Surveillance for Clostridium difficile infection

Continuous, ongoing surveillance of Clostridioides difficile (CDI) in hospitals is an important quality improvement activity that contributes to safer care for patients, and informs strategies to improve practice and minimise preventable CDI.

Clostridioides difficile infection* (CDI) is a serious gastrointestinal disease caused by toxins produced by the spore-forming bacterium Clostridioides difficile. CDI is associated with prolonged and unnecessary use of broad-spectrum antimicrobials, hospitalisation, advanced age and underlying morbidity.

Surveillance for CDI is well established in most Australian states and territories. The surveillance of hospital-identified CDI is not designed to be utilised as a hospital performance measure or to compare rates between hospitals; it is an indicator of the burden of CDI in the patient population presenting to a hospital, and captures both community and healthcare-associated events.

The Commission has produced the following resources to support hospitals in carrying out CDI surveillance.

Implementation Guide

Active surveillance of CDI within hospitals is imperative for the early detection and control of CDI outbreaks. The Commission has produced a surveillance implementation guide for CDI to support Australian hospitals in undertaking surveillance and reporting of CDI:

Guide, user guide or guidelines

Case definition – Hospital-identified CDI

Case definition for hospital-identified CDI:

A hospital-identified CDI case is a case of CDI identified for a patient attending a hospital (including positive specimens obtained from admitted patients and those attending the emergency department, and outpatient departments). This does not mean the case of CDI is attributed to or acquired at the hospital conducting the surveillance.

A case of CDI implies that the patient has the relevant clinical manifestations and must meet either: 1) Criterion A and either Criterion B1 or B2; or 2) Criterion A and Criterion C.

A case of hospital-identified CDI:

A B1 B2 C
X X    
X   X  
X     X

Not a case of hospital-identified CDI:

A B1 B2 C


Criterion A: Diarrhoea (usually defined as three or more loose stools in a 24-hour period) or, less commonly, ileus, toxic megacolon or pseudomembranous colitis (identified by colonoscopy).


Microbiological evidence of toxin producing C. difficile from at least one of the following criteria:

Criterion B1: Positive test laboratory test result for C. difficile toxin A and /or B tested on an unformed (diarrhoea) stool specimen.


Criterion B2: A toxin-producing C. difficile organism detected by culture or other laboratory means performed on an unformed stool sample.


Criterion C: Patient has evidence of pseudomembranous colitis on gross anatomic (includes endoscopic exams) or histopathologic exam.


• Cases where a known previous positive test has been obtained within the last eight weeks

• Patients less than two years old at date of admission.

For guidance on testing procedures for C. difficile see Public Health Laboratory Network. Clostridium difficile infection laboratory case definition:

Calculation of CDI rates

The following formula should be used to calculate the rate of C. difficile infection in acute inpatient hospitals:

Numerator: Patient episodes of hospital identified CDI (total hospital CDI cases) x 10,000
Denominator: Number of patient days  

A hospital’s CDI rate should be calculated routinely as per the local surveillance plan. For example, on a monthly or quarterly basis to enable early outbreak detection and ongoing evaluation of the local infection control program.

More information

The Commission annually monitors the prevalence of CDI in Australia. Learn more about the Commission’s work on CDI