A Point Prevalence Study of Hospital-based GI Clinic Environmental Contamination With Toxigenic Clostridium difficile

Background:   Outpatient clinics are largely unexplored as a source of C. difficile (CD) contamination despite recent population-based studies indicating that up to 50% of patients with community-acquired CD have recent outpatient clinic exposures. 

Objective: To examine the point prevalence of CDcontamination in a hospital-based outpatient gastroenterology (GI) clinic at UPMC Presbyterian.

Methods:  For each culture, multiple sites were sampled with a single sterile 2x2 inch cotton gauze pad moistened with 2 mL phosphate-buffered saline and transferred to an empty, sterile 50 mL conical tube.  Tubes were transferred to the lab within 60 minutes of collection and 10 mL pre-reduced CCMB-TAL (Anaerobe Systems) was added to each tube.  Samples were transferred to an anaerobic chamber (Coy) and incubated for 72 hours at 37 °C.   Fermenting samples were subcultured to pre-reduced 5% sheep blood agar (BBL). CD was identified by colony morphology and L-proline aminopeptidase activity (PRO disc, Remel).  Toxigenic isolates were confirmed by RT-PCR for tcdB  (Prodesse) with genomic DNA extracted using the nuclisens EasyMag™ platform (biomérieux).   Environmental sampling was performed on two different days 7 days apart after clinic hours.  On the 1^st sampling, 6 GI clinic rooms, the GI clinic waiting room, the GI physician charting area, the GI clinic phlebotomy room,  and a GI clinic patient bathroom were sampled, each at 10 high-contact sites per culture.  As controls, the dermatology clinic waiting room and Moh’s surgery procedure room were also sampled in the same manner at 10 high-contact sites.  On the 2^nd sampling, the 6 GI clinic exam rooms were surveyed at 10 different sites: computer keyboards, patient chairs, exam table, BP cuff, oto/ophthalmoscope handles, sink/soap dispenser handles, privacy curtain, physician chair, door handles, and patient pens).  Samples were batch cultured according to site for a total of 10 cultures. Negative controls were collected last on each sampling day by handling the moistened 2x2 inch gauze in open air for 60 seconds.   GI clinic staff was aware of the study and performed bleach wipe decontamination prior to sampling on 4/6 exam rooms.

Results: For the 1st sampling, 3/6 GI clinic rooms were positive for toxigenic CD while the other sites and negative control were negative.  All 3 positive exam rooms had been decontaminated with bleach wipes.  For the 2^nd sampling, 1/10 sites (computer keyboards) were positive. 

Conclusions: Outpatient clinics may be a source of CD contamination and could potentially result in acquisition among patients without traditional risk factors for CD infection.  Further studies are planned to assess the reproducibility of these findings. MLVA genotyping will be used to determine the association between outpatient and environmental CD isolates.  Frequent bleach disinfection of outpatient areas may be necessary to eliminate clinic contamination.