Hossain S, De Silva B C J, Dahanayake P S, Heo G-J
Veterinary Medical Center and College of Veterinary Medicine, Chungbuk National University, Cheongju, Korea.
Lett Appl Microbiol. 2018 Dec;67(6):598-605. doi: 10.1111/lam.13075. Epub 2018 Nov 12.
Aeromonas spp. are opportunistic pathogenic bacteria associated with a multitude of diseases in ornamental fish. In this study, virulence properties and antibiotic resistance patterns of 43 Aeromonas strains isolated from 46 zebrafish were investigated. The isolates were identified as Aeromonas veronii biovar veronii (n = 26), A. veronii biovar sobria (n = 3), Aeromonas hydrophila (n = 8), A. caviae (n = 3), Aeromonas enteropelogenes (n = 2) and Aeromonas dhakensis (n = 1) by gyrB gene sequencing. The sequence divergence within and between the species ranged from 0-5·80% and 4·90-8·00%. Each species formed a distinct group in a neighbour-joining phylogenetic tree. The lipase production, biofilm formation, DNase activity, gelatinase production, caseinase production and β-hemolysis were phenotypically observed in 34 (79·07%), 33 (74·74%), 30 (69·77%), 25 (58·14%), 22 (51·18%) and 21 (48·84%) isolates. The virulence genes were detected by polymerase chain reaction (PCR) in following frequencies- aer (86·05%), hlyA (83·72%), gcaT (83·72%), lip (72·09%), act (67·44%), fla (65·12%), ascV (58·14%), ast (55·81%), ser (41·86%), ahyB (39·53%) and alt (25·58%). Every isolate was resistant to at least four antibiotics in disk diffusion test. The multiple antibiotic resistance (MAR) index values ranged from 0·22-0·50 among the isolates. Our study suggests that zebrafish can be a potential reservoir of virulent and multi-drug resistant Aeromonas spp. SIGNIFICANCE AND IMPACT OF THE STUDY: Aeromonas spp. are Gram-negative and facultative anaerobic bacteria which are ubiquitous in aquatic environments. Virulence properties and antibiotic resistance of ornamental fish-borne Aeromonas spp. are poorly understood. The virulence factors as well as multiple antibiotic resistance profiles of zebrafish-borne Aeromonas spp. were characterized for the first time in Korea. Most of the isolates were positive for phenotypic virulence traits and harboured several virulence genes revealing the virulence potential of zebrafish-borne Aeromonas spp. Additionally, the high multiple antibiotic resistance (MAR) index values displayed by the isolates highlight the necessity of responsible use of antibiotics in the ornamental fish industry.
气单胞菌属是与观赏鱼多种疾病相关的机会致病菌。在本研究中，对从46条斑马鱼中分离出的43株气单胞菌菌株的毒力特性和抗生素耐药模式进行了调查。通过gyrB基因测序，将分离株鉴定为维罗纳气单胞菌维罗纳生物变种（n = 26）、维罗纳气单胞菌温和生物变种（n = 3）、嗜水气单胞菌（n = 8）、豚鼠气单胞菌（n = 3）、肠产气单胞菌（n = 2）和达卡气单胞菌（n = 1）。种内和种间的序列差异范围分别为0 - 5.80%和4.90 - 8.00%。在邻接法系统发育树中，每个物种都形成了一个独特的组。在34株（79.07%）、33株（74.74%）、30株（69.77%）、25株（58.14%）、22株（51.18%）和21株（48.84%）分离株中分别表型观察到脂肪酶产生、生物膜形成、DNA酶活性、明胶酶产生、酪蛋白酶产生和β溶血。通过聚合酶链反应（PCR）检测毒力基因的频率如下——aer（86.05%）、hlyA（83.72%）、gcaT（83.72%）、lip（72.09%）、act（67.44%）、fla（65.12%）、ascV（58.14%）、ast（55.81%）、ser（41.86%）、ahyB（39.53%）和alt（25.58%）。在纸片扩散试验中，每株分离株至少对四种抗生素耐药。分离株的多重抗生素耐药（MAR）指数值范围为0.22 - 0.50。我们的研究表明斑马鱼可能是有毒力和多重耐药气单胞菌属菌株的潜在储存宿主。研究的意义和影响：气单胞菌属是革兰氏阴性兼性厌氧菌，在水生环境中普遍存在。人们对观赏鱼携带的气单胞菌属的毒力特性和抗生素耐药性了解甚少。韩国首次对斑马鱼携带的气单胞菌属的毒力因子以及多重抗生素耐药谱进行了表征。大多数分离株的表型毒力性状呈阳性，并含有多个毒力基因，揭示了斑马鱼携带的气单胞菌属的毒力潜力。此外，分离株显示出的高多重抗生素耐药（MAR）指数值突出了观赏鱼产业中合理使用抗生素的必要性。
