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.

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.

Hygienic aspects of cattle slurry storage as tHe most popular and cHeapest metHod of Handling liquid animal excrements* * K r z y s z t o f S k o w r o n 1, 2♦ , H a l i n a O l s z e w s k a 2 , K a r o l i n a J a d w i g a S k o w r o n 3 , P i o t r P a l u s z a k 3 , B a r b a r a B r e z a -B o r u t a abstract slurry is a very valuable natural fertilizer, but its improper use in agriculture poses a serious sanitary threat. therefore its treatment before use for fertilization is advisable. one of such methods, which is still the most popular, is storage of liquid excrements. the aim of this study was to estimate the sanitization effectiveness of storage at 4ºc and 20ºc based on parameters describing the kinetics of changes in the population of some indicator bacteria in cattle slurry with different dry matter content. the material for the study was fresh cattle slurry. the liquid excrements used in the experiment had a dry matter content of 2, 6 and 14%. slurry was stored at 4ºc and 20ºc. Bacilli of Salmonella dublin, E. coli and enterococci were used as indicator bacteria. number of microorganisms was determined based on mpn method in a 3-tube design. Basic parameters of the bacteria inactivation kinetics were calculated and statistical analysis was made using the program sas 9.2 pl. in stored slurry a gradual elimination of all the studied microorganisms was observed. Hygienization effect of storage was smaller at 4ºc than at 20ºc and in excrements with a high dry matter content. depending on storage temperature and dry matter proportion, the theoretical times of survival ranged from 81.85 to 220.80 days for bacilli of Salmonella dublin, from 74.93 to 199.36 days for E. coli, and from 118.67 to 335.84 days for enterococci. the study showed explicitly that statutory time of slurry storage is insufficient to ensure its complete hygienization.

There are a lot of research on the effect of radiation on the number of bacteria in food products. However, there is almost no information about the effect of strain properties, such as drug susceptibility, virulence, etc., on their resistance to ionizing radiation. An increasing number of drug resistant bacterial strains isolated from food, encourages to take up this research subject.