Soto-Rodriguez S A, Lozano-Olvera R, Garcia-Gasca M T, Abad-Rosales S M, Gomez-Gil B, Ayala-Arellano J
CIAD, AC Mazatlan Unit for Aquaculture and Environmental Management, 82112 Mazatlan, Sinaloa, Mexico.
Dis Aquat Organ. 2018 Jul 4;129(2):107-116. doi: 10.3354/dao03247.
Aeromonas dhakensis (Ad) CAIM 1873 growth was evaluated at different conditions and antibiotic susceptibility. Mortality and histopathological damages in hybrid tilapia Oreochromis niloticus × O. mossambicus, and virulence factors caused by Ad bacterial cells and extracellular products (ECPs) were evaluated, and the whole genome was obtained. Ad grew between 0.0 and 5.5% NaCl at a pH of between 4 and 10 and from 4 to 37°C. The lowest minimum inhibitory concentration was found for enrofloxacin (<5 µg ml-1), and bacteria were resistant to erythromycin, amoxicillin and ampicillin. Ad bacterial cells (1.86 × 105 cells g-1) and ECPs (0.462 µg protein fish-1) were highly virulent to challenged hybrid tilapia and caused over 80% mortality at 24 h. The primary clinical sign caused was haemorrhage, and damage was most marked in the spleen, liver, kidney and brain of fish challenged with bacterial cells. To our knowledge, this is the first report that Ad causes pyknotic and karyorrhectic nuclei of erythrocytes in the internal organs of hybrid tilapia, which was the most striking histopathological observation. The virulence of Ad to hybrid tilapia may be primarily related to the activity of haemolysins (hlyA genes) and cytotoxins (aerolysin aerA), along with the production of siderophores and proteases. We also found β-lactamase, tetracycline and multiple antibiotic resistance genes, as well as adherence, iron acquisition, toxins (aerolysin family, haemolysins) and diverse protease genes.
对达卡气单胞菌（Ad）CAIM 1873在不同条件下的生长情况及抗生素敏感性进行了评估。对尼罗罗非鱼×莫桑比克罗非鱼杂交罗非鱼的死亡率、组织病理学损伤以及由Ad细菌细胞和细胞外产物（ECPs）引起的毒力因子进行了评估，并获得了其全基因组。Ad在pH值为4至10、温度为4至37°C、NaCl浓度为0.0%至5.5%的条件下生长。恩诺沙星的最低抑菌浓度最低（<5 µg ml-1），该细菌对红霉素、阿莫西林和氨苄西林耐药。Ad细菌细胞（1.86×105个细胞g-1）和ECPs（0.462 µg蛋白质/鱼）对受攻击的杂交罗非鱼具有高度毒性，在24小时内导致超过80%的死亡率。引起的主要临床症状是出血，在用细菌细胞攻击的鱼的脾脏、肝脏、肾脏和大脑中损伤最为明显。据我们所知，这是第一份关于Ad导致杂交罗非鱼内脏红细胞核固缩和核碎裂的报告，这是最显著的组织病理学观察结果。Ad对杂交罗非鱼的毒力可能主要与溶血素（hlyA基因）和细胞毒素（气溶素aerA）的活性以及铁载体和蛋白酶的产生有关。我们还发现了β-内酰胺酶、四环素和多重耐药基因，以及黏附、铁摄取、毒素（气溶素家族、溶血素）和多种蛋白酶基因。
