Effect of antibiotics and sanitizers on Salmonella biofilms associated with seafood contact surfaces

This study investigates the effect of antibiotics and sanitizers on biofilm forming Salmonella isolated from different seafood contact surfaces. Four Salmonella were isolated from 384 swab samples collected from various contact surfaces of fishing boats, fish landing centres and seafood processing plants. One out of four isolates was from the fishing boat (FB I -1) other three isolates were from the seafood processing plant (FPPII -4, FPPII- 5, FPPI-3). The ability of Salmonella to form biofilms on different contact surfaces (HDPE, stainless steel, wood, glass, tiles) was tested with the microbial load on different incubation days, and a higher count was observed on day five. The effect of sanitizer viz., sodium hypochlorite (20, 50, 100, 200 mg/l) and iodophor (2, 5, 10 mg/l) on the biofilm formed on different seafood contact surfaces were investigated. A reduction of 2-3 log was observed on surfaces of HDPE and stainless steel when they were treated with a minimum of 5 mg/l of iodophor or 20 mg/l of sodium hypochlorite after a contact time of 5 min. Antibiotic resistance of biofilm forming Salmonella was tested for different classes of antibiotics (penicillin, ß-lactams, quinolones, macrolides, aminoglycosides, phenol drugs, sulfonamides, cephalosporin). All four isolates showed intermediate resistance to ciprofloxacin, a quinolone drug. Only one isolate FB I -1 (fishing boat deck) expressed resistance to more drugs, viz., ßlactams (AMC, AMP, penicillin G), macrolides (AZM) and nitrofurantoin (NIT). These findings shall help the seafood processors to mitigate the formation of Salmonella biofilms on various seafood contact surfaces with different sanitizers and the antibiotic resistance of biofilm forming Salmonella shall give knowledge on human clinical treatments. With this study, we shall recommend the regulatory authorities control the contamination level of fish handling areas.