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Abstract. The global contribution of the Philippines in aquaculture production has fallen steadily from 5% to only a little over 1%. The increase in the utilization of antibiotics for aquaculture health management induces selective pressure, and consequently, the emergence of antibiotic-resistant pathogens. There are virtually however very few studies on the presence of antibiotic-resistant bacteria harbored by Philippine aquacultured organisms despite the alarming consequence to Filipino consumers. To determine the presence of antibiotic-resistant bacteria in two top Philippine aquacultured fishes, bacteria were isolated through swabbing of the inside of the vitreous sac of the eyes, gills, stomach, and intestines from 10 samples each of Chanos chanos (milkfish) and Oreochromis niloticus (tilapia), purchased from an aquaculture farm in Lingayen, Pangasinan, Philippines. The obtained bioluminescent bacterial isolates designated here as strains UPB-01 to UPB-03, were isolated from C. chanos, and strains UPB-04 to UPB-07 isolated from O. niloticus, were resistant to ampicillin (10 µg). Furthermore, bacterial strains UPB-01, UPB-06, and UPB-07 were found to be multiple-drug resistant, UPB-01 was also resistant to tetracycline (30 µg) while UPB-06 and UPB-07 were also resistant to polymyxin B (300 µg). Based on 16S rRNA gene sequence analysis, the isolates were determined to be under the genus Vibrio. The results of this study may provide grounds for the government to thoroughly regulate the use of antibiotics in aquaculture farms for risk assessment and to ultimately protect Filipino consumers from acquiring antibiotic resistance.
Key Words: Vibrio, quorum sensing, tilapia, milkfish, antibiotic-resistance.
Introduction. Aquaculture, the farming of aquatic organisms in both saltwater and freshwater areas involving interventions to enhance the growth of the organisms and their population, has a large contribution to the country's food security, employment and foreign exchange earnings (Food and Agriculture Organization of the United Nations 2015) and is therefore an important asset to the national economy (Yap 1999). Based on the 2012 statistics by the Bureau of Fisheries and Aquatic Resources (BFAR), about 52.4% of total fish production came from the aquaculture sector, compared to the 26.3% and 21.4% contribution of municipal and commercial fisheries, respectively (Philippine Statistics Authority 2016). The major aquacultured species in the Philippines are milkfish, tilapia, carp, seaweeds, shrimp, oyster, and mussel (Food and Agriculture Organization of the United Nations 2015; Bureau of Fisheries...