Sains Malaysiana 55(6)(2026): 974-985

http://doi.org/10.17576/jsm-2026-5506-03

 

Acinetobacter Species Strain IrC1: A Copper-Biosorbing, Antibiotic-Resistant Environmental Isolate

(Spesies Acinetobacter Strain IrC1: Pencilan Persekitaran Rintang Antibiotik, Biopenjerapan Kuprum)

 

GEOFFREY DARRIEN FIDELI¹, WAHYU IRAWATI² & JUANDY JO^1,3,*

 

¹Department of Biology, Faculty of Health Sciences, Universitas Pelita Harapan. M.H. Thamrin Boulevard 1100, Tangerang 15811, Banten, Indonesia

²Department of Biology Education, Faculty of Education, Universitas Pelita Harapan. M.H. Thamrin Boulevard 1100, Tangerang 15811, Banten, Indonesia

³Mochtar Riady Institute for Nanotechnology, Universitas Pelita Harapan. Boulevard Jendral Sudirman No.1688, Tangerang 15811, Banten, Indonesia

 

Diserahkan: 23 Oktober 2025/Diterima: 4 Jun 2026

 

Abstract

Copper and antibiotic co-contamination presents environmental challenges, requiring sustainable remediation strategies. Copper bioremediation using environmentally resilient bacteria, such as Acinetobacter species, offers a promising approach. This study evaluated Acinetobacter sp. strain IrC1, isolated from the copper-contaminated Rungkut River (Surabaya, Indonesia), for its copper resistance and biosorption potential under antibiotic stress. Susceptibility to 16 antibiotics was assessed using the Kirby-Bauer disk-diffusion method. Minimum inhibitory and minimum bactericidal concentrations (MIC and MBC, respectively) were subsequently determined for ceftazidime, ciprofloxacin, and erythromycin. These experiments were conducted with 4 mM CuSO₄ or none. Copper biosorption was further tested at 4 mM CuSO₄ in the presence of selected antibiotics. Whole-genome sequencing was conducted to characterize the isolate and to identify resistance determinants. Exposure to 4 mM CuSO₄ reduced the strain’s susceptibility to several antibiotics, as indicated by decreased median of inhibition zone diameters: piperacillin–tazobactam (22 to 19 mm), ceftazidime (19 to 15.5 mm), ciprofloxacin (25 to 19 mm), and erythromycin (16 to 12 mm). In subsequent MIC assays, the strain exhibited resistance to erythromycin under copper exposure (4 to 8 mg/L). However, its MBC remained unchanged. At 4 mM CuSO₄, ceftazidime and ciprofloxacin slightly decreased copper uptake, whereas erythromycin modestly increased biosorption (7.46 - 15.29%). However, these changes were not statistically significant (p > 0.05). Genomic analysis identified the strain as Acinetobacter pittii strain IrC1. Its copper resistance was associated with efflux pump systems, while antibiotic resistance involved both efflux mechanisms and antibiotic-inactivating enzymes. Most resistance genes were not located near insertion sequences, suggesting a low potential for horizontal gene transfer. These findings suggest that A. pittii IrC1 may have a potential to be used in copper bioremediation in environments contaminated by certain antibiotics.

Keywords: Acinetobacter pittii; antibiotics; biosorption; copper; multi resistance

 

Abstrak

Pencemaran bersama oleh kuprum dan antibiotik menimbulkan cabaran alam sekitar yang memerlukan strategi pemulihan mampan. Bioremediasi kuprum menggunakan bakteria yang tahan terhadap persekitaran, seperti spesies Acinetobacter, merupakan pendekatan yang berpotensi. Kajian ini menilai Acinetobacter sp. strain IrC1, yang dipencilkan dari Sungai Rungkut (Surabaya, Indonesia) yang tercemar kuprum, dari segi ketahanan terhadap kuprum dan potensi biopenjerapan di bawah tekanan antibiotik. Kerentanan terhadap 16 jenis antibiotik dinilai menggunakan kaedah resapan cakera Kirby–Bauer. Kepekatan perencatan minimum (MIC) dan kepekatan bakterisid minimum (MBC) kemudiannya ditentukan bagi ceftazidime, ciprofloxacin dan eritromisin dengan atau tanpa kehadiran 4 mM CuSO₄. Biopenjerapan kuprum turut diuji pada 4 mM CuSO₄ dalam kehadiran antibiotik terpilih. Penjujukan genom keseluruhan dijalankan untuk mencirikan pencilan dan mengenal pasti penentu rintangan. Pendedahan kepada 4 mM CuSO₄ mengurangkan kerentanan strain terhadap beberapa antibiotik, seperti ditunjukkan oleh penurunan diameter zon perencatan median: piperacillin–tazobactam (22 kepada 19 mm), ceftazidime (19 kepada 15.5 mm), ciprofloxacin (25 kepada 19 mm) dan eritromisin (16 kepada 12 mm). Dalam ujian MIC seterusnya, strain menunjukkan rintangan terhadap eritromisin di bawah pendedahan kuprum (4 kepada 8 mg/L), walaupun MBCnya kekal tidak berubah. Pada 4 mM CuSO₄, ceftazidime dan ciprofloxacin mengurangkan sedikit pengambilan kuprum, manakala eritromisin meningkatkan biopenjerapan secara sederhana (7.46 - 15.29%), namun perubahan ini tidak signifikan secara statistik (p >0.05). Analisis genom mengenal pasti strain ini sebagai Acinetobacter pittii IrC1. Rintangan terhadap kuprum dikaitkan dengan sistem pam efluks, manakala rintangan antibiotik melibatkan kedua-dua mekanisme efluks dan enzim penyahaktifan antibiotik. Kebanyakan gen kerintangan tidak terletak berhampiran jujukan sisipan, menunjukkan potensi rendah untuk pemindahan gen secara mendatar. Keputusan ini mencadangkan bahawa A. pittii IrC1 berpotensi digunakan dalam bioremediasi kuprum di persekitaran yang tercemar dengan antibiotik tertentu.

Kata kunci: Acinetobacter pittii; antibiotik; biopenjerapan; kuprum; rintang pelbagai

 

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*Pengarang untuk surat-menyurat; email: juandy.jo@uph.edu