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Figure 2.3(c). Occurrence of epidemiologic strains of Enterococcus, carrying the
DNA sequence marker CC17, within the population of Enterococcus faecium, along
the medical center-WWTP-river continuum (Leclercq et al., 2013) [LEC 13]
2.4. Estuary sediments: a vulnerable environment?
2.4.1. The resistome in estuary sediments
Bacteria of fecal origin and the chemical contaminants associated
with them (trace metals, organic contaminants and antibiotics) are
deposited on the mudflats, where bacteria rapidly lose their
cultivability. Thus, these mudflats could be a suitable area for
remedial capacity [BER 08]. However, the molecular detection of
class 1 integrons in the mudflats along the Risle-estuary transect,
where no culturable bacteria is present, suggests that the sediments of
an anthropized estuary could be a favorable environment for the
persistence of the DNA of fecal bacteria, and therefore, potentially for
antibiotic resistance genes. This area could therefore constitute a
favorable environment for the horizontal gene transfer mainly by
transformation and/or transposition 5 .
2.4.2. Impact of contamination by antibiotics on the functional
microbial community of sediments
Whereas concentrations of antibiotics are a priori too low to exert
a selective pressure on the environmental biota or the microbiota in
5 Incorporation of nucleic acids synthesized outside the genome.
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