Survival of Listeria monocytogenes on a conveyor belt material with or without antimicrobial additives

Survival of Listeria monocytogenes on a conveyor belt material with or without antimicrobial additives, in the absence or presence of food debris from meat, fish and vegetables and at temperatures of 10, 25 and 37 °C was investigated. The pathogen survived best at 10 °C, and better at 25 °C than at 37 °C on both conveyor belt materials. The reduction in the numbers of the pathogen on belt material with antimicrobial additives in the first 6 h at 10 °C was 0.6 log unit, which was significantly higher (P <0.05) than the reduction of 0.2 log unit on belt material without additives. Reductions were significantly less (P <0.05) in the presence of food residue. At 37 °C and 20% relative humidity, large decreases in the numbers of the pathogen on both conveyor belt materials during the first 6 h were observed. Under these conditions, there was no obvious effect of the antimicrobial substances. However, at 25 °C and 10 °C and high humidity (60–75% rh), a rapid decrease in bacterial numbers on the belt material with antimicrobial substances was observed. Apparently the reduction in numbers of L. monocytogenes on belt material with antimicrobial additives was greater than on belt material without additives only when the surfaces were wet. Moreover, the presence of food debris neutralized the effect of the antimicrobials. The results suggest that the antimicrobial additives in conveyor belt material could help to reduce numbers of microorganisms on belts at low temperatures when food residues are absent and belts are not rapidly drie

Listeria monocytogenes in Milk Products

peer-reviewedMilk and milk products are frequently identified as vectors for transmission of Listeria monocytogenes. Milk can be contaminated at farm level either by indirect external contamination from the farm environment or less frequently by direct contamination of the milk from infection in the animal. Pasteurisation of milk will kill L. monocytogenes, but post-pasteurisation contamination, consumption of unpasteurised milk and manufacture of unpasteurised milk products can lead to milk being the cause of outbreaks of listeriosis. Therefore, there is a concern that L. monocytogenes in milk could lead to a public health risk. To protect against this risk, there is a need for awareness surrounding the issues, hygienic practices to reduce the risk and adequate sampling and analysis to verify that the risk is controlled. This review will highlight the issues surrounding L. monocytogenes in milk and milk products, including possible control measures. It will therefore create awareness about L. monocytogenes, contributing to protection of public health

Inactivation of Listeria monocytogenes by disinfectants and bacteriophages in suspension and stainless steel carrier tests

To simulate food contact surfaces with pits or cracks, stainless steel plates with grooves (depths between 0.2 and 5 mm) were constructed. These plates were artificially contaminated with Listeria monocytogenes in clean conditions, with organic soiling, or after 14 days of biofilm formation after which inactivation of the pathogen by Suma Tab D4 (sodium dichloroisocyanurate, 240 and 300 mg/liter), Suma Bac D10 (quaternary ammonium compound, 740 mg/liter), and bacteriophage suspension (Listex P100) was determined. Both chemical disinfectants performed well in suspension tests and in clean carrier tests according to the European standard with a reduction of more than 5 and 4 log units, respectively, of Listeria cells after 5 min of contact time. However, for the plates with grooves, the reduction could not meet the standard requirement, although a higher reduction of L. monocytogenes was observed in the shallow grooves compared with the deeper grooves. Furthermore, presence of food residues and biofilm reduced the effect of the disinfectants especially in the deep grooves, which was dependent on type of food substrate. Bacteriophages showed the best antimicrobial effect compared with the chemical disinfectants (sodium dichloroisocyanurate and quaternary ammonium compound) in most cases in the shallow grooves, but not in the deep grooves. The chlorine based disinfectants were usually less effective than quaternary ammonium compound. The results clearly demonstrate that surfaces with grooves influenced the antimicrobial effect of the chemical disinfectants and bacteriophages because the pathogen is protected in the deep grooves. The use of bacteriophages to inactivate pathogens on surfaces could be helpful in limited cases; however, use of large quantities in practice may be costly and phage-resistant strains may develop

Quantification of transfer of Listeria monocytogenes between cooked ham and slicing machine surfaces

Transfer of Listeria monocytogenes was investigated from surface-inoculated cooked ham to commercial slicing machine surfaces, from spot-inoculated ham to the slicing machine blade, and vise-versa from a contaminated slicer to clean ham. With balances the proportion transfer from the source to the various destinations were investigated as well as the kinetics of transfer during successive slicing, using a difference equation. For inoculated ham, the transfer ratio to the machine was highest to the table (0.06), followed by the handle board (0.01) and plate, guard, and front and back of the blade

Quantification of transfer of Listeria monocytogenes between cooked ham and slicing machine surfaces

Transfer of Listeria monocytogenes was investigated from surface-inoculated cooked ham to commercial slicing machine surfaces, from spot-inoculated ham to the slicing machine blade, and vise-versa from a contaminated slicer to clean ham. With balances the proportion transfer from the source to the various destinations were investigated as well as the kinetics of transfer during successive slicing, using a difference equation. For inoculated ham, the transfer ratio to the machine was highest to the table (0.06), followed by the handle board (0.01) and plate, guard, and front and back of the blade

Antibacterial activity or reactive quaternary ammonium compounds is solution and in non-leachable coatings

Antibacterial polymers suitable for coating applications without leaching of the biocide component were obtained by UV photopolymerization of acrylic monomers containing quaternary ammonium moieties. Suitable quaternary ammonium monomers (QAMs) endowed with reactive undecylacryloil group and alkyl chains with 2, 8 and 16 carbon atoms have been synthesised and their biocide activity in solution has been verified against E. coli, S. aureus and L. monocytogenes strains in suspension or adhered to stainless steel surfaces. The QAMs showed sufficient reactivity to be copolymerized with a commercial urethane acrylic resin by UV irradiation. Crosslinked coatings containing QAM structural units linked to the polymer network have been obtained. The antibacterial properties of the coatings containing the quaternary ammonium biocide were tested and the biocidal activity ofthe coating surface was ascertaine