The role of merA gene of mercury-resistant Escherichia coli from Kahayan River, Central Kalimantan, Indonesia in emerging antibiotic resistance

This study collected nine water samples from the upstream, middle, and downstream parts of the Kahayan river, which was heavily contaminated with mercury (Hg). The water was sampled following the collection method of surface water sample (SNI 6989.57-2008). Escherichia coli has been found in the four samples out of nine samples collected. The merA gene of bacteria was identified at 1695 base pairs (bp), bla at 199 bp, tet at 494 bp, cat at 623 bp, and gyrA at 577 bp. The merA gene from S1 from the PCR results was identified at 219 bp. However, the merA gene was not amplified with a primer measuring 1695 bp. Then, sequencing was performed, and the results indicated a 48.551% homology with E. coli Tn5075 nucleotide sequences. On examination of the cat gene, all samples are positive, or target-specific bands are observed (i.e., samples 1, 5, 6, and 7). Following sequencing, 623 bp were found to have nucleotide sequences that were 100% identical to E. coli. In all samples, the gyrA gene is either positive or has a band that corresponds to the target. Meanwhile, the results of nucleotide sequence homology of 99.826% were identical to E. coli at 586 bp. No bla gene or tet gene was identified. Sample 1 plate 1, 3, 4, 5, and sample 5 plate 3 exhibited intermediate results for ampicillin antibiotics, while the remaining results are sensitive to the tested antibiotics. Therefore, the mercury-resistant merA gene found in E. coli from the Kahayan river in Central Kalimantan has not been conclusively linked to antibiotic resistance.