Growth and biofilm formation by Listeria monocytogenes in catfish mucus extract on four food-contact surfaces at 22°C and 10°C and their reduction by commercial disinfectants

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

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2017
Publication Date: 12/18/2017
Citation: Dhowlaghar, N., Abeysundara, P., Nannapaneni, R., Schilling, M.W., Chang, S., Cheng, W.H., Sharma, C.S. 2017. Growth and biofilm formation by Listeria monocytogenes in catfish mucus extract on four food-contact surfaces at 22°C and 10°C and their reduction by commercial disinfectants. Journal of Food Protection. 81(1):59-67.

Interpretive Summary: Catfish processing mainly includes receiving and weighing the live fish in the holding tank, deheading, evisceration, skinning, chilling and freezing/ice packing. During these stages, residues from catfish skin, mucus or water runoff may build up on processing surfaces at hard to remove places despite regular cleaning and sanitization. These residues may provide L. monocytogenes with nutrients for growth, adherence and biofilm formation on food processing surfaces. However, little is known about the influence of catfish mucus on the growth and biofilm formation of L. monocytogens on catfish processing surfaces. Therefore, the first objective of the present study was to determine the effects of strain, temperature, nutrient level and food-contact surface on the growth and biofilm formation of L. monocytogenes in catfish mucus extract and second objective of this study was to evaluate the efficacy of disinfectants at recommended concentrations and contact times for removing L. monocytogenes biofilm cells on stainless steel surface containing catfish mucus extract. Our results indicate that L. monocytogenes can grow and subsequently form biofilms on various food-contact processing surfaces in the presence of concentrations as low as 15 µg/ml of catfish mucus at 22°C and 10°C. The complete reduction of L. monocytogenes biofilm cells was achieved on stainless steel surface with a mixture of disinfectants, such as QAC with H2O2 or peracetic acid (PAA) with H2O2 and octanoic acid compared to QAC, chlorine or acid disinfectants alone.

Technical Abstract: The objective of this study was to determine the effect of strain and temperature on growth and biofilm formation by Listeria monocytogenes (Lm) in high and low concentrations of catfish mucus extract on different food-contact surfaces at 10°C and 22°C. The second objective of this study was to evaluate the efficacy of disinfectants at recommended concentrations and contact times for removing Lm biofilm cells on stainless steel surface containing catfish mucus extract. Growth and biofilm formation of all Lm 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 Lm on stainless steel reached to 4-5 log CFU/coupon at 10°C or 5-6 log CFU/coupon at 22°C in 7 days. In 375 µg/ml of catfish mucus extract, the biofilm levels of Lm on stainless steel surface reached to 5-6 log CFU/coupon at 10°C or 6-7.5 log CFU/coupon at 22°C in 7 days. No differences were observed between Lm strains tested for biofilm formation in catfish mucus extract on the stainless steel surface. The biofilm formation by Lm catfish isolate HCC23 was less (P < 0.05) on buna-n rubber when compared to stainless steel, polyethylene and polyurethane surfaces in catfish mucus extract. The contact angle method and Atomic Force Microscopy confirmed that buna-n rubber was highly hydrophobic with low surface energy and low roughness compared to other three surfaces. The complete reduction of Lm biofilm cells was achieved on stainless steel surface with a mixture of disinfectants, such as QAC’s with H2O2 or peracetic acid (PAA) with H2O2 and octanoic acid at 1/4 or 1/2 recommended concentration (RC) in 1 or 3 min as compared to QAC, chlorine or acid disinfectants alone.