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Pradhan SK, Devi R, Khan MIR, Kamilya D, Gon Choudhury T, Parhi J. Isolation of Aeromonas salmonicida subspecies salmonicida from aquaculture environment in India: Polyphasic identification, virulence characterization, and antibiotic susceptibility. Microb Pathog 2023; 179:106100. [PMID: 37028687 DOI: 10.1016/j.micpath.2023.106100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 04/05/2023] [Accepted: 04/05/2023] [Indexed: 04/09/2023]
Abstract
This study reports the polyphasic identification, characterization of virulence potential, and antibiotic susceptibility of Aeromonas salmonicida subspecies salmonicida COFCAU_AS, isolated from an aquaculture system in India. The physiological, biochemical, 16s rRNA gene sequencing and PAAS PCR test identified the strain as Aeromonas salmonicida. The MIY PCR tests established the subspecies as 'salmonicida'. The in vitro tests showed the isolated bacterium as haemolytic with casein, lipid, starch, and gelatin hydrolysis activity, indicating its pathogenic attributes. It also showed the ability to produce slime and biofilm, and additionally, it possessed an A-layer surface protein. In vivo pathogenicity test was performed to determine the LD50 dose of the bacterium in Labeo rohita fingerlings (14.42 ± 1.01 g), which was found to be 106.9 cells fish-1. The bacteria-challenged fingerlings showed skin lesions, erythema at the base of the fins, dropsy, and ulcer. Almost identical clinical signs and mortalities were observed when the same LD50 dose was injected into other Indian major carp species, L. catla and Cirrhinus mrigala. Out of the twelve virulent genes screened, the presence of nine genes viz., aerA, act, ast, alt, hlyA, vapA, exsA, fstA, and lip were detected, whereas ascV, ascC, and ela genes were absent. The A. salmonicida subsp. salmonicida COFCAU_AS was resistant to antibiotics such as penicillin G, rifampicin, ampicillin, and vancomycin while highly sensitive to amoxiclav, nalidixic acid, chloramphenicol, ciprofloxacin, and tetracycline. In summary, we have isolated a virulent A. salmonicida subsp. salmonicida from a tropical aquaculture pond which can cause significant mortality and morbidity in Indian major carp species.
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Affiliation(s)
- Subham Kumar Pradhan
- Dept. of Aquatic Health & Environment, College of Fisheries, CAU, Lembucherra, Tripura, 799210, India
| | - Rajashree Devi
- Dept. of Aquatic Health & Environment, College of Fisheries, CAU, Lembucherra, Tripura, 799210, India
| | - Md Idrish Raja Khan
- Dept. of Aquatic Health & Environment, College of Fisheries, CAU, Lembucherra, Tripura, 799210, India; Late Shri Punaram Nishad College of Fisheries, DSVCKU, Kawardha, 491995, Chhattisgarh, India
| | - Dibyendu Kamilya
- Dept. of Aquatic Health & Environment, College of Fisheries, CAU, Lembucherra, Tripura, 799210, India; Agricultural and Food Engineering Department, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, 721302, India
| | - Tanmoy Gon Choudhury
- Dept. of Aquatic Health & Environment, College of Fisheries, CAU, Lembucherra, Tripura, 799210, India.
| | - Janmejay Parhi
- Dept. of Fish Genetics & Reproduction, College of Fisheries, CAU, Lembucherra, Tripura, 799210, India
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Wang J, Xiu L, Qiao Y, Zhang Y. Virulence regulation of Zn2+ uptake system znuABC on mesophilic Aeromonas salmonicida SRW-OG1. Front Vet Sci 2023; 10:1172123. [PMID: 37065252 PMCID: PMC10090552 DOI: 10.3389/fvets.2023.1172123] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 03/14/2023] [Indexed: 03/31/2023] Open
Abstract
Psychrophilic Aeromonas salmonicida could not grow above 25°C and therefore thought unable to infect mammals and humans. In our previous study, a mesophilic A. salmonicida SRW-OG1 was isolated from Epinephelus coioides with furunculosis. Through the analysis of preliminary RNA-seq, it was found that the Zn2+ uptake related genes znuA, znuB and znuC might be involved in the virulence regulation of A. salmonicida SRW-OG1. Therefore, the purpose of this study was to explore the effect of znuABC silencing on the virulence regulation of A. salmonicida SRW-OG1. The results showed that the growth of the znuA-RNAi, znuB-RNAi, and znuC-RNAi strains was severely restricted under the Fe2+ starvation, but surprisingly there was no significant difference under the Zn2+ restriction. In the absence of Zn2+ and Fe2+, the expression level of znuABC was significantly increased. The motility, biofilm formation, adhesion and hemolysis of the znuA-RNAi, znuB-RNAi, and znuC-RNAi strains were significantly reduced. We also detected the expression of znuABC under different growth periods, temperatures, pH, as well as Cu2+ and Pb2+ stresses. The results showed that znuABC was significantly up-regulated in the logarithmic phase and the decline phase of A. salmonicida. Interestingly, the trend of expression levels of the znuABC at 18, 28, and 37°C was reversed to another Zn2+ uptake related gene zupT. Taken together, these indicated that the znuABC was necessary for A. salmonicida SRW-OG1 pathogenicity and environmental adaptability, and was cross regulated by iron starvation, but it was not irreplaceable for A. salmonicida SRW-OG1 Zn2+ uptake in the host.
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Affiliation(s)
- Jiajia Wang
- Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, Jimei University, Xiamen, Fujian, China
| | - Lijun Xiu
- Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, Jimei University, Xiamen, Fujian, China
| | - Ying Qiao
- Fourth Institute of Oceanography, Key Laboratory of Tropical Marine Ecosystem and Bioresource, Ministry of Natural Resources, Beihai, China
| | - Youyu Zhang
- Institute of Electromagnetics and Acoustics, School of Electronic Science and Engineering, Xiamen University, Xiamen, China
- *Correspondence: Youyu Zhang
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Cai H, Yu J, Qiao Y, Ma Y, Zheng J, Lin M, Yan Q, Huang L. Effect of the Type VI Secretion System Secreted Protein Hcp on the Virulence of Aeromonas salmonicida. Microorganisms 2022; 10:microorganisms10122307. [PMID: 36557560 PMCID: PMC9784854 DOI: 10.3390/microorganisms10122307] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 11/16/2022] [Accepted: 11/19/2022] [Indexed: 11/23/2022] Open
Abstract
Aeromonas salmonicida, a psychrophilic bacterial pathogen, is widely distributed in marine freshwater, causing serious economic losses to major salmon farming areas in the world. At present, it is still one of the most important pathogens threatening salmon farming. Hcp (haemolysin-coregulated protein) is an effector protein in the type-VI secretion system (T6SS), which is secreted by T6SS and functions as its structural component. The results of our previous genomic sequencing showed that hcp existed in the mesophilic A. salmonicida SRW-OG1 isolated from naturally infected Epinephelus coioides. To further explore the role of Hcp in A. salmonicida SRW-OG1, we constructed an hcp-RNAi strain and verified its effect on the virulence of A. salmonicida. The results showed that compared with the wild strain, the hcp-RNAi strain suffered from different degrees of decreased adhesion, growth, biofilm formation, extracellular product secretion, and virulence. It was suggested that hcp may be an important virulence gene of A. salmonicida SRW-OG1.
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Affiliation(s)
- Hongyan Cai
- Key Laboratory of Healthy Mariculture for the East China Sea, Fisheries College, Ministry of Agriculture, Jimei University, Xiamen 361021, China
| | - Jiaying Yu
- Key Laboratory of Healthy Mariculture for the East China Sea, Fisheries College, Ministry of Agriculture, Jimei University, Xiamen 361021, China
| | - Ying Qiao
- Fourth Institute of Oceanography, Ministry of Natural Resources, No. 26, New Century Avenue, Beihai 536000, China
| | - Ying Ma
- Key Laboratory of Healthy Mariculture for the East China Sea, Fisheries College, Ministry of Agriculture, Jimei University, Xiamen 361021, China
| | - Jiang Zheng
- Key Laboratory of Healthy Mariculture for the East China Sea, Fisheries College, Ministry of Agriculture, Jimei University, Xiamen 361021, China
| | - Mao Lin
- Key Laboratory of Healthy Mariculture for the East China Sea, Fisheries College, Ministry of Agriculture, Jimei University, Xiamen 361021, China
| | - Qingpi Yan
- Key Laboratory of Healthy Mariculture for the East China Sea, Fisheries College, Ministry of Agriculture, Jimei University, Xiamen 361021, China
- Correspondence: (Q.Y.); (L.H.)
| | - Lixing Huang
- Key Laboratory of Healthy Mariculture for the East China Sea, Fisheries College, Ministry of Agriculture, Jimei University, Xiamen 361021, China
- Correspondence: (Q.Y.); (L.H.)
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Preena PG, Dharmaratnam A, Swaminathan TR. A peek into mass mortality caused by antimicrobial resistant Edwardsiella tarda in goldfish, Carassius auratus in Kerala. Biologia (Bratisl) 2022; 77:1161-1171. [PMID: 35068493 PMCID: PMC8764882 DOI: 10.1007/s11756-022-01007-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 01/04/2022] [Indexed: 11/28/2022]
Abstract
Edwardsiella tarda is one of the serious threats affecting the worldwide aquaculture. In the present study, four isolates were recovered from diseased goldfish, showing hemorrhages, reported with 60% mass mortality in an ornamental fish farm, Ernakulam, Kerala. Based on the phenotypic and genotypic analysis, the bacteria were identified as Edwardsiella tarda, Citrobacter freundii, Acinetobacter junii and Comammonas testosteronii. Experimental challenge studies using healthy goldfish revealed that among the four isolates, E. tarda alone leads to 100% mortality of experimental fish within 175 degree days and the pathogen could be successfully re-isolated from the moribund fish. The LD50 value of E. tarda was calculated as 9.9 × 105 CFU/fish. The histopathology of the infected tissues of goldfish had shown the typical features of E .tarda infection. The pathogen was found positive for the virulence genes viz., hly, etfA, etfD and eseD as detected using PCR. Thus E. tarda was confirmed as the real causative agent of the disease outbreak. Multiple antimicrobial resistance (AMR) exhibited by the pathogen towards 19 tested antibiotics with the MAR index of 0.46 highlighted the exposure of antibiotics to the fish in the farm. The existence of antibiotic resistant genes within the plasmid as revealed through plasmid curing studies pointed out the possibility of rapid dissemination of AMR in aquaculture. Hence proper surveillance and appropriate diagnostic methods need to be implemented at regular intervals to mitigate the menace.
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Affiliation(s)
- Prasannan Geetha Preena
- Peninsular and Marine Fish Genetic Resources Centre of ICAR-NBFGR, CMFRI Campus, P.O. Number 1603, Kochi, 682018 India
| | - Arathi Dharmaratnam
- Peninsular and Marine Fish Genetic Resources Centre of ICAR-NBFGR, CMFRI Campus, P.O. Number 1603, Kochi, 682018 India
| | - Thangaraj Raja Swaminathan
- Peninsular and Marine Fish Genetic Resources Centre of ICAR-NBFGR, CMFRI Campus, P.O. Number 1603, Kochi, 682018 India
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