School of Natural Sciences, Macquarie University, New South Wales, Australia; Manchester Institute of Biotechnology, The University of Manchester, Greater Manchester, United Kingdom.
School of Natural Sciences, Macquarie University, New South Wales, Australia.
Sci Total Environ. 2024 Dec 1;954:176348. doi: 10.1016/j.scitotenv.2024.176348. Epub 2024 Sep 19.
Bacterial hosts in vegetable phylloplanes carry mobile genetic elements, such as plasmids and transposons that are associated with integrons. These mobile genetic elements and their cargo genes can enter human microbiomes via consumption of fresh agricultural produce, including uncooked vegetables. This presents a risk of acquiring antimicrobial resistance genes from uncooked vegetables. To better understand horizontal gene transfer of class 1 integrons in these compartments, we applied epicPCR, a single-cell fusion-PCR surveillance technique, to link the class 1 integron integrase (intI1) gene with phylogenetic markers of their bacterial hosts. Ready-to-eat salads carried class 1 integrons from the phyla Bacteroidota and Pseudomonadota, including four novel genera that were previously not known to be associated with intI1. We whole-genome sequenced Pseudomonas and Erwinia hosts of pre-clinical class 1 integrons that are embedded in Tn402-like transposons. The proximal gene cassette in these integrons was identified as a chlorite dismutase gene cassette, which we showed experimentally to confer chlorite resistance. Chlorine-derived compounds such as acidified sodium chlorite and chloride dioxide are used to disinfectant raw vegetables in food processing facilities, suggesting selection for chlorite resistance in phylloplane integrons. The spread of integrons conferring chlorite resistance has the potential to exacerbate integron-mediated antimicrobial resistance (AMR) via co-selection of chlorite resistance and AMR, thus highlighting the importance of monitoring chlorite residues in agricultural produce. These results demonstrate the strength of combining epicPCR and culture-based isolation approaches for identifying hosts and dissecting the molecular ecology of class 1 integrons.
叶际细菌宿主携带可移动遗传元件，如质粒和转座子，它们与整合子有关。这些可移动遗传元件及其携带的基因可以通过食用新鲜农产品（包括未煮熟的蔬菜）进入人体微生物组。这就带来了从未煮熟的蔬菜中获得抗生素耐药基因的风险。为了更好地了解这些环境中类 1 整合子的水平基因转移，我们应用了 epicPCR，一种单细胞融合-PCR 监测技术，将类 1 整合子整合酶（intI1）基因与细菌宿主的系统发育标记物联系起来。即食沙拉携带来自拟杆菌门和假单胞菌门的类 1 整合子，包括以前不知道与 intI1 相关的四个新属。我们对临床前类 1 整合子的假单胞菌和欧文氏菌宿主进行了全基因组测序，这些整合子嵌入在 Tn402 样转座子中。这些整合子中近端基因盒被鉴定为亚氯酸盐歧化酶基因盒，我们通过实验证明该基因盒赋予了亚氯酸盐抗性。在食品加工设施中，用于消毒生蔬菜的含氯化合物如酸化亚氯酸钠和二氧化氯，表明叶际整合子中选择了亚氯酸盐抗性。携带亚氯酸盐抗性的整合子的传播有可能通过亚氯酸盐抗性和抗生素耐药性的共同选择加剧整合子介导的抗生素耐药性（AMR），因此强调了监测农业生产中氯酸盐残留的重要性。这些结果表明，结合 epicPCR 和基于培养的分离方法来识别宿主和剖析类 1 整合子的分子生态学具有优势。
