Evaluation of Techniques for Measuring Microbial Hazards in Bathing Waters: A Comparative Study

PLoS One. 2016 May 23;11(5):e0155848. doi: 10.1371/journal.pone.0155848. eCollection 2016.

Abstract

Recreational water quality is commonly monitored by means of culture based faecal indicator organism (FIOs) assays. However, these methods are costly and time-consuming; a serious disadvantage when combined with issues such as non-specificity and user bias. New culture and molecular methods have been developed to counter these drawbacks. This study compared industry-standard IDEXX methods (Colilert and Enterolert) with three alternative approaches: 1) TECTA™ system for E. coli and enterococci; 2) US EPA's 1611 method (qPCR based enterococci enumeration); and 3) Next Generation Sequencing (NGS). Water samples (233) were collected from riverine, estuarine and marine environments over the 2014-2015 summer period and analysed by the four methods. The results demonstrated that E. coli and coliform densities, inferred by the IDEXX system, correlated strongly with the TECTA™ system. The TECTA™ system had further advantages in faster turnaround times (~12 hrs from sample receipt to result compared to 24 hrs); no staff time required for interpretation and less user bias (results are automatically calculated, compared to subjective colorimetric decisions). The US EPA Method 1611 qPCR method also showed significant correlation with the IDEXX enterococci method; but had significant disadvantages such as highly technical analysis and higher operational costs (330% of IDEXX). The NGS method demonstrated statistically significant correlations between IDEXX and the proportions of sequences belonging to FIOs, Enterobacteriaceae, and Enterococcaceae. While costs (3,000% of IDEXX) and analysis time (300% of IDEXX) were found to be significant drawbacks of NGS, rapid technological advances in this field will soon see it widely adopted.

Publication types

  • Comparative Study

MeSH terms

  • Bacterial Load
  • Bacteriological Techniques / economics
  • Bacteriological Techniques / methods*
  • Enterococcus / genetics
  • Enterococcus / isolation & purification
  • Environmental Monitoring / methods*
  • Escherichia coli / genetics
  • Escherichia coli / isolation & purification
  • Fresh Water / microbiology*
  • High-Throughput Nucleotide Sequencing
  • Sensitivity and Specificity

Grants and funding

The authors gratefully acknowledge the funding, data contribution, and support of Melbourne Water, the Environment Protection Authority (Victoria), Mornington Peninsula Shire, and the Australian Research Council Linkage Program (LP120100718). Melbourne Water provided financial support in the form of equipment budget, research materials, and sample analysis. Melbourne Water initially helped with the study design, provided assistance for the collection of samples, and helped prepare this manuscript. Melbourne Water involvement in this study did not influence the authors' decision to publish. Micromon did not provide any financial support for this research (other than in-kind). Micromon were responsible for the NGS sample processing and analysis provided the information necessary in the Methods section of this manuscript and provided the NGS data. Micromon did not have any additional role and did not influence the authors' decision to publish. The specific roles of these authors are also articulated in the “authors contributions" section in the online submission.