Anaeróbios

Clostridioides difficile

Spore-forming Gram-positive bacilli

Identification & Growth

Identification

Strict anaerobe, subterminal spore
Routine diagnosis by GDH plus toxin A/B testing, with confirmatory PCR

Growth Conditions

CCFA agar (cycloserine-cefoxitin-fructose): yellow colonies with a horse-manure odour and fluorescence
Anaerobic incubation, 35 °C, 48 h

Clinical Significance

Antibiotic-associated diarrhea and pseudomembranous colitis in hospitalized patients

Intrinsic Resistance

Cephalosporins, aztreonam, aminoglycosides

Bench Alerts

Do not test formed stools or repeat testing for test-of-cure
An isolated culture without toxin does not define disease
Contact precautions and soap-and-water hand hygiene (alcohol does not inactivate the spore)

Clinical Notes

Clinical presentations

Causes antibiotic-associated diarrhea, ranging from mild self-limited disease to severe pseudomembranous colitis.
Severe complications include toxic megacolon, intestinal perforation, and septic shock in fulminant cases.
Infection recurrence occurs in a significant proportion of patients after treatment of the initial episode.

Specimens and collection

Unformed (liquid or soft) stool specimen is mandatory for testing, as formed stool indicates colonization only.
Diagnostic algorithm combining glutamate dehydrogenase (GDH) testing, toxin immunoassay, and/or PCR increases diagnostic accuracy.
Test of cure is not recommended, as PCR may remain positive after clinical symptom resolution.

Epidemiology and at-risk populations

Prior broad-spectrum antimicrobial use is the main risk factor, due to disruption of the protective intestinal microbiota.
Advanced age, prolonged hospitalization, and proton pump inhibitor use increase infection risk.
The hypervirulent ribotype 027 strain is associated with hospital outbreaks with higher morbidity and mortality.

Resistance and therapeutic implications

Oral vancomycin and fidaxomicin are the first-line treatments recommended by current guidelines, with fidaxomicin associated with lower recurrence.
Metronidazole is currently reserved for mild cases when preferred therapies are unavailable.
Fecal microbiota transplantation is an established therapeutic option for multiple recurrent infection.

Bench and reporting notes

Molecular tests (PCR) detect toxin genes with high sensitivity but do not distinguish colonization from active disease, requiring clinical correlation.
Toxigenic culture is considered the reference standard in research settings but rarely used in routine clinical practice due to turnaround time.
Positive result should be interpreted in the clinical context of active diarrhea to avoid treating asymptomatic colonization.

Sources

Educational decision-support content. It does not replace laboratory validation, current guidelines or review by the responsible professional.

FAQ: Frequently Asked Questions

How to identify Clostridioides difficile in the lab?

Clostridioides difficile is identified through strict anaerobe, subterminal spore, routine diagnosis by gdh plus toxin a/b testing, with confirmatory pcr.

What are the intrinsic resistances of Clostridioides difficile?

This organism is naturally resistant to cephalosporins, aztreonam, aminoglycosides. These drugs should not be reported as susceptible.

Where is Clostridioides difficile commonly found?

It is typically associated with antibiotic-associated diarrhea and pseudomembranous colitis in hospitalized patients.

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