Infectious Diarrhea + CDI Flashcards
Definition of acute infectious diarrhea
<14 days
>3 loose/liquid stools OR more frequent than normal
Common bacterial pathogens in acute infectious diarrhea
Campylobacter jejuni, Salmonella typhi, Shigella spp, E. coli, Vibrio cholera
*Clostridioides difficile
Common viral and protozoal pathogens in acute infectious diarrhea
Protozoal: Giardia intestinalis, Entamoeba histolytica, Cryptosporidium parvum
Viral: norovirus, rotavirus, adenovirus
When are diagnostic tests used for acute infectious diarrhoea?
- Severe illness
- Persistent fever
- Bloody stools
- Immunosuppression (cancer, transplant)
- Unresponsive to treatment
How can we prevent acute infectious diarrhoea?
Good hand and food hygiene
Vaccinations:
- Cholera & Typhoid: travellers to endemic areas
- Rotavirus: 6mo - 5y
Indications for antibiotics in acute infectious diarrhoea
- Severe disease: fever + bloody diarrhea, mucoid stools, severe abdominal cramps/pain/tenderness
- Sepsis
- Immunocompromised
- Most cases are self-limiting and do not need abx
Empiric treatment of acute infectious diarrhoea
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
Monitoring for acute infectious diarrhoea
Symptom resolution + clinical improvement
-> do further workup if there are persistent symptoms
How is C difficile transmitted?
- Fecal-oral
- Contaminated environmental surfaces
- Hand carriage by healthcare workers
How might healthcare exposure increase the risk of CDI?
Healthcare exposure is the largest risk factor
- Prior hospitalization
- Duration of current hospitalization
- Residence in nursing home or long-term care facilities
Patient-related risk factors for CDI
- Multiple or severe comorbidities
- Immunosuppression
- Age >65y
- History of CDI
What kind of drugs may increase the risk of CDI?
- 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
Clinical presentation of mild and moderate CDI
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)
Clinical presentation of severe and fulminant CDI
Severe: WBC >15x10^9/L or SCr >133umol/L (1.5mg/dL)
Fulminant: hypotension or ileus or megacolon, pseudomembranous colitis
What happens in ileus?
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
How can we diagnose CDI?
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)
What is Clostridioides difficile?
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
What kind of tests are used to diagnose CDI?
Nucleic acid amplification test (NAAT)
- toxin enzyme immunoassay (EIA)
- glutamate dehydrogenase (GDH) EIA
Polymerase chain reaction (PCR)
When should we avoid testing for CDI?
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)
What precautions should we take before initiating C diff treatment?
Discontinue concurrent abx if possible: increase clinical response and decrease recurrence
Only initiate empiric treatment if:
- substantial delay in diagnostics (>48h)
- fulminant CDI
For initial episode of CDI, what is the recommended treatment?
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
If a patient is undergoing hemodialysis, what lab parameters should we assess to determine the severity of CDI?
Only WBC >15x10^9/L
- not SCr (may be high at baseline due to hemodialysis)
When might metronidazole still be used as 1st line for initial episode of CDI?
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
What are the indications for use of fidaxomicin?
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
What is the MOA of fidaxomicin? What are its benefits?
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)
Treatment for first recurrence of CDI
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
Treatment for subsequent recurrence of CDI
- 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
Monitoring of efficacy of therapy for CDI
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
Should we use probiotics to prevent or treat CDI?
No:
- limited evidence: include low-risk, exclude high CDI incidence, variations in formulation/dose/duration
- risk of infection (live bacteria in immunosuppressed patients)
Should anti-motility agents be used for symptomatic relief in CDI?
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)
