Background and Aim: Shrimp is one of the most commonly consumed types of seafood. It is a very nutritious healthy food. Shrimp is low in calories, rich in protein and healthy fats. It also contains a treasure trove of vitamins and minerals. On the negative side, it may be affected by many bacterial diseases which affect its health. Also, it may be incriminated as a vector of food-borne illnesses that range from mild gastrointestinal upset to life-threatening diseases. This study was designed to assess the clinical picture, zoonotic importance of Aeromonas and Vibrio infection in live shrimp and to study the anti-bacterial effect of citric acid (lemon juice) and acetic acid (vinegar) on these pathogens.
Materials and Methods: A total of 170 live shrimp (Metapenaeus monoceros) samples were collected from Suez City, Egypt. The samples were examined clinically, and then they were enriched into alkaline peptone water and cultivated on thiosulfate citrate bile salt sucrose agar (TCBS) and ampicillin MacConkey agar for isolation of Vibrio and Aeromonas species, respectively. The recovered isolates were confirmed biochemically and genotypically by using duplex PCR and sequencing. The germicidal effects of vinegar and lemon on artificially contaminated shrimp samples with Aeromonas hydrophila and Vibrio parahemolyticus at different times (0.25, 1, 1.5 and 24 hours) and temperatures (5º and 30ºC) were studied.
Results: The results revealed that some of the infected shrimp were hypoxic, lethargic with abnormal swimming behavior. In most cases, body appendages, telsons, uropodes and gills took black coloration. In addition, the hepatopancreas appeared soft, swollen and congested. The prevalence rates of vibriosis in each of the musculature and hepatopancreas were 4.7%. While the prevalence rates of Aeromonas infection in the musculature and hepatopancreas were 11.8% and 11.2%, respectively. Duplex PCR showed that Aeromonas isolates gave double bands; (237 bp) specific for gcat and (500 bp) specific for 16S rRNA. While, Vibrio spp. and Plesiomonas shigelloides isolates gave single band at 500 bp.
The effect of organic acid treatment showed that acetic acid (vinegar 5%) had an increasing reduction rates that reached its maximum level (100% inhibition) for A. hydrophila and (33.63% and 60 %) for V. parahemolyticus at refrigeration and at room temperatures after 24 hours. Moreover, acetic acid was more effective at room temperature than it at refrigeration temperature.
Concerning, the effect of lemon juice (citric acid), it was more effective than acetic acid at short marination (0.25 and one hour) at both temperatures for the two pathogens. Moreover, lemon was more effective at refrigeration temperature than at room temperature at the same aforementioned time. The difference between the reduction effects of the two acids on both pathogens was significant (p < 0.0001).
Conclusion: Overall, the examined shrimp samples were found to be vectors for Vibrio and Aeromonas spp. Application of hygienic measures during handling and cooking of shrimp should be esteemed. The organic acid treatment trial showed that vinegar and lemon juice could be used as a safe and economic method to limit the microbial contamination in seafood.
Key words: Shrimp, Vibrio, Aeromonas, sequencing, decontamination, acetic acid, citric acid
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