Carbapenem-resistant Enterobacteriaceae (CRE) looks set to becoming Singapore’s biggest antibiotic-resistant bacterial challenge for the immediate future, even more so than other members of the multidrug-resistant bacteria “alphabet soup”, viz. MRSA, VRE, XDR-AB, XDR-PA, etc. What is one unexpected consequence of having patients with CRE in our hospitals? Well, it gets into our sewage system. I have been waiting for this work by local microbiologists – led by A/Prof Tse Hsien Koh from the Singapore General Hospital – to be published for quite a long time, and finally it is available as a letter in the prestigious infection control journal Infection Control & Hospital Epidemiology. Essentially, the majority of the public sector hospitals (the private hospitals did not participate in the survey) had CRE found in their sewage, and in high concentrations given the rather “lax” and unsophisticated testing (without using any sample concentration techniques) performed. I include a screenshot of the relevant table from the article below.

Breakdown of types of CRE in sewage and clinical samples by participating hospital.

What happens to hospital sewage in Singapore? The majority of it – other than those from facilities that deal with radio- and chemotherapy – is treated like normal waste from commercial premises and households. You can find some nice slides of the sewage system in Singapore here (albeit somewhat outdated), or read about in on the PUB page, along with the description of the deep tunnel sewage system. The final effluent, after treatment, is pumped out at sea, whereas some of the sludge is used to generate plant fertiliser.

Is there an issue with CRE re-appearing back in the community environment in Singapore? Probably not – but I am not an expert here, and some countries including France have reported problems with ESBL-producing Enterobacteriaceae being released into the environment after wastewater treatment (link to abstract only, as paper is behind a paywall). In any case, this is good work by the local hospital microbiologists.