Combined effect of benzalkonium chloride and ultrasound against Listeria monocytogenes biofilm on plastic surface.

This study was performed to evaluate the effectiveness of benzalkonium chloride combined with ultrasound in eliminating Listeria monocytogenes biofilm from polystyrene surface. The test strain of L. monocytogenes, previously classified as strong biofilm producer, was grown to form biofilm in tryptic soy broth at 20°C for 6 days in polystyrene specimen containers. The biofilms formed on surface of containers were treated with ultrasound alone, benzalkonium chloride (100 and 400 mg l(-1)) alone and their combination for three different exposure times (1, 5 and 15 min) at room temperature. Sonication was performed using an ultrasound bath at a constant ultrasound frequency of 35 kHz. After treatments, levels of biofilm biomass and viable cells in biofilm were determined using crystal violet staining and XTT assays, respectively. The combined treatment of ultrasound and benzalkonium chloride resulted in significant (P < 0·05) more decrease in the level of viable cells in the L. monocytogenes biofilm compared to individual treatments of benzalkonium chloride. Our results suggest that the combination of benzalkonium chloride with ultrasound is useful approach for the elimination of L. monocytogenes biofilms from plastic surfaces.

Effects of early feed restriction on live performance, carcass characteristics, meat and liver composition, some blood parameters, heterophil-lymphocyte ratio, antibody production and tonic immobility duration.

The aim of this study was to determine the effects of early feed restriction on performance, carcass characteristics, meat and liver composition, some blood parameters, H-L ratio, antibody titers against SRBC and tonic immobility duration in broilers. One hundred ninety male chicks (Ross 308) were randomly allocated into two treatment groups each of 95 chicks. Broilers in one treatment fed ad libitum until 42 day of age, however in other treatment, broilers were deprived of feed for 4 h per day from 7 to 21 day. Body weight, feed consumption, feed to gain ratio, carcass characteristics and the percentage of examined organs except heart were not statistically significant in groups. Percentage of heart was higher (p < 0.05) in broilers fed ad libitum. At 41 d of age, H-L ratio (p < 0.05) and TI duration (p = 0.001) were higher, serum glucose (p < 0.05) and triglyceride (p < 0.001) levels were lower in broilers fed ad libitum. Chemical composition of breast and thigh and also fat and ash of liver were not affected by early feed restriction. Moisture of liver (p = 0.001) was lower and protein of liver (p < 0.01) was higher in broilers fed ad libitum.

Comparison of TEMPO EC and TBX medium for the enumeration of Escherichia coli in cheese.

AIMS: TEMPO EC (Escherichia coli) is based on glucuronidase activity and is a test for use with the TEMPO system for the automated 24 h enumeration of E. coli in food products. In this study, TEMPO EC was compared with TBX medium, the current standard plate method for the enumeration of E. coli in cheese. METHODS AND RESULTS: For comparative purposes, both naturally (92) and artificially contaminated (31) cheese samples were studied. Pearson correlation coefficients were determined as 0.954 and 0.978 between the two methods for naturally and artificially contaminated samples, respectively. Regression analysis yielded the following equations: log(10) TEMPO EC = 0.340 + 0.889 log(10) TBX medium and log(10) TEMPO EC = 0.174 + 0.899 log(10) TBX medium for naturally and artificially contaminated samples, respectively. In general, absolute differences did not exceed one log between results obtained by the two methods. CONCLUSIONS: Statistical analysis of the results showed good agreement between the two enumeration methods. SIGNIFICANCE AND IMPACT OF THE STUDY: TEMPO EC is a practical and reliable alternative to the current standard plate method for the enumeration of E. coli in foods.