Resistance to Broad-Spectrum Antibiotics in Aquatic Systems: Anthropogenic Activities Modulate the Dissemination of bla _CTX-M -Like Genes

Abstract

We compared the resistomes within polluted and unpolluted rivers, focusing on extended-spectrum beta-lactamase (ESBL) genes, in particular bla CTX-M . Twelve rivers from a Portuguese hydrographic basin were sampled. Physicochemical and microbiological parameters of water quality were determined, and the results showed that 9 rivers were classified as unpolluted (UP) and that 3 were classified as polluted (P). Of the 225 cefotaxime-resistant strains isolated, 39 were identified as ESBL-producing strains, with 18 carrying a bla CTX-M gene (15 from P and 3 from UP rivers). Analysis of CTX-M nucleotide sequences showed that 17 isolates produced CTX-M from group 1 (CTX-M-1, -3, -15, and -32) and 1 CTX-M that belonged to group 9 (CTX-M-14). A genetic environment study revealed the presence of different genetic elements previously described for clinical strains. ISEcp1 was found in the upstream regions of all isolates examined. Culture-independent bla CTX-M -like libraries were comprised of 16 CTX-M gene variants, with 14 types in the P library and 4 types in UP library, varying from 68% to 99% similarity between them. Besides the much lower level of diversity among CTX-M-like genes from UP sites, the majority were similar to chromosomal ESBLs such as bla RAHN-1 . The results demonstrate that the occurrence and diversity of bla CTX-M genes are clearly different between polluted and unpolluted lotic ecosystems; these findings favor the hypothesis that natural environments are reservoirs of resistant bacteria and resistance genes, where anthropogenic-driven selective pressures may be contributing to the persistence and dissemination of genes usually relevant in clinical environments.

Aeromonas spp. simultaneously harbouring blaCTX-M-15, blaSHV-12, blaPER-1 and blaFOX-2, in wild-growing Mediterranean mussel (Mytilus galloprovincialis) from Adriatic Sea, Croatia

“…Aeromonas strains from river water were reported to carry bla CTX-M-27 (Lu et al, 2010) and bla CTX-M-3 (Tacăo et al, 2012), while bla CTX-M-15 gene was previously identified only in a clinical isolate of A. hydrophila (Gómez-Garcés et al, 2011). The production of SHV ESBLs has been even more rarely detected in Aeromonas spp.…”

“…It has been found that environmental pollution strongly contributes to the promotion of antibiotic resistance traits in Aeromonas spp. (Figueira et al, 2011;Tacăo et al, 2012), particularly in term of acquisition of resistance determinants not intrinsic to this genus (Henriques et al, 2006;Girlich et al, 2011;Tacăo et al, 2012). Thus, we considered the Kaštela Bay a good model for studying the prevalence and genetic background of antibiotic resistance in aeromonads.…”

Characteristics of Extended-Spectrum β-Lactamase- and Carbapenemase-Producing Enterobacteriaceae Isolates from Rivers and Lakes in Switzerland

“…The number of studies investigating rivers as potential reservoirs of ESBL producers is still very limited (19,20,21,22,23), and data from only one river (Seine River, Paris, France) in central Europe are available (22). Rivers and lakes are considered especially relevant as putative reservoirs of multiresistant bacteria, since they collect surface waters containing materials from different origins, e.g., wastewater plants, water of urban or industrial effluents, agricultural activities, or rain.…”

Trends in Human Fecal Carriage of Extended-Spectrum β-Lactamases in the Community: Toward the Globalization of CTX-M

“…This has been the case not only for wastewater in China (24), the Czech Republic (25), Austria (26), India (27), Brazil (28), and Congo (29) but also for many rivers or aquatic ecosystems. ESBL-E have indeed been isolated from well water in Nicaragua (30) and from diverse other aquatic environments in Switzerland (31), the United Kingdom (32), China (33), South Korea (34), Portugal (35), and Tunisia (36). Even seawater from beaches in Algeria (37) and water from the Antarctic have been found to be positive for ESBL-E (38), suggesting that the current reservoir of these bacteria is in reality massive (Fig.…”