Department of Environmental and Occupational Health Sciences, School of Public Health, Seattle, WA 98195, USA.
Department of Laboratory Medicine, School of Medicine, Seattle, WA 98195, USA.
J Antimicrob Chemother. 2019 Aug 1;74(8):2176-2180. doi: 10.1093/jac/dkz159.
Limited studies have investigated the microbial diversity of wild marine mammals.
This study characterized Escherichia coli isolates collected from fresh faecal samples of endangered southern resident killer whales (Orcinus orca) located by detection dogs.
WGS of each strain was done to determine ST (using MLST), clonotype (C:H), antimicrobial resistance and virulence profile. Conjugation experiments were done to determine the mobility of the tet(B) tetracycline resistance gene.
All isolates belonged to extraintestinal pathogenic E. coli (ExPEC) clonal lineages ST73 (8/9) and ST127 (1/9), often associated with human community-acquired urinary tract disease. Clonotyping using fumC and fimH alleles showed divergence in clonal lineages, with ST73 isolates belonging to the C24:H10 clade and the ST127 isolate belonging to C14:H2. The eight ST73 isolates carried multiple acquired antibiotic resistance genes, including aadA1, sul1 and tet(B), encoding aminoglycoside, sulphonamide and tetracycline resistance, respectively. Conjugative transfer of the resistance gene tet(B) was observed for three of the eight isolates. ST127 did not carry any of these acquired resistance genes. Virulence-associated genes identified included those encoding adhesins (iha, papC, sfaS), toxins (sat, vat, pic, hlyA, cnf1), siderophores (iutA, fyuA, iroN, ireA), serum survival/protectins (iss, ompT), capsule (kpsM) and pathogenicity island marker (malX).
Orca whales can carry antibiotic-resistant potentially pathogenic strains of E. coli. Possible sources include contamination of the whale's environment and/or food. It is unknown whether these isolates cause disease in southern resident killer whales, which could contribute to the ongoing decline of this critically endangered population.
有限的研究调查了野生海洋哺乳动物的微生物多样性。
本研究从通过检测犬定位的濒危南方居民杀人鲸（虎鲸）的新鲜粪便样本中分离出大肠杆菌，并对其进行了特征描述。
对每个菌株进行 WGS 测序以确定 ST（使用 MLST）、克隆型（C:H）、抗生素耐药性和毒力谱。进行了接合实验以确定 tet(B) 四环素耐药基因的可移动性。
所有分离株均属于肠外致病性大肠杆菌（ExPEC）克隆谱系 ST73（9/9）和 ST127（1/9），通常与人类社区获得性尿路感染疾病有关。使用 fumC 和 fimH 等位基因进行的克隆分型显示出克隆谱系的分化，其中 ST73 分离株属于 C24:H10 分支，而 ST127 分离株属于 C14:H2。这 8 个 ST73 分离株携带多种获得性抗生素耐药基因，包括编码氨基糖苷类、磺胺类和四环素类耐药的 aadA1、sul1 和 tet(B)。观察到 8 个分离株中有 3 个可进行耐药基因 tet(B)的接合转移。ST127 未携带任何这些获得性耐药基因。鉴定出的与毒力相关的基因包括编码粘附素（iha、papC、sfaS）、毒素（sat、vat、pic、hlyA、cnf1）、铁载体（iutA、fyuA、iroN、ireA）、血清存活/保护素（iss、ompT）、荚膜（kpsM）和致病性岛标记（malX）。
虎鲸可能携带抗生素耐药的潜在致病性大肠杆菌菌株。可能的来源包括鲸鱼环境和/或食物的污染。目前尚不清楚这些分离株是否会导致南方居民杀人鲸患病，这可能是导致这种极度濒危种群持续下降的原因之一。
