Flush With Germs: Lidless Toilets Spread C difficile

Jenni Laidman

December 29, 2011

December 29, 2011 — Put a lid on it. That is the conclusion of research examining the amount of Clostridium difficile that flies into the air and contaminates surrounding surfaces with the flush of a lidless toilet.

The investigation, published online December 2 in the International Journal of Hospital Infection, is the work of E. L. Best from the Microbiology Department, Old Medical School, Leeds General Infirmary, Leeds Teaching Hospital National Health Service Trust, United Kingdom, and colleagues. Using fecal suspensions of C difficile, the researchers measured airborne suspension of the bacteria in addition to surface contamination by the bacteria after flushing of both lidless and lidded toilets.

Air samples 25 cm above the commode, which is about the height of the handle, contained C difficile, with the highest numbers coming from samples taken immediately after flushing. The number of viable bacteria declined 8-fold within an hour, from 36 colony-forming units (cfu) collected at seat height to 8 cfu, and by 90 minutes, the number fell to 3 cfu. Surrounding surfaces were contaminated within 90 minutes of flushing, with relatively large droplets released in the immediate environment. The mean number of droplets was between 15 and 47, depending on toilet design, the report states.

Researchers also found the number of viable bacteria to be 12-fold higher from open toilets compared with the same toilet when the lid was closed. They collected 35 cfu at seat height within 30 minutes of flushing an open toilet, but only 3 cfu at seat height within 30 minutes of flushing a lidded commode.

Even with the implementation of strict disinfecting protocols, the authors write, C difficile clusters continue to spring up in healthcare settings, prompting a search for unaddressed contamination sources. Research published in 2008 and 2010, in BMC Infectious Diseases and Clinical Infectious Diseases, respectively, revealed a potential for aerial dissemination of C difficile, especially from patients with recent onset of diarrhea.

"Our study is the first to investigate the effect of a lid closure on the aerosolization and deposition of C difficile associated with toilet flushing," the authors write.

Previous studies that suggested a low probability of environmental contamination from hospital toilets did not use anaerobes or spore-forming bacteria, the authors state. "Notably, there was a 100-fold variation in the magnitude of airborne bacteria released when toilets were flushed, depending on which bacterial species was examined," the authors write.

To collect air samples, researchers clamped sampling tubes at 3 heights above a toilet bowl that had been thoroughly cleaned, inside and out, before the experiment. The tube air sampler was placed at toilet seat height, at 10 cm above the seat, and at handle height (25 cm) above both lidded and opened commodes. In addition, agar plates selective for C difficile were placed atop the toilet tank, to the right and left of the toilet seat, and on the floor around the toilet.

In separate experiments to determine the extent of droplets created by flushing, researchers added food coloring to 10 different toilets and stretched a sheet of cling film across the top of the seat before flushing. After flushing, they placed the cling film on filter paper and counted the droplets.

When the lid was closed, researchers recovered no C difficile from agar plates on any surface. With the lid open, bacteria were recovered at all sampling plates except those on the left side of the toilet, which the authors say may be a result of the hydrodynamics of the flush. Researchers found a mean of 1 to 3 cfu/plate.

"Lidless conventional toilets increase the risk of C. difficile environmental contamination, and thus we suggest that their use is discouraged, particularly in settings where [C. difficile infection] is common," the authors conclude.

The authors have disclosed no relevant financial relationships.

J Hosp Infect. Published online December 2, 2011. Abstract