Tenacibaculosis caused by Tenacibaculum maritimum: Updated knowledge of this marine bacterial fish pathogen.

Tenacibaculosis occurs due to the marine bacterial pathogen Tenacibaculum maritimum. This ulcerative disease causes high mortalities for various marine fish species worldwide. Several external clinical signs can arise, including mouth erosion, epidermal ulcers, fin necrosis, and tail rot. Research in the last 15 years has advanced knowledge on the traits and pathogenesis mechanisms of T. maritimum. Consequently, significant progress has been made in defining the complex host-pathogen relationship. Nevertheless, tenacibaculosis pathogenesis is not yet fully understood. Continued research is urgently needed, as demonstrated by recent reports on the re-emerging nature of tenacibaculosis in salmon farms globally. Current sanitary conditions compromise the development of effective alternatives to antibiotics, in addition to hindering potential preventive measures against tenacibaculosis. The present review compiles knowledge of T. maritimum reported after the 2006 review by Avendaño-Herrera and colleagues. Essential aspects are emphasized, including antigenic and genomic characterizations and molecular diagnostic procedures. Further summarized are the epidemiological foundations of the T. maritimum population structure and elucidations as to the virulence mechanisms of pathogenic isolates, as found using biological, microbiological, and genomic techniques. This comprehensive source of reference will undoubtable serve in tenacibaculosis prevention and control within the marine fish farming industry. Lastly, knowledge gaps and valuable research areas are indicated as potential guidance for future studies.

Insight Into Whole Genome of Aeromonas veronii Isolated From Freshwater Fish by Resistome Analysis Reveal Extensively Antibiotic Resistant Traits.

Aeromonas veronii outbreaks in tilapia farming caused relatively high mortalities, and the bacteria was resistant to many kinds of antimicrobials used in Thailand aquaculture. According to the CLSI standard, the determination of antimicrobials efficacy has been limited to phenotypic analyses, and a genomics study is required. This research aimed to analyze the resistome of A. veronii isolated from diseased tilapia in Chainat, Nong Khai, and Uttaradit provinces in Thailand. A total of 12 isolates of A. veronii were identified based on the gyrB sequencing and then, the MIC values to eight antimicrobials (AMP, AML, GEN, ENR, OXO, OTC, SXT, and FFC) were determined. According to the MIC patterns, whole genome sequencing (WGS) of five representatives and resistome analysis were performed, including 15 genomes of A. veronii isolated from freshwater fish available in the NCBI. All tilapia isolates were susceptible to FFC but resistant to AML and AMP while OTC resistance was the most dominant. In addition to the WGS analysis, 4.5 Mbp of A. veronii was characterized. A total of 20 ARGs were detected by resistome analysis and 16 genes were shared among the A. veronii population. In conclusion, A. veronii strains isolated from tilapia exhibited a resistance to several antimicrobials and multidrug resistance (MDR) which was related to the presence of multiple ARGs. Aeromonas veronii shared the ARGs in their population worldwide with a possibility of a plasmid-mediated acquisition due to the presence of resistance islands.

Emerging MDR-Pseudomonas aeruginosa in fish commonly harbor oprL and toxA virulence genes and blaTEM, blaCTX-M, and tetA antibiotic-resistance genes.

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 (blaTEM, tetA, and blaCTX-M). 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 blaTEM, blaCTX-M, 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 blaCTX-M, blaTEM, 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.

Influence of stocking density on growth, digestive enzyme activities, immune responses, antioxidant of Oreochromis niloticus fingerlings in biofloc systems.

A 120-day feeding trial was conducted to evaluate the effect of different stocking densities on growth, the non-specific immunities, antioxidant status and digestive enzyme activities of Oreochromis niloticus fingerlings under a zero-water exchange biofloc system. Tilapias (0.51 ±â€¯0.05 g) were randomly distributed in twelve tanks, each with 300 L water. The experimental design was completely randomized using three replications with four treatments 166 orgs m-3 (LD, low density), 333 orgs m-3 (MD, middle density) and 600 orgs m-3 (HD, high density) with glucose added as biofloc groups, and a clear water group without glucose added as a control 333 orgs m-3. The fish cultured in LD and MD group showed higher final body weight. For the digestive enzymes, the lipase, trypsin, and amylase activities were all depressed in HD group and control group. Regarding the immune and antioxidant abilities, significantly lower values (P < 0.05) of the lysozyme, complement 3, and glutathione were observed for the fish that reared in the control group and HD group. The stress indicator, the cortisol, 5-hydroxytryptamine, and glucose concentrations were also depressed in HD group and control group, meanwhile the alanine aminotransferase, aspartate transaminase and alkaline phosphatase were all higher in HD group and control group. The significant higher survival was observed in the LD and MD group after Vibrio harveyi challenge test. The results of the experiment indicated that the biofloc in situ had the effects of anti-crowding stress.

Establishment and characterization of a skin epidermal cell line from mud loach, Misgurnus anguillicaudatus, (MASE) and its interaction with three bacterial pathogens.

A continuous skin epidermal cell line from mud Loach (Misgurnus anguillicaudatus) (MASE cell line) was established with its application in bacteria infection demonstrated in this study. Primary MASE cell culture was initiated at 26 °C in Dulbecco's modified Eagle medium/F12 medium (1:1; pH7.2) supplemented with 20% fetal bovine serum (FBS). The primary MASE cells in spindle morphology proliferated into a confluent monolayer within 2 weeks, and were continuously subcultured even in 10% FBS- DMEM/F12 after 10 passages. Impacts of medium and temperature on the growth of the cells were examined. The optimum growth was found in DMEM/F12 with 20% FBS and at 26 °C. The MASE cells have been subcultured steadily over Passage 90 with a population doubling time of 53.3 h at Passage 60. Chromosome analysis revealed that 60.5% of MASE cells at Passage 60 maintained the normal diploid chromosome number (50) with a normal karyotype of 10m+4sm + 36t. Bacteria from the three species (Aeromonas veronii, Vibrio parahaemolyticus and Escherichia coli) were used to investigate the interactions between bacteria and cellular hosts. The three strains could be attached to the MASE cells and replicate at different levels. A. veronii could induce apoptosis in the MASE cells, with highest adherence rate among the three strains, whereas V. parahaemolyticus could cause highest cell death rate through a non-apoptotic cell death pathway, with high level of replication. The results revealed that different bacteria could interact with the MASE cells in different manners, and divergent pathways might lie in mediating cell death when cellular hosts confronted with pathogen infection. Therefore, the MASE cell line may serve as a useful tool for studying the interaction between skin bacteria and fish cells.

Production, purification and characterization of bacteriocin from Lactobacillus murinus AU06 and its broad antibacterial spectrum

Objective: To study the production, purification and characterization of bacteriocin fromLactobacillus murinus against fish pathogens.Methods:AU06 isolated from marine sediments and its broad spectrum of inhibition bacteriocin. In addition, purified bacteriocin was tested for its antimicrobial activity against fish pathogens.Results:In the present study, the bacteriocin production was found to be higher at 35 °C, pH The selected strain was used in production, purification and characterized of 6.0 and was purified to 4.74 fold with 55. 38 U/mg of specific activity with the yield of 28.92%. The molecular weight of the purified bacteriocin was estimated as 21 kDa. The purified bacteriocin exhibited complete inactivation of antimicrobial activity when treated with proteinase K, pronase, chymotrypsin, trypsin, pepsin and papain. The purified bacteriocin exhibited broad inhibitory spectrum against both Gram positive and negative bacteria.Conclusions:It is concluded that the ability of bacteriocin in inhibiting a wide-range of pathogenic bacteria is of potential interest for food safety and may have future applications in food preservative.

Production, purification and characterization of bacteriocin from Lactobacillus murinus AU06 and its broad antibacterial spectrum

<p><b>OBJECTIVE</b>To study the production, purification and characterization of bacteriocin from Lactobacillus murinus AU06 isolated from marine sediments and its broad spectrum of inhibition against fish pathogens.</p><p><b>METHODS</b>The selected strain was used in production, purification and characterized of bacteriocin. In addition, purified bacteriocin was tested for its antimicrobial activity against fish pathogens.</p><p><b>RESULTS</b>In the present study, the bacteriocin production was found to be higher at 35 °C, pH 6.0 and was purified to 4.74 fold with 55. 38 U/mg of specific activity with the yield of 28.92%. The molecular weight of the purified bacteriocin was estimated as 21 kDa. The purified bacteriocin exhibited complete inactivation of antimicrobial activity when treated with proteinase K, pronase, chymotrypsin, trypsin, pepsin and papain. The purified bacteriocin exhibited broad inhibitory spectrum against both Gram positive and negative bacteria.</p><p><b>CONCLUSIONS</b>It is concluded that the ability of bacteriocin in inhibiting a wide-range of pathogenic bacteria is of potential interest for food safety and may have future applications in food preservative.</p>