Biofilm formation by Salmonella spp. in catfish mucus extract under industrial conditions

Authors: DHOWLAGHAR, N - Mississippi State University; ABEYSUNDARA, P - Mississippi State University; NANNAPANENI, R - Mississippi State University; SCHILLING, N - Mississippi State University; CHANG, S - Mississippi State University; CHENG, W - Mississippi State University; SHARMA, C - Mississippi State University

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2017
Publication Date: 9/28/2017
Citation: Dhowlaghar, N., Abeysundara, P., Nannapaneni, R., Schilling, N.W., Chang, S., Cheng, W.H., Sharma, C.S. 2017. Biofilm formation by Salmonella spp. in catfish mucus extract under industrial conditions. Food Microbiology. 70(4):172-180.

Interpretive Summary: Salmonella is widely distributed in nature and aquatic environments. Recently, the persistence of Salmonella spp. in fish meal and fish factories was linked with its ability to form biofilms. During catfish processing, residues such as water runoff, muscle extract and mucus present on the skin surface may promote Salmonella persistence. There is a lack of information on the factors promoting biofilm formation of Salmonella spp. in the catfish processing environment. Therefore, objectives of the present study were to determine the growth and biofilm formation of Salmonella spp. in the presence of catfish mucus extract under different environmental conditions and to evaluate the efficacy of commercial disinfectant cleaners at reducing Salmonella biofilms that were formed on the stainless steel surface containing catfish mucus. Our studies show that Salmonella isolates were able to grow and form biofilms in concentration of catfish mucus extract concentrations low as 15 µg/ml. The growth rate and biofilm formation increased with increasing concentration and temperature. No major differences were found among the Salmonella strains that were tested for their ability to form biofilm in catfish mucus extract. Biofilm production of Salmonella Blockley on buna-N rubber was less than stainless steel, polyethylene and polyurethane surfaces in catfish mucus extract. Disinfectants containing a mix of QAC with H2O2 or PAA with H2O2 and octanoic acid were effective at reducing of biofilm cells on the stainless steel surface such that they were non-detectable.

Technical Abstract: The objective of this study was to determine the effect of strain and temperature on the growth and biofilm formation of Salmonella spp. in high and low concentrations of catfish mucus extract on different food-contact surfaces at 22°C and 10°C. The second objective of this study was to evaluate the efficacy of disinfectants at recommended concentrations and contact times for removing Salmonella biofilms cells on a stainless steel surface containing catfish mucus extract. Growth and biofilm formation of all Salmonella strains increased with higher concentrations of catfish mucus extract at both 10°C and 22°C. In 15 µg/ml of catfish mucus extract inoculated with 3 log CFU/ml, the biofilm levels of Salmonella on stainless steel surface reached to 3.5 log CFU/cm2 at 10°C or 5.5 log CFU/cm2 at 22°C in 7 days. In 375 µg/ml of catfish mucus extract inoculated with 3 log CFU/ml, the biofilm levels of Salmonella on the stainless steel surface reached 4.5 log CFU/cm2 at 10°C and 6.5 log CFU/cm2 at 22°C in 7 days. No differences were observed between Salmonella strains tested for biofilm formation in catfish mucus extract on the stainless steel surface. The biofilm formation by Salmonella Blockley (7175) in catfish mucus extract was less (P < 0.05) on buna-N rubber when compared to stainless steel, polyethylene and polyurethane surfaces. Salmonella biofilm cells were not detectable on the stainless steel surface after treatment with a mixture of disinfectants but were still present when single compound disinfectants were used.