Monitoring Antibiotic-Resistant Bacteria in Tapak River Estuary, Semarang City, Indonesia

Abstract

The estuary of the Tapak River in the Tugu Subdistrict, Semarang City, has been classified as lightly polluted by domestic and industrial waste from Tambak Aji Village. Waste discharges flow into ponds and the open coast, potentially increasing bacterial resistance and impacting aquatic life. This study aims to identify antibiotic-resistant bacterial isolates in the area. The research was conducted from January to April 2024 using an exploratory descriptive method, with sediment samples taken from three stations. Two Gram-positive bacterial isolates resistant to Ciprofloxacin were found: DI.C_10-5/2 (with a 15.39 mm inhibition zone) and DI.C_10-5/3 (with a 15.19 mm inhibition zone). One of the isolates, DI.C_10-5/3, was identified as closely related to Bacillus licheniformis (99.75% similarity) using 16S rRNA gene sequencing. These findings highlight the need for regular monitoring of resistant bacteria in aquatic environments to prevent the uncontrolled spread of antibiotic resistance.