**Identification of Selected Antibiotic Resistance Genes in Two Di** ff**erent Wastewater Treatment Plant Systems in Poland: A Preliminary Study**

#### **Magdalena Pazda 1, Magda Rybicka 2, Stefan Stolte 3, Krzysztof Piotr Bielawski 2, Piotr Stepnowski 1,\*, Jolanta Kumirska 1, Daniel Wolecki 1 and Ewa Mulkiewicz 1**


Academic Editor: Teresa A. P. Rocha-Santos Received: 30 April 2020; Accepted: 18 June 2020; Published: 20 June 2020

**Abstract:** Antibiotic resistance is a growing problem worldwide. The emergence and rapid spread of antibiotic resistance determinants have led to an increasing concern about the potential environmental and public health endangering. Wastewater treatment plants (WWTPs) play an important role in this phenomenon since antibacterial drugs introduced into wastewater can exert a selection pressure on antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Therefore, WWTPs are perceived as the main sources of antibiotics, ARB and ARG spread in various environmental components. Furthermore, technological processes used in WWTPs and its exploitation conditions may influence the e ffectiveness of antibiotic resistance determinants' elimination. The main aim of the present study was to compare the occurrence of selected tetracycline and sulfonamide resistance genes in raw influent and final e ffluent samples from two WWTPs di fferent in terms of size and applied biological wastewater treatment processes (conventional activated sludge (AS)-based and combining a conventional AS-based method with constructed wetlands (CWs)). All 13 selected ARGs were detected in raw influent and final e ffluent samples from both WWTPs. Significant ARG enrichment, especially for *tet*(*B*, *K*, *L*, *O*) and *sulIII* genes, was observed in conventional WWTP. The obtained data did not show a clear trend in seasonal fluctuations in the abundance of selected resistance genes in wastewaters.

**Keywords:** antibiotic resistance genes (ARGs); antibiotic-resistant bacteria (ARB); wastewater treatment plants (WWTPs); activated sludge (AS); constructed wetlands (CWs); environmental pollution; spread of resistance; tetracyclines; sulfonamides
