Antibiofilm Activity of Bacteriophage Isolated from Sewage-Polluted Water against Escherichia coli

 

Antibiofilm Activity of Bacteriophage Isolated from Sewage-Polluted Water against Escherichia coli

Acharya Amrit^{1, 2}, Ayushma Tamrakar^1†, Smirti Yando^1†, Avinash Chaudhary¹, Upendra Thapa Shrestha^1,2, Dev Raj Joshi², Binod Lekhak²

 

¹ Department of Microbiology, Sainik Awasiya Mahavidhyalaya, Bhaktpur, Nepal

² Central Department of Microbiology, Tribhuvan University, Kathmandu, Nepal

†The first three authors contributed equally.

*Corresponding author: Amrit Acharya, Central Department of Microbiology, Tribhuvan University, Kathmandu, Nepal, E-mail: amrit.805710@iost.tu.edu.np

ABSTRACT

 

Objectives: This study aimed to explore bacteriophages, viruses that infect bacteria, as an alternative antibiofilm agent.

Methods: A laboratory-based, cross-sectional study was conducted at the Sainik Awasiya Mahavidyalaya Laboratory from February to July 2025. The water samples that were contaminated with effluents were collected from eight rivers and ponds across the Kathmandu valley. E. coli isolates were used as the host strain after being confirmed by biochemical tests. Phages were isolated and enriched from wastewater using centrifugation, filtration, and multiple cycles of incubation with log-phage host bacteria to gain high titres. The plaque assay, host range by spot assay, and Efficacy of Plating (EOP) were performed. Antibiofilm activity was evaluated using the microtiter plate crystal violet assay. The study compared biofilm formation in the isolated E. coli (E.C 8) with that of the standard E. coli (ATCC 8739). Statistical significance was determined using the t-test (p ≤ 0.05).

Results: Bacteriophages were found in six of eight samples. Only Mulpani had a lytic phage with a titre of 7.5 PFU/ml, which was used for further testing. The phage exhibited moderate EOP, ranging from 0.28 to 0.60, and a moderate host range. The isolated phage showed selected antibiofilm activity, as it effectively reduced the biofilm of the isolated E. coli (22.8%).

Conclusion: This emphasizes the ability of lytic phages as antibiofilm agents.

 

Keywords: Effluent, Antibiotic Resistance, Biofilm, Extracellular Polymeric Substances, Bacteriophage

 

Date of Submission: November 03, 2025     Date of Acceptance: December 05, 2025

Published Online: December, 2025               DOI: https://doi.org/10.3126/tujm.v12i1.88373

Citation: Acharya, A., Tamrakar, A., Yando, S., Chaudhary, A., Thapa Shrestha, U., Joshi, D. R., & Lekhak, B. (2025). Antibiofilm Activity of Bacteriophage Isolated from Sewage-Polluted Water against Escherichia coli. Tribhuvan University Journal of Microbiology, 12(1), 89–99. https://doi.org/10.3126/tujm.v12i1.88373

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Quinolones residue in poultry meat and eggs; an alarming public health issue in Nepal (BMC Research Notes)

  

Quinolones residue in poultry meat and eggs; an alarming public health issue in Nepal

Nabaraj Shrestha¹, Sundar Layalu², Serene Amatya³, Samrat Shrestha³, Shobha Basnet⁴, Divya Pradhan⁵ and Upendra Thapa Shrestha^{5 *}

¹Department of Livestock Services, Hariharbhawan, Lalitpur, Nepal

²Clark University, Worcester, USA

³Himalayan College of Agricultural Sciences and Technology (HICAST), Kalanki, Kathmandu, Nepal

⁴ZEST Laboratory, Bhaktapur, Balkot, Nepal

⁵Central Department of Microbiology, Tribhuvan University, Kirtipur, Kathmandu, Nepal

 

*Correspondence: Upendra Thapa Shrestha; upendrats@gmail.com; upendra.thapashrestha@cdmi.tu.edu.np

 

 Abstract

Objective Quinolones, critically important antimicrobials, pose public health risks due to potential antimicrobial resistance, allergic reactions, and other toxicities when residues persist in food. This study aimed to qualitatively and quantitatively assess quinolone residues in chicken meat and eggs supplied to Kathmandu, Nepal. Additionally, data on antibiotic usage trends were collected through a standardized questionnaire using Epicollect + Android application. A total of 120 chicken meat and 120 eggs were collected from five designated sectors. Initial screening for quinolone residues was performed using Enzyme-Linked Immunosorbent Assay, and samples exceeding the maximum residue limit (MRL) were further analyzed using High-Performance Liquid Chromatography.

Results Quinolone residues were detected in 88.3% of chicken meat and 80% of egg samples. Three chicken meat samples from Kathmandu exceeded the MRL (> 100ppb), with Enrofloxacin found in commercial and education sectors and both Enrofloxacin and Ciprofloxacin in the health sector. In eggs, residue prevalence was 83.9% in Kathmandu followed by Bhaktapur (76.9%) and Lalitpur (65%). Household eggs had the most residues (100%), and the education sector had the least (66.7%) (p = 0.0219). These findings indicate widespread and unregulated quinolone use in poultry production, highlighting the urgent need for prudent antibiotic stewardship to reduce antimicrobial resistance and associated health risks.

 

Keywords Antimicrobial residue, Enrofloxacin, Ciprofloxacin, Quinolones, Maximum residue limit

Citation: Shrestha N, Layalu S, Amatya S, Shrestha S, Basnet S, Pradhan D, Shrestha UT. Quinolones residue in poultry meat and eggs; an alarming public health issue in Nepal. BMC Res Notes. 2026 Jan 6;19(1):49. doi: 10.1186/s13104-025-07627-z. PMID: 41495852; PMCID: PMC12870818.

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Molecular Detection of CTX-M Type ESBL Genes in Clinical Isolates of Klebsiella Species

 Molecular Detection of CTX-M Type ESBL Genes in Clinical Isolates of Klebsiella Species

Neesha Shrestha¹, Kuntala Shrestha¹, Upendra Thapa Shrestha², Komal Raj Rijal², Gayatri Karki³, Ishworiya Lamichhane¹, Kiran Sapkota⁴, Sanjib Adhikari² ,Shyam Prakash Dumre², Nabaraj Adhikari^2*

¹Kantipur College of Medical Science, Tribhuvan University, Sitapaila, Kathmandu, Nepal

²Central Department of Microbiology, Tribhuvan University

³Himal Hospital Pvt. Ltd., Thirbum Marg, Kathmandu

⁴Sam Houston State University, Huntsville, Texas, USA

^*Corresponding author: Nabaraj Adhikari, Assistant Professor, Central Department of Microbiology, TU, Email: nabaraj.adhikari@cdmi.tu.edu.np

 

ABSTRACT

Objective: The objective of this study is to determine the prevalence of Extended-Spectrum β-Lactamase (ESBL) production and CTX-M genes among Klebsiella species isolated from clinical specimens.

Methods: A total of 1,815 clinical samples—including urine, blood, sputum, pus, and body fluids were collected at Himal Hospital Kathmandu, during 2019–2020. Standard microbiological techniques were used for isolation and identification of bacterial pathogens. Antimicrobial susceptibility testing was performed using the modified Kirby–Bauer disk diffusion method following CLSI (2019) guidelines. ESBL screening was conducted using third-generation cephalosporins, and confirmation was done via the Double Disk Synergy Test (DDST). Molecular detection of the CTX-M gene was performed using PCR with specific primers targeting a 544 bp amplicon.

Results: Among 1,815 clinical samples, urine constituted the majority (65.8%), followed by blood (25.1%). Escherichia coli was the predominant isolate (89.1%), while Klebsiella pneumoniae (6.2%) and Klebsiella oxytoca (0.74%) comprised a smaller proportion. Of the 28 Klebsiella spp. isolates, the highest antibiotic sensitivity was observed toward Amikacin (60.7%) and Meropenem (57.1%), whereas complete resistance to Amoxicillin (100%) and high resistance to Cefixime (89.3%) and Cefotaxime (75.0%) were recorded. ESBL screening identified 22 (78.6%) potential ESBL producers, of which 18 (64.3%) were confirmed phenotypically. PCR analysis revealed the CTX-M gene in 7 of the 18 ESBL-positive isolates, demonstrating a notable presence of CTX-M–mediated resistance among Klebsiella spp.

Conclusion: The findings highlight a concerning prevalence of ESBL production and CTX-M genes in Klebsiella species in the study population, underscoring the need for continuous surveillance, rational antibiotic use, and strengthened antimicrobial stewardship programs to limit the spread of multidrug-resistant strains.

Keywords: Klebsiella spp., ESBL producer and CTX-M

 

Date of Submission: November 12, 2025     Date of Acceptance: December 22, 2025

Published Online: December, 2025               DOI: https://doi.org/10.3126/tujm.v12i1.88388

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