Caruso G1* and Caruso R2
1National Research Council, Institute for Coastal Marine Environment (CNR-IAMC), Messina, Italy 2Hospital Agency A.O.U. “G. Martino”, Messina, Italy
Received: 16 December, 2015; Accepted: 30 December, 2015; Published: 31 December, 2015
Gabriella Caruso, Graduate in Biological Sciences, Specialist in Applied Microbiology. Researcher at: CNR-IAMC, Address: Spianata S. Raineri 86, 98122 Messina, Italy, Tel: +39-0906015423; Fax: +39-090669007; E-mail:
Caruso G, Caruso R (2015) Escherichia coli Viability in Coastal Marine Environments: A Case Study. J Clin Microbiol Biochem Technol 1(1): 020-027..
© 2015 Caruso G, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Seawater; Coastal monitoring; Escherichia coli; Viability; CTC; PI
E. coli: Escherichia coli; FC: Fecal Coliforms; FA: Fluorescent Antibody; FITC: Fluorescein Isothiocyanate Conjugate; CTC: 5-Cyano-2,3-ditolyl Tetrazolium Chloride; VBNC: Viable But Not Culturable; PI: Propidium Iodide; DVC: Direct Viable Count;
Background: The assessment of the bacteriological quality of coastal marine waters through the search of Escherichia colias an indicator of fecal pollution is a topic of public concern.
The context and purpose of the study: During a coastal monitoring program, the abundance and distribution of the actively respiring and dead fraction within the total E. coli population along the Messina coastline (Sicily, Italy) were investigated using a fluorescent-antibody method coupled with the stains 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) or propidium iodide (PI) in order to assess the potential risk related to the viability of this microorganism.
Results: This study confirm that the proposed analytical protocols are suitable for E. coli monitoring in seawater, providing in a short time (less than 2 hours from sampling) results comparable to plate count methods currently in use.
Main findings: The obtained E. coli counts showed spatial and temporal variations - although not significant - in the percentage of CTC+ cells, suggesting that some cells were still retaining their viability properties, and their abundance was affected by the presence of streams and by the hydrodynamic regimen of the Messina Straits.
Conclusions: This study is a contribution to the knowledge of the distribution and viability properties of E. coli present in the waters of Messina coastline in terms of its active and dead components.
Brief summary: The cell viability assay through fluorescent antibody and viability dyes offers an interesting research perspective, with important implications for a more reliable estimate of the bacteriological quality of seawater.
Any potential implications: The determination of the different physiological states coexisting within the E. coli population is of great significance for human health protection, since it may provide information on the effective risk played by the living component of this microorganism.
The assessment of the bacteriological quality of coastal waters is a topic of public concern and has important implications on the activities (i.e. aquaculture, fishing, tourism) pursued in coastal and transitional areas. The anthropogenic impact on coastal environments is a function of the human density along the coasts, assuming different aspects, such as eutrophication, spread of sewage wastes or organic pollution. The pollutant inputs cause the worsening of water quality, resulting in limitations of their recreational and productive uses, and involving serious risks to human health. The risk of contracting waterborne diseases is strictly dependent on the level of fecal pollution of aquatic environments. The monitoring of the health quality of coastal waters is critical to readily detect areas exposed to potential pollution (“early warning”) and establish appropriate remediation measures in order to prevent the outbreak of infectious diseases.
Escherichia coliis recognized as the main bacterial indicator of faecal contamination for monitoring the hygienico-sanitary quality of coastal seawater for recreational use [1,2].
The search for rapid analytical methods for the detection of bacterial pathogens in seawater aims at overcoming the limitations of conventional culture methods in terms of long analysis times and response, which hinder their application in environmental monitoring.
Of particular interest is also the assessment of cell viability of fecal bacteria, which is crucial for human safety. The enteric bacteria introduced in the aquatic environment can survive in a “Viable But Not Culturable” state ; under this form, they lose the ability to grow on culture media, keeping however some physiological activities, with potential risks related to the possibility of recovery of pathogenicity when environmental conditions become favorable . This underlines the importance of determining the physiological state of potentially pathogenic bacteria present in the water.
The present note refers to the distribution of E. coli cells in some coastal sites along the town of Messina (Sicily, Italy), focusing in particular on the fraction of cells keeping some viability properties, such as culturability, active respiratory metabolism and membrane integrity. To this goal, a protocol based on the combination of a typical indirect fluorescent antibody (FA) method with the viability stains 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) and propidium iodide (PI) was used.
Materials and Methods
Five stations located along the shoreline of the Messina Straits, further indicated as North coastline, Annunziata stream, S. Francis Pier, Europa and Tremestieri (Figure 1), were sampled during several months, June, October-December, January, March-April, corresponding to the summer, autumn, Winter and Spring seasons, respectively. A sterile plastic bottle was used for collection of 1-litre sample, which was kept at +5°C until analysis and treated within 2 hours from sampling.