It was just six and a half years ago that Professor Timothy Walsh et al. published their study Emergence of a new antibiotic resistance mechanism in India, Pakistan, and the UK: a molecular, biological, and epidemiological study describing the NDM-1 enzyme.
The NDM (New Delhi metallo-ß-lactamase) gene – conveys resistance to the Carbapenem class of antibiotics, which are often used as the drug of last resort for treating difficult bacterial infections, including Escherichia coli (E. coli) and Klebsiella pneumoniae.
Since then we’ve seen a steady stream of reports of NDM-1 (and variants, like NDM-2, NDM-4, NDM-5, etc) turn up around the globe. Worse, the NDM gene can be carried by plasmids - tiny pieces of mobile DNA - that can be shared between different types of bacteria.
Since it requires physical contact between two different types of bacteria for plasmids to make this transfer, man-made environments where many types of bacteria are thrown together - such as sewage treatment plants and contaminated water supplies - are viewed as potential breeding sites for resistant bacteria.
- In late 2013, we looked at a study (see NDM-1 Bacteria Survive & Thrive In Two Chinese Wastewater Treatment Plants) that found the (New Delhi metallo-β-lactamase) enzyme not only survived processing in two Chinese WWTPs, they actually were found to multiply in that environment.
- A year earlier, in Study: MRSA In Waste Water Treatment Plants (WWTPs) we learned that MRSA can survive the waste water treatment process, and potentially could end up redistributed via reclaimed irrigation water.
- And in 2011, in Study: Adaptation Of Plasmids To New Bacterial Species, we looked at the ability of plasmids – tiny snippets of portable DNA that can carry resistance enzymes – to transfer horizontally to other strains of bacteria.
A 2014 study – conducted by the UK’s University of Warwick – made huge headlines (see Drug-resistant bacteria: Sewage-treatment plants described as giant 'mixing vessels' after scientists discover mutated microbes in British river).
We looked at the actual report in WWTPs As `Mixing Vessels’ For Resistant Bacteria.
Today the ECDC's Eurosurveillance Journal has a report of environmental contamination of a public beach in Ireland with NDM-producing E. coli bacteria - apparently shed by a nearby waste water treatment plant.
I've only posted some excerpts, so follow the link to read the report in its entirety.
Eurosurveillance, Volume 22, Issue 15, 13 April 2017
Indistinguishable NDM-producing Escherichia coli isolated from recreational waters, sewage, and a clinical specimen in Ireland, 2016 to 2017
BM Mahon 1 , C Brehony 1 , E McGrath 2 3 , J Killeen 1 , M Cormican 1 2 3 , P Hickey 4 , S Keane 4 , B Hanahoe 3 , A Dolan 5 , D Morris 1
Euro Surveill. 2017;22(15):pii=30513. DOI: http://dx.doi.org/10.2807/1560-7917.ES.2017.22.15.30513
Received:00 March 2017; Accepted:12 April 2017
In this study, New Delhi metallo-beta-lactamase (NDM)-producing Enterobacteriaceae were identified in Irish recreational waters and sewage. Indistinguishable NDM-producing Escherichia coli by pulsed-field gel electrophoresis were isolated from sewage, a fresh water stream and a human source. NDM-producing Klebsiella pneumoniae isolated from sewage and seawater in the same area were closely related to each other and to a human isolate. This raises concerns regarding the potential for sewage discharges to contribute to the spread of carbapenemase-producing Enterobacteriaceae.
We report the finding of New Delhi metallo-beta-lactamase (NDM)-producing Enterobacteriaceae in fresh water and seawater samples collected at two beaches located near an untreated human sewage ocean discharge. Isolates of NDM-producing Escherichia coli derived from the sewage collection system, the sewage storage tank and the outflow were 100% identical by pulsed-field gel electrophoresis (PFGE) to those derived from a fresh water stream on one of the beaches, and to a clinical isolate.(SNIP)
We consider that contamination of the environment with NDM-producing Enterobacteriaceae from the human sewage outflow is likely to be the source, and that the fresh water streams were contaminated by backwash of sewage onto the beach by tidal currents. The presence of NDM-producing Enterobacteriaceae in the bathing water (seawater) and at a separate bathing site ca 950 m in a direct line indicates the extent of this contamination. It is important to note that by the established regulatory standards, the bathing water quality in the area concerned has been consistently of sufficient quality .
Notwithstanding compliance with regulatory standards however, it is reasonable to conclude that those using a beach such as this for recreational purposes might be at least intermittently exposed to NDM-producing Enterobacteriaceae. Although, to date, there is no evidence that NDM-producing Enterobacteriaceae has been acquired as a result of exposure to this beach environment, Leonard et al. have recently reported on the level of risk of exposure to antibiotic resistant bacteria in coastal waters and its relationship to different types of water sports .(Continue. . . )
It appears therefore that there is potential for environmental contamination to contribute to a transition of CPE from largely healthcare-associated organisms, to organisms affecting the general population and the veterinary sector. From a public health perspective, the findings focus attention on the need to accelerate programmes to cease discharge of untreated sewage into the environment. This practice should be unacceptable in the context of discharges in the vicinity of popular bathing and recreation areas where human exposure is highly likely.
For a look at some other unintended consequences arising from WWTPs, you may wish to revisit: