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PR3124 Finals > Infectious Diarrhea + CDI > Flashcards

Infectious Diarrhea + CDI Flashcards

1
Q

Definition of acute infectious diarrhea

A

<14 days

>3 loose/liquid stools OR more frequent than normal

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2
Q

Common bacterial pathogens in acute infectious diarrhea

A

Campylobacter jejuni, Salmonella typhi, Shigella spp, E. coli, Vibrio cholera
*Clostridioides difficile

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3
Q

Common viral and protozoal pathogens in acute infectious diarrhea

A

Protozoal: Giardia intestinalis, Entamoeba histolytica, Cryptosporidium parvum
Viral: norovirus, rotavirus, adenovirus

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4
Q

When are diagnostic tests used for acute infectious diarrhoea?

A
  • Severe illness
  • Persistent fever
  • Bloody stools
  • Immunosuppression (cancer, transplant)
  • Unresponsive to treatment
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5
Q

How can we prevent acute infectious diarrhoea?

A

Good hand and food hygiene
Vaccinations:
- Cholera & Typhoid: travellers to endemic areas
- Rotavirus: 6mo - 5y

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6
Q

Indications for antibiotics in acute infectious diarrhoea

A
  • Severe disease: fever + bloody diarrhea, mucoid stools, severe abdominal cramps/pain/tenderness
  • Sepsis
  • Immunocompromised
  • Most cases are self-limiting and do not need abx
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7
Q

Empiric treatment of acute infectious diarrhoea

A

IV ceftriaxone 2g q24h
PO ciprofloxacin 500mg BD - outpatient or penicillin allergy
Duration: 3-5 days
- Extended if patient has bacteremia, extra-intestinal infections or is immunocompromised

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8
Q

Monitoring for acute infectious diarrhoea

A

Symptom resolution + clinical improvement

-> do further workup if there are persistent symptoms

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9
Q

How is C difficile transmitted?

A
  • Fecal-oral
  • Contaminated environmental surfaces
  • Hand carriage by healthcare workers
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10
Q

How might healthcare exposure increase the risk of CDI?

A

Healthcare exposure is the largest risk factor

  • Prior hospitalization
  • Duration of current hospitalization
  • Residence in nursing home or long-term care facilities
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11
Q

Patient-related risk factors for CDI

A
  • Multiple or severe comorbidities
  • Immunosuppression
  • Age >65y
  • History of CDI
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12
Q

What kind of drugs may increase the risk of CDI?

A
  • Exposure to systemic antibiotics (IV or PO): no. of agents, duration of therapy
  • High-risk antibiotics: clindamycin, fluoroquinolones, 2nd/higher gen cephalosporins
  • Gastric acid suppressive therapy (PPI or H2RA): increase ease of spores surviving
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13
Q

Clinical presentation of mild and moderate CDI

A 
Mild: loose stools, abdominal cramps
Moderate: 
- systemic: fever, nausea, malaise
- abdominal cramps and distension
- leukocytosis
- hypovolemia/dehydration
Lab: WBC <15x10^9/L + SCr <133 umol/L (1.5mg/dL)
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14
Q

Clinical presentation of severe and fulminant CDI

A

Severe: WBC >15x10^9/L or SCr >133umol/L (1.5mg/dL)
Fulminant: hypotension or ileus or megacolon, pseudomembranous colitis

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15
Q

What happens in ileus?

A

Slow down/stop of peristaltic movement

  • A lot of inflammation -> overwhelms normal gut mechanism
  • stools, mucus etc all can’t exit, so colon dilates -> toxic megacolon
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16
Q

How can we diagnose CDI?

A

Clinical suspicion:
- unexplained + new onset diarrhea (3 unformed stools in 24h) OR
- radiologic evidence of ileus or toxic megacolon (done if there is pain)
Confirmatory test:
- positive stool test result for C difficile or toxins
- histopathological findings of pseudomembranous colitis (rarely test colon tissue)

17
Q

What is Clostridioides difficile?

A

Gram-positive, spore-forming anaerobic bacillus
- produce toxin A & B -> symptoms of severe diarrhoea
Most common cause of nosocomial diarrhoea: increases duration of hospitalization and healthcare cost

18
Q

What kind of tests are used to diagnose CDI?

A

Nucleic acid amplification test (NAAT)
- toxin enzyme immunoassay (EIA)
- glutamate dehydrogenase (GDH) EIA
Polymerase chain reaction (PCR)

19
Q

When should we avoid testing for CDI?

A

Do not test:

  • asymptomatic patient: no need to treat
  • repeat in <7 days
  • test of cure (remain positive despite successful treatment e.g. asymptomatic carrier)
20
Q

What precautions should we take before initiating C diff treatment?

A

Discontinue concurrent abx if possible: increase clinical response and decrease recurrence
Only initiate empiric treatment if:
- substantial delay in diagnostics (>48h)
- fulminant CDI

21
Q

For initial episode of CDI, what is the recommended treatment?

A

10 days, extend to 14 days if not completely resolved
1st line (non-severe and severe):
- PO vancomycin 125mg QDS
- PO fidaxomicin 200mg BD
Alt (non-severe): PO metronidazole 400mg TDS (non-severe)
Fulminant:
IV Metronidazole q8h + PO vancomycin 500mg QDS
+/- PR vancomycin 500mg QDS

22
Q

If a patient is undergoing hemodialysis, what lab parameters should we assess to determine the severity of CDI?

A

Only WBC >15x10^9/L

- not SCr (may be high at baseline due to hemodialysis)

23
Q

When might metronidazole still be used as 1st line for initial episode of CDI?

A

Non-severe CDI

  • Cost: cheaper than vancomycin
  • Logistics: more convenient than vanvomycin oral syringe
  • avoid repeated or prolonged course:
  • poorer treatment response +
  • cumulative & possibly irreversible neurotoxiity
24
Q

What are the indications for use of fidaxomicin?

A

Limited to severe and/or recurrent cases non responsive to maximal standard therapy

  • Very expensive $2k vs vancomycin $30
  • Compared to vancomycin:
    i) may improve cure in immunocompromised patients
    ii) may reduce recurrence
25
Q

What is the MOA of fidaxomicin? What are its benefits?

A

Narrow spectrum macrocyclic abx active against Gram-positive (bactericidal against C difficile)
MOA: inhibit transcription and protein synthesis by binding to RNA polymerase enzyme
Benefits: lower MIC than metronidazole & vanco, long PAE (5.5-12.5h), less alteration of normal GI flora (Bacteriodes spp)

26
Q

Treatment for first recurrence of CDI

A

Metronidazole:
- PO vancomycin 125mg QDS x10d
1st line regimen:
- PO vancomycin taper: preferred due to cost
-> allow time for normal gut flora to regrow, some vancomycin can control remnants of C difficile
- PO fidaxomicin 200mg BD x10d

27
Q

Treatment for subsequent recurrence of CDI

A
  • 1st line: PO vancomycin taper
  • PO fidaxomicin 200mg BD x10d
  • PO vancomycin 125mg QDS x10d, then PO rifamixin 300mg TDS x20d: not common, more expensive than oral vancomycin
  • Fecal microbiota transplant: last line, uncommon
28
Q

Monitoring of efficacy of therapy for CDI

A

Efficacy: clinical improvement in 5-7d

  • Poor response: additional diagnostics or consider escalation
  • Do not exceed 10 days of abx: no evidence of decreased recurrence
29
Q

Should we use probiotics to prevent or treat CDI?

A

No:

  • limited evidence: include low-risk, exclude high CDI incidence, variations in formulation/dose/duration
  • risk of infection (live bacteria in immunosuppressed patients)
30
Q

Should anti-motility agents be used for symptomatic relief in CDI?

A

Symptomatic relief: inhibit contraction of smooth muscle
No:
- reduce bowel output -> affect stool testing ability
- associated with poor outcomes -> toxins & infected stools have more difficulty coming out (especially if diarrhoea is not treated appropriately)

PR3124 Finals (5 decks)

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