Indicator organisms for estuarine and marine waters

Abstract

The use of indicator organisms for estuarine and coastal waters has been reviewed. The natural flora of the environment must be considered in selecting an indicator organism, but, more importantly, recent work which shows a viable but non-recoverable stage of pathogens entering the marine environment demonstrates that the conventional detection of indicator microorganisms is misleading, if not inaccurate. Results suggest that the newly developed epifluorescent/immunofluorescent direct detection of pathogens in the environment may be the most reliable method for determining public health hazards in marine and estuarine waters. INTRODUCTIONThe microbiology of the world oceans and coastal waters has been under study since the late nineteenth century. Among the earliest investigations concerning the number of bacteria and their * To whom correspondence should be addressed. distribution in seawater was that of Russell [1][2][3] who conducted a survey of the distribution of bacteria in the Gulf of Naples. The early workers established general distributional patterns for bacteria in the sea, using agar plate and dilution methods for the enumeration of bacteria. Bacteria were found in small numbers, uniformly distributed in water several miles from shore and at all depths. Early workers also found that the water of harbors and bays may contain large numbers of bacteria, but that the number of bacteria becomes very small at comparatively short distances from shore [4,5]. The work of Fischer is, of course, classic, since he investigated sea water over a wide area of the Atlantic Ocean and found bacteria throughout, the largest numbers being found near land or in the presence of floating seaweed [6,7].Seasonal studies were done by Lloyd [8] in the Clyde Sea, where the waters are relatively shallow. the surface waters were richest in bacteria, the number decreasing with depth but usually increasing slightly at the bottom. A variety of studies was done in the early )'ears of marine microbiology, summarized by Benecke [9] and ZoBell [10]. The observation that direct microscopic examination of seawater showed bacteria to be much more abundant in seawater than cultural methods would 0168-6445/85/$03.30

Detection of induced β‐galactosidase activity in individual non‐culturable cells of pathogenic bacteria by quantitative cytological assay

“…However, in most natural environments only a limited fraction of the microbes present can be enumerated by such conventional culture techniques. Recognition that SCCs often grossly underestimate the number of a particular organism in a sample (Elliot and Colwell, 1985;Roszak and Colwell, 1987a) and that large discrepancies occur between such counts and direct cell counts determined by microscopic or other means Roszak and Colwell, 1987b;Duncan et aL, 1994) has called into question the use of culture techniques to determine the distribution, influence and properties of a particular organism. Moreover, as such discrepancies are observed in experimental monocultures (Nilsson et aL, 1991;Kaprelyants and Kell, 1992;Duncan et aL, 1994) their significance is not confined to environmental studies.…”

An improved procedure for shipboard enumeration of faecal indicator bacteria in marine sediments from sewage sludge disposal areas

“…Evidence is accumulating which suggests that debilitation with extended survival is common amongst faecal bacteria exposed to natural aquatic environments (Xu et al 1983;Roszak et al 1984;Rollins & Colwell 1986;Grimes & Colwell 1986). Such 'viable but non-recoverable' (Elliot & Colwell 1985) faecal bacteria can rarely grow directly on conventional selective media at elevated incubation temperatures (Grimes et al 1986) possibly because of damage to the structure of the cell envelopes, resulting in abnormal sensitivity to selective components such as bile salts or surfactants used in isolation media (Chai 1983).…”

“…The sediment was allowed to settle before filtration of the supernatant fluid through membranes, which were incubated at 44°C on pads impregnated with 4% Teepol-lactose broth. As this medium and temperature are highly selective it is unlikely that sublethally injured cells would be recovered without a resuscitation stage (Mossel & Van Netten 1984; Elliot & Colwell 1985). In addition, since the development of the MAFF method, ultrasonication procedures for extraction of bacteria from marine sediments have been reported (Emerson & Cabelli 1982;McDaniel & Capone 1986).…”

An extracellular stress‐sensing protein is activated by heat and u.v. irradiation as well as by mild acidity, the activation producing an acid tolerance‐inducing protein

“…Enterobacteria can be exposed to a wide range of stresses in the environment (Elliott and Colwell 1985), in domestic, commercial and hospital situations, in foods and food preparation locations (Humphrey 1981) and in the animal or human body (Lee and Gemmell 1972). These stresses can be chemical, involving the effects of natural agents such as chlorine (Hicks and Rowbury 1986), acidity (Rowbury et al 1989), alkalinity (Humphrey 1981) or man-made agents such as antibiotics, antiseptics, disinfectants and detergents (Russell 1982(Russell , 1984 or can be physical agencies such as heat, cold or irradiation (Mackey and Derrick 1986;Wolffe 1995).…”