Document Type : Original Articles
Authors
1
1. Zoonoses Research Center, Tehran University of Medical Sciences, Tehran, Iran 2. Food Microbiology Research Center, Tehran University of Medical Sciences, Tehran, Iran
2
Department of pathobiology, Tehran University of Medical Sciences, Tehran, Iran
3
Department of Pathobiology, Tehran University of Medical Sciences, Tehran, Iran
4
1. Food Microbiology Research Center, Tehran University of Medical Sciences, Tehran, Iran 2. Department of Pathobiology, Tehran University of Medical Sciences, Tehran, Iran
10.66224/ari.2026.371555.3963
Abstract
Introduction
Effective disease management in aquaculture depends largely on preventive strategies and enhancement of the fish immune system. Farmed fish represent a major portion of seafood consumption in Iran. However, limited information is available regarding the prevalence of Vibrio parahaemolyticus strains harboring enterotoxin genes and the potential mitigating effects of probiotics in Iranian aquaculture systems. Considering the pathogenic potential of this bacterium and its impact on public health, updated data are essential.
Objective
The present study aimed to investigate the occurrence of V. parahaemolyticus in farmed carp and trout in Tehran, evaluate the presence of enterotoxin-related genes, determine antibiotic susceptibility patterns, and assess the inhibitory and gene expression–modulating effects of two probiotic species, Lactobacillus fermentum (L. fermentum) and Lactobacillus plantarum (L. plantarum).
Material and Methods
A total of 264 fish samples, including carp and trout, were collected from fish farms in Tehran. Isolation of V. parahaemolyticus was performed using enrichment media followed by biochemical identification tests. Molecular confirmation and detection of enterotoxin-associated genes were carried out using Polymerase Chain Reaction (PCR). Antibiotic susceptibility testing was conducted to determine resistance patterns. The antagonistic activity of L. fermentum and L. plantarum against the isolates was evaluated using in vitro assays. The impact of these probiotics on enterotoxin gene expression was analyzed through real-time PCR.
Results
Out of 264 examined fish samples, 20 (7.57%) were positive for V. parahaemolyticus, including 14 carp (10.6%) and 6 trout (4.54%). All isolates carried the 16S rRNA gene, confirming species-level identification. The tdh gene was detected in 16 isolates (80%), while the trh gene was not identified. Both probiotic strains exhibited significant inhibitory effects on bacterial growth in vitro. Real-time PCR analysis demonstrated a significant reduction in tdh gene expression following exposure to either probiotic strain.
Conclusion
The detection of the tdh virulence gene in V. parahaemolyticus isolates from farmed fish highlights the necessity for continuous surveillance and strengthened biosecurity measures in aquaculture systems. The inhibitory and gene expression–reducing effects of the tested probiotics suggest their potential as preventive strategies. Strict hygiene during fish handling and proper cooking are recommended to reduce public health risks.
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