Distribution of Vibrionaceae in farmed Asian sea bass, Lates calcarifer in Thailand and their high prevalence of antimicrobial resistance.

This study describes the etiological agent of Vibriosis along with its distribution and antimicrobial resistance profiles among farmed Asian sea bass (Lates calcarifer) in Thailand. The study isolated 283 Vibrionaceae from 15 Asian sea bass farms located around the provinces of the Andaman Sea and Gulf of Thailand coasts to uncover the distribution and antimicrobial resistance profiles. Bacterial identification based on a combination of the biochemical characteristics, Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry (MS) analysis, and the species-specific PCR demonstrated the predominant Vibrionaceae were Vibrio harveyi (n = 56), Photobacterium damselae (n = 35), and V. vulnificus (n = 31), respectively. According to a laboratory challenge experiment, among the six isolates, only V. harveyi was found to cause clinical signs of muscle necrosis and scale loss in Asian sea bass. Antibiotics resistance test results exhibited high resistance to antibiotics such as metronidazole (100%), streptomycin (97%), clindamycin (96%), colistin sulphate (70%) and amoxicillin (59%). Remarkably, 100% of Vibrionaceae isolates are susceptible to florfenicol. The 28 of 29 resistance profiles were multidrug resistances (MDR), with V. vulnificus having the highest MAR value (0.66). The findings of this study advise that a surveillance program, as well as preventive and control measures, be developed for Vibrionaceae to reduce production loss, pathogen proliferation, and antibiotic abuse, whereas AMR data indicate substantial health problems for aquatic animals and humans.

Diversity and antimicrobial susceptibility profiles of Aeromonas spp. isolated from diseased freshwater fishes in Thailand.

Motile Aeromonas septicemia (MAS), a disease caused by Aeromonas spp., is recognized as a major disease in freshwater aquaculture. This study aimed to investigate the distribution and diversity of Aeromonas spp. and their antimicrobial susceptibility patterns. A total of 86 isolates of Aeromonas spp. were recovered from diseased freshwater fishes from 13 farms in Thailand. All isolates were identified using biochemical characteristics, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), polymerase chain reaction assays, and the gyrB gene sequence analysis. The result of MALDI-TOF MS showed 100% (86 isolates) accuracy at genus-level identification, and 88.4% (76 isolates) accuracy at species-level identification. Six species of Aeromonas were confirmed through nucleotide sequencing and phylogenetic analysis of the gyrB gene Aeromonas veronii (72.1%), Aeromonas jandaei (11.6%), Aeromonas schubertii (9.3%), Aeromonas diversa (3.5%), Aeromonas hydrophila (2.3%), and Aeromonas punctata (1.2%). Antimicrobial susceptibility tests for all isolates revealed resistance against amoxicillin (99%), ampicillin (98%), oxolinic acid (81.4%), oxytetracycline (77%), trimethoprim-sulfamethoxazole (24%), and enrofloxacin (21%). The multiple antibiotic resistance (MAR) index varied between 0.14 and 0.86, with MAR values more than 0.2 in 99% of isolates. Furthermore, four diverse multidrug-resistant (MDR) patterns were found among Aeromonas isolates. Our finding show that A. veronii is the most abundant species in Thai cultured freshwater fish with the highest MDR patterns.

Potential influence of jaggery-based biofloc technology at different C:N ratios on water quality, growth performance, innate immunity, immune-related genes expression profiles, and disease resistance against Aeromonas hydrophila in Nile tilapia (Oreochromis niloticus).

Biofloc technology is increasingly becoming the most promising aquaculture tool especially in places where water is scarce and the land is very expensive. The dynamics of water quality, as well as plankton and microbial abundance, are collectively necessary for successful fish farming. The prospective use of jaggery as a potential carbon source and its influence on water quality, growth performance, innate immunity, serum bactericidal capacity, and disease resistance to Aeromonas hydrophila was investigated in Oreochromis niloticus. A completely randomized design was used in triplicates, where the control group was reared in a water system with no carbon source, while T1, T2, and T3 groups were raised in biofloc systems at C:N ratios of C:N12, C:N15, and C:N20, respectively. Water specimens were collected daily and fortnightly, while blood, serum, and head kidneys were collected at 75 days of experimental period for further analysis. TAN, nitrite, and ammonia values were considerably reduced, while the TSS values elevated significantly in all treated groups compared to the control. Jaggery-based biofloc system (JB-BFT) has a pronounced effect on hematological and growth performance parameters rather than control. Similarly, serum antioxidants, lysozyme, protease, antiprotease and bactericidal capacity were significantly increased (p < 0.05) in the treated groups in a dose-dependent manner. LYZ, TNF-α, and IL-1ß genes were upregulated in proportion to C:N ratios with the highest fold in C:N20. Furthermore, fish treated with JB-BFT presented lower cumulative mortalities and better relative levels of production (RLP) after experimental challenge with A. hydrophila compared to control. In conclusion, JB-BFT has a robust influence on Nile tilapia (O. niloticus) innate immunity through favorable innovation of various immune-cells and enzymes as well as upregulating the expression levels of immune-related genes. This study offers jaggery as a new carbon source with unique properties that satisfy all considerations of biofloc technology in an eco-friendly manner.

In situ synthesis of silver nanoparticles into TEMPO-mediated oxidized bacterial cellulose and their antivibriocidal activity against shrimp pathogens.

Vibrionaceae is bifolded drug resistant emerging pathogens, active in various aquaculture sectors especially in shrimp culture around the world. V. parahaemolyticus are most dreadful viral outbreaks to shrimp culture. During the last decade the shrimp production level has been increased and also accompanied with various diseases. In the present research bacterial cellulose (BC) membrane produced by Gluconacetobacter xylinus in cell suspension. Further, TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) oxidation was done to activate carboxyl group subsequently, TEMPO oxidized BC immersed in AgNO3 solution to generate AgNP anchored with BC to increase vibriocidal activity. Investigation of pure BC, TEMPO-BC and AgNP deposited BC was done by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Further vibriocidal effect was observed against the pathogen V. parahaemolyticus and V. harveyi. We found AgNP-BC more effective as compare pure BC, TEMP-BC, and AgNO3. Therefore AgNP deposited BC, is promising alternative to control the shrimp pathogen.

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 from Lactobacillus murinus AU06 isolated from marine sediments and its broad spectrum of inhibition against fish pathogens. METHODS: 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. RESULTS: 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. 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.

Thermostable, haloalkaline cellulase from Bacillus halodurans CAS 1 by conversion of lignocellulosic wastes.

An extracellular thermostable, haloalkaline cellulase by bioconversion of lignocellulosic wastes from Bacillus halodurans CAS 1 was purified to homogeneity with recovery of 12.54% and purity fold 7.96 with the molecular weight of 44 kDa. The optimum temperature, pH and NaCl for enzyme activity was determined as 60°C, 9.0 and 30% and it retained 80% of activity even at 80°C, 12 and 35% respectively. The activity was greatly inhibited by EDTA, indicating that it was a metalloenzyme and significant inhibition by PMSF revealed that serine residue was essential for catalytic activity. The purified cellulase hydrolyzed CMC, cellobiose and xylan, but not avicel, cellulose and PNPG. Furthermore, the cellulase was highly stable in the presence of detergents and organic solvents such as acetone, n-hexane and acetonitrile. Thus, the purified cellulase from B. halodurans utilizing lignocellulosic biomass could be greatly useful to develop industrial processes.