Biofilm forming Listeria monocytogenes in seafood contact surfaces of Tuticorin region, Tamil Nadu
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Date
2015
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Fisheries College and Research Institute, Thoothukudi, Tamil Nadu Dr. J. Jayalalithaa Fisheries University
Abstract
Biofilm forming Listeria monocytogenes was screened from different seafood contact surfaces viz. fish hold, boat deck, fish basket, fish transport tricycle, auction hall floor, fish cutting board, fishermen hand, insulated vehicle, raw material receiving chute, grading machine, grading table, soaking tank, weighing balance, weighing balance table, individually quick frozen (IQF) table, block freezing conveyor belt, freezer pan, freezer, cooking boiler, depanning conveyor belt, wall tiles, cold store, fish display board, brine tank, and fish curing yard floor in five sampling sites of fishing harbour, fish landing centers, seafood processing plants, fish market, and fish curing yards of Tuticorin region, Tamil Nadu along the East Coast of India. About 115 swab samples were collected and tested for the presence of L. monocytogenes by conventional and molecular methods. Overall, 5.22% of swab samples collected were positive for L. monocytogenes. The fishing harbour had high incidence (10.3%) of L. monocytogenes followed by that of fish landing centers (5.9%), and seafood processing plants (4.1%). Boat deck, fish transport tricycle were the two important seafood contact surfaces in fishing harbour which had high incidence of L. monocytogenes. About 25 and 28.5% of swab samples from fish transport tricycle and boat deck were positive for L. monocytogenes, respectively. The swab samples from fish market and fish curing yards were negative for L. monocytogenes. All the isolated colonies of L. monocytogenes were confirmed by PCR assay targeting virulent hlyA gene. The DNA of all the isolates yielded a product of 174 bp on PCR amplification in comparison with L. monocytogenes Type culture (MTCC 1143). All the isolates were sequenced and the sequence showed above 96% confirmation on NCBI data base on L. monocytogenes. The isolates of L. monocytogenes were allowed to grown biofilm on different artificial seafood contact surfaces (stainless steel, aluminium, plastic, tile, glass, and wood) in vitro condition. The initial attachment of L. monocytogenes was more on wood followed by aluminium, and tile. However, the biofilm formation was rapid on stainless steel, plastic, and aluminium substrates. The live biofilm cells of L. monocytogenes from different artificial contact surfaces were confirmed by RT-PCR targeting mRNA luxS gene that resulted in a product of 486 bp. The biofilm produced by all the isolates of L. monocytogenes were found to contain mRNA luxS gene. The commonly used sanitizers in food industries at recommended levels like sodium hypochlorite (200 ppm), iodine (25 ppm), hydrogen peroxide (200 ppm), and calcium hypochlorite (200 ppm) were tested for their efficacy in controlling the biofilm forming L. monocytogenes. Among the sanitizers tested, calcium hypochlorite (200 ppm) was found to be most effective in controlling biofilm of L. monocytogenes on different artificial contact surfaces, as it destructed the biofilm cells completely, followed by sodium hypochlorite (200 ppm). The effect of iodine (25 ppm), and hydrogen peroxide (200 ppm) on controlling the biofilm cells of L. monocytogenes was not significant.
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