Medical researchers from Galway believe it is the first discovery of the virulent NDM enzyme in bathing seawater in Europe.
They claim there is a high risk that such bacteria could be found wherever raw sewage is pumped into coastal waters.
One of the lead researchers, Martin Cormican of NUI Galway’s School of Medicine and University Hospital Galway, said the findings also raised concerns that existing tests on the quality of bathing water might be insufficient to detect such bacteria.
“We have known for more than 100 years that proper control of sewage is a foundation stone for protection of public health, but in 2017 we are still allowing sewage to flow into the sea and rivers because we have not organised ourselves to build the treatment systems we need,” said Prof Cormican.
The study identified an outflow of untreated human sewage as the likely source of the contamination at the unnamed beaches in the Republic, which was discovered in samples taken since last July.
However, the Irish Examiner has established that the beaches are located in Co Galway.
NDM, which was first identified in 2009, is a type of carbapenemase-producing Enterobacteriaceae — CPEs — a so-called “superbug” which is immune to some of the last-line antibiotics available to hospitals.
In February the World Health Organisation declared CPEs a “critical priority” for which new antibiotics were urgently needed due to the high levels of such resistant bugs found in large parts of Asia, the Middle East, Latin America, and southern Europe.
The study claimed two freshwater streams located near one of the beaches had also become contaminated by the backwash of such sewage by tidal currents.
Positive samples for NDM found in the streams were resistant to eight widely used antibiotics including ampicillin and cefoxitin, while NDM in the seawater was resistant to 12 antibiotics.
Another researcher, Bláthnaid Mahon, said it was important to note that tests carried out by the EPA had consistently found that bathing water quality in the area of the two beaches had met regulatory standards.
The researchers said there was no evidence anyone had been infected by exposure to antibiotic-resistant bacteria in the area of the beaches.