Effect of Radiant Catalytic Ionization and Ozonation on Salmonella spp. on Eggshells.

Three Salmonella enterica strains were used in the study (serovars: S. enteritidis, S. typhimurim and S. virchow). This study evaluated the efficacy of radiant catalytic ionization (RCI) and ozonation against Salmonella spp. on eggshell (expressed as log CFU/egg). The egg surface was contaminated three different bacterial suspension (103 CFU/mL, 105 CFU/mL and 108 CFU/mL) with or without poultry manure. Experiments were conducted at 4 °C and 20 °C in three different time period: 30 min, 60 min and 120 min. Treatment with RCI reduced Salmonella numbers from 0.26 log CFU/egg in bacterial suspension 108 CFU/mL, 4 °C and 20 °C, with manure for 30 min to level decrease in bacteria number below the detection limit (BDL) in bacterial suspension 105 CFU/mL, 20 °C, with or without manure for 120 min. The populations of Salmonella spp. on eggs treated by ozonizer ranged from 0.20 log CFU/egg in bacteria suspension 108 CFU/mL, 20 °C, with manure for 30 min to 2.73 log CFU/egg in bacterial suspension 105 CFU/mL, 20 °C, with manure for 120 min. In all treatment conditions contamination with poultry manure decrease effectiveness the RCI and ozonation. In summary, RCI technology shows similar effectiveness to the ozonation, but it is safer for poultry plant workers and consumers.

Prevalence and antimicrobial susceptibility of Listeria monocytogenes strains isolated from a meat processing plant.

INTRODUCTION AND OBJECTIVE: The ability of L. monocytogenes to create biofilm results in the higher resistance to disinfectants and determines the need to search for effective methods of eradication. The aim of the study was to assess the level of L. monocytogenes contamination in the environment of a meat processing plant. The sensitivity of tested isolates to various antimicrobials used for disinfection purposes was also estimated. MATERIAL AND METHODS: The samples were taken from raw materials, semi-finished and final products, as well as food contact surfaces inthe production hall and deli meat packaging department. The number of L. monocytogenes and the effect of eight different biocides on bacteria planktonic forms and biofilm formed on stainless steel and polypropylene was investigated. The effect of blood and albumin on L. monocytogenes resistance to disinfectants was also analysed. RESULTS: The prevalence of L. monocytogenes on food contact surfaces was estimated at 2.93% (10 of 340 swabs taken). The samples of raw and processed products were not contaminated. Various disinfectants reduced the growth of planktonic L. monocytogenes forms at both tested concentrations 0.5% and 0.1% (irrespective of time exposure). The highest efficacy against L. monocytogenes biofilm was reported for agents containing hydrogen peroxide. The reduction of bacteria number ranged from 6.93-7.21 log CFU × cm-2, and was dependent on the surface type and time of agent application. CONCLUSIONS: In this study, the effectiveness of various disinfectants against planktonic bacteria and Listeria biofilm was observed. For the majority of disinfectants, the extension of time exposure increased bacteria elimination from the biofilm. The presence of blood resulted in reduction of the antilisterial action of most of the disinfectants applied at low concentrations.

Assessment of the Prevalence and Drug Susceptibility of Listeria monocytogenes Strains Isolated from Various Types of Meat.

Listeria monocytogenes are the etiological factor of listeriosis, and their main source for humans is food. The aim of the current study was to assess the contamination of various types of meat and the drug susceptibility of isolated L. monocytogenes. Between 2016-2018, 6000 swabs were taken (2000 annually) from the surface of pork, beef, and poultry. The analysis of intermediate and finished product samples was carried out in accordance with ISO 11290-1 (International Organization for Standardization). The genetic similarity assessment of the isolates obtained was based on the Pulsed Field Gel Electrophoresis (PFGE) method, and drug-sensitivity assessment using the disc-diffusion method. We found 2.1% of collected samples were L. monocytogenes positive. The level of meat contamination varied depending on its matrix. Most L. monocytogenes were isolated from poultry. It was shown that 39 (32.5%) strains were sensitive to all tested antibiotics and eight (6.7%) were resistant to all five tested antimicrobials. Most strains tested were resistant to cotrimoxazole (55; 45.8%) and meropenem (52; 43.3%), followed by erythromycin (48; 40.0%), penicillin (31; 25.8%), and ampicillin (21; 17.5%). High prevalence of this pathogen may be a serious problem, especially when linked with antibiotic resistance and high percentage of serotypes responsible for listeriosis outbreaks.

Disinfectant Susceptibility of Biofilm Formed by Listeria monocytogenes under Selected Environmental Conditions.

Listeria monocytogenes is a one of the most important food-borne pathogens. Its ability to form biofilm contributes to increased resistance to disinfectants and inefficient disinfection, posing a serious threat for the food industry, and in the end the consumer. The aim of this study was the comparison of the biofilm formation ability of L. monocytogenes strains on stainless steel, under different environmental conditions (temperature, pH, NaCl concentration, nutrients availability), and the assessment of biofilm susceptibility to disinfectants. The bactericidal activity of four disinfectants in two concentrations (100% and 50% of working solution) against biofilm was conducted on four clinical strains, four strains isolated from food and one reference strain ATCC 19111. It was found that biofilm susceptibility to disinfectants was influenced by environmental conditions. Biofilm susceptibility correlated with the decrease of temperature, pH, nutrients availability and salinity of the environment. The least sensitive to disinfectants was biofilm produced at pH = 4 (the bacterial number ranged from 0.25 log CFU × cm-2 to 1.72 log CFU × cm-2) whereas the most sensitive was biofilm produced at pH = 9 (5.16 log CFU × cm-2 to 7.84 log CFU × cm-2). Quatosept was the most effective disinfectant, regardless of the conditions. In conclusion, biofilm susceptibility to disinfectants is strain-dependent and is affected by environmental conditions.

UV-C radiation as a factor reducing microbiological contamination of fish meal.

Fish meals, added to feeds as a source of protein, may contain pathogenic bacteria. Therefore, effective methods for their sanitizing, such as UV-C radiation, are needed to minimize the epidemiological risk. The objective of this study was to evaluate the effect of UV-C radiation on the sanitary state of fish meals. The research materials included salmon and cod meals. Samples of the fish meals were inoculated with suspensions of Salmonella, E. coli, enterococci, and C. sporogenes spores and exposed to the following surface UV-C fluencies: 0-400 J·m⁻² for bacteria and 0-5000 J·m⁻² for spores. For the vegetative forms, the highest theoretical lethal UV-C dose, ranging from 670.99 to 688.36 J·m⁻² depending on the meal type, was determined for Salmonella. The lowest UV-C fluency of 363.34-363.95 J·m⁻² was needed for the inactivation of Enterococcus spp. Spores were considerably more resistant, and the UV-C doses necessary for inactivation were 159571.1 J·m⁻² in salmon meal and 66836.9 J·m⁻² in cod meal. The application of UV-C radiation for the sanitization of fish meals proved to be a relatively effective method for vegetative forms of bacteria but was practically ineffective for spores.

Use of the Filter-Sandwich carriers in continuous effectiveness monitoring of slurry treatment methods as an element improving biosafety in agriculture.

Slurry, due to high microbiological contamination, requires hygienization before spreading. The agricultural usage of treated slurry has to guarantee biosafety. Therefore, constant monitoring of the slurry treatment process should be conducted. The use of Filter-Sandwich carriers seems to be a prospective solution. The aim of the research was to test whether Filter-Sandwich carriers influence the survivability of microorganisms during the slurry hygienization process and hence, whether they are safe for the environment. Raw cattle and swine slurry with different dry matter content was the research material. Salmonella Senftenberg W775 rods were introduced directly into the slurry and into the carriers placed in the liquid excrements stored at 4 and 20ºC, and underwent anaerobic digestion at 35ºC. The number of tested bacteria obtained from the slurry and carriers was determined using the MPN method with proper microbiological media. The values of physicochemical parameters of the raw and treated slurry were determined, both for the carriers and for slurry only. Biosafety control was also conducted for the carriers in slurry containers. The differences in the theoretical survivability between Salmonella Senftenberg W775 re-isolated from the slurry and the carriers, and in the values of the selected physicochemical parameters obtained at the end of the process, were not statistically significant. The re-contamination of the sterile slurry caused by the bacteria in the carrier was not observed after placement of the carrier with inoculated material. The conducted research proves the usefulness of Filter-Sandwich carriers for continuous hygienization monitoring of the slurry treatment process. This refers not only to the semi-technical scale, but also to the full-scale process.

Sanitization efficacy of anaerobic digestion and aeration of slurry from the aspect of limiting emission of Salmonella into the environment.

The aim of this study was to estimate the usefulness of mesophilic anaerobic digestion and aeration for sanitization of slurry from the aspect of limiting transmission of Salmonella into the environment. Material for the study was fresh pig slurry. Collected samples were subjected to anaerobic digestion at 35°C and aeration with an initial temperature of 35°C. The efficacy of both methods was examined based on determination of the elimination rate and theoretical time of survival of Salmonella Senftenberg W(775), Salmonella Enteritidis and Salmonella Typhimurium introduced into slurry in carriers of type Filter-Sandwich. Samples for the study were collected every 24 hours and the number of bacilli was determined with the MPN (Most Probably Number) method. The study indicated that fermentation is a more effective method for slurry sanitization. A higher rate of elimination and shorter time of survival of all the tested bacteria was observed, compared with the use of aeration. The experiment allowed us to prove the high sanitization efficacy of both examined methods. They ensure the full elimination of the tested serotypes of Salmonella in only slightly more than 10 days. The use of fermentation or aeration as a way of slurry treatment for agricultural purposes makes it possible to obtain a fertilizer which is valuable and safe for humans and the environment.