Enterococci in the New Zealand environment: implications for water quality monitoring

Abstract

Faecal enterococci ecology outside the host is of great relevance when using these organisms as indicators of water quality. As a complement to New Zealand epidemiological studies of bathing water quality and health risk, a study of the environmental occurrence of these organisms has been undertaken. Specific concerns over the use of enterococci derive from the unique situation in New Zealand which has few chlorinated sewage effluents, a high ratio of grazing animals to humans, and significant inputs of animal processing effluents into the environment. Human and animal faecal wastes are the main sources, with 106–107cfu/100ml found in human sewage. Analysis of domestic and feral animal faeces found enterococci in the range of 101–106cfu/g with considerable variation between species. The latter observations support the notion that a considerable proportion of the load in urban/rural catchments and waterways (typically 102–103 enterococci cfu/100ml) is derived from non-human sources. Previous studies of enterococci quiescence in marine/fresh waters indicate that they enter a non-growth phase, exposure to sunlight markedly reducing culturability on selective and non-selective media. Enterococci were also found to survive/multiply within specific non-faecal environments. Enterococci on degrading drift seaweed at recreational beaches exceeded seawater levels by 2–4 orders of magnitude, suggesting that expansion had occurred in this permissive environment with resultant potential to contaminate adjacent sand and water. These studies suggest that multiple sources, environmental persistence, and environmental expansion of enterococci within selected niches add considerable complexity to the interpretation of water quality data.

Enterococci in the Environment

“…Other aquatic macrophytes that have been identified as sources of enterococci include decaying seaweed (11,131,167). In New Zealand, Anderson et al (11) observed that the densities of enterococci in drifting seaweed exceeded those in seawater by 2 to 4 orders of magnitude; Grant et al (131) found densities of enterococci as high as a 450,000 most probable number (MPN)/100 g in a marsh in southern California.…”

“…In New Zealand, Anderson et al (11) observed that the densities of enterococci in drifting seaweed exceeded those in seawater by 2 to 4 orders of magnitude; Grant et al (131) found densities of enterococci as high as a 450,000 most probable number (MPN)/100 g in a marsh in southern California. In addition to seaweed, recent studies have expanded the occurrence of enterococci to submerged aquatic vegetation (SAV) (mostly Hydrilla verticillata) (15,16).…”

Ubiquity and Persistence of Escherichia coli in a Midwestern Coastal Stream

“…Regulatory and management agencies generally assume that the source of E. coli is humans and warm-blooded animals. However, it has become increasingly clear that E. coli and other fecal bacterial indicators (e.g., enterococci) can persist and perhaps replicate in soil and water and on plants under certain tropical and even temperate conditions (2,4,10,14,17,19,24). Nonpoint sources generated within the watershed are generally ignored in most sanitary surveys because there is limited acceptance of the existence of significant background reservoirs of E. coli (15).…”

Emissários submarinos de esgotos como alternativa à minimização de riscos à saúde humana e ambiental

“…A significant correlation has been found between coliform decay rates and solar radiation levels 7,[9][10][11][12][13][15][16][17][18][19][20][21][22][23][24] . Pathogenic microorganisms such as Giardia, Cryptosporidium, Poliovirus e Salmonella presented a higher survival in the absence of solar radiation 25 .…”