Bacteriology, Mycology and Immunology Department, Faculty of Veterinary Medicine, Suez Canal University, Ismailia, 41522, Egypt.
Department of Fish Diseases and Management, Faculty of Veterinary Medicine, Suez Canal University, Ismailia, 41522, Egypt.
Sci Rep. 2020 Sep 29;10(1):15961. doi: 10.1038/s41598-020-72264-4.
This study aimed to investigate the prevalence, antibiogram of Pseudomonas aeruginosa (P. aeruginosa), and the distribution of virulence genes (oprL, exoS, phzM, and toxA) and the antibiotic-resistance genes (bla, tetA, and bla). A total of 285 fish (165 Oreochromis niloticus and 120 Clarias gariepinus) were collected randomly from private fish farms in Ismailia Governorate, Egypt. The collected specimens were examined bacteriologically. P. aeruginosa was isolated from 90 examined fish (31.57%), and the liver was the most prominent infected organ. The antibiogram of the isolated strains was determined using a disc diffusion method, where the tested strains exhibited multi-drug resistance (MDR) to amoxicillin, cefotaxime, tetracycline, and gentamicin. The PCR results revealed that all the examined strains harbored (oprL and toxA) virulence genes, while only 22.2% were positive for the phzM gene. On the contrary, none of the tested strains were positive for the exoS gene. Concerning the distribution of the antibiotic resistance genes, the examined strains harbored bla, bla, and tetA genes with a total prevalence of 83.3%, 77.7%, and 75.6%, respectively. Experimentally infected fish with P. aeruginosa displayed high mortalities in direct proportion to the encoded virulence genes and showed similar signs of septicemia found in the naturally infected one. In conclusion, P. aeruginosa is a major pathogen of O. niloticus and C. gariepinus. oprL and toxA genes are the most predominant virulence genes associated with P. aeruginosa infection. The bla, bla, and tetA genes are the main antibiotic-resistance genes that induce resistance patterns to cefotaxime, amoxicillin, and tetracycline, highlighting MDR P. aeruginosa strains of potential public health concern.
本研究旨在调查埃及伊斯梅利亚省私人鱼类养殖场中，鱼类（罗非鱼 165 尾，鲶鱼 120 尾）中铜绿假单胞菌（P. aeruginosa）的流行率、药敏谱、毒力基因（oprL、exoS、phzM 和 toxA）和抗生素耐药基因（bla、tetA 和 bla）的分布情况。从采集的标本中分离出 90 株铜绿假单胞菌（31.57%），肝脏是最易感染的器官。采用纸片扩散法对分离株进行药敏试验，结果显示受试菌株对阿莫西林、头孢噻肟、四环素和庆大霉素表现出多药耐药性（MDR）。PCR 结果显示，所有检测菌株均携带 oprL 和 toxA 毒力基因，而 phzM 基因阳性率仅为 22.2%。相反，检测菌株均未携带 exoS 基因。在抗生素耐药基因的分布方面，检测菌株携带 bla、bla 和 tetA 基因的总流行率分别为 83.3%、77.7%和 75.6%。用铜绿假单胞菌人工感染的鱼类死亡率与编码的毒力基因呈正相关，并表现出与自然感染鱼类相似的败血症症状。总之，铜绿假单胞菌是罗非鱼和鲶鱼的主要病原体。oprL 和 toxA 基因是与铜绿假单胞菌感染相关的最主要的毒力基因。bla、bla 和 tetA 基因是诱导头孢噻肟、阿莫西林和四环素耐药模式的主要抗生素耐药基因，凸显出具有潜在公共卫生关注的 MDR 铜绿假单胞菌菌株。
