Infectious Diseases I

dormant in spores increases the potential for environmental spread.

C. difficile is pathogenic through the production and expression of two primary toxins, C. difficile toxin

A (TcdA) and C. difficile toxin B (TcdB). North America has seen a recent emergence of strains with

increased virulence (e.g., BI/NAP1 strain) through increased production of toxins A and B, production

of additional toxins, and enhanced sporification.

CDI is responsible for almost 30% of antibiotic-associated diarrhea and is the most common cause of

infectious diarrhea in health care settings. The estimated incidence of CDI is 3–10 cases per 10,000

patient-days. Community-acquired CDI has increased in prevalence.

The clinical manifestations of CDI range from asymptomatic carrier to CDI spanning mild or moderate

diarrhea to fulminant and sometimes fatal pseudomembranous colitis, toxic megacolon, or colonic

perforation. Post-colectomy small bowel enteritis and rectal pouchitis related to CDI have been reported.

Additional complications of severe CDI include:

SIRS

Hypovolemia

Electrolyte disturbances

Multiple organ failure

CDI is associated with medical costs greater than $3 billion per year.

Attributable mortality from CDI is estimated to be below 10%. However, crude mortality is as high

as 75% in patients presenting with septic shock, colonic perforation, or toxic megacolon. Subtotal

colectomy in patients with a severe CDI is associated with an in-hospital mortality rate of up to 42%.

CDI is defined as the presence of symptoms (e.g., diarrhea) and a stool test result positive for C.

difficile toxin, toxigenic C. difficile (e.g., DNA amplification detecting toxin-coding genes), or

pseudomembranous colitis on colonoscopic examination. The most recent guidelines for CDI diagnosis

and management include those from the American College of Gastroenterology in 2021 (Kelly CR, et

from IDSA/SHEA in 2021 related to management of CDI. The ACG 2021 guidelines are updated from

the 2013 version to harmonize CDI severity categories with IDSA/SHEA while expanding a focus on

diagnostic methods and management of patients with concomitant chronic inflammatory bowel disease.

IDSA 2017 and 2021; ACG 2021

WBC 15 x 103 cells/mm3 or greater and

ii.

Serum creatinine (SCr) 1.5 times or greater than the premorbid level

Fulminant (IDSA 2017 and 2021; ACG 2021) CDI is defined as:

Severe CDI plus one of the following:

Hypotension or evidence of shock

ii.

Ileus

iii.

Megacolon

Recurrence is defined as the relapse of a recent infection or a reinfection after definitive therapy.

Additional categorizations of CDI are used for infection control surveillance and institutional/ICU

quality review. These are related to the locations of C. difficile acquisition (e.g., community acquired or

health care associated) and onset of symptoms (e.g., community onset vs. health care onset).