Detection of Resistant Bacteria through Molecular Identification from Traditional Ponds in Tirang Beach, Semarang, Indonesia

The Tirang Beach area in Indonesia is a coastal area with many fish farming ponds, raising milkfish (Chanos chanos), saline tilapia (Oreochromis niloticus), and deep-bodied mojarra fish (Gerres erythrourus). Aquaculture activities in this area are often hampered by bacteria that infect the farmed fish. The use of antibiotics to prevent disease is a growing trend; however, it can lead to antibiotic resistance and residues in the environment. Antibiotic resistance is a global problem that is important to research. This study aimed to monitor the existence of resistant bacteria in sediment and fish from a traditional pond as well as to identify the most resistant bacteria using a molecular approach. The research was carried out from January to April 2024, with data collection using a random sampling method. Samples were taken from the pond sediment and fish gills at three different points. Based on the results, the abundance of bacteria in the sediment and fish gills from the traditional ponds in the Tirang Beach area ranged from 1.53 x 106 to 2.45 x 107 CFU/mL and 7.2 x 105 to 5.52 x 106 CFU/mL, respectively. Furthermore, the resistance level of bacteria against Tetracycline (30 µg), Chloramphenicol (30 µg), Erythromycin (15 µg), and Ciprofloxacin (5 µg) was 36.67, 6.67, 30.00, and 56.67 percent, respectively. Therefore, the antibiotic resistance tests showed that the highest resistance was to Ciprofloxacin. Even though the abundance of bacteria in the sediment was higher than in the fish gills, the resistance bacteria in the fish gills was 82% greater than in the sediment. Moreover, observation through the 16S rRNA gene revealed that the most resistant fish bacteria was Vibrio alginolyticus, which is a rod-shaped Gram-negative bacterium; the most resistant bacteria in the sediment was identified as Vibrio parahaemolyticus, a harmful bacterium well-known as a causative agent of Acute Hepatopancreatic Necrosis Disease (AHPND). Hence, the residual antibiotic in the environment could trigger resistance in Vibrio spp. associated with fish and sediment in the traditional pond, despite the absence of antibiotics usage in this farming.