INFECTION CONTROL
colonies found on the floor-based settle plates, microbes were still being captured from the air eight minutes after the flush, indicating collection of ‘droplet nuclei’ bio- aerosols. Droplet nuclei are the tiny particles that remain after the water in a droplet evaporates. They have negligible settling velocity, and will float with natural air currents. Jessen observed that the amount of bio-aerosol increased with increasing flush energy. In 2005 Barker et al experimented with toilet bowls, and found that although a single flush reduced the level of microorganisms in the toilet bowl water when contaminated at concentrations reflecting pathogen shedding, large numbers of microorganisms persisted on the toilet bowl surface, and in the bowl water, which were disseminated into the air by further flushes.21
C. difficile colonisation In 2011, Best et al performed in-situ testing, using faecal suspensions of C. difficile to simulate the bacterial burden found during disease, to measure C. difficile aerosolisation.22
They also
measured the extent of splashing occurring during flushing of two different toilet types commonly used in hospitals. Their findings were as follows: C. difficile was recoverable from air sampled at heights up to 25 cm above the toilet seat. The highest numbers of C. difficile bacteria were recovered from air sampled immediately following flushing, and then declined eight-fold after 60 minutes and a further three-fold after 90 minutes. Surface contamination with C. difficile occurred within 90 minutes of flushing, demonstrating that relatively large droplets are released which then
An Angel Guard washbasin designed to limit the risk of aerosol and splashing.
contaminate the immediate environment. The mean numbers of droplets emitted upon flushing by the lidless toilets in clinical areas were 15-47, depending on design. C. difficile aerosolisation and surrounding environmental contamination occur when a lidless toilet is flushed. They concluded that lidless conventional toilets increase the risk of C. difficile environmental contamination, and went on to suggest that their use should be discouraged, particularly in settings where C. difficile is common.
Hospital bathroom measuring In a 2018 study, particle and bioaerosol concentrations were measured in hospital bathrooms across three sampling conditions; no waste no flush, no waste with flush, and faecal waste with flush.
Particle and bioaerosol concentrations were measured with a particle counter bioaerosol sampler both before and after a toilet flushing event at distances of 0.15, 0.5, and 1 m from the toilet for 5, 10, and 15 minutes. The results showed that particle concentrations measured before and after the flush were found to be significantly different (0.3-10 μm). Bioaerosol concentrations when flushing faecal waste were found to be significantly greater than background concentrations (p-value=0.005). However, the bioaerosol concentrations were not different across time (p-value=0.977) or distance (p-value=0.911) from the toilet, suggesting that aerosols generated may remain for longer than 30 minutes post-flush. Toilets produce aerosol particles when flushed, with the majority of the particles being 0.3 μm in diameter. The particles aerosolised include microorganisms remaining from previous use or from faecal wastes. Differences in bioaerosol concentrations across conditions also suggest that toilet flushing is a source of bioaerosols that may result in transmission of pathogenic microorganisms.23 Unfortunately, despite these findings, it is still common practice in UK healthcare that toilets within clinical areas have no lid, and the aerosol created continues to create a risk of infection within a healthcare environment. It has also been found that the use of hand dryers, especially the increasingly common ‘jet’ air dryers, might have the potential for increasing the risk of aerosols. A recent study by E Best et al concluded that multiple examples of significant differences in surface bacterial contamination, including by faecal and antibiotic-resistant bacteria, were
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Delivering Excellence as Standard 06/08/2020 09:45 September 2020 Health Estate Journal 25
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