Division for Marine and Environmental Research, Ruđer Bošković Institute, Bijenička 54, P.O. Box 180, 10 002 Zagreb, Croatia.
Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, P.O. Box 180, 10 002 Zagreb, Croatia.
Sci Total Environ. 2020 Dec 20;749:142357. doi: 10.1016/j.scitotenv.2020.142357. Epub 2020 Sep 14.
Environments polluted with excessively high levels of antibiotics released from manufacturing sites can act as a source of transferable antibiotic resistance (AR) genes to human commensal and pathogenic bacteria. The aim of this study was to evaluate AR of bacteria isolated from the Sava river sediments (Croatia) at the discharge site of effluents from azithromycin production compared to those from the upstream site and isolates collected in Croatian hospitals. A total of 228 environmental strains of azithromycin-resistant bacteria were isolated and identified, with 124 from the discharge site and 104 from the upstream site. In addition, a total of 90 clinical, azithromycin-resistant streptococcal and staphylococcal isolates obtained from the Croatian Reference Center for Antibiotic Resistance Surveillance were analyzed. PCR screening of isolates on 11 relevant macrolide-resistance genes (MRGs) showed that discharge isolates had greater detection frequencies for 4 gene targets (ermB, msrE, mphE and ermF) compared to upstream isolates. Among clinical isolates, the most frequently detected gene was ermB, followed by msrD, mefE and mefC. The discharge site demonstrated a greater abundance of isolates with co-occurrence of two different MRGs (predominantly msrE-mphE) than the upstream site, but a lower abundance than the clinical sources (most commonly msrD-mefE). The simultaneous presence of three or even four MRGs was specific for the discharge and clinical isolates, but not for the upstream isolates. When MRG results were sorted by gene mechanism, the ribosomal methylation (erm) and protection genes (msr) were the most frequently detected among both the discharge and the clinical isolates. Following sequencing, high nucleotide sequence similarity was observed between ermB in the discharge isolates and the clinical streptococcal isolates, suggesting a possible transfer of the ermB gene between bacteria of clinical and environmental origin. Our study highlights the importance of environmental bacterial populations as reservoirs for clinically relevant macrolide-resistance genes.
环境中抗生素水平过高会导致可转移抗生素耐药性（AR）基因转移到人类共生菌和病原菌中。本研究旨在评估从阿奇霉素生产废水排放点和上游点分离的以及从克罗地亚医院收集的细菌的 AR。共分离和鉴定了 228 株阿奇霉素耐药菌环境株，其中 124 株来自排放点，104 株来自上游点。此外，还分析了从克罗地亚抗生素耐药监测参考中心获得的 90 株临床、阿奇霉素耐药链球菌和葡萄球菌分离株。对 11 种相关大环内酯类耐药基因（MRGs）的分离物 PCR 筛选显示，与上游分离物相比，排放分离物对 4 种基因靶标（ermB、msrE、mphE 和 ermF）的检测频率更高。在临床分离株中，最常检测到的基因是 ermB，其次是 msrD、mefE 和 mefC。与上游分离物相比，排放点的分离物中两种不同 MRGs（主要是 msrE-mphE）共存的比例更高，但与临床来源相比则较低（最常见的是 msrD-mefE）。同时存在三种甚至四种 MRGs 是排放和临床分离株的特征，但不是上游分离株的特征。当按基因机制对 MRG 结果进行分类时，核糖体甲基化（erm）和保护基因（msr）是排放和临床分离株中最常检测到的基因。测序后，观察到排放分离株中的 ermB 与临床链球菌分离株的核苷酸序列高度相似，表明 ermB 基因可能在临床和环境来源的细菌之间发生了转移。我们的研究强调了环境细菌种群作为临床相关大环内酯类耐药基因库的重要性。
