Seong Wei Lee

Multiple Antibiotic Resistance and Heavy Metal Resistance Profile of Bacteria Isolated from Giant Freshwater Prawn (Macrobrachium rosenbergii) Hatchery

Abstract In this article, antibiogram and heavy metal resistance profile of bacteria isolated from giant freshwater prawn ( Macrobrachium rosenbergii ) hatchery in Malaysia are described. Although giant freshwater prawn was introduced into Malaysia since the 1980s, there was no database information on antibiogram and heavy metal resistance profile of bacteria from giant freshwater prawn ( M. rosenbergii ) hatchery in Malaysia. Therefore, this study was carried out to determine the effectiveness of antibiotic and heavy metal resistance profile to control bacterial diseases in M. rosenbergii hatchery. The results can provide valuable information for local M. rosenbergii post-larval producer. Antibiotic sensitivity test was carried out by disk-diffusion method against 15 types of antibiotics as follows: oxolinic acid (2 μg), ampicillin (10 μg), erythromycin (15 μg), furazolidone (15 μg), lincomycin (15 μg), amoxicillin (25 μg), colistin sulphate (25 μg), doxycycline (30 μg), florfenicol (30 μg), flumequine (30 μg), nalidixic acid (30 μg), tetracycline (30 μg), oleandomycin (15 μg), fosfomycin (50 μg), and spiramycin (100 μg), whereas heavy metal resistance profile of the present bacterial isolates was determined by 2-fold agar dilution technique. In this study, 5 types of bacteria were successfully isolated; they were Aeromonas spp. (n = 77), Escherichia coli (n = 73), Edwardsiella spp. (n = 62), Salmonella spp. (n = 75), and Vibrio spp. (n = 43). The result showed that furazolidone was the most effective antibiotic to control the bacteria isolated in this study, approximately 89.7% of the bacterial isolates were sensitive to this antibiotic. Multiple antibiotic resistance (MAR) index indicated that the hatchery water source and M. rosenbergii post-larval and sediment tanks were at high-risk exposure to the tested antibiotic. Furthermore, all the tested heavy metals (Cd 2+ , Cr 6+ , Hg 2+ , and Cu 2+ ) failed to inhibit the growth of the bacterial isolates. Therefore, it indicated that the water source of the hatchery is contaminated with both antibiotic residues and heavy metal.

Antimicrobial Property of 2-Hydroxypropane-1,2,3-Tricarboxylic Acid Isolated from Citrus microcarpa Extract

Abstract This article described antimicrobial property and structure analysis of 2-hydroxypropane-1,2,3-tricarboxylic acid isolated from the crude extract of Citrus microcarpa. Presently, there was no report on compound from C. microcarpa that possessed antimicrobial property against fish pathogenic bacteria. Therefore, in this study, the bioactive principle in C. microcarpa extract was isolated using thin layer chromatography. Its structure was elucidated based on nuclear magnetic resonance (NMR) spectroscopic data, such as proton NMR (1HNMR), correlation spectroscopy, carbon 13 NMR, and heteronuclear multiple bond correlation data. This study showed that the bioactive compound isolated from C. microcarpa was 2-hydroxypropane-1,2,3-tricarboxylic acid monohydrate. The minimum inhibitory concentration (MIC) values of crude C. microcarpa extract and its bioactive component, 2-hydroxypropane-1,2,3-tricarboxylic acid as well as commercially available synthetic 2-hydroxypropane-1,2,3-tricarboxylic acid, were determined against 18 isolates of Edwardsiella tarda and 7 bacterial reference strains, namely, Escherichia coli (ATCC 25922), Citrobacter freundii (ATCC 8090), Aeromonas hydrophila (ATCC 49140), Pseudomonas aeruginosa (ATCC 35032), Streptococcus agalatiae (ATCC 13813), E. tarda (ATCC 15947), and Yersinia enterocolitica (ATCC 23715), using two-fold microdilution method. The MIC values for both the natural 2-hydroxypropane-1,2,3-tricarboxylic acid and the synthetic one were ranging from 15.6 to 62.5 mg mL−1, whereas that of the crude extract was ranging from 7.8 to 31.3 mg mL−1. These findings showed that both the crude extract and its bioactive component might have potential as antimicrobial agent for aquaculture use.

Phenotypic and genotypic characteristics of Mycobacterium isolates from fighting fish Betta spp. in Malaysia.

Mycobacteriosis due to mycobacteria is one of the most common bacterial diseases in ornamental fish. We describe here the phenotypic and genotypic characteristics of Mycobacterium isolates from fighting fish Betta spp. using ATCC Mycobacterium marinum, Mycobacterium fortuitum and Mycobacterium chelonae as references. A total of four isolates (M1, M2, M3, M4) were obtained from four out of 106 fish samples using selective agar, and identified to Mycobacterium genus using acid-fast staining and 16s rRNA gene-based genus specific polymerase chain reaction. DNA sequencing and NCBI-BLAST analysis further identified isolate M1 as M. marinum and isolates M2, M3, M4 as M. fortuitum. Morphological, physiological and biochemical tests were carried out for phenotypic characterizations. Universal M13 and wild-type phage M13 RAPD dendogram was generated to illustrate the genetic relationship of the isolates and reference strains.