January 2016 What Lies Beneath - Antibiotics and Antibiotic Resistant Bacteria in our Sewers

NUI Galway study highlights the discharge of antibiotic resistant bacteria from inadequately treated sewage to the environment in Ireland, Europe and the wider world is a serious risk to health

Scientists at the School of Medicine in NUI Galway together with colleagues in UCD have carried out a study on whether antibiotics and antibiotic resistant bacteria are present in hospital sewage, and city sewage. The results found high levels of bacteria resistant to all antibiotics in urban sewage from hospitals and from general city sewage, but that risk can be reduced greatly by an effective wastewater treatment.

Antibiotic resistance is one of the greatest threats to public health. Bacteria are becoming resistant to more and more antibiotics and infections are more and more difficult to treat. Hospitals today are fighting the problem of infections caused by bacteria resistant to so many antibiotics that patients with these infections are very difficult to treat.

Antibiotic resistance is driven by contact between bacteria and antibiotics. When we take antibiotics to treat an infection the antibiotic impacts on all the bacteria in the body not just the one causing the infection. This can drive many bacteria in the gut and skin towards antibiotic resistance.

In the past we have paid much less attention to contact between antibiotics and bacteria outside the body. However a lot of the antibiotics we swallow come out in urine or faeces. Bacteria are also shed in faeces and become mixed with water and soil bacteria in sewers and treatment plants. In recent years there has been growing interest in the way in which this melting pot of bacteria and antibiotics might also contribute to this major problem of antibiotic resistance.

Hospitals use a lot of antibiotics. About 1 in 3 patients in hospital are on antibiotics at any one time. Hospitals tend to use high doses or the newest and most broadly acting antibiotics because of the nature of the infections in hospitalised patients. Scientists at the School of Medicine at NUI Galway and colleagues at UCD, funded by the Environmental Protection Agency, looked at whether antibiotics and antibiotic resistant bacteria are present in hospital sewage, and city sewage. They tested to see if the antibiotic resistant bacteria can survive wastewater treatment processes and examined what is the possible risk of antibiotic resistant bacteria that are discharged into seawater from treatment plants getting back into people.

The research team found high levels of bacteria resistant to all antibiotics in urban sewage from hospitals and from the general city sewage. Hospital sewage was different in that there were high levels of bacteria resistant to a number of “newer” antibiotics. The number of antibiotic resistant bacteria present were reduced greatly by effective wastewater treatment but some antibiotic resistant bacteria survive and are discharged to seawater. The team consider that the chance that people will pick up antibiotic resistant bacteria from swimming in seawater receiving properly treated sewage is very low.

The team found that the predicted discharges of antibiotics into the environment from hospitals is substantial. There is evidence that some antibiotics may persist in the water and soil for long periods. Because of the effects of dilution and other factors, it is unlikely that people are exposed to sufficient antibiotics to cause direct harmful effects. However the persistence of antibiotics at low levels in soil and water may contribute to the development of antibiotic resistant bacteria.

Dr Dearbhaile Morris, Bacteriologist from the School of Medicine at NUI Galway said: “This study highlights a part of the problem of antibiotic resistance that does not receive very much attention. Our work shows that there is a risk related to antibiotics and antibiotic resistant bacteria in sewage but that a high standard of sewage treatment goes a long way to reduce that risk. This is one more reason why the discharge of untreated or inadequately treated sewage to the environment in Ireland or indeed anywhere in Europe or the wider world is an unacceptable risk to our health.”

For a link to the study visit: http://www.epa.ie/pubs/reports/research/health/researchreport162.html#.VpaBUFLXsSk

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