Bacteria associated with golden pompano (Trachinotus blochii) broodstock from commercial hatchery in Malaysia with emphasis on their antibiotic and heavy metal resistances Abstract This paper was the first report on pathogenic bacteria isolated from golden pompano (Trachinotus blochii) with the antibiogram, as well as the heavy metal resistance pattern. Golden pompano becomes popular among Malaysian fish farmers due to its high value and demand from local and oversea markets. However, the baseline information on antibiogram of pathogenic bacteria associated with golden pompano is not well established. Therefore, the information from this study may be useful to fish farmers in selecting appropriate antibiotic for treatment and prophylactive purpose in golden pompano culture. Isolation of bacterial isolates was carried out using 5% of Horse Blood agar, Tryptic Soy Agar (TSA), Mac Conkey, Thiosulphate Citrate Bile Salt (TCBS), Eosin Methylene Blue (EMB), Glutamate Starch Pseudomonas (GSP), Xylose Lysine Deoxycholate (XLD), and Baird Parker media. The bacterial isolates were then identified using conventional biochemical tests and confirmed by commercial bacterial identification kit. Antibiotic susceptibility test of bacterial isolates against 21 antibiotics (oxolinic acid 2 µg, ampicillin 10 µg, erythromycin 15 µg, furazolidone 15 µg, lincomycin 15 µg, oleandomycin 15 µg, amoxicillin 25 µg, colistin sulphate 25 µg, sulphamethoxazole 25 µg, chloramphenicol 30 µg, doxycycline 30 µg, florfenicol 30 µg, flumequine 30 µg, kanamycin 30 µg, nalidixic acid 30 µg, novobiocin 30 µg, oxytetracycline 30 µg, tetracycline 30 µg, nitrofurantoin 50 µg, fosfomycin 50 µg, and spiramycin 100 µg) was determined using disk diffusion method, whereas the heavy metal resistance pattern (mercury Hg 2+ , cadmium Cd 2+ , chromium Cr 6 + , and copper Cu 2+ ) of the bacterial isolates was characterized using two-fold agar dilution method. Five bacterial species were successfully found from 50 diseased golden pompano. They were Streptococcus spp. (n = 12), Escherichia coli (n = 30), Salmonella spp. (n = 20), Pseudomonas spp. (n = 36), and Vibrio spp. (n = 50). More than 80% of the bacterial isolates were found sensitive to 11 out of 21 antibiotics (tetracycline, nitrofurantoin, florfenicol, chloramphenicol, oxytetracycline, nalidixic acid, doxycycline, furazolidone, flumequine, fosfomycin, and oxolinic acid. However, all bacterial isolates were found resistant to all tested heavy metals except for copper and cadmium. The multiple antibiotic resistance (MAR) index of the present study indicated that the fish samples were under high risk exposure to the tested antibiotics. Florfenicol is suggested to be used as antimicrobial agent for golden pompano culture since all bacterial isolates were sensitive to it.
Antibacterial activity of cell-free supernatant from Escherichia coli E against selected pathogenic bacteria in food and aquaculture was the highest against Edwardsiella tarda 3, a significant aquaculture pathogen. Biochemical properties of the bacteriocins were studied and bacteriocin was found to be sensitive to proteinase K, demonstrating its proteinaceous nature. In addition, pH and temperature affected bacteriocin activity and stability. The bacteriocins were partially purified by ammonium sulfate precipitation. The antibacterial activity was only detected in 20% ammonium sulfate fraction and direct detection of its activity was performed by overlaying on the indicator strains. The inhibition zone associated with the antibacterial activity was detected in the sample overlaid by E. tarda 3 and Staphylococcus aureus DMST8840 with the relative molecular mass of about 27 kDa and 10 kDa, respectively. Bacteriocin showed no cytotoxic effect on NIH-3T3 cell line; however, two virulence genes, aer and sfa, were detected in the genome of E. coli E by PCR. The characteristics of bacteriocins produced by E. coli E exhibited the antibacterial activity against both Gram-positive and Gram-negative pathogenic bacteria and the safe use determined by cytotoxicity test which may have interesting biotechnological applications.
Comparative study on antibiogram of Vibrio spp. isolated from diseased postlarval and marketable-sized white leg shrimp (Litopenaeus vannamei) Abstract This paper compared antibiotic sensitivity between Vibrio spp. isolated from diseased postlarval and marketable-sized white leg shrimp (Litopenaeus vannamei). Recently, white leg shrimp become target species of shrimp culture among shrimp farmers in Malaysia to replace tiger shrimp (Penaeus monodon) culture. However, the baseline information on antibiogram of pathogenic bacteria especially Vibrio spp., the causative agent of vibriosis in white leg shrimp culture is not well established. Therefore, this study was conducted to reveal the antibiogram of Vibrio spp. isolated from diseased postlarval and marketable-sized white leg shrimp. The information gained from this study is useful for shrimp farmers in selecting appropriate antibiotic during disease outbreak. Antibiogram of present bacterial isolates was determined through disk diffusion method against 21 antibiotics (oxolinic acid 2 µg, ampicillin 10 µg, erythromycin 15 µg, furazolidone 15 µg, lincomycin 15 µg, oleandomycin 15 µg, amoxicillin 25 µg, colistin sulphate 25 µg, sulphamethoxazole 25 µg, chloramphenicol 30 µg, doxycycline 30 µg, florfenicol 30 µg, flumequine 30 µg, kanamycin 30 µg, nalidixic acid 30 µg, novobiocin 30 µg, oxytetracycline 30 µg, tetracycline 30 µg, nitrofurantoin 50 µg, fosfomycin 50 µg, and spiramycin 100 µg). A total of 47 Vibrio spp. isolates (Vibrio parahaemolyticus, 24, and V. alginolyticus, 23) from postlarval white leg shrimp and 49 Vibrio spp. isolates (Vibrio parahaemolyticus, 13, Vibrio alginolyticus, 28, and luminous Vibrio parahaemolyticus, 8) from marketable-sized white leg shrimp were successfully identified. Results of antibiotic sensitivity test from the present study showed that more than 80% Vibrio spp. from diseased postlarval and marketable-sized white leg shrimp, respectively, were sensitive to 14 out of the 21 tested antibiotics. Vibrio spp. isolated from marketablesized white leg shrimp were found more susceptible to the tested antibiotics than Vibrio spp. isolated from postlarval white leg shrimp. This was due to 100% sensitive case against eight antibiotics found among Vibrio spp. isolated from marketable-sized white leg shrimp, whereas only three antibiotics were found sensitive to all Vibrio spp. isolated from postlarval white leg shrimp. Furthermore, the multiple antibiotic resistance (MAR) index indicated that marketable-sized white leg shrimp were not under high risk exposure to the tested antibiotics. On the other hand, the postlarvae were highly exposed to the tested antibiotics.
A novel approach for the synthesis of graphene oxide silver alginate has been developed for the antibacterial performance. Graphene oxide (GO) was used as a supporting material towards formation of silver nanoparticle (AgNPs) by a rapid microwave irradiation on mixture of GO and silver complexes and layered on alginate film. The obtained nanocomposite were characterized by using Ultraviolet-visible spectroscopy (UV-Vis), Xray diffraction (XRD) to confirm the formation of GOAgAlginate. The surface morphological studies for the nanocomposite was done by using scanning electron microscope (SEM). Nanometer-sized AgNPs (an average diameter of about 70 nm) with spherical-shape structure loaded on the GO Alginate layer showed a good antibacterial towards E.Coli and Methicillin-resistant Staphylococcus aureus (MRSA).
Aquaculture is one of the fastest growing industries in the world. This industry supplies half of thefisheries products consumed annually, and future global demand can only be supplied by increasingaquaculture production, which, in turn, requires more aquafeed. Alternative ingredients must beincreasingly used to supply significant proportions of protein and energy in aquafeeds, creatingboth challenges and opportunities for researchers and industry. Nowadays, there are too manyresearches on fish disease, growth and health but less in a fish feed especially a replacement ofprotein from plant sources in the fish feed. One of the alternative ways to optimise the growth andhealth condition of the fish is provide them a good protein from plant as a replacement in fish mealwith the natural source protein instead of giving a good rearing condition and caring of the fish.The present article was constructed to highlight a replacement of plant protein sources as analternative of fish meal for fish feed in African catfish, Clarias gariepinus that has been done byresearchers. However, the application of replacement from plant protein sources in fish meal is nowgradually gaining importance in commercial aquaculture practices and opened the door for theresearchers to expend of this application, thus more detailed studies on molecular basis should belooked as to get the quality and enough nutrient fish feed for good production of aquacultureindustry.
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