INFECTION PREVENTION AND CONTROL A
Splashes landing on culture plates
Water from outlet directly hitting sieve at top of drain
No growth on agar plates
U-bend inoculated with bacterial suspension
B
Biofilm growing up drain to sieve in sink
Carbon source
Figure 4: A and B. Both images show a sink with an attached waste pipe and U-bend. Water from an outlet is hitting the sieve at the top of the waste pipe, creating splashes. Some of the droplets from the splashes land on surrounding bacterial culture plates. The U-bend in both A and B has been inoculated with a high concentration of bacteria. The only difference between set-ups A and B is that a carbon (food) source has been placed in the U-bend in B. In A the water splashes do not lead to bacterial growth on the agar plates, but in B the addition of a food source to the U-bend results in a bacterial biofilm growing up the drain at a remarkable 1 mm/hour. Once the biofilm reaches the sieve, water hitting this area from the outlet causes the bacteria to be carried by splashes. Those landing on the culture plates now grow into visible bacterial colonies.
Thus, bacteria can use the wastewater
system as a superhighway to spread within a healthcare facility, and to escape from there to cause infection and spread antimicrobial resistance. Much effort and resource to counteract
the threat of AMR is going into developing new antibiotics, antimicrobial stewardship, and infection control. However, counteracting the risk from healthcare wastewater systems has yet to be addressed. Germany has produced guidance in this area. The O’Neill report viewed issues on sanitation to be restricted to developing countries,1
but this is not the
case. In the most sophisticated healthcare facilities globally, faecal organisms are
42 Health Estate Journal April 2023
being transmitted to patients from wastewater systems. England has a great opportunity to lead globally in this area. The first step is acknowledgement of the issue across the industry, including by manufacturers, producers of guidance, architects, design teams, construction companies, maintenance personnel, and clinical teams.
n In the next two articles, two of Dr Weinbren’s industry colleagues will look, respectively, at current issues with the design, construction, commissioning, and occupation, of buildings in relation to wastewater systems, and at potential future areas for research.
References 1 Tackling drug-resistant infections globally: Final Report and Recommendations. The review on Antimicrobial Resistance, chaired by Jim O’Neill, Wellcome Trust and HM Government, May 2016. https://
tinyurl.com/bp96dyzb
2 Kadri SS, Lai YL, Warner S, Strich JR, Babiker A, Ricotta EE et al. forming the National Insititutes of Health Antimicrobial Resistance Outcomes Research Initiative (NIH-ARORI). Inappropriate empirical antibiotic therapy for bloodstream infections based on discordant in-vitro susceptibilities: a retrospective cohort analysis of prevalence, predictors, and mortality risk in US hospitals. Lancet Infect Dis February 2021; (2): 241-251.
3 Hota S, Hirji Z, Stockton K, Lemieux C, Dedier H, Wolfaardt G et al. Outbreak of multidrug-resistant Pseudomonas aeruginosa colonization and infection secondary to imperfect intensive care unit room design. Infect Control Hosp Epidemiol 2009; 30:25e33.
4 Kotay S, Chai W, Guilford W, Barry K, Mathers AJ. Spread from the sink to the patient: In situ study using green fluorescent protein (GFP)-expressing Escherichia coli to model bacterial dispersion from hand-washing sink-trap reservoirs. Appl Environ Microbiol 2017; 83:e03327-016.
Bacterial colonies on agar plates
Dr Mike Weinbren
Dr Mike Weinbren is a consultant medical microbiologist with a special interest in water and wastewater systems. The Chair of the Healthcare Infection Society Working Party on Water/Wastewater, he has authored a number of publications in this area, and contributed to HTM 04-01 and the new British Standard BS 8580-2: 2022. He is currently employed at King’s Mill Hospital in Sutton-in-Ashfield in Nottinghamshire by Sherwood Forest Hospitals NHS Foundation Trust, and is also a Specialist Advisor, Microbiology, on the New Hospital Programme.
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