摘要

      在撒哈拉以南非洲，大约有10亿人居住，很少有关于抗生素耐药基因（ARG）对环境造成污染的信息。在这项研究中，我们用qPCR测定了三个基因（sul1、sul2和intI1）的丰度，作为尼日利亚西南部四个城市湿地沉积物中ARGs污染环境的指标。此外，我们还通过PCR和DNA测序分析了从湿地分离的抗磺胺甲恶唑/甲氧苄啶（SMX/TRI）细菌中1类整合子的可变区。所有湿地中均存在指示ARGs，sul1的平均绝对拷贝数/克沉积物介于4.7x106和1.2x108之间，sul2的平均绝对拷贝数/克沉积物介于1.1x107和1x108之间，intI1的平均绝对拷贝数/克沉积物介于5.3x105和1.9x107之间。相对丰度（ARG/16srrna拷贝数）在10-3～10-1之间。这些ARG污染水平与之前报道的世界其他地区污染环境的水平相似。整合酶基因intI1和intI2分别在72%和11.4%的SMX/TRI耐药菌株中检测到。在34株（59.6%）阳性菌株中检测到5种不同的盒阵列类型（dfrA7；aadA2；aadA1 | dfrA1；acc（6’）lb-cr | arr3 | dfrA27；arr3 | acc（6’）lb-cr | dfrA27）。在9株intI2阳性菌株中未发现基因盒。这些结果表明，受人为活动影响的非洲城市生态系统是携带可转移ARG的细菌库。

       There is little information about environmental contamination with antibiotic resistance genes (ARG) in Sub-Saharan Africa, home to about 1 billion people. In this study we measured the abundance of three genes (sul1, sul2, and intI1) used as indicators of environmental contamination with ARGs in the sediments of four urban wetlands in southwestern Nigeria by qPCR. In addition, we characterised the variable regions of class 1 integrons in sulfamethoxazole/trimethoprim (SMX/TRI)-resistant bacteria isolated from the wetlands by PCR and DNA sequencing. The indicator ARGs were present in all wetlands with mean absolute copy numbers/gram of sediment ranging between 4.7x106 and 1.2x108 for sul1, 1.1x107 and 1x108 for sul2, and 5.3x105 and 1.9x107 for intI1. The relative abundances (ARG/16S rRNA copy number) ranged from about 10-3 to 10-1. These levels of ARG contamination were similar to those previously reported for polluted environments in other parts of the world. The integrase genes intI1 and intI2 were detected in 72% and 11.4% SMX/TRI-resistant isolates, respectively. Five different cassette array types (dfrA7; aadA2; aadA1|dfrA1; acc(6')lb-cr|arr3|dfrA27; arr3|acc(6')lb-cr|dfrA27) were detected among 34 (59.6%) intI1-positive isolates. No gene cassettes were found in the nine intI2-positive isolates. These results show that African urban ecosystems impacted by anthropogenic activities are reservoirs of bacteria harbouring transferable ARG.

        https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6264143/