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Background Vibriosis is an important bacterial disease of cultured marine fishes worldwide. However, information on the virulence and antibiotic resistance of Vibrio spp. isolated from fish are scarce. This study investigates the distribution of virulence associated genes and antibiotic resistance patterns of Vibrio spp. isolated from cage-cultured marine fishes in Malaysia. Results A total of 63 Vibrio spp. isolated from 62 cultured marine fishes in various geographical regions in Peninsular Malaysia were analysed. Forty-two of the isolates (66.7%) were positive for all chiA , luxR and vhpA , the virulence genes produced by pathogenic V. harveyi . A total of 62 Vibrio isolates (98%) had tlh gene of V. parahaemolyticus , while flaC gene of V. anguillarum was detected in 43 of isolates (68%). Other virulence genes, including tdh , trh , hlyA and toxR vc were absent from any of the isolates. Multiple antibiotic resistance (MAR) was exhibited in all strains of Harveyi clade, particularly against ampicillin, penicillin, polypeptides, cephems and streptomycin. The MAR index ranged between 0.06 and 0.56, and 75% of the isolates have MAR index of higher than 0.20. Host species and geographical origin showed no correlation with the presence of virulence genes and the antibiotic resistance patterns of Vibrio spp. Conclusions The study indicates that majority of Vibrio spp. isolated from cultured marine fishes possess virulence genes, but were not associated with human pathogen. However, the antibiotics resistance is a real concern and warrants ongoing surveillance. These findings represent an updated knowledge on the risk of Vibrio spp. to human health, and also provides valuable insight on alternative approaches to combat vibriosis in cultured fish.

Currently the development of green chemistry approach with the use of biomaterial-based activities of microbial cells in the synthesis of various nanostructures has attracted a great attention. In this study, we report on the use of bacterium, Bacillus cereus as a biotemplating agent for the formation of zinc oxide nanoparticles with raspberry- and plate-like structures through a simple thermal decomposition of zinc acetate by maintaining the original pH of the reaction mixtures. Possible mechanism on the formation of the nanostructures is proposed based on the surface chemistry and biochemistry processes involved organic-inorganic interactions between zinc oxide and the microbial cells.

This study investigated the environmental factors associated with the presence of Vibrionaceae in economically important cage‐cultured tropical marine fishes: the Asian Seabass Lates calcarifer, snapper Lutjanus sp., and hybrid grouper Epinephelus sp. Fish sampling was conducted at monthly intervals between December 2016 and August 2017. The body weight and length of individual fish were measured, and the skin, eye, liver, and kidney were sampled for bacterial isolation and identification. Water physicochemical parameters during the sampling activities were determined, and the enumeration of total Vibrionaceae count was also conducted from water and sediment samples. Nine species of Vibrio were identified, including V. alginolyticus, V. diabolicus, V. harveyi, V. campbellii, V. parahaemolyticus, V. rotiferianus, V. furnissii, V. fluvialis, and V. vulnificus. Photobacterium damselae subsp. damselae was also identified. A total of 73% of the isolated Vibrio belonged to the Harveyi clade, followed by the Vulnificus clade (5.5%) and Cholera clade (0.6%). Highest occurrence of Vibrio spp. and P. damselae subsp. damselae was found in hybrid grouper (72%), followed by Asian Seabass (48%) and snapper (36%). The associations of Vibrio spp. and P. damselae subsp. damselae with the host fish were not species specific. However, fish mortality and fish size showed strong associations with the presence of some Vibrio spp. On average, 60% of the infected cultured fish exhibited at least one clinical sign. Nevertheless, inconsistent associations were observed between the pathogens and water quality. The yearlong occurrence and abundance of Vibrionaceae in the environmental components indicate that they might serve as reservoirs of these pathogens.

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Zinc oxide nanoparticles (ZnONPs) were synthesized by the sol-gel method at various pH values. XRD, FTIR, FESEM, UV-vis and PL were accomplished to characterize the structural, functional groups, morphology, and optical properties of the samples. The disk diffusion method was conducted to investigates the antibacterial properties of the ZnONPs. The particle sizes of the ZnONPs synthesized between pH 7-11 was explored vary from 59.56-46.45 nm and mostly in spherical shape. Ultraviolet-visible analysis (UV-vis) also revealed the optical properties with the optical band gap of 3.29, 3.31, 3.33, 3.31 and 3.29 eV correspond to ZnONPs in pH 7-11. While the highest PL spectra of ZnONPs display a blue emission band around 484 nm in the UV range at pH 9. The highest diameter of inhibition zone after 120 h was found at 4.4 ± 0.1 cm at pH 11 of ZnONPs. In this research, the average particles size of ZnONPs and the intensities of the XRD pattern decreases with the increasing pH values. However, with the increasing pH values, the antibacterial activity becomes effective.