Tail Rot Disease Research Articles

Isolation and characterization of two virulent Aeromonads associated with haemorrhagic septicaemia and tail-rot disease in farmed climbing perch Anabas testudineus

Diseased Anabas testudineus exhibiting signs of tail-rot and ulcerations on body were collected from a fish farm in Assam, India during the winter season (November 2018 to January 2019). Swabs from the infected body parts were streaked on sterilized nutrient agar. Two dominant bacterial colonies were obtained, which were then isolated and labelled as AM-31 and AM-05. Standard biochemical characterisation and 16S rRNA and rpoB gene sequencing identified AM-31 isolate as Aeromonas hydrophila and AM-05 as Aeromonas jandaei. Symptoms similar to that of natural infection were observed on re-infecting both bacteria to disease-free A. testudineus, which confirmed their virulence. LC50 was determined at 1.3 × 104 (A. hydrophila) and 2.5 × 104 (A. jandaei) CFU per fish in intraperitoneal injection. Further, PCR amplification of specific genes responsible for virulence (aerolysin and enterotoxin) confirmed pathogenicity of both bacteria. Histopathology of kidney and liver in the experimentally-infected fishes revealed haemorrhage, tubular degeneration and vacuolation. Antibiotic profiles were also assessed for both bacteria. To the best of our knowledge, the present work is a first report on the mortality of farmed climbing perch naturally-infected by A. hydrophila as well as A. jandaei, with no records of pathogenicity of the latter in this fish.

Isolation, identification, and biological control in vitro of tail rot pathogen strain from Hippocampus kuda.

Tail rot disease is associated with major economic losses in the seahorse aquaculture in China. This study aimed to isolate and identify the pathogen causing tail rot disease in seahorses. Three culturable intestinal bacteria strains were isolated from Hippocampus kuda specimens with tail rot disease. Strain HL11, HL12, and HL13 were identified as Pseudoalteromonas spongiae, Bacillus subtilis and Photobacterium ganghwense based on its morphological characteristics, physiological and biochemical properties, through 16S rRNA and gyrB sequencing, respectively. Challenge experiments using these strains on healthy H. kuda and bacterial re-isolation from challenged diseased seahorses showed that the bacteria strain named HL11 induced identical pathological symptoms, indicating that it is the causative pathogen of the disease. Antibiotic-resistance tests against of 32 antibiotics revealed that HL11 was highly sensitive to 13 kinds, while exhibited intermediate susceptibility to 6, and resistance to 13 kinds. Antibacterial tests of the bioactive agents showed that HL11 was susceptible to five kinds, including tea polyphenols, lactic acid, gallic acid, allicin, and polylysine; however, it was not susceptible to the other 13 kinds of bioactive agents. The results demonstrate the potential of using bioactive agents to replace antibiotics to generate an environmentally friendly mode of culturing seahorses.

Liver transcriptome analysis and cortisol immune-response modulation in lipopolysaccharide-stimulated in channel catfish (Ictalurus punctatus)

Channel catfish (Ictalurus punctatus) is an important aquaculture species in China. In channel catfish, diseases such as haemorrhagic, sepsis and tail-rot disease are all caused by bacteria as general in China. Most of the pathogenic bacteria are Gram-negative bacteria. Liver transcriptome analysis of the co-injection of cortisol and lipopolysaccharide (LPS) was performed in this study. Preliminary evidence from the results suggest that after the emergence of immune stress, cortisol will up-regulate the complement cascade pathway, down-regulate the coagulation cascade pathway, down-regulate the platelet activation pathway, down-regulate antigen presentation pathway, and show complex regulation relationship to inflammatory factors. At 12 h, the number of differential genes regulated by cortisol was about half less than the number of differential genes regulated by LPS. At 24 h, there was no significant difference between the number of differential genes regulated by cortisol and LPS, but the types of differential genes vary widely. KEGG enrichment analysis found that cortisol regulated LPS-stimulated immune responses mainly focus on cytokines, complement and coagulation cascades pathways, antigen presentation pathways, haematopoiesis, and inflammation. It is suggested that there may be some strategic choice in the regulation of immune response by cortisol. These results will help understand the pathogenesis and host defence system in bacterial disease caused by Gram-negative bacteria.

Vibrio parahaemolyticus a causative bacterium for tail rot disease in ornamental fish, Amphiprion sebae

The present study was performed to identify the tail rot disease causing bacterium in marine ornamental fish, Amphiprion sebae. Bacteria were isolated from the infected immune organs and tail region of A. sebae. Five different bacterial isolates (S1-S5) with different shape, size and colour were chosen for the infection study. The isolated strains were individually challenged with A. sebae at a constant dose of 1×107 CFU/fish. The virulent strain was found to be S-3, which showed maximum reproducing ability in A. sebae by causing typical tail rot disease and mortality. Furthermore, S-3 strain was identified as Vibrio parahaemolyticus by 16S rRNA gene sequencing (KF738005), biochemical analysis and amplification of tox R gene. Subsequently, extracellular products (ECPs) of V. parahaemolyticus were prepared by cellophane overlay method. The LD50 value of V. parahaemolyticus and its ECPS were found to be 1×105 CFU and 5μg/fish. The histology results revealed that V. parahaemolyticus and its ECPS are the major cause of tail rot disease in A. sebae.

Identification and characterization of pathogen Vibrio rotiferianus , a pathogen isolated from Hippocampus erectus with tail-rot disease

Identification and characterization of pathogen <i>Vibrio rotiferianus</i> , a pathogen isolated from <i>Hippocampus erectus</i> with tail-rot disease

Citrobacter freundii: a Causative Agent for Tail Rot Disease in Freshwater Cultured Japanese Eel Anguilla japonica

Tail rot disease causes significant economic damage in freshwater farmed Japanese eel Anguilla japonica, yet information on Citrobacter freundii as a possible causal agent for this disease is scarce. In this study, a virulent strain, temporarily named MINA, was isolated from diseased A. japonica suffering from tail rot disease. It was identified through phylogenetic analysis and phenotypic characteristics and thus compared to other known isolates. Isolate MINA has developed multiple resistances to penicillin, quinolones and sulfonamide antibiotics as well as to amide alcohols, cephalosporin, glycopeptide and macrolide drugs used in aquaculture when screened against a range of common antibiotics. To the best of our knowledge, this is the first report of tail rot disease caused by C. freundii in freshwater farmed A. japonica.

Aeromonas hydrophila: a Causative Agent for Tail Rot Disease in Freshwater Cultured Murray Cod Maccullochella peelii

Tail rot disease is the cause of significant economic damage in freshwater farmed Murray cod Maccullochella peelii. Only scarce information is available on Aeromonas hydrophila as a possible causal agent for this disease. In this study, a virulent strain, temporarily named XY3, was isolated from diseased codfish suffering from tail rot disease, and identified as A. hydrophila through phylogenetic analysis and phenotypic characteristics. A. hydrophila possesses multiple virulence genes including aerA, ahpA, alt, ast and hlyA genes. In addition, it appears that isolate XY3 has developed multiple resistances to cephalosporin, chloromycetin, glycopeptides, macrolides, nitrofuran, and penicillin drugs, as well as to aminoglycosides, sulfonamides, and tetracyclines antibiotics for veterinary uses in aquaculture as revealed when screened against a range of common antibiotics. To the best of our knowledge, this is the first report of tail rot disease caused by A. hydrophila in freshwater farmed codfish.

Tail Rot Disease in Macrobrachium idella idella (Hilgendorf, 1898)

Shell disease may also be referred to as black spot, brown spot or spot disease and was recognized early this century as a problem in impounded population of aquatic animals. The chitinoclastic bacteria which cause shell disease are ubiquitous and infect a wide range of crustaceans, including prawns. All wild and cultured prawns are susceptible to infections; however disease rarely in wild crustaceans due to a lack of overcrowding and less mechanical damage. In the present study the Tail rot disease noticed in the M. idella idella (prawn), which is not common for prawns. The tail rot diseased prawn was tested to bacteriological for enumeration, isolation and biochemical identification of the microorganism.

NovelMycobacteriumSpecies in Seahorses with Tail Rot

To the Editor: Seahorses (Hippocampus guttulatus and H. hippocampus) with signs of tail rot disease (lethargy, lack of appetite, white spots on the skin, and necrotic tail lesions) were collected from aquaria at the Institute of Marine Research, Spain, during March 2007 through May 2009 (Figure A1). Microscopic examination of cutaneous lesions after Ziehl-Neelsen staining disclosed acid-fast bacilli. Microbiologic analysis showed unidentified Mycobacterium strains. Subsequently, we used PCR amplification of repetitive bacterial DNA elements to group the strains (1). The results showed an identical PCR pattern for the strains; thus, we selected strain BFLP-6T for analysis. On the basis of phenotypic and genotypic data, we consider the unknown acid-fast bacillus to represent a novel species of the genus Mycobacterium, for which the name M. hippocampi sp. nov. is proposed. Extraction and amplification of genomic DNA for 16S rRNA sequence analysis were conducted as described (2), and the RNA polymerase B (rpoB) gene was amplified and sequenced as described by Adekambi et al. (3). Sequences obtained were compared against the sequences available in the GenBank, EMBL, and DDBJ databases obtained from the National Center for Biotechnology Information by using the BLAST program (4). Phylogenetic analysis were performed by using MEGA version 4.0 (5) after multiple alignments of data by ClustalX (6). Distances (distance options according to the Kimura 2-parameter model) and clustering with the neighbor-joining method were determined by using bootstrap values for 1,000 replications. The 16S rRNA sequence of strain BFLP-6T was a continuous stretch of 1,473 bp (GenBank accession no. {type:entrez-nucleotide,attrs:{text:FN430736,term_id:254527702,term_text:FN430736}}FN430736). Sequence similarity calculations after a neighbor-joining analysis indicated that the closest relatives of strain BFLP-6T were M. flavescens (98.26%), M. goodii (98.01%), M. duvalii (97.94%), M. smegmatis (97.92%), and M. novocastrense (97.86%) (Figure). Similar results were obtained for strain BFLP-6T when the maximum-parsimony algorithm was used. The rpoB gene has also been proposed as a useful marker for inferring bacterial phylogeny (7,8). A pair-wise analysis of the rpoB sequence of strain BFLP-6T (GenBank accession no. {type:entrez-nucleotide,attrs:{text:FR775976,term_id:320202798,term_text:FR775976}}FR775976) showed low levels of similarity (<89.8%) with other species of the genus Mycobacterium. The G + C content of DNA, as measured by the thermal denaturation method, was 66.7 mol%. Strain BFLP-6T was found to consist of gram-positive–staining, aerobic, acid-alcohol–fast, nonmotile, and nonsporulating cells. A scanning electron micrograph showed that strain BFLP-6T is irregular, rod-shaped, ≈1.2–1.4 μm in length, and 0.4 μm in diameter. Colonies on Lowenstein-Jensen medium supplemented with 1.5% (wt/vol) sodium chloride were orange after incubation at 25°C for 5 days. The colonies were positive for catalase, glucose fermentation, arginine dihydrolase, urease, and aesculin, and assimilation of glucose, mannitol, potassium gluconate, and malate. The colonies were negative for nitrate reduction to nitrite, oxidase, indole production, gelatin hydrolysis, N-acetyl-d-glucosamine; and assimilation of arabinose, mannose, maltose, caprate, adipate, citrate, and phenylacetate. The major fatty acids were C18:1ω9c, C16:0, and C16:1ω6c. Mycolic acids included α-mycolates, keto-mycolates, and nonhydroxylated fatty acid methyl esters. In addition, strain BFLP-6T showed resistance to isoniazid, thiophene-2-carboxylic hydrazide, hydroxylamine, thiacetazone, and picrate. However, the strain exhibited susceptibility to ciprofloxacin, clarithromycin, and rifampin. The type strain BFLP-6T has been deposited in the German Collection of Microorganisms and Cell Cultures, under reference DSM 45391T; and in the Belgian Coordinated Collections of Microorganisms under reference LMG 25372T. Figure Neighbor-joining phylogenetic tree constructed from 16S rRNA gene sequences, showing the position of strain BFLP-6T (in boldface) among other Mycobacterium species. Numbers at node indicate bootstrap values (expressed as percentages of 1,000 replications); ...

Identification and Pathogenicity of Aeromonas sobria on Tail-rot Disease in Juvenile Tilapia Oreochromis niloticus

Thirty-six strains, numbered from PY01 to PY36, were isolated from six moribund Oreochromis niloticus. The biochemical characteristics of all strains conformed to the species description of Aeromonas sobria on the basis of API 20E and Biolog GN system. Furthermore, gyrB sequence of strain PY36 was sequenced and showed high similarity (99.8%) with A. sobria in Genbank. Antibiotic-resistance of strain PY36 was assessed by the Kirby-Bauer disk diffusion method, and the results showed it was susceptible and moderately susceptible to 12 and 3 of the 19 antimicrobials tested. Virulence of strain PY36 to juvenile tilapia was also tested, and we found that LD₅₀ was about 4.17 × 10³ CFU per fish in intraperitoneal injection. This is the first article to report that A. sobria was the pathogenic agent of tail-rot disease in juvenile tilapia. A. sobria was multi-resistant to the most frequently used antimicrobial drugs in China, so the antimicrobial resistance test should be carried out when these bacteria are isolated from biological samples in order to avoid therapeutic failures and spread of the pathogenic organisms in the environment.

Identification of Vibrio harveyi as a causative bacterium for a tail rot disease of sea bream Sparus aurata from research hatchery in Malta

A bacterial disease was reported from gilthead sea bream (Sparus aurata) within a hatchery environment in Malta. Symptoms included complete erosion of tail, infection in the eye, mucous secretion and frequent mortality. A total of 540 strains were initially isolated in marine agar from different infected body parts and culture water sources. Subsequently 100 isolates were randomly selected, identified biochemically and all were found to be Vibrio harveyi-related organisms; finally from 100 isolates a total of 13 numbers were randomly selected and accurately identified as V. harveyi by 16S rRNA gene sequencing and species-specific PCR. Ribotyping of these strains with HindIII revealed total of six clusters. In vivo challenge study with representative isolates from each cluster proved two clusters each were highly pathogenic, moderately pathogenic and non-pathogenic. All 13 isolates were positive for hemolysin gene, a potential virulence factor. Further analysis revealed probably a single copy of this gene was encoded in all isolates, although not in the same locus in the genome. Although V. harveyi was reported to be an important pathogen for many aquatic organisms, to our knowledge this might be the first report of disease caused by V. harveyi and their systematic study in the sea bream hatchery from Malta.