Escherichia coli in marine water: Comparison of methods for the assessment of recreational bathing water samples

- 477 seawater samples were examined for E. coli presence using reference method and six alternative methods
- The temperature modified ISO 9308-1 (44 °C) seems to be a suitable method for marine bathing water quality assessment
- Previously used TSA/TBA media possibly overestimate the E. coli count
- Colilert-18 in marine water results inconclusive, hence need exists to expand research to diverse geographical locations
- In order to improve health protection, application of rapid method is required

Bathing Water Directive (2006/7/EC) specifies two reference methods for Escherichia coli detection: ISO 9308-1 and 9308-3. The revised ISO 9308-1 is recommended only for waters with a low bacterial background flora. Considering the extended time needed for analysis and, generally, the lack of experience in using ISO 9308-3 in the Mediterranean, the suitability of ISO 9308-1 for the examination of E. coli in bathing water was evaluated. The present study was aimed at a comparison of data obtained by the reference method in seawater samples (110 beaches, N = 477) with data received from six alternative methods. Results show that recently used TSA/TBA method may overestimate E. coli numbers in marine waters. The temperature modified ISO 9308-1 (44 °C) did not significantly alter the results, but outperformed the antibiotic supplemented agar at reducing non-E. coli bacteria on the plates, allowing the use of the respective method for monitoring coastal water.