Aeromonas load and species composition in tilapia (Oreochromis niloticus) cultured in earthen ponds in the Philippines

Aeromonas load and species composition in the rearing water, sediment, gills and intestines of healthy tilapia Oreochromis niloticus collected every 2 weeks from Days 30 to 120 after stocking in six earthen ponds in the Philippines were determined. Presumptive Aeromonas counts (PACs) in the water and sediment ranged from 101–103 c.f.u./ml and 101–103 c.f.u./g while in the gills and intestines, PACs ranged from 104–107 c.f.u./g and 102–105 c.f.u./g, respectively. Presumptive Aeromonas counts in the water, sediment, and gills of tilapia varied among days of culture while in the intestines of tilapia, PACs markedly dropped by approximately 2 logs at Day 75 and either remained in the same level or decreased by another 1 log at Day 120 of grow‐out culture. Aeromonas hydrophila predominantly constituted 94% of all presumptive Aeromonas spp. examined (n = 343), followed by A. sobria (4%) and A. salmonicida (2%). Taken together, current data provide some putative threshold levels of tilapia reared in earthen ponds to Aeromonas spp. The dominance of A. hydrophila together with negligible population of A. salmonicida and A. sobria indicate that Aeromonas are common commensal bacteria in tilapia and their environment which under conditions of stress could instigate disease epizootics.This study was funded by the Department of Science and Technology-National Research Council of the Philippines (DOST-NRCP; NRCP project no. E-225) and partly by SEAFDEC AQD (study code: FH02-F2013-T). We would like to thank Dr. Evelyn Grace de Jesus-Ayson for the critical review of the manuscript, and Mr. Eric Ledesma and the laboratory staff of NPPMCI for the invaluable assistance during our sampling

Quantitative and qualitative analyses of the bacterial microbiota of tilapia (Oreochromis niloticus) cultured in earthen ponds in the Philippines

The quantity and composition of the bacterial microbiota in the rearing water, sediment, gills and intestines of tilapia Oreochromis niloticus collected every 2 weeks from Day 30 to Day 120 after stocking for grow-out culture in 6 earthen brackish water ponds in the Philippines were examined. The total heterotrophic aerobic bacterial counts obtained in the water, sediment, gills and intestines of tilapia ranged from 103 to 104 c.f.u. ml−1, 103–105, 105–107 and 104–107 c.f.u. g−1, respectively. In terms of composition, a total of 20 bacterial genera and 31 species were identified with the preponderance of gram-negative bacteria constituting 84% of all bacterial isolates examined. Aeromonas hydrophila, Bacillus spp., Plesiomonas shigelloides, Shewanella putrefaciens, Pseudomonas fluorescens, Staphylococcus spp. and Vibrio cholerae were the dominant bacteria identified in the gills and intestine of tilapia. These bacteria also dominated in the pond sediment and rearing water, except for the nil isolation of S. putrefaciens and V. cholerae in the water samples examined, indicating that resident bacteria in the pond water and sediment congruently typify the composition of bacterial microbiota in the gills and intestine of tilapia which under stressful conditions may propel the ascendance of disease epizootics

Integration of finfish in shrimp (Penaeus monodon) culture: an effective disease prevention strategy

A farm trial on integration of finfish (i.e., tilapia) in shrimp (Penaeus monodon) culture was conducted in Negros Occidental, Philippines to prevent luminous vibriosis in shrimp. The farm engaged in shrimp monoculture from 1987 to 1995. However, the prevailing luminous vibriosis outbreaks that started in 1994 prompted the farm operator to shift to tilapia culture in 1995-1996. The farm resumed shrimp operations in 1996 but by this time tilapia had already been integrated in the culture system. This paper reports on the results of the trial for 1999 using three ponds (ponds 7, 9, 29). These ponds had previously been used for tilapia culture for two years. During shrimp culture, they drew water from reservoirs stocked with tilapia and within the shrimp ponds tilapia are also stocked inside cages. This technology integrates crop rotation, biological pretreatment and polyculture into one system. During the culture period the chemical and bacteriological quality of soil, water and shrimp were monitored. Water quality parameters were within normal ranges for shrimp culture. Luminous bacterial counts in water and shrimp were consistently below 10 colony forming units (cfu)/ml and 103 cfu/hepatopancreas (hp), respectively. These levels are below threshold levels associated with luminous vibriosis outbreaks. With a stocking density of 19.43 shrimp postlarvae (PL)/m2, pond 7 yielded 2,605 kg shrimp/ha with an estimated survival of 35.65% after 109 days of culture (DOC). With a stocking density of 18.69 PL/ m2, pond 9 yielded 5,472 kg shrimp/ha with survival of 100% after 148 DOC. With a stocking density of 19.33 PL/m2, Pond 29 yielded 5,702 kg shrimp/ha with survival of 82.66% after 151 DOC. The relatively low production in pond 7 can be attributed to the inferior quality of the batch of stocked shrimp PL that already had a low survival of 50% at DOC 30. Comparing the production performance from this present trial with that of this and other farms before the 1994 outbreaks, these good results cannot simply be attributed to chance despite of the lack of control in this farm trial. These results are consistent with the results of a previous trial of the same farm, the ongoing verification trials in Negros Occidental, and the observations of many farmers in other parts of the country on the potential of shrimp-finfish integration in preventing luminous vibriosis in shrimp

Motile aeromonads recovered from tilapia (Oreochromis niloticus) cultured in earthen ponds in the Philippines: Assessment of antibiotic susceptibility and multidrug resistance to selected antibiotics

A total of 177 motile Aeromonas spp., comprised of A. hydrophila (n=162) and A. sobria (n=15), isolated from the water, sediment, gills and intestines of tilapia collected from the grow-out culture earthen ponds in the Philippines were investigated for their antimicrobial susceptibility to 10 antibiotics commonly used in fish aquaculture. All motile Aeromonas spp. tested generally exhibited a very high percentage of resistance to amoxicillin (A. hydrophila: 95%; A. sobria: 100%), erythromycin (99%;100%), neomycin (83%;100%), and oxytetracycline (92%;100%), respectively. On the contrary, they showed substantial susceptibility to chloramphenicol, nitrofurantoin, doxycycline, enrofloxacin and norfloxacin. Results of the antimicrobial susceptibility testing demonstrated that 94.4% and 100% of A. hydrophila and A. sobria isolates tested were resistant to antibiotics belonging to at least 3 or more categories and therefore considered as multiple drug resistant strains. The multiple antibiotic resistance (MAR) indexing of A. hydrophila and A. sobria strains showed that they originated from high-risk sources.This study was funded by the Department of Science and Technology-National Research Council of the Philippines (DOST-NRCP) (NRCP Project No. E-225) and partly by SEAFDEC/AQD (study code: FH02-F2013-T)

Vibrio harveyi and the 'green water culture' of Penaeus monodon

The 'green water culture' of the tiger shrimp, Penaeus monodon, is an innovative culture technique for the grow-out rearing of shrimps. This culture method involves the use of rearing water of tilapia for the rearing of tiger shrimp in grow-out ponds and on the polyculture of shrimp with tilapia. This culture technique was reported to present disease outbreaks attributed to luminescent Vibrio. To understand the possible mechanisms of luminous Vibrio control in the green water culture system several studies were conducted. This review summarizes the highlights obtained so far from these studies consisting of a) effect of rearing waters from tilapia culture and shrimp cultured with tilapia on Vibrio harveyi; b) estimation and preliminary identification of cultivable bacteria, fungi and phytoplankton flora associated with the 'green water culture' system and c) detection of anti-Vibrio harveyi metabolites from bacteria, yeast, filamentous fungi and phytoplankton indigenous to the 'green water culture' system

Motile aeromonads recovered from tilapia (Oreochromis niloticus) cultured in earthen ponds in the Philippines: Assessment of antibiotic susceptibility and multidrug resistance to selected antibiotics

A total of 177 motile Aeromonas spp., comprised of A. hydrophila (n=162) and A. sobria (n=15), isolated from the water, sediment, gills and intestines of tilapia collected from the grow-out culture earthen ponds in the Philippines were investigated for their antimicrobial susceptibility to 10 antibiotics commonly used in fish aquaculture. All motile Aeromonas spp. tested generally exhibited a very high percentage of resistance to amoxicillin (A. hydrophila: 95%; A. sobria: 100%), erythromycin (99%;100%), neomycin (83%;100%), and oxytetracycline (92%;100%), respectively. On the contrary, they showed substantial susceptibility to chloramphenicol, nitrofurantoin, doxycycline, enrofloxacin and norfloxacin. Results of the antimicrobial susceptibility testing demonstrated that 94.4% and 100% of A. hydrophila and A. sobria isolates tested were resistant to antibiotics belonging to at least 3 or more categories and therefore considered as multiple drug resistant strains. The multiple antibiotic resistance (MAR) indexing of A. hydrophila and A. sobria strains showed that they originated from high-risk sources.This study was funded by the Department of Science and Technology-National Research Council of the Philippines (DOST-NRCP) (NRCP Project No. E-225) and partly by SEAFDEC/AQD (study code: FH02-F2013-T)

Vibrio load and percentage composition of sucrose‐fermenting vibrios in Nile tilapia (Oreochromis niloticus) cultured in brackish water earthen ponds and biocontrol potential of recycled tilapia‐conditioned greenwater against population growth of V. parahaemolyticus and non‐sucrose‐fermenting vibrios in the grow‐out culture of white leg shrimp (Litopenaeus vannamei)

Vibrio are known opportunistic pathogens of pond-cultured fish and shrimp. This study determined the presumptive Vibrio count (PVC) and percentage composition of “beneficial” sucrose-fermenting vibrios (SFVs) and “pathogenic” non-SFVs in the water, sediment, gills and intestines of healthy tilapia Oreochromis niloticus collected every 2 weeks from Days 30 to 120 post-stocking in brackish water earthen ponds. PVCs in water and sediment ranged from 102–104 CFU/ml/CFU/g while in tilapias' gills and intestines, PVCs ranged from 103–106 CFU/g and 102–106 CFU/g, respectively, with SFVs dominating in water, sediment, gills (≥50%), and intestines (≥80%) of tilapia. Because use of tilapia-conditioned green water (TCGW) for shrimp's grow-out culture has been reported effective against acute hepatopancreatic necrosis disease outbreaks caused by V. parahaemolyticus, PVC, SFVs/non-SFVs (%), and V. parahaemolyticus count (VPC) in the recycled TCGW and Litopenaeus vannamei's hepatopancreas were also examined from stocking until 105 days of culture (DOC) in earthen ponds. PVCs ranging from 102–103 CFU/ml and 103–104 CFU/g were noted in water and shrimp's hepatopancreas, respectively. While non-SFVs population in water varied, a downward trend typified by an abrupt 50% reduction was noted in hepatopancreas at DOC 42, and remained or further dropped until DOC 105. VPCs in water likewise varied (undetectable–102 CFU/ml) while in hepatopancreas, counts dropped to undetectable level from DOC 70 onwards. Current data illustrate that remarkable shift of SFVs' dominance in the water and concomitantly in shrimp's hepatopancreas, plays a pivotal role in regulating non-SFVs proliferation in shrimp's hepatopancreas via competitive exclusion.This study was funded by SEAFDEC AQD (study code: FH02-F2013-T) and in part by the Department of Science and Technology-National Research Council of the Philippines (DOST-NRCP) (NRCP Project No. E-225)

Microbiological quality and heavy metal concentrations in slipper oyster (Crassostrea iredalei) cultured in major growing areas in Capiz Province, Western Visayas, Philippines: Compliance with international shellfish safety and sanitation standards

The increasing demand for slipper oyster (Crassostrea iredalei) has propelled farmers to expand oyster cultivation areas in the Philippines, chiefly for local consumption and feasibly for export overseas. As filter feeders, oysters can accumulate pathogens from the surrounding waters, and these pathogens can cause foodborne diseases in consumers. Therefore, oyster farming areas must be monitored for microbiological quality and heavy metal concentrations. In the present study, the microbiological quality of oysters and their growing waters in the major oyster farming areas of the Cogon and Palina Rivers and Cabugao Bay (in Roxas City and the Municipality of Ivisan, respectively, Capiz Province, Western Visayas, Philippines) were examined monthly during the wet (May to October) and dry (November to April) seasons over 12 months. Regardless of the sampling period, high levels of fecal coliforms in the water and Escherichia coli in oysters were found, clearly illustrating that these oyster growing areas would meet only the class B standard under the European Union classification system and would be considered “prohibited” for growing oysters under the U.S. classification system. Although Salmonella was occasionally detected in oysters, Vibrio cholerae was not detected and Vibrio parahaemolyticus was within acceptable limits. The heavy metal concentrations in oyster meat were also determined during the wet (July) and dry (March) seasons. Zinc and copper were the most abundant metals detected, and concentrations of lead, cadmium, mercury, and chromium were below the regulatory limits set by the European Union and the U.S. Food and Drug Administration. These oyster culture areas should be rehabilitated immediately to improve the microbiological quality of the oysters. Oysters harvested from these sites must be depurated or relayed to ensure quality and safety.We express our heartfelt gratitude to Southeast Asian Fisheries Development Center/Aquaculture Department, Bureau of Fisheries and Aquatic Resources—Region VI, Negros Prawn Producers Cooperative, the local government units of the Municipality of Ivisan and Roxas City, and collaborators from Palina Greenbelt Ecopark, Barangay Cabugao, and Barangay Cogon. This study was funded by the Department of Science and Technology, Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (study code 6286-T-RD-DOST03)

Phytochemical composition antioxidant and antibacterial activity of the Philippine marine green alga (Ulva pertusa)

The phytochemical constituents, total phenolic and flavonoid contents, antioxidant and antimicrobial activities of the ethanolic extract of the marine green alga Ulva pertusa collected from floating fish net cages off the coast of Guimaras island, Philippines, were investigated. Qualitative phytochemical analysis revealed the presence of bioactive compounds including alkaloids, flavonoids, phenols, saponins, tannins, and terpenoids. Quantitatively, total phenolic and flavonoid contents of the extract were 20.54±2.08 mg gallic acid equivalent (GAE) g-1 and 539.07±6.36 mg rutin equivalent (RE) g-1, respectively. The antioxidant activity of the extract using 1,1-diphenyl-1-picrylhydrazyl (DPPH) assay exhibited a concentration-dependent radical scavenging capacity. Additionally, the ethanolic extract inhibited the growth of Staphylococcus aureus ATCC25923, Escherichia coli ATCC25922, Streptococcus agalactiae, Aeromonas hydrophila, A. sobria, and Vibrio harveyi in a concentration-dependent manner with strong inhibitory activity at 100 mg mL-1 concentration. Taken together, U. pertusa contains bioactive compounds that possess potent antibacterial activity and remarkable antioxidant capacities. These substances are promising candidates that may be utilized in the synthesis of novel drugs.This study was funded by the Government of Japan Trust Fund V through the Regional Disease Project (study code: FH01-F2010-T) and partly by SEAFDEC AQD

Production, feeding and storage of Tetraselmis tetrathele paste by electrolytic flocculation

An innovative microalgae harvesting technique using electroflocculation was carried out at different voltage treatments (4, 7, and 9 V) using a fabricated voltage regulator and compared with harvesting by electroflocculation at 12 V using a car battery to efficiently electroflocculate Tetraselmis tetrathele. This study was conducted to determine the ideal voltage settings that could improve the quality of harvested paste in terms of nutritional value and metal contamination for its later use in aquaculture. The use of 7 V achieved low Pb content producing the best harvest biomass (1.4 kg, 87 min) which is comparable to the harvest biomass (1.7 kg, 68 min) using a 12 V car battery. Storage of T. tetrathele paste is best done in a chiller (2 ± 1 °C) rather than a freezer (-20 ± -4 °C) for ease in reactivation and maintaining higher cell viability for later use as a starter in aquaculture. Storage in a chiller allows T. tetrathele paste to be resuspended after six months and used as a starter culture.This study was funded by the Aquaculture Department, Southeast Asian Fisheries Development Center (SEAFDEC/AQD) Study code: Nr-01-Y2018T