Collaborative Researches

Bacterial microbiota of African catfish Clarias gariepinus during the hatchery and nursery phases of culture in the Philippines

2026-03-10T03:29:09Z

Bacterial microbiota of African catfish Clarias gariepinus during the hatchery and nursery phases of culture in the Philippines Pakingking, Rolando Jr; Solis, Faye Danielle; Palma, Peter; Dela Peña, Leobert The bacterial microbiota of African catfish (Clarias gariepinus) during hatchery and nursery phases were examined across eight production cycles in two commercial farms in the Philippines. Bacterial identification was performed using conventional methods and the API 20E test, with further confirmation of selected isolates via 16S rRNA gene sequencing. Heterotrophic plate count (HPC), presumptive Aeromonas count (PAC), and presumptive Vibrio count (PVC) varied in hatchery rearing water (10³–10⁵ CFU/mL for HPC; 10²–10⁴ CFU/mL for PAC and PVC) and fry samples (10⁴–10⁷ CFU/g for HPC; undetectable–10⁶ CFU/g for PAC; 10²–10⁴ CFU/g for PVC). In the nursery phase, similar fluctuations were observed in rearing water, fingerlings, and sediment. Microbial diversity analysis revealed 21 species (15 genera) in hatchery rearing water and 14 species (8 genera) in fry, with Aeromonas hydrophila, A. sobria, and Vibrio cholerae as predominant species (>15%). In the nursery phase, 29 species (16 genera), 28 species (15 genera), and 21 species (14 genera) were identified from rearing water, sediment, and fingerlings, respectively, with A. hydrophila, A. sobria, and Bacillus subtilis dominating (>14%). This study highlights the dynamic composition of bacterial communities in catfish culture systems, with rearing environments shaping the microbiota of juvenile fish. The presence of opportunistic and zoonotic pathogens underscores the risk of disease outbreaks, particularly under suboptimal conditions. These findings emphasize the need for stringent biosecurity measures and improved hatchery and nursery management practices to enhance fish health, prevent economic losses, and ensure the sustainability of aquaculture production. Educating hatchery and nursery workers on safe aquaculture practices and hygiene protocols is crucial to minimizing health risks to both fish and humans while ensuring efficient and responsible catfish production. Journal article

Abundance, diversity, and antibiotic resistance of Aeromonas spp. in well water from selected Barangays in Iloilo City, Philippines

2026-03-09T06:45:51Z

Abundance, diversity, and antibiotic resistance of Aeromonas spp. in well water from selected Barangays in Iloilo City, Philippines Recalcar, Lois; Leñar, Therese Angela; Luzano, Kylene Marie; Matandac, William Jr; Pentojo, Miles Roland; Robles, Simon John; Sabinay, Stephen; Palma, Peter; Pakingking, Rolando Jr This study investigated the abundance, diversity, and antibiotic resistance patterns of Aeromonas spp. in well water from five selected barangays (villages) in Iloilo City, alongside heterotrophic bacterial counts and physicochemical parameters during the dry (March to May) and wet (June to August) seasons. Presumptive Aeromonas counts reached 10³ CFU/mL during the dry season and 10² CFU/mL during the wet season, while heterotrophic plate counts peaked at 10⁴ CFU/mL and 10³ CFU/mL, respectively. Seasonal variations significantly influenced water quality, with higher temperatures, biochemical oxygen demand, and total dissolved solids recorded during the dry season, while dissolved oxygen levels were elevated during the wet season (p < 0.05). Aeromonas hydrophila was the most prevalent (59%), followed by A. veronii (21%). Other predominant bacterial species included Escherichia coli (12%), Enterococcus faecium (5%), and Staphylococcus aureus (7%), the latter found only in the wet season. Antimicrobial susceptibility testing of 10 antibiotics commonly used in human-veterinary medicine, and aquaculture, revealed high resistance to amoxicillin (A. hydrophila: 98.6%; A. veronii: 96%; E. faecium: 100%; E. coli: 100%; : 100%), erythromycin (100%; 60%; 100%; 100%; 100%), and neomycin (97.1%; 92%; 50%; 57.1%; 100%). Multidrug resistance was widespread, with MAR indices exceeding 0.2, indicating substantial antibiotic exposure and contamination from high-risk sources. This is the first report on the load, composition, and antibiotic resistance of Aeromonas spp. in well water in the Philippines, underscoring the need for continuous microbial monitoring, improved well-water disinfection, and strengthened antibiotic stewardship to mitigate public health risks associated with contaminated groundwater sources. Journal article

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

2023-07-12T01:48:13Z

Production, feeding and storage of Tetraselmis tetrathele paste by electrolytic flocculation Villa‑Franco, Annie U.; Teves, Christine Marie L.; Dato‑on, Knessa Louie G.; de Jesus-Ayson, Evelyn Grace T.; Usero, Roselyn; de la Peña, Milagros R. 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. Journal article

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)

2023-03-06T00:19:48Z

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) Pakingking, Rolando; Palma, Peter; de Jesus-Ayson, Evelyn Grace T.; Usero, Roselyn 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. Journal article