MONITORING OF FARMED SHRIMPS (PENAEUS VANNAMEI) FROM NAGAPATTINAM REGION OF TAMIL NADU FOR SALMONELLA CONTAMINATION

Loading...
Thumbnail Image
Date
2019
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
This study was undertaken to monitor the farmed shrimps (Penaeus vannamei) cultured in six shrimp farms namely Hitide seafarms, Ravikumar aquafarms, Certitude farms, Matha aquafarms, MKA star aquafarms and Bismi aquafarms of Nagapattinam region of Tamil Nadu for Salmonella contamination. Samples included shrimp, water, sediment, feed and probiotics which were collected once a month from April 2019 to July 2019, corresponding to one culture cycle. In addition, water and sediment samples were also collected from 23 selected creeks that provided source water to the shrimp farms from December 2018 to May 2019. Samples were tested for the presence of Salmonella by conventional and molecular methods. Out of the total 157 samples collected from the shrimp farms, 43 samples were identified to contain Salmonella by biochemical confirmation test, which accounted for 27.38%. The incidence of Salmonella was high in water samples (40.8%) followed by 7 shrimps (22.4%), probiotics (16.6%) and sediment (7.6%). The incidence of Salmonella was high in Farm 6 (36.9%) followed by Farm 2 (23.1%), Farm 3 (19.2%), Farm 4 and 5 (16.6%) and Farm 1 (15%). Out of the 188 samples collected from natural creeks, 51 samples showed positive for Salmonella through by biochemical confirmation test, which accounted for 27.1%. The highest incidence of Salmonella was observed in Thambikottai, Vadakadu (75%) and Kattur South (66.6%) creeks. The incidence of Salmonella was high (32.6%) in the month of March. Biochemically positive Salmonella isolates were further confirmed by molecular method by targeting the invA gene of product size 275 bp. Out of the total 43 biochemically positive isolates from shrimp farms, only 13 isolates showed the presence of invA gene, which accounted for 30.2%. similarly, out of the total 51 isolates obtained from natural creeks, only 12 isolates showed the presence of invA gene, which accounted for 23.5%. The total prevalence of Salmonella after molecular confirmation in shrimp farms was 8.28% and in creeks was 6.38%. The environmental parameters such as pH, salinity, ammonia, nitrite and nitrate were analysed in the water of shrimp farms and creeks. The pH ranged from 7.2 to 8.6, salinity from 13 to 45 ppt, ammonia from 0 to 0.3 ppm, nitrite from 0 to 0.5 ppm, nitrate from 0 to 20 ppm in shrimp farms. The variation observed was higher in Farm 6 as compared to other farms. In the creek waters, the highest pH and ammonia recorded was in Vellapallam creek, the salinity was high in Muthupettai creek, nitrite in Periyathumbar creek and nitrate in Karuvelankadai creek. The values of all the water quality parameters were high during the summer months. PCR positive Salmonella isolates (25 No.) were tested for their antibiotic resistance against the allegedly used antibiotics in shrimp farms viz. sulphonamides (SF), tetracycline 8 (TC), chloromphenicol (CAP) and furazolidone (FZ). All the isolates were resistant to SF, but sensitive to TC, CAP and FZ. The MIC of CAP against Salmonella isolates of shrimp farms ranged from 10 to 30 ppm, TC from 2 to 10 ppm, and FZ from 20 to 40 ppm, while the MBC ranged from 20 to 40 ppm for CAP, from 4 to 20 for TC and from 30 to 50 ppm for FZ. The isolates that had shown more resistance to TC was F6- MW1, to CAP were F2- W2 and F6- BWR and to FZ were F6- Sh14, F6- MW1, F6- BWR and F3- S4. Most of the resistant isolates collected from Farm 6 water and shrimp. The isolates from creek waters that exhibited more resistance to antibiotics viz. TC, C13- IVW, C2- VS and C18- VIS and FZ were C10- IIW, C13- IVW and C2- VS these isolates were collected from water and sediment samples Thopputhurai, Thennalakudi, Karuvelankadai and Poopuhar creeks, respectively. One isolate, C13-IVW, exhibited resistance to more than one antibiotic viz. FZ (80 ppm) and CAP (50 ppm) this isolate has been identified as Salmonella enterica serovar Montevideo, which is a pathogenic strain frequently associated with human salmonellosis.
Description
Keywords
null
Citation
Fisheries College and Research Institute , Tamil Nadu Dr. J. Jayalalithaa Fisheries University, Thoothukudi
Collections