Background and Objective: Microorganisms, including bacteria, serve as major players in various processes affecting both the quality of aquatic sediment as well as the fate of pollutants released into such matrix. This study, evaluated the similarity in bacterial community structure between sediments collected from aquaculture and non aquaculture sites of a tropical lake. Describing and comparing the bacterial community present in each site may provide clues on the impact of aquaculture practices on aquatic ecosystems.
Methodology: Microbial DNA was extracted using PowerSoil® DNA Isolation Kit for all sediment samples. DNA isolates were used as template in the analysis of the hypervariable region of 16S rDNA through nested polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE). Excised representative 16S rDNA DGGE bands were sequenced and identified through BLAST analysis.
Results: Based on the generated mean Dice similarity coefficient of 57.77%, the bacterial community structure between aquaculture and non-aquaculture sediments was highly similar but certain taxa were found unique for each site. Bacteria belonging to Proteobacteria and Firmicutes dominated the aquaculture sediments while Proteobacteria, Firmicutes, and Chloroflexi dominated the non-aquaculture sediments. Certain physicochemical parameters operating in the two sites may have influenced the shift in representative microbes. Shewanella baltica and Trichococcus sp. were found only in aquaculture sediment owing to their ability to tolerate quantities of ammonia and high organic matter from their environment.
Conclusions: This study described the applicability of 16S rDNA PCR-DGGE as a culture-independent technique for describing and comparing the similarity between bacterial communities in sediment. Based on the generated similarity index, the bacterial community between aquaculture and non-aquaculture sediments of Taal Lake was highly similar but interestingly, harbored unique bacterial populations as seen in the DGGE profiles. The shift in dominant taxa and unique representatives per site may have been influenced by certain differences between each site's physico-chemical parameters.

Aims: Aquaculture has grown tremendously in Malaysia over the past decades. However, guaranteeing aquaculture sustainability is a big challenge in terms of maintaining continuous output with a safe environment. Furthermore, the cultured species should be free from antibiotic resistance bacterial and antibiotic residue. This study aimed to monitor the existence and prevalence of antibiotic resistant bacteria associated with aquaculture farms in Sarawak. Methodology and results: Samples of water, sediment and fish were collected from five aquaculture farms within Sarawak. The samples were plated on trypticase soy agar and incubated at 28 °C for 24 h. A total of 204 bacterial isolates were isolated and analysed by (GTG)5-fingerprinting to determine genetic similarity among the bacterial isolates, so that representatives could be selected from similar clonal isolates. Based on the (GTG)5 profiles, 50 representative isolates were chosen for species identification using 16S rRNA sequencing. The identified bacteria were tested against 25 antibiotics using standard disk diffusion method. The 16S rRNA analysis revealed that the isolates constitute of 14 genera of bacteria including Bacillus (38%), Exiguobacterium (16%), Enterobacter (14%), Aeromonas (6%), Acinetobacter (4%), Citrobacter (4%), Staphylococcus (4%), Achromobacter (2%), Chitinophaga (2%), Fictibacillus (2%), Plesiomonas (2%), Pseudomonas (2%), Pseudoxanthomonas (2%) and Stenotrophomonas (2%). The antibiotic resistance analysis revealed that the highest percentage of resistance was recorded against streptomycin (75.0%), followed by ampicillin (66.0%), ceftriaxone (50.0%), rifampin (43.3%), aztreonam (36.8%) and ceftazidime (31.6%). Resistance to more than two antibiotics was observed in 40.0% of isolates with an overall multiple antibiotic resistant (MAR) index ranging from 0 to 0.79. Conclusion, significant and impact of study The variability of antibiotic resistance patterns exhibited by different bacterial species suggests a dependence on selective pressures exhibited in different geographical locations. Our results show that the occurrence of MAR bacteria in an aquaculture environment with unknown history of antibiotics usage in the aquaculture system is possible, indicating a need to continuously monitor the presence of antibiotic resistant bacteria in the aquaculture system.
Drug Resistance, Microbial ; Aquaculture ; Malaysia

OBJECTIVEThis work is an evaluation of the efficiency of a sand-gravel or unwoven fabric bed system and Lolium perenne Lam as plant biofilter in the reduction of solids and nutrients removal from aquaculture discharge water.

METHODSThe first step consisted of the collection of wastewater in the tank and the distribution at three different hydraulic loading regimes (0.5, 1, 1.5 L/hour) to the different experimental systems. The second step was to evaluate the performance of the different systems. The first system consisted of a bucket filled with a substrate of sand/gravel (20 cm in depth), on the bottom of which was a 80 mesh/inch2 of nylon (S1); the second was similar, but was planted with Lolium perenne lam (S2); the third was planted with a grass plate consisting of 7 layers of unwoven fabric planted with L perenne (S3).

RESULTSThe second system showed the best performance in reducing solids as well as in nutrients (TN, TP, and COD) reduction. The removal rates for TS, TN, and TP were negatively correlated with the loading regimes, with 0.5 L/hour being the most efficient and thus taken as the reference.

CONCLUSIONSSolids management using a sand/gravel substrate as bed culture and Lolium perenne L. as plant biofilter has proved to be an efficient technique for solids reduction with low operating cost. This grass plays an important role in wastewater eco-treatment by absorbing dissolved pollutants (TAN) as nutrients for its growth.

Many members of the Saprolegniales (Oomycete) cause mycoses and disorders of fishes, of which Achlya and Saprolegnia are most ubiquitous genera worldwide. During a survey of the diversity of freshwater oomycetes in Korea, we collected seven isolates of Achlya, for which morphological and molecular phylogenetic analyses enabled them to identify as Achlya americana and Achlya bisexualis. In Korea, only a species of Achlya, A. prolifera, has been previously found to cause seedling rot on rice (Oryza sativa), but none of the two species have been reported yet. Importantly, A. bisexualis was isolated from a live fish, namely rice fish (Oryzias sinensis), as well as freshwater, and this is the first report of Achlya-causing mycoses on freshwater fishes in Korea. The presence of A. americana and A. bisexualis on live fish in Korea should be closely monitored, as considering the well-known broad infectivity of these species it has the potential to cause an important emerging disease on aquaculture industry.
Achlya ; Aquaculture ; Fishes ; Fresh Water ; Korea ; Mycoses ; Oomycetes ; Saprolegnia ; Seedlings

By activity-guided fractionation, gliotoxin was isolated as an antibacterial metabolite of the fungus Penicillium decumbens which was derived from the jellyfish Nemopilema nomurai. Gliotoxin was further evaluated for antibacterial activity against several piscine and human MDR (multidrug resistance) pathogens. Gliotoxin showed significant antibacterial activity against Gram-positive piscine pathogens such as Streptococcus iniae FP5228, Streptococcus iniae FP3187, Streptococcus parauberis FP3287, Streptococcus parauberis SPOF3K, S. parauberis KSP28, and Lactococcus garvieae FP5245. Gliotoxin showed strong activity especially against S. parauberis SPOF3K and S. iniae FP5228, which are resistant to oxytetracycline. It is noteworthy that gliotoxin effectively suppressed streptococci which are the major pathogens for piscine infection and mortality in aquaculture industry. Gliotoxin also showed strong antibacterial activity against multidrug-resistant human pathogens (MDR) including Enterococcus faecium 5270 and MRSA (methicillin-resistant Staphylococcus aureus) 3089.
Aquaculture ; Enterococcus faecium ; Fungi ; Gliotoxin ; Humans ; Lactococcus ; Methicillin-Resistant Staphylococcus aureus ; Mortality ; Oxytetracycline ; Penicillium ; Staphylococcus ; Streptococcus

Ten eels (Anguilla japonica) from a fish farm in Korea were examined and diagnosed with a Heterosporis infection. The gross lesions on the trunk were uneven and the concave parts were pasty. Histopathologically, lyses of the trunk muscles, degenerative muscle fibers and the scattered spores were observed. The sporophorocyst (SPC) contained several spores with a variety of shapes. Some SPC were disrupted and the spores in the SPC were scattered in the muscle tissues. Macrophages existed near the scattered spores. Electron microscopy revealed special structures such as sporophorocyst containing various developmental parasitic stages such as meronts, sporonts, sporophorous vesicles and spores.
*Anguilla ; Animals ; Aquaculture ; Fish Diseases/*parasitology/pathology ; Histocytochemistry/veterinary ; Korea ; Microscopy, Electron, Scanning Transmission/veterinary ; Microsporidia/*growth & development/ultrastructure ; Microsporidiosis/parasitology/pathology/*veterinary ; Muscular Diseases/parasitology/pathology/*veterinary

From July 2008 to June 2009, livers of the swamp eels (Monopterus alba) were investigated for advanced third-stage larvae (AL3) of Gnathostoma spinigerum. Results revealed that 10.2% (106/1,037) and 20.4% (78/383) of farmed eels from Aranyaprathet District, Sa Kaeo Province and those of wild-caught eels obtained from a market in Min Buri District of Bangkok, Thailand were infected, respectively. The prevalence was high during the rainy and winter seasons. The infection rate abruptly decreased in the beginning of summer. The highest infection rate (13.7%) was observed in September and absence of infection (0%) in March-April in the farmed eels. Whereas, in the wild-caught eels, the highest rate (30.7%) was observed in November, and the rate decreased to the lowest at 6.3% in March. The average no. (mean+/-SE) of AL3 per investigated liver in farmed eels (1.1+/-0.2) was significantly lower (P=0.040) than those in the caught eels (0.2+/-0.03). In addition, the intensity of AL3 recovered from each infected liver varied from 1 to 18 (2.3+/-0.3) in the farmed eels and from 1 to 47 (6.3+/-1.2) in the caught eels, respectively. The AL3 intensity showed significant difference (P=0.011) between these 2 different sources of eels. This is the first observation that farmed eels showed positive findings of G. spinigerum infective larvae. This may affect the standard farming of the culture farm and also present a risk of consuming undercooked eels from the wild-caught and farmed eels.
Animals ; Aquaculture ; Fish Diseases/*epidemiology/*parasitology ; Gnathostoma/*isolation & purification ; Gnathostomiasis/epidemiology/parasitology/*veterinary ; Larva ; Liver/parasitology ; Parasite Load ; Prevalence ; Seasons ; Smegmamorpha/*parasitology ; Thailand/epidemiology

Ecdysis is a common phenomenon that happens throughout the life phase of the giant freshwater prawn Macrobrachium rosenbergii. It is vital to better understand the correlation between cannibalism and biochemical compound that exists during the moulting process. The objective of the present study was to determine the amino acid profile released by M. rosenbergii during the ecdysis process that promotes cannibalism. To accomplish this, changes in amino acid levels (total amino acid (TAA) and free amino acid (FAA)) of tissue muscle, exoskeleton, and sample water of culture medium from the moulting (E-stage) and non-moulting (C-stage) prawns were analysed using high-performance liquid chromatography (HPLC). Comparison study revealed that among the TAA compounds, proline and sarcosine of tissues from moulting prawn were found at the highest levels. The level of FAA from water that contains moulting prawns (E-stage) was dominated by tryptophan and proline. Significant values obtained in the present study suggested that these amino acid compounds act as a chemical cue to promote cannibalism in M. rosenbergii during ecdysis. The knowledge of compositions and compounds that were released during the moulting process should be helpful for better understanding of the mechanism and chemical cues that play roles on triggering cannibalism, and also for future dietary manipulation to improve feeding efficiencies and feeding management, which indirectly impacts productivity and profitability.
Amino Acids/chemistry* ; Animals ; Aquaculture ; Cannibalism ; Chromatography, High Pressure Liquid ; Feeding Behavior ; Fresh Water ; Malaysia ; Molting ; Palaemonidae/physiology* ; Proline/chemistry* ; Tryptophan/chemistry*

Streptococcus sp. is gram-positive coccus that causes streptococcal infections in fish due to intensification of aquaculture and caused significant economic losses in fish farm industry. A streptococcal infection occurred from cultured diseased olive flounder (Paralichthys olivaceus) in May, 2005 at a fish farm in Jeju Island, Korea. The diseased flounder exhibited bilateral exophthalmic eyes and rotten gills; water temperature was 16~18oC when samples were collected. Of the 22 fish samples collected, 3 samples were identified as Lactococcus garvieae and 18 samples were identified as Streptococcus parauberis by culture-based, biochemical test. Serological methods such as slide agglutination, hemolysis and antimicrobial susceptibility test were also used as well as multiplex PCRbased method to simultaneously detect and confirm the pathogens involved in the infection. S. parauberis and L. garvieae have a target region of 700 and 1100 bp., respectively. One fish sample was not identified because of the difference in the different biochemical and serological tests and was negative in PCR assay. In the present study, it showed that S. parauberis was the dominant species that caused streptococcosis in the cultured diseased flounder.
Agglutination Tests/veterinary ; Animals ; Aquaculture ; DNA, Bacterial/chemistry/genetics ; Fish Diseases/*microbiology ; *Flounder ; Hemolysis ; Korea ; Microbial Sensitivity Tests/veterinary ; Polymerase Chain Reaction/veterinary ; Streptococcal Infections/microbiology/*veterinary ; Streptococcus/genetics/*isolation&purification

Although Vietnam has a high risk of fishborne zoonotic trematode (FZT) infections for humans, little information exists on the epidemiology of these infections in the country's fish. Because of the importance of cultured catfish and snakehead production in An Giang province, a major production area in the Mekong Delta of Vietnam, a survey for FZTs was carried out in randomly selected fish farms between June 2005 and March 2006. For comparison, wild fish from the same area were also surveyed. A total of 852 cultured fish from 4 districts were collected and examined by pepsin digestion to determine their FZT infection status. In Tra catfish, the prevalence of all types of metacercariae was 2.6%, of which the prevalence of Haplorchis pumilio was 0.7%. The overall prevalence of metacercariae in wild fish was 30.6%, of which 10.3% harbored zoonotic species: H. pumilio (2.8%) and Procerovum sp. (5.6%). The prevalence of Opisthorchis metacercariae, which were diagnosed as O. viverrini, was 1.9%. No metacercariae were found in cultured snakehead fish, although wild-caught snakehead fish had a FZT prevalence of 10.3%: 5.1% were O. viverrini; 2.6% H. pumilio; and 2.6% were Procerovum sp. These are the first reports of H. pumilio, Procerovum sp., and O. viverrini metacercariae in Vietnamese fish. These results indicate that consumption of improperly prepared fish represents a significant risk of acquiring FZTs in this south Vietnam region.
Animals ; Aquaculture ; Fish Diseases/*epidemiology/parasitology ; Fishes ; Intestinal Diseases, Parasitic/epidemiology/parasitology/*veterinary ; Liver Diseases, Parasitic/epidemiology/parasitology/*veterinary ; Prevalence ; Trematoda/growth & development/*isolation & purification ; Trematode Infections/epidemiology/parasitology/*veterinary ; Vietnam/epidemiology ; Zoonoses/*epidemiology/parasitology