The objective of this study was to screen Lactobacillus plantarum strains isolated from the traditional Slovak raw sheep milk cheese for their inhibitory potential. Seventy-two strains were obtained from samples of raw sheep milk and raw sheep milk cheeses collected from April 2017 to September 2018, in 23 geographical areas of Eastern Slovakia, by inoculation of de Man, Rogosa, and Sharpe agar plates (Oxoid, Basingstoke, UK). Using both the genus- and species-specific PCR methods, 43 strains were identified as Lactobacillus spp., and 10 strains were confirmed as Lb. plantarum. First, the whole bacterial cultures of Lb. plantarum strains were tested by disc diffusion assay. All showed very good antibacterial activities against 6 selected foodborne pathogens, including Escherichia coli, Salmonella Enteritidis, Pseudomonas aeruginosa, Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus. Then, cell-free neutralized supernatants and partially purified bacteriocins were prepared from the 4 Lb. plantarum strains that exhibited the best antibacterial potential, and they were tested the same way as the whole bacterial cultures. Seven of the 10 Lb. plantarum strains harbored the plnEF gene, 3 strains harbored the plnD gene, and 2 strains possessed both the plnA and plnC genes that encode the production of the respective plantaricins. The presence of both plnR and plnL genes was only detected in a single Lb. plantarum isolate. Based on the results of this study, 4 strains of Lb. plantarum appeared to be suitable candidates for further testing in the dairy manufacturing sector, particularly in the production of raw sheep milk products.

The topic of this work is the detection of antimicrobial resistance to Staphylococcus warneri strains and the genes encoding staphylococcal enterotoxins. It is considered a potential pathogen that can cause various—mostly inflammatory—diseases in immunosuppressed patients. The experimental part of the paper deals with the isolation of individual isolates from meat samples of Oryctolagus cuniculus, Oncorhynchus mykiss, Scomber scombrus, chicken thigh, beef thigh muscle, pork thigh muscle, and bryndza cheese. In total, 45 isolates were obtained and subjected to phenotypic (plasma coagulase activity, nuclease, pigment, hemolysis, lecithinase, and lipase production) and genotypic analyses to confirm the presence of the S. warneri species. The presence of genes encoding staphylococcal enterotoxins A (three isolates) and D (six isolates) was determined by PCR. Using the Miditech system, the minimum inhibitory concentration for various antibiotics or antibiotics combinations was determined, namely for ampicillin; ampicillin + sulbactam; oxacillin; cefoxitin; piperacillin + tazobactam; erythromycin; clindamycin; linezolid; rifampicin; gentamicin; teicoplanin; vancomycin; trimethoprim; chloramphenicol; tigecycline; moxifloxacin; ciprofloxacin; tetracycline; trimethoprim + sulfonamide; and nitrofurantoin. Resistance to ciprofloxacin and tetracycline was most common (73%). At the same time, out of a total of 45 isolates, 22% of the isolates were confirmed as multi-resistant. Isolates that showed phenotypic resistance to β-lactam antibiotics were subjected to mecA gene detection by PCR.

Penicillium species belong to main causative agents of food spoilage leading to significant economic losses and potential health risk for consumers. These fungi have been isolated from various food matrices, including table eggs. In this study, both conventional Polymerase Chain Reaction (PCR) and Polymerase Chain Reaction-Internal Transcribed Spacer-Restriction Fragment Length Polymorphism (PCR-ITS-RFLP) methods were used for species identification of Penicillium (P.) spp. isolated from the eggshells of moldy chicken eggs. Seven restriction endonucleases (Bsp1286I, XmaI, HaeIII, HinfI, MseI, SfcI, Hpy188I) were applied to create ribosomal restriction patterns of amplified ITS regions. To identify P. verrucosum, P. commune, and P. crustosum with the help of conventional PCR assay, species-specific primer pairs VERF/VERR, COMF/COMR, and CRUF/CRUR were designed on the base of 5.8 subunit-Internal Transcribed Spacer (5.8S-ITS) region. Altogether, 121 strains of microscopic filamentous fungi were isolated by traditional culture mycological examination. After morphological evaluation of both macroscopic and microscopic features, 96 strains were classified in Penicillium spp. Two molecular methods used have confirmed eight isolates as P. verrucosum, 42 isolates as P. commune, and 19 isolates as P. crustosum. Both PCR-ITS-RFLP and conventional PCR assays appear to be suitable alternatives for rapid identification of the above mentioned Penicillium species.

Bactericidal activity of caprylic acid (CA) and hydrogen peroxide (HP) was investigated in this study in order to design a suitable formulation for use in the food-processing industry. Antibacterial effects of the two chemicals were tested in vitro against the reference strains of Salmonella enterica subsp. enterica serotype Enteritidis CCM 4420, Escherichia coli CCM 3988, Listeria monocytogenes CCM 5578 and Staphylococcus aureus CCM 4223, as well as against the wild bacterial strains obtained from various food commodities (poultry meat, rabbit meat, raw milk sheep cheese 'Bryndza') and potable water. First, suspension test was carried out to determine the minimum bactericidal concentrations for individual chemical compounds. While most Gram-negative bacteria tested were effectively inhibited by HP at a 0.5% concentration, the growth of Gram-positive bacterial strains was stopped by a 2% solution. CA showed similar antibacterial effect on all bacterial strains tested except for Staph. aureus showing the same susceptibility as Gram-negative bacteria. The wild strains generally had higher resistance to both chemicals than the reference strains. Combination of HP and CA at concentrations of 0.01%; 0.05% and 0.1% was further tested by the suspension test, carrier test, and carrier test with simultaneous exposure to UV light. The total bactericidal activity against selected foodborne pathogens was already observed at a concentration of 0.1% and the efficiency was significantly increased by the use of UV radiation. A novel disinfectant based on the combination of HP with CA appears to be a suitable binary formulation for potential use in the food sector.

The aim of this study was to monitor the quality and mycobiota composition of table eggs during storage period. The most significant changes in the egg weight and water activity were observed on Day 7. To identify the mycobiota present on the eggshell by PCR method, a newly designed procedure for the extraction of fungal DNA based on a combination of commercial isolation kit, proteinase K and ultrasound was implemented. Identified mold genera included Penicillium spp., Cladosporium spp., Fusarium spp. and Alternaria alternata group. Their ratio varied considerably during storage with the dominance of Penicillium spp. on Day 14.

The eggshells of 120 experimental one-day-old table eggs were contaminated with the spore suspension of Cladosporium cladosporioides, divided into three groups (A–C) and stored at three different temperatures (3 °C, 11 °C and 20 °C) for 28 days. Visible growth of molds on/in experimental eggs was not observed within the entire storage period. No significant differences in the numbers of molds were found between particular groups of eggs. However, the composition of egg mycoflora was greatly influenced by storage conditions. Three mold genera were identified using the PCR method. The highest mold numbers were determined on Day 14 (Groups A and C) and Day 21 (Group B) when the maximum relative humidity and dew point temperature were recorded. On the same days, the dominance of Penicillium spp. and the minimum eggshell firmness were observed. Noticeable changes in egg quality were observed in eggs stored at 20 °C, and most of these eggs were downgraded at the end of storage period. The growth ability differed significantly among three mold genera. Penicillium spp. and Fusarium spp. showed better growth intensity at increased values (0.91–0.94) of water activity (a_w) indicating a possible risk associated with the occurrence of mycotoxins in the egg contents.