Are bacteria in the coastal zone a threat to human health?

Abstract

Faecal pollution regularly contaminates surface waters, introducing microorganisms, including bacteria and bacteria resistant to antibiotics, to coastal waters. People can come into contact with these potentially harmful microbes when they enjoy recreational activities in the sea. Understanding the risk to bathers of acquiring infections from the sea is important for developing effective intervention strategies to protect human health. This thesis consists of four original studies which aim to answer the question ‘are bacteria in the coastal zone a threat to human health’? First, we describe a systematic review on the risk of acquiring infections from recreational use of coastal waters. Synthesising risk estimates of reporting various symptoms of ill health, we quantify this risk as well as appraise the evidence that these infections are acquired from bathing in coastal waters. The results of the second study - a large online survey - corroborate these findings and provide updated estimates of risk for UK bathers. Third, we assess the risk of ingesting antibiotic resistant bacteria among UK coastal water users. In the final study, we measured the prevalence of faecal carriage of antibiotic resistant bacteria among a highly exposed group – surfers, and in an unexposed group (non-surfers). We conclude that despite improvements made to the collection, treatment and discharge of sewage, and initiatives to communicate water quality to members of the public in recent years, people who bathe in coastal waters are still at an increased risk of adverse health outcomes, whether this is experiencing symptoms of ill health, or exposure to and colonisation by antibiotic resistant bacteria.