In Vitro Evaluation of the Impact of Marine Environmental Stress on the Modulation of β-lactam Antibiotic Resistance in Salmonella Montevideo

• Karuppannan Iswarya ^[1] ; Muralidharan Nagarajan ^[1] ; Shanmugam Sundhar ^[2] ; Rajendran Shalini ^[2] ; Balasubramanian Sivaraman ^[2] ; Ulaganathan Arisekar ^[2] ; H Sanath Kumar ^[3] ; Robinson Jeya Shakila ^[4]
  1. [1] Department of Fish Processing Technology, Tamil Nadu Dr. J. Jayalalithaa Fisheries University
  2. [2] Department of Fish Quality Assurance and Management, Tamil Nadu Dr. J. Jayalalithaa Fisheries University
  3. [3] Fisheries Resources, Harvest & Post-harvest Management Division, ICAR- Central Institute of Fisheries Education (CIFE), Mumbai
  4. [4] Tamil Nadu Dr. J. Jayalalithaa Fisheries University, Dr. M. G. R. Fisheries College and Research Institute

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• Localización: Thalassas: An international journal of marine sciences, ISSN 0212-5919, Vol. 42, Nº. 2, 2026
• Idioma: inglés
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• Resumen

  • Environmental stress influences antibiotic resistance in bacterial pathogens in aquatic systems. In the present study, the antibiotic resistance dynamics of antibiotic-resistant and susceptible strains of Salmonella Montevideo under single and dual environmental stress conditions were investigated. Five β-lactam antibiotics (amoxicillin, ampicillin, penicillin, cefotaxime, and ceftriaxone) were used for the resistance study, and significant differences (p < 0.05) were observed between the control and stressed groups. Under controlled conditions (37 °C, pH 7), the resistant strain expressed resistance to amoxicillin, ampicillin, penicillin, and cefotaxime, with intermediate resistance to ceftriaxone. Simultaneously, the susceptible strain expressed resistance only to penicillin and cefotaxime. When exposed to single stress conditions, nearly 65% variation in the resistance profile of the resistant strain was observed, particularly at pH 10 and 50‰ salinity conditions. In contrast, a hardness of 5000 ppm induced the reversion of antibiotic resistance in 25–40% of the resistant strain (p < 0.05). Under dual stress conditions, that is, 26 combinations, reversion in the resistant profile was mostly observed. The resistant strain showed resistance in only six out of 26 combinations, whereas the susceptible strain newly acquired resistance in four combinations. In contrast to single stress conditions, both strains expressed a 50–70% reduction in the resistance frequency to the dual stressors across all β-lactam antibiotics, indicating stress-mediated variations. While an over 1000-generation evolutionary study revealed that antibiotic-resistant strains regain resistance to amoxicillin and ampicillin under dual stress conditions, particularly 5 ppm NH3-37 °C, pH 10.0-40 °C, and 5 ppm NH3–10‰S, whereas the susceptible strain acquired intermediate resistance after 500 to 750 generations. Hence, this study concluded that environmental stressors significantly influence antibiotic resistance and its reversion in S. Montevideo. Furthermore, the results highlight the influence of resistance to β-lactam antibiotics under combined stress conditions, suggesting potential ecological and evolutionary implications for antimicrobial persistence in aquatic environments