Affiliation:
1. Department of Marine Sciences, Polytechnic University of Marche, Ancona, Italy
2. Department of Biomedical Sciences, Section of Microbiology, Polytechnic University of Marche, Ancona, Italy
3. Istituto Superiore per la Ricerca e Protezione Ambientale, Rome, Italy
Abstract
ABSTRACT
Despite the recognized potential of long-term survival or even growth of fecal indicators bacteria (FIB) in marine sediments, this compartment is largely ignored by health protection authorities. We conducted a large-scale study over approximately 50 km of the Marche coasts (Adriatic Sea) at depths ranging from 2 to 5 m. Total and fecal coliforms (FC) were counted by culture-based methods.
Escherichia coli
was also quantified using fluorescence
in situ
hybridization targeting specific 16S rRNA sequences, which yielded significantly higher abundances than culture-based methods, suggesting the potential importance of viable but nonculturable
E. coli
cells. Fecal coliforms displayed high abundances at most sites and showed a prevalence of
E. coli.
FC isolates (
n
= 113) were identified by API 20E, additional biochemical tests, and internal transcribed spacer-PCR.
E. coli
strains, representing 96% of isolates, were then characterized for genomic relatedness and phylogenetic group (A, B1, B2, and D) of origin by randomly amplified polymorphic DNA and multiplex-PCR. The results indicated that
E. coli
displayed a wide genotypic diversity, also among isolates from the same station, and that 44 of the 109
E. coli
isolates belonged to groups B2 and D. Further characterization of B2 and D isolates for the presence of 11 virulence factor genes (
pap
,
sfa/foc
,
afa
,
eaeA
,
ibeA
,
traT
,
hlyA
,
stx
1
,
stx
2
,
aer
, and
fyuA
) showed that 90% of B2 and 65% of D isolates were positive for at least one of these. Most of the variance of both
E. coli
abundance and assemblage composition (>62%) was explained by a combination of physical-chemical and trophic variables. These findings indicate that coastal sediments could represent a potential reservoir for commensal and pathogenic
E. coli
and that
E. coli
distribution in marine coastal sediments largely depends upon the physical and trophic status of the sediment. We conclude that future sampling designs aimed at monitoring the microbiological quality of marine coastal areas should not further neglect the analysis of the sediment and that monitoring of these environments can be improved by including molecular methods as a complement of culture-based techniques.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology