Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2018

Microbiological evaluation of the DEKO-190 Washer/Disinfector’s ability to remove Clostridium difficile spores from bedpan surfaces (#224)

Deirdre A Collins 1 2 , Thomas V Riley 1 2 3 4
  1. School of Pathology and Laboratory Medicine, University of Western Australia, Crawley, WA, Australia
  2. School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
  3. Department of Microbiology, PathWest Laboratory Medicine (WA), Nedlands, WA, Australia
  4. School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA, Australia

Background and aims

Clostridium difficile is a major nosocomial pathogen that causes disease varying from mild diarrhoea to life-threatening pseudomembranous colitis. C. difficile spores are particularly resistant to disinfectants and frequently contaminate hospital equipment, including bedpans. Washer/Disinfectors (WDs) are commonly used to clean and decontaminate soiled equipment in health care facilities. This study aimed to evaluate the effectiveness of the DEKO-190 WD in removing C. difficile spores from contaminated bedpans.


Plastic carriers were inoculated with 0.2ml of a suspension of sterile human faeces containing ³ 1×107 CFU/ml non-toxigenic C. difficile spores and then taped to a sterile plastic bedpan. The bedpan and sterile negative controls were subjected to short, long or intensive wash cycles in the WD using one of two test detergents : Formula A (generic) and Formula B (highly alkaline). Counts of any residual spores on carriers were determined and mean log10 reductions in spores were calculated for each wash cycle.  


Mean log10 reductions were 3.21(SEM ±0.20) and 2.82 (±0.13) for Formula A and B, respectively, for the short cycle. The mean log10 reductions using the long wash cycle were 3.65 (±0.44) using Formula A, and 5.30 (±0.43) using Formula B, while log10 reductions were 3.37 (±0.58) (Formula A) and 4.64 (±0.47) (Formula B) for the intensive cycle. Residual spores were isolated from negative control carriers placed inside the machine for every wash cycle. Residual CFU titres were lower for the intensive wash program compared with the long program.


In conclusion, washing with the DEKO-190 significantly reduced spore concentrations on carrier surfaces on a bedpan.  However, the temperature inside the DEKO-190 was not sufficient to inactivate all spores, which exhibited high temperature resistance in other heat tests. Spore counts were most effectively reduced when carriers were washed on a long or intensive wash cycle using an alkaline detergent.