Hladicz Alexander, Kittinger Clemens, Zarfel Gernot
Center for Molecular Biology, University of Vienna, 1030 Vienna, Austria.
Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, Neue Stiftingtalstrasse 2, 8010 Graz, Austria.
Int J Environ Res Public Health. 2017 Oct 3;14(10):1169. doi: 10.3390/ijerph14101169.
Antibiotic-resistant bacteria are spreading worldwide in medical settings but also in the environment. These resistant bacteria illustrate a major health problem in our times, and last-line antibiotics such as tigecycline represent an ultimate therapy option. Reports on tigecycline non-susceptible are presented with regard to medical settings but are rare with that for the environment. The aim of this study was to characterize two tigecycline non-susceptible isolates from the river Mur, and to question the resistance mechanism. The screening for chromosomal mutations revealed a deletion and a silent point mutation in one isolate and a point mutation in the other isolate all within the allele. RamR acts as repressor and prevents overexpression of . These mutations are likely to cause a resistant phenotype due to the overexpression of AcrAB-TolC. MLST revealed that the isolates belonged to two unrelated MLST types (ST2392 and ST2394). Both isolates only revealed resistance to tigecycline and tetracycline. This is one of the rare reports of tigecycline-resistant from surface water. The presence of two genetically different isolates suggests that the river water may bear substances that favor mutations that can lead to this efflux pump-driven resistance.
抗生素耐药菌正在全球范围内的医疗机构以及环境中传播。这些耐药菌是我们这个时代的一个重大健康问题，而替加环素等最后一线抗生素是最终的治疗选择。关于替加环素不敏感的报告多与医疗机构有关，而关于环境方面的报告则很少。本研究的目的是对从穆尔河分离出的两株替加环素不敏感菌株进行特征描述，并探究其耐药机制。对染色体突变的筛查发现，一株菌株在等位基因内存在一个缺失和一个沉默点突变，另一株菌株存在一个点突变。RamR作为阻遏物，可防止AcrAB-TolC的过度表达。这些突变可能由于AcrAB-TolC的过度表达而导致耐药表型。多位点序列分型（MLST）显示，这些分离株属于两种不相关的MLST类型（ST2392和ST2394）。两株分离株仅对替加环素和四环素耐药。这是关于地表水分离出替加环素耐药菌的罕见报告之一。两种基因不同的分离株的存在表明，河水可能含有有利于导致这种由外排泵驱动的耐药性突变的物质。
