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Veterinary World Aug 2021The emergence of antibiotic-resistant bacterial pathogens has been increasingly reported, which has resulted in a decreasing ability to treat bacterial infections....
BACKGROUND AND AIM
The emergence of antibiotic-resistant bacterial pathogens has been increasingly reported, which has resulted in a decreasing ability to treat bacterial infections. Therefore, this study investigated the presence of spp., including its antibiotic resistance in various fish samples, spp., , and , obtained from Kelantan and Terengganu, Malaysia.
MATERIALS AND METHODS
In this study, 221 fish samples, of which 108 ( spp., n=38; , n=35; and , n=35) were from Kelantan and 113 ( spp., n=38; , n=35; and , n=40) were from Terengganu, were caught using cast nets. Then, samples from their kidneys were cultured on a Rimler Shott agar to isolate spp. Polymerase chain reaction (PCR) was used to confirm this isolation using specific gene primers for species identification. Subsequently, the isolates were tested for their sensitivity to 14 antibiotics using the Kirby-Bauer method, after which the PCR was conducted again to detect resistance genes: , -, , , , -, and .
RESULTS
From the results, 61 isolates were identified as being from the genus using PCR, of which 28 were , 19 were , seven were , and seven were . Moreover, 8, 12, and 8 of ; 4, 3, and 12 of ; 6, 0, and 1 of ; and 3, 3, and 1 of were obtained from spp., , and , respectively. In addition, the isolates showed the highest level of resistance to ampicillin (100%), followed by streptomycin (59.0%), each kanamycin and nalidixic acid (41.0%), neomycin (36.1%), tetracycline (19.7%), sulfamethoxazole (14.8%), and oxytetracycline (13.1%). Resistance to gentamicin and ciprofloxacin both had the same percentage (9.8%), whereas isolates showed the lowest resistance to norfloxacin (8.2%) and doxycycline (1.6%). Notably, all isolates were susceptible to chloramphenicol and nitrofurantoin. Results also revealed that the multiple antibiotic resistances index of the isolates ranged from 0.07 to 0.64, suggesting that the farmed fish in these areas were introduced to the logged antibiotics indiscriminately and constantly during their cultivation stages. Results also revealed that the gene was detected in 19.7% of the isolates, whereas the tetracycline resistance genes, and , were detected in 27.9% and 4.9% of the isolates, respectively. However, β-lactam resistance genes, and , were found in 44.3% and 13.1% of isolates, respectively, whereas and genes were found in 3.3% and 13.1% of the isolates, respectively.
CONCLUSION
This study, therefore, calls for continuous surveillance of antibiotic-resistant spp. in cultured freshwater fish to aid disease management and better understand their implications to public health.
PubMed: 34566322
DOI: 10.14202/vetworld.2021.2064-2072 -
Genome Announcements Jun 2018We report here the whole-genome sequencing results of two bacterial isolates, IMET J and IMET F, that inhibit (possibly due to denitrifying gene clusters) and promote...
Draft Genome Sequences of Cloacibacterium normanense IMET F, a Microalgal Growth-Promoting Bacterium, and Aeromonas jandaei IMET J, a Microalgal Growth-Inhibiting Bacterium.
We report here the whole-genome sequencing results of two bacterial isolates, IMET J and IMET F, that inhibit (possibly due to denitrifying gene clusters) and promote (possibly due to an ammonification system), respectively, the growth of the microalgal strains HTB1 and 1807.
PubMed: 29903817
DOI: 10.1128/genomeA.00503-18 -
FEBS Open Bio Jun 2018Understanding the role of specific amino acid residues in the molecular mechanism of a protein's function is one of the most challenging problems in modern biology. A...
Understanding the role of specific amino acid residues in the molecular mechanism of a protein's function is one of the most challenging problems in modern biology. A systematic bioinformatic analysis of protein families and superfamilies can help in the study of structure-function relationships and in the design of improved variants of enzymes/proteins, but represents a methodological challenge. The pyridoxal-5'-phosphate (PLP)-dependent enzymes are catalytically diverse and include the aspartate aminotransferase superfamily which implements a common structural framework known as type fold I. In this work, the recently developed bioinformatic online methods Mustguseal and Zebra were used to collect and study a large representative set of the aspartate aminotransferase superfamily with high structural, but low sequence similarity to l-threonine aldolase from (LTAaj), in order to identify conserved positions that provide general properties in the superfamily, and to reveal family-specific positions (FSPs) responsible for functional diversity. The roles of the identified residues in the catalytic mechanism and reaction specificity of LTAaj were then studied by experimental site-directed mutagenesis and molecular modelling. It was shown that FSPs determine reaction specificity by coordinating the PLP cofactor in the enzyme's active centre, thus influencing its activation and the tautomeric equilibrium of the intermediates, which can be used as hotspots to modulate the protein's functional properties. Mutagenesis at the selected FSPs in LTAaj led to a reduction in a native catalytic activity and increased the rate of promiscuous reactions. The results provide insight into the structural basis of catalytic promiscuity of the PLP-dependent enzymes and demonstrate the potential of bioinformatic analysis in studying structure-function relationship in protein superfamilies.
PubMed: 29928580
DOI: 10.1002/2211-5463.12441 -
Frontiers in Bioengineering and... 2019Most of biochemical and mutagenesis studies performed with L-threonine aldolases were done with respect to natural activity, the cleavage of L-threonine and sometimes...
Most of biochemical and mutagenesis studies performed with L-threonine aldolases were done with respect to natural activity, the cleavage of L-threonine and sometimes L-β-phenylserine. However, the properties of variants and the impact of mutations on the product synthesis are more interesting from an applications point of view. Here we performed site-directed mutagenesis of active site residues of L-threonine aldolase from to analyze their impact on the retro-aldol activity and on the aldol synthesis of L-β-phenylserine and L-α-alkyl-β-phenylserines. Consequently, reduced retro-aldol activity upon mutation of catalytically important residues led to increased conversions and diastereoselectivities in the synthetic direction. Thus, L-β-phenylserine can be produced with conversions up to 60% and .'s up to 80% () under kinetic control. Furthermorem, the donor specificity of L-threonine aldolase was increased upon mutation of active site residues, which enlarged the pocket size for an efficient binding and stabilization of donor molecules in the active site. This study broadens the knowledge about L-threonine aldolase catalyzed reactions and improves the synthetic protocols for the biocatalytic asymmetric synthesis of unnatural amino acids.
PubMed: 31192202
DOI: 10.3389/fbioe.2019.00119