Tacão Marta, Correia António, Henriques Isabel S
1 Biology Department and CESAM, University of Aveiro , Aveiro, Portugal .
2 Biology Department and iBiMED, University of Aveiro , Aveiro, Portugal .
Microb Drug Resist. 2015 Oct;21(5):497-506. doi: 10.1089/mdr.2015.0072. Epub 2015 Jun 2.
Carbapenems are last-resort antibiotics to handle serious infections caused by multiresistant bacteria. The incidence of resistance to these antibiotics has been increasing and new resistance mechanisms have emerged. The dissemination of carbapenem resistance in the environment has been overlooked. The main goal of this research was to assess the prevalence and diversity of carbapenem-resistant bacteria in riverine ecosystems. The presence of frequently reported carbapenemase-encoding genes was inspected. The proportion of imipenem-resistant bacteria was on average 2.24 CFU/ml. Imipenem-resistant strains (n=110) were identified as Pseudomonas spp., Stenotrophomonas maltophilia, Aeromonas spp., Chromobacterium haemolyticum, Shewanella xiamenensis, and members of Enterobacteriaceae. Carbapenem-resistant bacteria were highly resistant to other beta-lactams such as quinolones, aminoglycosides, chloramphenicol, tetracyclines, and sulfamethoxazole/trimethoprim. Carbapenem resistance was mostly associated with intrinsically resistant bacteria. As intrinsic resistance mechanisms, we have identified the blaCphA gene in 77.3% of Aeromonas spp., blaL1 in all S. maltophilia, and blaOXA-48-like in all S. xiamenensis. As acquired resistance mechanisms, we have detected the blaVIM-2 gene in six Pseudomonas spp. (5.45%). Integrons with gene cassettes encoding resistance to aminoglycosides (aacA and aacC genes), trimethoprim (dfrB1b), and carbapenems (blaVIM-2) were found in Pseudomonas spp. Results suggest that carbapenem resistance dissemination in riverine ecosystems is still at an early stage. Nevertheless, monitoring these aquatic compartments for the presence of resistance genes and its host organisms is essential to outline strategies to minimize resistance dissemination.
碳青霉烯类抗生素是治疗多重耐药菌引起的严重感染的最后一道防线。对这些抗生素的耐药率一直在上升，并且出现了新的耐药机制。碳青霉烯类耐药性在环境中的传播一直被忽视。本研究的主要目的是评估河流生态系统中耐碳青霉烯类细菌的流行情况和多样性。检测了常见的碳青霉烯酶编码基因的存在情况。耐亚胺培南细菌的比例平均为2.24 CFU/ml。耐亚胺培南菌株（n = 110）被鉴定为假单胞菌属、嗜麦芽窄食单胞菌、气单胞菌属、溶血嗜铬杆菌、厦门希瓦氏菌和肠杆菌科成员。耐碳青霉烯类细菌对其他β-内酰胺类抗生素、喹诺酮类、氨基糖苷类、氯霉素、四环素以及磺胺甲恶唑/甲氧苄啶具有高度耐药性。碳青霉烯类耐药性大多与固有耐药菌有关。作为固有耐药机制，我们在77.3%的气单胞菌属中鉴定出blaCphA基因，在所有嗜麦芽窄食单胞菌中鉴定出blaL1基因，在所有厦门希瓦氏菌中鉴定出blaOXA-48样基因。作为获得性耐药机制，我们在6株假单胞菌属（5.45%）中检测到blaVIM-2基因。在假单胞菌属中发现了携带编码对氨基糖苷类（aacA和aacC基因）、甲氧苄啶（dfrB1b）和碳青霉烯类（blaVIM-2）耐药性的基因盒的整合子。结果表明，碳青霉烯类耐药性在河流生态系统中的传播仍处于早期阶段。然而，监测这些水体环境中耐药基因及其宿主生物的存在对于制定将耐药性传播降至最低的策略至关重要。
