for MSSA) - Clindamycin or Septra

What does the ARENSMAN trial say about IV to oral transition in SSTI with GAS bactemeria?

1. Give at least 3 days (72 hours) of IV beta-lactam (as long as some improvement by day 3) before transitioning to oral 2. Transition to HIGH (maximized) dose oral beta-lactam when you do switch Stepping down before day 3 is more likely to fail

What is the overall steps for management of SSTI with S. aureus bacteremia (3)

1. Consult ID 2. Always look for endovascular or metastic infection - remove IV lines 3. Repeat culture q48 hours until negative

What is ID consult associated with? (2)

Decreased mortality and decreased relapse

What is the most to least common sites of Staph aureus metastatic infection?

Heart valve (infective endocarditis) Joints (septic arthritis) Lungs (septic PE) Bone (vertebral osteomyelitis) Muscle Spine (Epidural abscess)

What does the SABATO trial tell us about IV- oral switch in SSTI with staph. aureus MSSA bacteremia? Most commom PO drug used in this trial?

Can transition from IV to HIGH oral dose after 5-7 days of IV therapy (14 days total) - Cloxacillin or cefazolin are viable IV options Trial used Sulfatrim as PO abx

What is defined as uncomplicated MSSA Bacteremia (4)

- no evidence of metastatic infection - no indwelling devices or prosthetic valves - clearance of MSSA on culture in ≤48 hours - no fever within 72 hours of ABX therapy