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PR3124 PT3 > Infectious Diarrhea & CDI > Flashcards

Infectious Diarrhea & CDI Flashcards

1
Q

Define “acute infectious diarrhea”.

A

Acute: Increased frequency of defecation lasting < 14 days
Diarrhea: >= 3 loose or liquid stools OR more frequent than normal for an individual
Caused by one or more microorganisms

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2
Q

Describe the microbiology of acute infectious diarrhea.

A

Common pathogens include:
Bacteria: Campylobacter jejuni, Salmonella typhi, Shigella spp., E. coli, Vibrio cholera, Clostridioides difficile
Protozoal: Giardia intestinalis, Entamoeba histolytica, Cryptosporidium parvum
Viral: Norovirus, Rotavirus, Adenovirus

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3
Q

What are some diagnostic tests available to diagnose whether a patient has acute infectious diarrhea?

A

1) Fecal occult blood
- non-specific test that detects blood in diarrhea
- indicative of GIT damage
2) Ova & parasite test
3) Stool cultures
4) Polymerase chain reaction (PCR)
- more rapid turnover of results for identification of pathogens

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4
Q

Under what conditions will a diagnostic test be required to determine if a patient indeed experiencing acute infectious diarrhea?

A

Usually not indicated due to self-limiting nature.
Reserved for selected patients:
- Severe illness
- Persistent fever
- Bloody stools
- Immunosuppression
- Unresponsive to self-care Tx (e.g. fluid rehydration therapy, probiotics, adsorbents & antiperistaltics)

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5
Q

How can acute infectious diarrhea be prevented?

A

Good hand & food hygiene practices
Vaccinations
- Cholera & Typhoid prior to travel to endemic areas
- Rotavirus as part of childhood immunisation schedule

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6
Q

What are some non-pharmacological recommendations for the treatment of acute infectious diarrhea?

A

Early re-feeding as tolerated

Feed easily digestible food (e.g. crackers, toast, cereal, bananas)

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7
Q

When is Abx indicated for the Tx of acute infectious diarrhea?

A

Most cases are self-limiting & do not require antibiotics.
Indications for Abx:
- Severe disease: fever w/ bloody diarrhea OR mucoid stools (bacterial in nature) OR severe abdominal pain/cramps/tenderness
- Sepsis
- Immunocompromised

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8
Q

If Abx is indicated, what is the recommended Tx for pt experiencing acute infectious diarrhea?

A

1) IV Ceftriaxone 2g q24h x 3-5 days
- Pt. usually have severe symptoms requiring hospitalisation, thus IV Abx can be used.
2) PO Ciprofloxacin 500mg BD x 3-5 days
- ONLY for severe penicillin allergy

Tx duration may be extended to 10-14 days in pt w/ bacteremia, extra-intestinal infections or are immunocompromised.

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9
Q

What should we monitor for during Abx Tx of patients w/ acute infectious diarrhea?

A

Resolution of symptoms & clinical improvement
Further workup if persistent symptoms
Step down therapy if applicable.

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10
Q

Describe the morphological characteristics of Clostridioides difficile.

A

Gram-positive, spore-forming anaerobic bacillus that produces toxin A & B
Most common cause of nosocomial diarrhea

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11
Q

How is C. difficile transmitted?

A

Fecal-oral transmission
Contact with contaminated environmental surfaces (fomites)
Hand carriage by healthcare workers

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12
Q

Describe the pathogenesis of C. difficile infection (CDI).

A

1) C. difficile contains endospores that can survive acidity of stomach & reach large intestine.
2) Normal gut flora altered by broad-spectrum Abx
- most notably: clindamycin, fluoroquinolones, 2nd generation & higher cephalosporins, amoxicillin & ampicillin
3) Resulting in C. difficile flourishing w/in colon
4) Production of toxins A & B causes mucosal damage & subsequently pseudomembranous colitis if prolonged
- yellowish plaques formed over damaged epithelium
5) Results in fever, crampy abdominal pain & diarrhea

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13
Q

What are some risk factors associated with CDI?

A

1) Healthcare Exposure (highest risk)
- Prior hospitalisation
- Duration of hospitalisation
- Residence in nursing homes / long-term care facilities
2) Pharmacotherapy
- Systemic Abx -> no. of agents & duration used
- Use of high-risk Abx: clindamycin, 2nd or higher cephalosporins, FQ, ampicillin & amoxicillin
- Use of gastric acid suppressive therapy (i.e. antacids, H2RA & PPIs) -> decrease gastric pH increases CDI risk
3) Patient-Related Factors
- Multiple or severe comorbidities (DM, stroke, CHD etc)
- Immunosuppression
- > 65 y/o
- Hx of CDI

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14
Q

Explain the classification of CDI with respect to its clinical presentation.

A 
Mild: loose stools, abdominal cramps
Moderate: 
- Fever, nausea, malaise
- Abdominal cramps & distension
- Leukocytosis (increased WBC)
- Hypovolemia
Severe/Fulminant:
- Ileus (intestinal paralysis due to immense inflammation; diarrhea is stopped)
- Toxic megacolon (often hand-in-hand w/ ileus)
- Pseudomembranous colitis
- Perforation
- Death
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15
Q

How is CDI clinically diagnosed?

A

Based on BOTH clinical suspicion based on signs & symptoms AND confirmatory test or finding.

1) Clinical Suspicion: EITHER/OR
- Unexplained & new-onset diarrhea (i.e. >= 3 unformed stools in 24h) OR
- Radiological evidence of ileus or toxic megacolon
+
2) Confirmatory Test/Finding: EITHER/OR
- Positive diagnostic test results for C. difficile or its toxins OR
- Histopathological findings of pseudomembranous colitis

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16
Q

Why is stool cultures not routinely performed to diagnose whether a patient has CDI?

A

Long turnaround time

17
Q

What are some “don’ts” in the diagnosis of CDI?

A

DON’T test asymptomatic patients
DON’T repeat testing in < 7 days
DON’T perform test of cure
- > 60% of pt remain positive despite successful Tx

18
Q

What are some infection control methods to minimise the risk of CDIs?

A

Healthcare:

  • Practice hand hygiene
  • Contact precautions recommended until 48h after diarrhea resolves
  • Wear PPE & wash hands with SOAP & WATER (preferred) after pt care

Home:

  • Wash hands w/ soap & water after using bathroom
  • Use separate bathroom where possible
  • Clean toilets, linens, towels, clothing w/ bleach
19
Q

What are some diagnostic tests available, besides stool cultures, for the diagnosis of CDI?

A

1) Nucleic acid amplification tests (NAAT):
- Toxin enzyme immunoassay (EIA) -> presence of toxins A & B
- Glutamate dehydrogenase EIA -> enzyme present w/ C. difficile
2) Polymerase chain reaction (PCR)

20
Q

What are some factors to consider for in the pharmacological treatment of CDI?

A

If possible, discontinue all other concurrent Abx
- increase clinical response & reduce recurrence
Empiric CDI Tx is recommended ONLY if:
- Substantial delay (> 48h) in diagnostics
- Fulminant CDI

21
Q

Define the various types of CDI according to IDSA guidelines.

A

Non-Severe: WBC < 15x10^9 /L AND SCr < 133 umol/L
Severe: WBC >= 15 x 10^9 /L OR SCr >= 133 umol/L
Fulminant: same lab parameters as severe AND hypotension / ileus / toxic megacolon / psuedomembranous colitis

22
Q

58 y/o male with PMH of T2DM and HTN is receiving a 4-week course of piperacillin/tazobactam for DFI caused by P. aeruginosa. 2 weeks into his antibiotic course, he complained of new-onset loose stools (5 episodes/day).

T 38.4 deg C, BP 126/86, HR 76, RR 22
WBC 11.8 x 10^9 /L, creatinine 117 umol/L
Allergies: no known drug allergies
C. difficile PCR: positive

Assuming that this is his first episode of CDI, recommend an appropriate management strategy.

A

For non-severe CDI:
Vancomycin 125mg PO QDS x 10 days OR
Fidaxomicin 200mg PO BD x 10 days

Alternative (less preferred):
Metronidazole 400mg PO TDS x 10 days

Extend to 14 days if symptoms are not completely resolved.

23
Q

55 y/o male with PMH of T2DM and HTN is receiving a 4-week course of piperacillin/tazobactam for DFI caused by P. aeruginosa. 2 weeks into his antibiotic course, he complained of new-onset loose stools (5 episodes/day) and abdominal discomfort.

T 38.4 deg C, BP 126/86, HR 76, RR 22
WBC 11.8 x 10^9 /L, creatinine 140 umol/L
Allergies: no known drug allergies
C. difficile PCR: positive

Assuming that this is his first episode of CDI, recommend an appropriate management strategy.

A

For severe CDI:
Vancomycin 125mg PO QDS x 10 days OR
Fidaxomicin 200mg PO BD x 10 days

Extend to 14 days if symptoms are not completely resolved.

24
Q

56 y/o female with PMH of T2DM and HTN is receiving a 4-week course of piperacillin/tazobactam for DFI caused by P. aeruginosa. 2 weeks into her antibiotic course, she complained of new-onset loose stools (5 episodes/day) and severe abdominal discomfort.

T 38.4 deg C, BP 96/56, HR 76, RR 22
WBC 16.8 x 10^9 /L, creatinine 141 umol/L
Allergies: no known drug allergies
C. difficile PCR: positive

Assuming that this is her first episode of CDI, recommend an appropriate management strategy.

A

For fulminant CDI w/o ileus:
Vancomycin 500mg PO QDS + Metronidazole 500mg IV q8h x 10 days

Extend to 14 days if symptoms are not completely resolved.

25
Q

54 y/o female with PMH of T2DM and HTN is receiving a 4-week course of piperacillin/tazobactam for DFI caused by P. aeruginosa. 2 weeks into her antibiotic course, she complained of severe abdominal discomfort at the A&E. She mentioned that she had new-onset loose stools (5 episodes/day) yesterday but her diarrhea has stopped suddenly today.

T 38.4 deg C, BP 96/56, HR 76, RR 22
WBC 16.8 x 10^9 /L, creatinine 141 umol/L
Allergies: no known drug allergies
C. difficile PCR: positive

Assuming that this is her first episode of CDI, recommend an appropriate management strategy.

A

For fulminant CDI w/ ileus:
Vancomycin 500mg PO QDS + Vancomycin 500mg PR QDS + Metronidazole 500mg IV q8h x 10 days

Extend to 14 days if symptoms are not completely resolved.

26
Q

Postulate a reason why metronidazole may still be used as first-line Tx for CDI in some patients locally.

A

Cost & logistical considerations

  • IV Vancomycin is the only formulation available in SG, thus it can be inconvenient to administer.
  • However, avoid prolonged / repeated courses of metronidazole due to cumulative & potentially irreversible neurotoxicity.
27
Q

What is the mechanism of action of fidaxomicin?

A

Narrow-spectrum macrocyclic (novel macrolide) Abx that inhibits transcription & protein synthesis of C. difficile by binding to RNA polymerase enzyme

28
Q

What is the spectrum of activity of fidaxomicin?

A

Primarily gram-positive aerobes & anaerobes

Bactericidal against C. difficile

29
Q

List some potential benefits of fidaxomicin.

A

Lower MIC than for metronidazole & vancomycin
Significant PAE (post-Abx effect) against C. difficile (5.5-12h)
Less effect on normal Bacteriodes spp. in gut

30
Q

Postulate a reason why fidaxomicin is not widely used for the treatment of CDI despite being a first-line drug recommended in IDSA guidelines.

A

Very expensive
- $2k&raquo_space; $30 when comparing fidaxomicin 200mg PO BD x 10 days vs vancomycin 125mg PO QDS x 10 days
Thus, clinical use is limited to severe and/or recurrent non-responsive cases to maximise standard therapy

31
Q

58 y/o male with PMH of T2DM and HTN is receiving a 4-week course of piperacillin/tazobactam for DFI caused by P. aeruginosa. 2 weeks into his antibiotic course, he complained of new-onset loose stools (5 episodes/day).

T 38.4 deg C, BP 126/86, HR 76, RR 22
WBC 11.8 x 10^9 /L, creatinine 117 umol/L
Allergies: no known drug allergies
C. difficile PCR: positive

Assuming that this is his second episode of CDI, recommend an appropriate management strategy.

A

If metronidazole for initial episode:
Vancomycin 125 mg PO QDS x 10 days

If vancomycin/fidaxomicin for initial episode:

1) Fidaxomicin 200mg PO BD x 10 days OR
2) Vancomycin PO taper
- e.g. 125 mg QDS x 10 days, 125mg BD x 1 week, 125mg OD x 1 week, 125mg q2-3 daysx 2-8 weeks

32
Q

What are some monitoring parameters we should look out for during Abx Tx of CDI?

A

Clinical improvement expected in 5-7 days
Additional diagnostics or consider escalation of pharmacological Tx if poor response
Do NOT continue CDI Tx for as long as Tx duration of concurrent Abx for an ongoing infection!!
- e.g. DFI, pressure ulcer infection

33
Q

Probiotics can be recommended for routine use to prevent or treat CDI. True or false?

A

False

34
Q

Antiperistaltics, such as loperamide, diphenoxylate & atropine has limited role in infectious diarrhea and should not be recommended as adjunctive Tx. True or false?

A

True.
Anti-motility agents reduces bowel input, which reduces ability to perform stool testing & are associated with poor outcomes esp. if diarrhea is not treated appropriately.

PR3124 PT3 (12 decks)

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