The effect of Perasafe® and sodium dichloroisocyanurate (NaDCC) against spores of Clostridium difficile and Bacillus atrophaeus on stainless steel and polyvinyl chloride surfaces

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Abstract

Clostridium difficile is an important cause of nosocomial diarrhoea. The aim of this study was to evaluate the potential for Perasafe®, a recently introduced biocide, to contribute to control of C. difficile spores in the patient environment, in comparison with the chlorine-releasing agent sodium dichloroisocyanurate (NaDCC). These agents were evaluated against a water control, in a surface test on stainless steel and polyvinyl chloride (PVC) floor covering, materials commonly found in the hospital environment. The organisms studied were a toxigenic clinical isolate of C. difficile, and Bacillus atrophaeus (formerly B. subtilis var niger). The data indicate that in our in vitro system, Perasafe was significantly more active than NaDCC (1000 ppm available chlorine) against C. difficile spores dried on stainless steel surfaces, and against B. atrophaeus on PVC floor covering material, achieving mean log10 reduction factors in viable counts of 6 and 5.5, respectively, at 10 min exposures. Perasafe appeared to be less lethal in 10 min exposures to C. difficile spores fixed on PVC floor covering material. In general, 1000 ppm chlorine generated from NaDCC showed lower log10 reduction factors in viable counts at 10 min, ranging from 0.7 to 1.5, than Perasafe which ranged from 2.7 to 6.0. The potential efficacy of Perasafe in reducing the density of C. difficile spores in the patient environment in hospitals, nursing homes or other long-stay facilities should be evaluated in field studies.

Introduction

Nosocomial diarrhoea due to Clostridium difficile is recognized as a significant cause of hospital-acquired morbidity in many centres,1 including ours.2 The manner of transmission between patients and care givers poses difficult problems for infection control teams. Accumulation and persistence of spores in the hospital environment is one factor contributing to this situation,3., 4., 5. making cleaning and decontamination important in controlling cross-infection due to this organism.6., 7.

The agent most frequently used for environmental decontamination of C. difficile spores is hypochlorite (HOCl) in various formulations.6., 7., 8. The use of so-called organic chlorine-releasing agents has not been promoted, presumably as compounds such as sodium dichloroisocyanurate (NaDCC) are less effective than HOCl in spore inactivation.9., 10. The choice of NaDCC for this study was determined by the observation that it is in common use in Israeli hospitals for situations in which environmental decontamination is required. Furthermore, Bloomfield and Uso11 showed that NaDCC has a distinct advantage over HOCl, being less susceptible to inactivation by organic material.

The manufacturer's claim of a useful sporicidal effect for the recently introduced product Perasafe® (Antec International, Sudbury, UK), its ease of preparation and lack of odour, suggested it might be a useful agent for dealing with spores of C. difficile in the environment. It would therefore be of interest to compare the effect of Perasafe with NaDCC on C. difficile spores dried on surfaces of materials frequently found in the patient environment in the hospital. For this purpose, stainless steel and the polyvinyl chloride (PVC) floor covering in use at our hospital were chosen. For comparison, we used Bacillus atrophaeus, previously known as Bacillus globigii and Bacillus subtilis var. niger, which has frequently served as a test organism in evaluating disinfection and sterilization processes. This species has also been used recently as a surrogate for Bacillus anthracis in a study of hand decontamination.12

Section snippets

Biocides

Perasafe is a mixed formulation described by the manufacturer as a peroxygen system generating peracetyl ions in equilibrium at pH 8.0 equivalent to peracetic acid at 0.26%. The solution also contains hydrogen peroxide and acetic acid. Perasafe was freshly prepared before each experiment from the powder according to the manufacturer's instructions. NaDCC at a concentration of 1000 ppm available chlorine was prepared for each experiment from Presept® tablets (Johnson and Johnson, Shefayim,

Results

NaDCC had little effect on C. difficile spores after 10 min exposure, on both steel and PVC surfaces. Its effect on spores of B. atrophaeus was somewhat greater, although at 10 min, the log10 reduction factor achieved was only 1.5. In general, Perasafe appeared to fare better (Figure 1, Figure 2).

Discussion

Environmental spore control may contribute to reducing the risk or incidence of C. difficile-associated disease in hospital settings, although the data are not consistent. In an early study,8 disinfection of a ward with hypochlorite at a concentration of 500 ppm available chlorine was associated with a 79% reduction of positive environmental cultures compared with pre-intervention rates, and cessation of an outbreak. Mayfield et al.6 claimed an effect for hypochlorite in reducing the incidence

Acknowledgements

This study was supported by a grant from Antec International, Sudbury, UK.

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