Antibiotic Resistance is Widespread in Urban Aquatic Environments of Rio de Janeiro, Brazil

Bacterial resistance to antibiotics has become a public health issue. Over the years, pathogenic organisms with resistance traits have been studied due to the threat they pose to human well-being. However, several studies raised awareness to the often disregarded importance of environmental bacteria as sources of resistance mechanisms. In this work, we analyze the diversity of antibiotic-resistant bacteria occurring in aquatic environments of the state of Rio de Janeiro, Brazil, that are subjected to distinct degrees of anthropogenic impacts. We access the diversity of aquatic bacteria capable of growing in increasing ampicillin concentrations through 16S rRNA gene libraries. This analysis is complemented by the characterization of antibiotic resistance profiles of isolates obtained from urban aquatic environments. We detect communities capable of tolerating antibiotic concentrations up to 600 times higher than the clinical levels. Among the resistant organisms are included potentially pathogenic species, some of them classified as multiresistant. Our results extend the knowledge of the diversity of antibiotic resistance among environmental microorganisms and provide evidence that the diversity of drug-resistant bacteria in aquatic habitats can be influenced by pollution

Environmental distribution of bacterial orders.

<p>Canonical correspondence analysis of sampling sites libraries from JM(e), BL(e) and JOA(e). Environmental parameters included in this analysis are: total phosphorus (Ptotal), ammonia (NH₃), turbidity (Turb), nitrite (NO₂⁻), temperature (Temp), salinity (Sal), pH, nitrate (NO₃⁻), dissolved oxygen (OD) and orthophosphate (PO₄⁻).</p

Match and similarities between bacterial communities.

<p>Principal coordinates plots (PCoA) were generated using the pairwise unweighted UniFrac distances. (<b>A</b>) Comparison between libraries from bulk-environmental DNA (BE), enrichment Cultures (EC) and isolates. (<b>B</b>) Comparison between bulk-environmental DNA libraries (e) of marine (JOA), brackish (BL) and freshwater (JM) sampling points, and (<b>C</b>) Comparison between enrichment culture libraries (c) of marine (JOA), brackish (BL) and freshwater (JM) sampling points. Venn diagrams (<b>D</b>) from libraries of bulk-environmental DNA (BE), enrichment cultures (EC) and isolates. (<b>E</b>) Venn diagrams from bulk-environmental DNA libraries (e) of marine (JOA), brackish (BL) and freshwater (JM) sampling points, and (<b>F</b>) Venn diagrams from enrichment culture libraries (c) of marine (JOA), brackish (BL) and freshwater (JM) sampling points.</p

Phylogenetic tree of bacterial clones from BHI enriched culture.

<p>Reference sequences from GenBank showcased in bold. OTUs were defined by using a distance level of 3% by using the furthest neighbor algorithm in MOTHUR. Access number from each OTU is displayed. Tree topology is based on neighbor joining and bootstrap analysis was performed with 1000 replications. Bootstrap value <50 are not shown.</p

Bacterial taxonomic classes in environmental and cultured libraries.

<p>Sequences obtained from 16S rRNA gene libraries retrieved from environmental samples (black) and from enrichment cultures (grey) taxonomic assignment was performed through the RDP Classifier tool.</p

Phylogenetic tree of bacterial clones from environmental bulk DNA.

<p>Reference sequences from GenBank are shown in bold. OTUs were defined by using a distance level of 3% by the furthest neighbor algorithm in MOTHUR. Access number from each OTU is displayed. Tree topology is based on neighbor joining and bootstrap analysis was performed with 1000 replications. Bootstrap value <50 are not shown.</p

Physico-chemical data from sampling stations.¹

*<p><i>MiliSiemens</i> – mS/cm; ** Nefelométric Turbidity Unity – NTU; *** mg/L.</p>1<p>Additional information on physico-chemical parameters of the sampling sites can be found at INEA (<a href="http://www.inea.rj.gov.br" target="_blank">http://www.inea.rj.gov.br</a>).</p

Sampling sites and experimental strategy.

<p>Stars (<>\vskip -1 \scale 60%\raster="rg1"<>) mark sampling points in the lagoon system.</p