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Abstract <p>Indian mackerel (<i>Rastrelliger kanagurta</i>) is a commercially important and essential dietary marine fin-fish rich in omega-3 fatty acids, which contributes substantially to the food and nutritional security. Specific Spoilage Organisms (SSOs) contribute significantly to spoilage in Indian mackerel. However, the SSOs in Indian mackerel, their spoilage potential, and antimicrobial resistance (AMR) patterns remain understudied. In the present study, ninety-nine presumptive SSOs were isolated from Indian mackerel procured from seven retail fish vending units. The predominant bacterial flora identified by 16S rRNA gene sequence analysis were <i>Shewanella</i> sp. (<i>n</i> = 38), <i>Aeromonas</i> sp. (<i>n</i> = 36), and <i>Pseudomonas</i> sp. (<i>n</i> = 14); which constituted 88% of the bacterial flora. Evaluation of spoilage potential by trimethylamine oxide (TMAO) reduction assay revealed that 70% of the isolated bacteria contributed to trimethylamine (TMA) production, among which, <i>Aeromonas molluscorum</i> (54.7 mg%) produced the maximum, followed by <i>Shewanella baltica</i> (53.2 mg%). Substantial resistance to imipenem, an antibiotic of last resort, was observed among <i>Aeromonas</i> sp. (44%) and <i>Shewanella</i> sp. (47%). Furthermore, resistance to colistin and ciprofloxacin was detected in <i>Shewanella</i> sp. and <i>Pseudomonas</i> sp., respectively. The optimal temperatures for the growth of SSOs were observed to be at 25°C, followed by 15°C, and 5°C. In the wake of the menace of antimicrobial resistance (AMR), carbapenem resistance in the SSOs needs greater research focus. This study opens new vistas for the research community to concentrate on the SSO control approach for preserving the shelf-life of Indian mackerel and strengthening the antimicrobial resistance surveillance strategies in the country.</p> Research Highlights <p><UnorderedList Mark="Bullet"> <ItemContent> <p>The major spoilage bacteria associated with spoilage in Indian mackerel is found to be <i>Aeromonas</i> sp. and <i>Shewanella</i> sp.</p> </ItemContent> <ItemContent> <p>Around 70% of the total isolates contributed to the spoilage in Indian mackerel.</p> </ItemContent> <ItemContent> <p><i>Aeromonas molluscorum</i> (54.73 mg%) and <i>S. baltica</i> (53.2 mg%) were the top producers of TMA in Indian mackerel. <i>Pseudomonas</i> sp., is not a producer of TMA.</p> </ItemContent> <ItemContent> <p><i>Shewanella</i> sp. developed significant resistance to imipenem and colistin, while <i>Aeromonas</i> sp. were resistant to imipenem.</p> </ItemContent> <ItemContent> <p><i>Aeromonas</i> sp. were able to grow optimally at 25°C, whereas, <i>Shewanella</i> sp. at 15°C and <i>Pseudomonas</i> sp. grew between 15°C and 25°C.</p> </ItemContent> </UnorderedList></p>

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Aeromonas molluscorum and Shewanella baltica: The highest trimethylamine producing spoilage bacteria identified in Rastrelliger kanagurta displaying varied antimicrobial resistance and growth

  • 期刊论文

  • 发表日期：

    2025年9月20日

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  • Ammu Lakshmi Devadas,
  • Murugadas Vaiyapuri,
  • Visnuvinayagam Sivam,
  • Remya Sasikala,
  • Joshy Chalil George,
  • Sreejith Vyyokaran Narayanan,
  • Reshmi Koombankallil,
  • Madhusudana Rao Badireddy,
  • Toms Cheriyath Joseph

摘要

Abstract

Indian mackerel (Rastrelliger kanagurta) is a commercially important and essential dietary marine fin-fish rich in omega-3 fatty acids, which contributes substantially to the food and nutritional security. Specific Spoilage Organisms (SSOs) contribute significantly to spoilage in Indian mackerel. However, the SSOs in Indian mackerel, their spoilage potential, and antimicrobial resistance (AMR) patterns remain understudied. In the present study, ninety-nine presumptive SSOs were isolated from Indian mackerel procured from seven retail fish vending units. The predominant bacterial flora identified by 16S rRNA gene sequence analysis were Shewanella sp. (n = 38), Aeromonas sp. (n = 36), and Pseudomonas sp. (n = 14); which constituted 88% of the bacterial flora. Evaluation of spoilage potential by trimethylamine oxide (TMAO) reduction assay revealed that 70% of the isolated bacteria contributed to trimethylamine (TMA) production, among which, Aeromonas molluscorum (54.7 mg%) produced the maximum, followed by Shewanella baltica (53.2 mg%). Substantial resistance to imipenem, an antibiotic of last resort, was observed among Aeromonas sp. (44%) and Shewanella sp. (47%). Furthermore, resistance to colistin and ciprofloxacin was detected in Shewanella sp. and Pseudomonas sp., respectively. The optimal temperatures for the growth of SSOs were observed to be at 25°C, followed by 15°C, and 5°C. In the wake of the menace of antimicrobial resistance (AMR), carbapenem resistance in the SSOs needs greater research focus. This study opens new vistas for the research community to concentrate on the SSO control approach for preserving the shelf-life of Indian mackerel and strengthening the antimicrobial resistance surveillance strategies in the country.

Research Highlights

The major spoilage bacteria associated with spoilage in Indian mackerel is found to be Aeromonas sp. and Shewanella sp.

Around 70% of the total isolates contributed to the spoilage in Indian mackerel.

Aeromonas molluscorum (54.73 mg%) and S. baltica (53.2 mg%) were the top producers of TMA in Indian mackerel. Pseudomonas sp., is not a producer of TMA.

Shewanella sp. developed significant resistance to imipenem and colistin, while Aeromonas sp. were resistant to imipenem.

Aeromonas sp. were able to grow optimally at 25°C, whereas, Shewanella sp. at 15°C and Pseudomonas sp. grew between 15°C and 25°C.