Persistence and diversity of faecal coliform and enterococci populations in faecally polluted waters

Abstract

Aim: To assess the persistence and diversity of faecal bacterial populations (faecal coliforms and enterococci) that have recently been included in microbial source tracking (MST) predictive models. Methods and Results: The analysed bacterial populations included members of the enterococci group (ENT) [Enterococcus faecium (FM), Enterococcus faecalis (FS) and Enterococcus hirae (HIR)] and the faecal coliform group (FC) [diverse Escherichia coli phenotypes (ECP) and cellobiose‐negative faecal coliforms (CNFC)]. The inactivation of these distinct groups was monitored over time on‐site in river by biochemical fingerprinting, and diversity indices were calculated. Among the different analysed species belonging to the ENT group, HIR persisted longer and was able to replicate in the environment at a higher rate. On the other hand, ECP and NCFC showed a similar persistence throughout the different seasons. The diversity index (Di) for FC increased substantially in the summer after 96 h to a maximum value of 0·96. On the other hand, the Di for ENT diminished over the same period to a value of 0·86, suggesting a different persistence for the different species integrating this group. Conclusions: The persistence of ECP, CNFC, FM and FS in the aquatic environment is high, particularly for the members of the FC and in the summer season. On the contrary, HIR is able to replicate in the environment at a high rate even in winter, and therefore, its inclusion in MST predictive models is discouraged. Significance and Impact of the Study: ECP, CNFC, FMFS and HIR have been proposed as additional variables in MST predictive models. However, the different persistence of HIR compared with the other variables should be taken into account for the development of such models.

Changes in Enterococcal Populations and Related Antibiotic Resistance along a Medical Center-Wastewater Treatment Plant-River Continuum

“…However, since sampling was performed only in December, we cannot rule out the influence of seasonal variations not only on the amounts of enterococci in water but also on the relative proportions of the various enterococcal species (23). In a recent study, persistence of enterococci in winter months in water was dependent upon the bacterial species (24). In particular, E. hirae was able to replicate in the environment at a high rate even in winter.…”

Predicting fecal sources in waters with diverse pollution loads using general and molecular host-specific indicators and applying machine learning methods

“…The system also estimated the importance of each indicator in the training matrix at different concentration levels, generating a heat map that presents all MST indicators sorted by the frequency with which they were selected by the best predictive models at each level of aging and dilution. Since persistence in the environment is dependent on season, the importance of indicators and MST methods in two different seasons (summer and winter) was taken into account (Ballesté and Blanch, 2010;Bonjoch et al, 2011Bonjoch et al, , 2009Muniesa et al, 1999).…”