Seasonal variations in antibiotic resistance gene transport in the almendares river, havana, cuba.

Charles W Knapp,Susana Olivares-Rieumont,Emma Bowen,David Werner,David W Graham,Lazaro Lima

doi:10.3389/fmicb.2012.00396

Abstract

Numerous studies have quantified antibiotic resistance genes (ARG) in rivers and streams around the world, and significant relationships have been shown that relate different pollutant outputs and increased local ARG levels. However, most studies have not considered ambient flow conditions, which can vary dramatically especially in tropical countries. Here, ARG were quantified in water column and sediment samples during the dry- and wet-seasons to assess how seasonal and other factors influence ARG transport down the Almendares River (Havana, Cuba). Eight locations were sampled and stream flow estimated during both seasons; qPCR was used to quantify four tetracycline, two erythromycin, and three beta-lactam resistance genes. ARG concentrations were higher in wet-season versus dry-season samples, which combined with higher flows, indicated much greater ARG transport downstream during the wet-season. However, water column ARG levels were more spatially variable in the dry-season than the wet-season, with the proximity of waste outfalls strongly influencing local ARG levels. Results confirm that dry-season sampling provides a useful picture of the impact of individual waste inputs on local stream ARG levels, whereas the majority of ARGs in this tropical river were transported downstream during the wet-season, possibly due to re-entrainment of ARG from sediments.

Highlights

Growing evidence suggests that antibiotic resistance (AR) and antibiotic resistance genes (ARG) are increasing in the environment from domestic and industrial wastewater discharges (Iwane et al, 2001; Schwartz et al, 2003; Pruden et al, 2006; Li et al, 2009; Zhang et al, 2009b), agricultural use and releases (Chee-Sanford et al, 2001; Smith et al, 2004; Pei et al, 2006; Peak et al, 2007; Martinez, 2008), and other causes (Seveno et al, 2002; Knapp et al, 2010, 2011)
Limited attention has been placed on rates of ARG movement in the environment, which may be of greater importance from an exposure perspective
This may be of particular importance when considering ARG transport in tropical streams because considerable data suggest that sediments, which may be mobilized during high flow events, are primary harbors for ARG in aquatic systems (Seveno et al, 2002; Engemann et al, 2008; Zhang et al, 2009a; Allen et al, 2010)

Summary

Introduction

Growing evidence suggests that antibiotic resistance (AR) and antibiotic resistance genes (ARG) are increasing in the environment from domestic and industrial wastewater discharges (Iwane et al, 2001; Schwartz et al, 2003; Pruden et al, 2006; Li et al, 2009; Zhang et al, 2009b), agricultural use and releases (Chee-Sanford et al, 2001; Smith et al, 2004; Pei et al, 2006; Peak et al, 2007; Martinez, 2008), and other causes (Seveno et al, 2002; Knapp et al, 2010, 2011). ARG were quantified in water column and sediment samples during the dry- and wetseasons to assess how seasonal and other factors influence ARG transport down the Almendares River (Havana, Cuba). Seasonal antibiotic resistance gene transport conditions at eight locations in the Almendares River in wet- and dry-seasons to compare ARG levels and transport rates.

Results

Conclusion