Antibiotic resistance continues to be an emerging threat both in clinical and environmental settings. Among the many causes, the impact of postchlorinated human wastewater on antibiotic resistance has not been well studied. Our study compared antibiotic susceptibility among Aeromonas spp. in postchlorinated effluents to that of the recipient riverine populations for three consecutive years against 12 antibiotics. Aeromonas veronii and Aeromonas hydrophila predominated among both aquatic environments, although greater species diversity was evident in treated wastewater. Overall, treated wastewater contained a higher prevalence of nalidixic acid-, trimethoprim-sulfamethoxazole (SXT)-, and tetracycline-resistant isolates, as well as multidrug-resistant (MDR) isolates compared to upstream surface water. After selecting for tetracycline-resistant strains, 34.8% of wastewater isolates compared to 8.3% of surface water isolates were multidrug resistant, with nalidixic acid, streptomycin, and SXT being the most common. Among tetracycline-resistant isolates, efflux pump genes tetE and tetA were the most prevalent, though stronger resistance correlated with tetA. Over 50% of river and treated wastewater isolates exhibited cytotoxicity that was significantly correlated with serine protease activity, suggesting many MDR strains from effluent have the potential to be pathogenic. These findings highlight that conventionally treated wastewater remains a reservoir of resistant, potentially pathogenic bacterial populations being introduced into aquatic systems that could pose a threat to both the environment and public health.

IMPORTANCE Aeromonads are Gram-negative, asporogenous rod-shaped bacteria that are autochthonous in fresh and brackish waters. Their pathogenic nature in poikilotherms and mammals, including humans, pose serious environmental and public health concerns especially with rising levels of antibiotic resistance. Wastewater treatment facilities serve as major reservoirs for the dissemination of antibiotic resistance genes (ARGs) and resistant bacterial populations and are, thus, a potential major contributor to resistant populations in aquatic ecosystems. However, few longitudinal studies exist analyzing resistance among human wastewater effluents and their recipient aquatic environments. In this study, considering their ubiquitous nature in aquatic environments, we used Aeromonas spp. as bacterial indicators of environmental antimicrobial resistance, comparing it to that in postchlorinated wastewater effluents over 3 years. Furthermore, we assessed the potential of these resistant populations to be pathogenic, thus elaborating on their potential public health threat.

在临床和环境中，抗生素耐药性仍然是新兴的威胁。在许多原因中，尚未充分研究后氯化人类废水对抗生素耐药性的影响。我们的研究比较了气单胞菌之间的抗生素敏感性。连续三年对接收者河流人口的后氯化废水排放量进行了比较，结果表明它们对12种抗生素的使用情况没有变化。Veronii气单胞菌和亲水性气单胞菌尽管在经过处理的废水中物种多样性更大，但在两种水生环境中都占主导地位。总体而言，与上游地表水相比，处理后的废水中萘啶酸，甲氧苄啶，磺胺甲恶唑（SXT）和耐四环素的分离株以及耐多药（MDR）的分离株患病率更高。选择四环素抗性菌株后，有34.8％的废水分离物与8.3％的地表水分离物具有多药耐药性，其中萘啶酸，链霉素和SXT最常见。在四环素抗性分离株中，外排泵基因tetE和tetA最普遍，尽管较强的抗性与tetA相关。超过50％的河流和处理过的废水分离株表现出与丝氨酸蛋白酶活性显着相关的细胞毒性，这表明许多废水中的MDR菌株具有致病性。这些发现表明，经过常规处理的废水仍然是耐药菌的潜在潜在病原菌种群，这些种群被引入水生系统，可能对环境和公共健康构成威胁。

重要提示：气单胞菌是革兰氏阴性，孢子状棒状细菌，在淡水和微咸水中都是自生的。它们在高温疗法和哺乳动物（包括人类）中的致病性引起严重的环境和公共卫生问题，尤其是随着抗生素耐药性水平的提高。废水处理设施是传播抗生素抗性基因（ARG）和抗药性细菌种群的主要水库，因此是水生生态系统中抗药性种群的潜在主要贡献者。然而，很少有纵向研究来分析人类废水及其接收者的水生环境之间的抵抗力。在这项研究中，考虑到它们在水生环境中的普遍性，我们使用了气单胞菌spp。作为环境抗微生物性的细菌指标，将其与3年后的氯化后废水进行比较。此外，我们评估了这些耐药人群的致病性，从而详细说明了其潜在的公共卫生威胁。