A Novel Quantitative Sampling Technique for Detection and Monitoring of Clostridium difficile Contamination in the Clinical Environment

Abstract

The horizontal transmission of Clostridium difficile in the hospital environment is difficult to establish. Current methods to detect C. difficile spores on surfaces are not quantitative, lack sensitivity, and are protracted. We propose a novel rapid method to detect and quantify C. difficile contamination on surfaces. Sponge swabbing was compared to contact plate sampling to assess the in vitro recovery of C. difficile ribotype 027 contamination (∼10 0 , 10 1 , or 10 2 CFU of spores) from test surfaces (a bed rail, a stainless steel sheet, or a polypropylene work surface). Sponge swab contents were concentrated by vacuum filtration, and the filter membrane was plated onto selective agar. The efficacy of each technique for the recovery of C. difficile from sites in the clinical environment that are touched at a high frequency was evaluated. Contact plates recovered 19 to 32% of the total contamination on test surfaces, whereas sponge swabs recovered 76 to 94% of the total contamination, and contact plates failed to detect C. difficile contamination below a detection limit of 10 CFU/25 cm 2 (0.4 CFU/cm 2 ). In use, contact plates failed to detect C. difficile contamination (0/96 contact plates; 4 case wards), while sponge swabs recovered C. difficile from 29% (87/301) of the surfaces tested in the clinical environment. Approximately 74% (36/49) of the area in the vicinity of the patient was contaminated (∼1.34 ± 6.88 CFU/cm 2 C. difficile spores). Reservoirs of C. difficile extended to beyond the areas near the patient: a dirty utility room sink (2.26 ± 5.90 CFU/cm 2 ), toilet floor (1.87 ± 2.40 CFU/cm 2 ), and chair arm (1.33 ± 4.69 CFU/cm 2 ). C. difficile was present on floors in ∼90% of case wards. This study highlights that sampling with a contact plate may fail to detect C. difficile contamination and result in false-negative reporting. Our sponge sampling technique permitted the rapid and quantitative measurement of C. difficile contamination on surfaces with a sensitivity (limit, 0 CFU) greater than that which is otherwise possible. This technique could be implemented for routine surface hygiene monitoring for targeted cleaning interventions and as a tool to investigate routes of patient-patient transmission in the clinical environment.