Antibiotic resistance and prevalence of class 1 and 2 integrons in Escherichia coli isolated from two wastewater treatment plants, and their receiving waters (Gulf of Gdansk, Baltic Sea, Poland).

Ewa Kotlarska,Marta Pisowacka,Artur Burzyński,Aneta Łuczkiewicz

doi:10.1007/s11356-014-3474-7

Abstract

In this study, antimicrobial-resistance patterns were analyzed in Escherichia coli isolates from raw (RW) and treated wastewater (TW) of two wastewater treatment plants (WWTPs), their marine outfalls (MOut), and mouth of the Vistula River (VR). Susceptibility of E. coli was tested against different classes of antibiotics. Isolates resistant to at least one antimicrobial agent were PCR tested for the presence of integrons. Ampicillin-resistant E. coli were the most frequent, followed by amoxicillin/clavulanate (up to 32 %), trimethoprim/sulfamethoxazole (up to 20 %), and fluoroquinolone (up to 15 %)-resistant isolates. Presence of class 1 and 2 integrons was detected among tested E. coli isolates with rate of 32.06 % (n = 84) and 3.05 % (n = 8), respectively. The presence of integrons was associated with increased frequency of resistance to fluoroquinolones, trimethoprim/sulfamethoxazole, amoxicillin/clavulanate, piperacillin/tazobactam, and presence of multidrug-resistance phenotype. Variable regions were detected in 48 class 1 and 5 class 2 integron-positive isolates. Nine different gene cassette arrays were confirmed among sequenced variable regions, with predominance of dfrA1-aadA1, dfrA17-aadA5, and aadA1 arrays. These findings illustrate the importance of WWTPs in spreading of resistance genes in the environment and the need for inclusion of at least monitoring efforts in the regular WWTP processes.

Highlights

Safe and economical way of wastewater disposal is an important problem requiring proper receiver-oriented management
The objective of this study was to investigate antibioticresistance profiles in E. coli isolated from two local wastewater treatment plants, their marine outfalls located in the Gulf of Gdansk, the Baltic Sea (Poland), and from major tributary of the Baltic Sea—the Vistula River
The impact posed by treated wastewater on the receiving waters was evaluated using E. coli isolates

Summary

Introduction

Safe and economical way of wastewater disposal is an important problem requiring proper receiver-oriented management. Wastewater treatment focuses mainly on parameters that may cause oxygen depletion and eutrophication of the receiving waters: organic matter, nitrogen, and phosphorus. Other important aspects of wastewater discharge are currently under debate. It is suspected that clinically relevant bacteria and mobile genetic elements can survive the wastewater treatment plant processes (Reinthaler et al 2003; D’Costa et al 2006; Łuczkiewicz et al 2010) and be disseminated in the receiving waters (Iwane et al 2001; Li et al 2009; Czekalski et al 2012). Human-associated bacteria are regarded as important vectors of gene transmission (D’Costa et al 2006). Domestic and municipal wastewater should be considered in global antibiotic resistance gene dissemination

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