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<p>Soil associated with intensive poultry farming serves as a seminal reservoir of antimicrobial resistance genes. This study employed an integrated approach that combined metagenomics, phenotypic analysis, and whole-genome sequencing to investigate the soil resistome of poultry farms in the Jorhat district, Northeast India, and to evaluate <i>Bacillus altitudinis</i> as an environmental potential indicator for antimicrobial resistance. Metagenomic analysis of poultry-affected soil revealed a diverse array of resistance genes, including 753 unique resistance ontologies related to β-lactam, glycopeptide, macrolide, aminoglycoside, chloramphenicol, and colistin resistance. Culture-based testing of soil and fecal isolates (400 isolates) showed high resistance rates to colistin and ciprofloxacin (~60%), as well as notable resistance to erythromycin and kanamycin, indicating strong antibiotic selection pressures in these ecosystems. Among multidrug-resistant strains, <i>B. altitudinis</i> S2 was particularly notable, exhibiting high minimum inhibitory concentrations for last-line antibiotics such as vancomycin (&gt;50&#xa0;µg/mL), colistin (&gt;50&#xa0;µg/mL), and fourth-generation cephalosporins. It also demonstrated multidrug β-lactam resistance supported by synergistic inhibitors. Whole-genome sequencing (3.7&#xa0;Mb) uncovered a complex antimicrobial resistance gene (ARG) profile, including <i>vanZ</i>, <i>mcr-1</i>, <i>catA</i>, <i>mph</i>, <i>aph</i>, and <i>oxa</i>-type β-lactamase genes, alongside multiple SMR, MATE, and RND efflux mechanisms. Many of these genes were located within genomic islands, prophage traces, and mobile genetic elements, strongly indicating horizontal gene transfer from various bacteria, including gut-associated enterococci. The genome also contained genes for resistance to heavy metals and oxidative stress, suggesting co-selection processes that sustain ARGs in soil. The study tries to show <i>B. altitudinis</i> as a crucial environmental indicator for ARGs, serving a genetic bridge between poultry gut microbiota and soil antimicrobial resistance pools, highlighting its significance for One Health antimicrobial resistance surveillance.</p>

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Ecological and genomic insights into Bacillus altitudinis as a potential indicator of resistance genes in soil antimicrobial resistance pools

  • 期刊论文

  • 发表日期：

    2026年4月1日

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  • Abhilash Bhattacharjee,
  • Anil Kumar Singh

摘要

Soil associated with intensive poultry farming serves as a seminal reservoir of antimicrobial resistance genes. This study employed an integrated approach that combined metagenomics, phenotypic analysis, and whole-genome sequencing to investigate the soil resistome of poultry farms in the Jorhat district, Northeast India, and to evaluate Bacillus altitudinis as an environmental potential indicator for antimicrobial resistance. Metagenomic analysis of poultry-affected soil revealed a diverse array of resistance genes, including 753 unique resistance ontologies related to β-lactam, glycopeptide, macrolide, aminoglycoside, chloramphenicol, and colistin resistance. Culture-based testing of soil and fecal isolates (400 isolates) showed high resistance rates to colistin and ciprofloxacin (~60%), as well as notable resistance to erythromycin and kanamycin, indicating strong antibiotic selection pressures in these ecosystems. Among multidrug-resistant strains, B. altitudinis S2 was particularly notable, exhibiting high minimum inhibitory concentrations for last-line antibiotics such as vancomycin (>50 µg/mL), colistin (>50 µg/mL), and fourth-generation cephalosporins. It also demonstrated multidrug β-lactam resistance supported by synergistic inhibitors. Whole-genome sequencing (3.7 Mb) uncovered a complex antimicrobial resistance gene (ARG) profile, including vanZ, mcr-1, catA, mph, aph, and oxa-type β-lactamase genes, alongside multiple SMR, MATE, and RND efflux mechanisms. Many of these genes were located within genomic islands, prophage traces, and mobile genetic elements, strongly indicating horizontal gene transfer from various bacteria, including gut-associated enterococci. The genome also contained genes for resistance to heavy metals and oxidative stress, suggesting co-selection processes that sustain ARGs in soil. The study tries to show B. altitudinis as a crucial environmental indicator for ARGs, serving a genetic bridge between poultry gut microbiota and soil antimicrobial resistance pools, highlighting its significance for One Health antimicrobial resistance surveillance.