Performance Characteristics of the Temperature-Modified ISO 9308-1 Method for the Enumeration of Escherichia Coli in Marine and Inland Bathing Waters

Mar Pollut Bull. 2018 Oct;135:150-158. doi: 10.1016/j.marpolbul.2018.07.002. Epub 2018 Jul 10.

Abstract

This study defines performance characteristics of the temperature-modified ISO 9308-1 method for E. coli enumeration in bathing water. After a 4-hour resuscitation period at 36 ± 2 °C, the incubation temperature was changed to 44 ± 0.5 °C. Elevated incubation temperature significantly suppressed the growth of thermo-intolerant bacteria, and enhanced the selectivity of Chromogenic Coliform Agar (CCA) up to 49.5% for inland and up to 66.0% for coastal water. Consequently, most of the selectivity-related performance characteristics are improved. Relative recovery was determined by comparing an alternative method against the reference, ISO 9308-1:2014 method, following the criteria set out in ISO 17994:2014. Temperature modification did not significantly alter the results and the methods were evaluated as "not different" for both, coastal and inland waters. Chromogenic Coliform Agar was assessed as a suitable medium for reliable E. coli enumeration in bathing water when incubated for 17-19 h at 44 ± 0.5 °C after the 4-5 h resuscitation period at 36 ± 2 °C.

Keywords: Bathing water; Chromogenic coliform agar; Escherichia coli; Performance characteristics; Temperature-modified method.

MeSH terms

  • Agar
  • Bacteriological Techniques / methods*
  • Bathing Beaches
  • Culture Media
  • Escherichia coli* / growth & development
  • Escherichia coli* / isolation & purification
  • Seawater / microbiology
  • Temperature
  • Water Microbiology*

Substances

  • Culture Media
  • Agar