Researchers Investigate the Prevalence of Colonization Among ICU Patients

A prospective study was performed by Zhang, et al. (2016) to investigate the prevalence of colonization among ICU patients and to examine whether asymptomatic carriers were the source of subsequent C. difficile infection (CDI) and acquisition of toxigenic C. difficile.

Rectal swabs were collected from adult patients on admission to and at discharge from a 50-bed medical ICU of a major referral hospital in western China, from August to November 2014. Stools were collected from patients who developed ICU-onset diarrhea. Both swabs and stools were screened for tcdB (toxin B gene) by PCR. Samples positive to tcdB were cultured for C. difficile and isolates recovered were screened for tcdB and the binary toxin genes by PCR. Strain typing was performed using multilocus sequence typing and isolates belonging to the same sequence type (ST) were further typed using multiple-locus variable number tandem repeat analysis (MLVA).

During the four-month period, rectal swabs were collected from 360 (90.9%) out of 396 patients who were admitted to the ICU. Among the 360 patients, 314 had stayed in the ICU more than three days, of which 213 (73.6%) had a rectal swab collected within the three days prior to discharge from ICU. The prevalence of toxigenic C. difficile colonization was 1.7% (six cases) and 4.3% (10 cases) on admission and discharge, respectively. Only four (1.1%) out of 360 patients had CDI, corresponding to 10.7 cases per 10,000 ICU days. None of the four cases had toxigenic C. difficile either on admission or at discharge. Toxigenic C. difficile isolates were recovered from all swabs and stool samples positive for tcdB by PCR and belonged to 7 STs (ST2, 3, 6, 37, 54, 103 and 129). None of the isolates belonging to the same ST had identical MLVA patterns. Binary toxin genes were detected in one ST103 isolate that caused colonization.

The researchers conclude that prevalence of colonization with toxigenic C. difficile among patients on admission to ICU was low in their setting. ICU-acquired toxigenic C. difficile were not linked to those detected on admission. Active screening for toxigenic C. difficile may not be a resource-efficient measure in settings with a low prevalence of colonization.

Reference: Zhang X, Wang X, Yang J, Liu X, Cai L and Zong Z. Colonization of toxigenic Clostridium difficile among ICU patients: a prospective study. BMC Infectious Diseases. 201616:397