Extraintestinal Escherichia coli Carrying Virulence Genes in Coastal Marine Sediments

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 physicalchemical 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.Marine environments contaminated by fecal material, derived from human or animal waste, may contain a large variety of pathogenic microorganisms. Health protection and monitoring programs analyze the contamination of aquatic ecosystems (20) but, due to technical and practical difficulties, the search of fecal indicator bacteria (FIB) is routinely preferred to the systematic search of all potential pathogens to assess the sanitary risk of a water body (17). Recreational seawaters are, for instance, classified on the basis of the concentration of Escherichia coli and Enterococcus spp. (21,33,40), assumed to be indicators of fecal contamination and of the presence of other pathogenic enteric bacteria. Exposure to waters contaminated with E. coli and Enterococcus spp. have been associated with an increased risk of contracting gastrointes...

Antibiotic resistance and virulence genes of extraintestinal pathogenic Escherichia coli from tropical estuary, south India

“…Clinical isolates of ExPEC typically belong to phylogenetic group B2 and, to a lesser extent, group D [32]. In agreement with several authors [33][34][35], we observed a link between phylogenetic groups and extraintestinal pathogenic strains because the majority of the strains belonged predominantly to phylogenetic group B2 and, to a lesser extent, to group D, whereas they were sparsely represented within groups A and B1. Strains belonging to group B2 harboured a greater number of virulence factors compared to strains from other phylogenetic groups, suggesting a putative association between virulence factors and pathogenic potential [36].…”

New Sequence Types and Multidrug Resistance among Pathogenic Escherichia coli Isolates from Coastal Marine Sediments

“…A total of 109 E. coli strains previously isolated from marine coastal sediments in the Adriatic Sea and assigned to phylogenetic groups A (n ϭ 38), B1 (n ϭ 27), B2 (n ϭ 21), and D (n ϭ 23) were used in this study. All details regarding sampling sites and procedure, microbiological tests (including strain isolation from the sediment matrix) and the presence of virulence factors in B2 and D strains were reported by Luna et al (23). Data regarding some virulence genes frequently found in commensal and enteropathogenic strains, i.e., intimin (eaeA), toxins (east1, cnf1), and iron acquisition systems (aer, fyuA, iutA, iroN), were available for A and B1 group strains (Vignaroli et al, unpublished).…”

Tracking the Primary Sources of Fecal Pollution in a Tropical Watershed in a One-Year Study

“…For instance, currently used FIB can occur naturally in water accumulated in tropical epiphytic plants (3), can survive in tropical marine waters in the presence of nutrients (4), and can proliferate in tropical soils (5,6). Studies in Mediterranean coastal areas have shown that Escherichia coli densities are often high in the sediments, serving as important sources of FIB and pathogens (7). Collectively, these studies suggest that the detection of FIB in tropical and subtropical water systems does not strictly imply fecal origin.…”