Identification and pathogenicity study of emerging fish pathogens Acinetobacter junii and Acinetobacter pittii recovered from a disease outbreak in Labeo catla (Hamilton, 1822) and Hypophthalmichthys molitrix (Valenciennes, 1844) of freshwater wetland in West Bengal, India
Identification and pathogenicity study of emerging fish pathogens Acinetobacter junii and Acinetobacter pittii recovered from a disease outbreak in Labeo catla (Hamilton, 1822) and Hypophthalmichthys molitrix (Valenciennes, 1844) of freshwater wetland in West Bengal, India
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DOI：
10.1111/are.14584
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发表时间：
2020-06-01
影响因子：
2
通讯作者：
Das, Basanta Kumar
中科院分区：
文献类型：
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作者：
Malick, Ramesh Chandra;Bera, Asit Kumar;Das, Basanta Kumar
湿地养殖系统中的病害暴发是导致鱼类死亡的主要原因。在各种细菌性败血病中，不动杆菌属引起的鱼类死亡率最高。在不同的鱼类中也有报道。对印度西孟加拉一处湿地的鱼病暴发进行了调查，以确定涉及的病原学因素。对濒死的鱼进行检查并进行细菌分离。经生化鉴定和16 S rRNA基因扩增鉴定，2株病原菌分别为琼氏不动杆菌和皮特氏不动杆菌。两株菌均为氧化酶阴性、硝酸盐阴性、过氧化氢酶阳性和吲哚阴性。16 S rRNA基因测序和系统发育树分析进一步证实了这2株不动杆菌属。相似度为97%~ 99%。耐药谱显示，这两种细菌均对β-内酰胺、头孢氨苄、头孢噻吩、阿莫西林、头孢呋辛、头孢羟氨苄、克林霉素、万古霉素和青霉素耐药。此外，A.皮特氏菌对头孢他啶和头孢噻肟等头孢菌素类抗生素也有耐药性。在挑战实验中，A. junii和A.结果表明，两种鱼的LD_（50）分别为1.24 × 10 ~（5）和1.88 × 10 ~（7）cfu/鱼。鳃、肝脏和肾脏的组织学检查显示支持细菌性败血症的显著变化。首次报道了A. junii和多药耐药（MDR）-A. pittii作为一种新的鱼类病原体，在淡水湿地引起猫Labeo catla和鲢鱼Hypophthalmichthys molitrix的严重死亡。
The disease outbreaks in aquaculture system of wetlands are the major cause of fish mortality. Among various bacterial septicaemic diseases, fish mortality caused by Acinetobacter spp. is recently reported in different fish species. Fish disease outbreak was investigated in a wetland of West Bengal, India to identify the aetiological factors involved. The moribund fish were examined and subjected to bacterial isolation. Two bacterial causative agents were identified as Acinetobacter junii and Acinetobacter pittii by biochemical characterization and 16S rRNA gene amplification. Both the isolates were oxidase-negative, nitrate-negative, catalase-positive and indole-negative. The molecular identification using 16S rRNA gene sequencing and phylogenetic tree analysis further confirmed the two Acinetobacter spp. with 97%-99% similarity. The antibiotic resistance patterns of these two bacteria revealed that both of them were resistant to beta-lactam, cefalexin, cephalothin, amoxyclav, cefuroxime, cefadroxil, clindamycin, vancomycin and penicillin. In addition, A. pittii was also resistant to other antibiotics of cephams group such as ceftazidime and cefotaxime. In the challenge experiment, both A. junii and A. pittii were found to be pathogenic with LD50 of 1.24 x 10(5) and 1.88 x 10(7) cfu/fish respectively. Histopathological examination of gill, liver and kidney revealed prominent changes supporting bacterial septicaemia. The investigation reports for the first time on concurrent infection by A. junii and multidrug-resistant (MDR)-A. pittii as emerging fish pathogens to cause severe mortality in Labeo catla and Hypophthalmichthys molitrix in a freshwater wetland.