Biological Characterization and Genomic Analysis of Three Novel Serratia- and Enterobacter-Specific Virulent Phages.

Due to the high microbiological contamination of raw food materials and the increase in the incidence of multidrug-resistant bacteria, new methods of ensuring microbiological food safety are being sought. One solution may be to use bacteriophages (so-called phages) as natural bacterial enemies. Therefore, the aim of this study was the biological and genomic characterization of three newly isolated Serratia- and Enterobacter-specific virulent bacteriophages as potential candidates for food biocontrol. Serratia phage KKP_3708 (vB_Sli-IAFB_3708), Serratia phage KKP_3709 (vB_Sma-IAFB_3709), and Enterobacter phage KKP_3711 (vB_Ecl-IAFB_3711) were isolated from municipal sewage against Serratia liquefaciens strain KKP 3654, Serratia marcescens strain KKP 3687, and Enterobacter cloacae strain KKP 3684, respectively. The effect of phage addition at different multiplicity of infection (MOI) rates on the growth kinetics of the bacterial hosts was determined using a Bioscreen C Pro growth analyzer. The phages retained high activity in a wide temperature range (from -20 °C to 60 °C) and active acidity values (pH from 3 to 12). Based on transmission electron microscopy (TEM) imaging and whole-genome sequencing (WGS), the isolated bacteriophages belong to the tailed bacteriophages from the Caudoviricetes class. Genomic analysis revealed that the phages have linear double-stranded DNA of size 40,461 bp (Serratia phage KKP_3708), 67,890 bp (Serratia phage KKP_3709), and 113,711 bp (Enterobacter phage KKP_3711). No virulence, toxins, or antibiotic resistance genes were detected in the phage genomes. The lack of lysogenic markers indicates that all three bacteriophages may be potential candidates for food biocontrol.

Research on the Electron Structure and Antimicrobial Properties of Mandelic Acid and Its Alkali Metal Salts.

This article investigated the structure, and the spectroscopic and antimicrobial properties of mandelic acid and its alkali metal salts. The electron charge distribution and aromaticity in the analyzed molecules were investigated using molecular spectroscopy methods (FT-IR, FT-Raman, 1H NMR, and 13C NMR) and theoretical calculations (structure, NBO, HOMO, LUMO, energy descriptors, and theoretical IR and NMR spectra). The B3LYP/6-311++G(d,p) method was used in the calculations. The antimicrobial activities of mandelic acid and its salt were tested against six bacteria: Gram-positive Listeria monocytogenes ATCC 13932, Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633, and Loigolactobacillus backii KKP 3566; Gram-negative Escherichia coli ATCC 25922 and Salmonella Typhimurium ATCC 14028, as well as two yeast species, Rhodotorulla mucilaginosa KKP 3560 and Candida albicans ATCC 10231.

Newly Isolated Virulent Salmophages for Biocontrol of Multidrug-Resistant Salmonella in Ready-to-Eat Plant-Based Food.

Due to irrational antibiotic stewardship, an increase in the incidence of multidrug resistance of bacteria has been observed recently. Therefore, the search for new therapeutic methods for pathogen infection treatment seems to be necessary. One of the possibilities is the utilization of bacteriophages (phages)-the natural enemies of bacteria. Thus, this study is aimed at the genomic and functional characterization of two newly isolated phages targeting MDR Salmonella enterica strains and their efficacy in salmonellosis biocontrol in raw carrot-apple juice. The Salmonella phage vB_Sen-IAFB3829 (Salmonella phage strain KKP 3829) and Salmonella phage vB_Sen-IAFB3830 (Salmonella phage strain KKP 3830) were isolated against S. I (6,8:l,-:1,7) strain KKP 1762 and S. Typhimurium strain KKP 3080 host strains, respectively. Based on the transmission electron microscopy (TEM) and whole-genome sequencing (WGS) analyses, the viruses were identified as members of tailed bacteriophages from the Caudoviricetes class. Genome sequencing revealed that these phages have linear double-stranded DNA and sizes of 58,992 bp (vB_Sen-IAFB3829) and 50,514 bp (vB_Sen-IAFB3830). Phages retained their activity in a wide range of temperatures (from -20 °C to 60 °C) and active acidity values (pH from 3 to 11). The exposure of phages to UV radiation significantly decreased their activity in proportion to the exposure time. The application of phages to the food matrices significantly reduced the level of Salmonella contamination compared to the control. Genome analysis showed that both phages do not encode virulence or toxin genes and can be classified as virulent bacteriophages. Virulent characteristics and no possible pathogen factors make examined phages feasible to be potential candidates for food biocontrol.

Characterization and Genome Study of Novel Lytic Bacteriophages against Prevailing Saprophytic Bacterial Microflora of Minimally Processed Plant-Based Food Products.

The food industry is still searching for novel solutions to effectively ensure the microbiological safety of food, especially fresh and minimally processed food products. Nowadays, the use of bacteriophages as potential biological control agents in microbiological food safety and preservation is a promising strategy. The aim of the study was the isolation and comprehensive characterization of novel bacteriophages with lytic activity against saprophytic bacterial microflora of minimally processed plant-based food products, such as mixed leaf salads. From 43 phages isolated from municipal sewage, four phages, namely Enterobacter phage KKP 3263, Citrobacter phage KKP 3664, Enterobacter phage KKP 3262, and Serratia phage KKP 3264 have lytic activity against Enterobacter ludwigii KKP 3083, Citrobacter freundii KKP 3655, Enterobacter cloacae KKP 3082, and Serratia fonticola KKP 3084 bacterial strains, respectively. Transmission electron microscopy (TEM) and whole-genome sequencing (WGS) identified Enterobacter phage KKP 3263 as an Autographiviridae, and Citrobacter phage KKP 3664, Enterobacter phage KKP 3262, and Serratia phage KKP 3264 as members of the Myoviridae family. Genome sequencing revealed that these phages have linear double-stranded DNA (dsDNA) with sizes of 39,418 bp (KKP 3263), 61,608 bp (KKP 3664), 84,075 bp (KKP 3262), and 148,182 bp (KKP 3264). No antibiotic resistance genes, virulence factors, integrase, recombinase, or repressors, which are the main markers of lysogenic viruses, were annotated in phage genomes. Serratia phage KKP 3264 showed the greatest growth inhibition of Serratia fonticola KKP 3084 strain. The use of MOI 1.0 caused an almost 5-fold decrease in the value of the specific growth rate coefficient. The phages retained their lytic activity in a wide range of temperatures (from -20 °C to 50 °C) and active acidity values (pH from 4 to 11). All phages retained at least 70% of lytic activity at 60 °C. At 80 °C, no lytic activity against tested bacterial strains was observed. Serratia phage KKP 3264 was the most resistant to chemical factors, by maintaining high lytic activity across a broader range of pH from 3 to 11. The results indicated that these phages could be a potential biological control agent against saprophytic bacterial microflora of minimally processed plant-based food products.

Dipicolinic Acid Release and the Germination of Alicyclobacillus acidoterrestris Spores under Nutrient Germinants.

The presence of Alicyclobacillus, a thermoacidophilic and spore-forming bacterium, in acidic fruit juices poses a serious problem for the processing industry. A typical sign of spoilage in contaminated juices is a characteristic phenolic off-flavour associated with the production of guaiacol. Spores are formed in response to starvation and in a natural environment re-access the nutrients, e.g.: L-alanine and AGFK - a mixture of asparagine, glucose, fructose and potassium, triggers germination. The aim of this study was to estimate the impact of L-alanine and AGFK on the germination of the spores of two Alicyclobacillus acidoterrestris strains and to evaluate the relationship of the germination rate with dipicolinic acid (DPA) release. The spores were suspended in apple juice or in buffers at pH 4 and pH 7, followed by the addition of L-alanine and AGFK. Suspensions were or were not subjected, to a temperature of 80°C/10 min and incubated for various periods of time at 45°C. Optical density (OD660) was used to estimate the number of germinated spores. The amount of DPA released was determined using HPLC. The results indicate that the degree of germination of A. acidoterrestris spores depended on the strain and time of incubation and the nutritious compounds used. The data obtained show that the amount of DPA released correlated to the number of A. acidoterrestris spores germinated.

Germination and Inactivation of Alicyclobacillus acidoterrestris Spores Induced by Moderate Hydrostatic Pressure.

Given the importance of spoilage caused by Alicyclobacillus acidoterrestris for the fruit juice industry, the objective of this work was to study the germination and inactivation of A. acidoterrestris spores induced by moderate hydrostatic pressure. Hydrostatic pressure treatment can induce the germination and inactivation of A. acidoterrestris spores. At low pH, spore germination of up to 3.59-3.75 log and inactivation of 1.85-2.04 log was observed in a low pressure window (200-300 MPa) applied at 50 degrees C for 20 min. Neutral pH suppressed inactivation, the number of spores inactivated at pH 7.0 was only 0.24-1.06 log. The pressurization temperature significantly affected spore germination and inactivation. The degree of germination in apple juice after pressurization for 30 min with 200 MPa at 20 degrees C was 2.04 log, with only 0.61 log of spores being inactivated, while at 70 degrees C spore germination was 5.94 log and inactivation 4.72 log. This temperature strongly stimulated germination and inactivation under higher (500 MPa) than lower (200 MPa) pressure. When the oscillatory mode was used, the degree of germination and inactivation was slightly higher than at continuous mode. The degree of germination and inactivation was inversely proportional to the soluble solids content and was lowest in concentrated apple juice.

ANCA-positive and ANCA-negative phenotypes of eosinophilic granulomatosis with polyangiitis (EGPA): outcome and long-term follow-up of 50 patients from a single Polish center.

OBJECTIVES: The aim of the study was to compare the course of the disease and treatment outcomes in ANCA-positive and ANCA-negative eosinophilic granulomatosis with polyangiitis (EGPA) patients from one Polish tertiary referral centre. METHODS: Retrospective and prospective cohort study carried out on 50 patients treated in our department between 1998 and 2012. EGPA diagnosis was based on the American College of Rheumatology (ACR) criteria. Treatment protocol was based primarily on the predictive Five Factor Score (FFS) scale. Clinical characteristics of the patients, general symptoms, organ involvement, treatment regimen, and follow-up outcomes were evaluated according to ANCA status. RESULTS: Fifteen ANCA-positive patients and 35 ANCA-negative patients were enrolled. At the time of diagnosis ANCA-positive patients had a higher incidence of renal involvement (53% vs. 7.7%; p<0.001), skin involvement (93.3% vs. 57.1%; p=0.03), and peripheral neuropathy in the form of mononeuritis multiplex (60% vs. 25.7%; p=0.021). ANCA-negative patients had significantly more frequent cardiac manifestations, but only with regard to the entire period of follow-up (68.6% vs. 33.3%; p=0.021). Patients in both groups were under the same treatment regimens, however steroid dose necessary to maintain remission of the disease was significantly higher in the group of ANCA-positive patients (9±2.5 vs. 7.4±1.9 mg/day of methylprednisolone; p=0.023). The presence of ANCA did not affect the frequency of relapses. CONCLUSIONS: Our results confirm the differences in clinical disease presentation based on ANCA status and indicate that ANCA-positive patients should be treated more aggressively.

Granulomatosis with polyangiitis (Wegener's granulomatosis) with hard palate and bronchial perforations treated with rituximab - a case report.

We present a case of a 57-year-old woman suffering from granulomatosis with polyangiitis (GPA), who in the seventh months of immunosuppressive treatment (cyclophosphamide) progressed with new pulmonary changes and perforations of the hard palate and bronchi. Rituximab was introduced resulting in B-cell depletion and disappearance of anti-PR3 antibody. Palatal holes have substantially diminished and all bronchial perforations disappeared, covered by fibrous tissue. In the fourth month after rituximab administration, large scarring obstruction of the right main bronchus with upper and middle lobes atelectasis emerged. Because of increasing dyspnoea, stenotic bronchus was re-opened by bronchoscopy. Intervention was complicated by bilateral pneumothorax and later, on the seventh day, by fatal pulmonary bleeding. To our knowledge, this is the first report of GPA refractory to cyclophosphamide complicated by palatal and bronchial perforations.

Exacerbation of eosinophilic granulomatosis with polyangiitis (EGPA) with heart involvement mimicking acute coronary syndrome.

A case of a 49-year-old male with exacerbation of eosinophilic granulomatosis with polyangiitis (EGPA) with heart involvement mimicking acute coronary syndrome is presented. Institution of intensive immunosupresive treatment resulted in the improvement of clinical condition and systolic left ventricular function. Coronary angiography excluded atherosclerosis as a primary cause of heart damage.

Characterization and Genome Study of a Newly Isolated Temperate Phage Belonging to a New Genus Targeting Alicyclobacillus acidoterrestris.

The spoilage of juices by Alicyclobacillus spp. remains a serious problem in industry and leads to economic losses. Compounds such as guaiacol and halophenols, which are produced by Alicyclobacillus, create undesirable flavors and odors and, thus, decrease the quality of juices. The inactivation of Alicyclobacillus spp. constitutes a challenge because it is resistant to environmental factors, such as high temperatures, and active acidity. However, the use of bacteriophages seems to be a promising approach. In this study, we aimed to isolate and comprehensively characterize a novel bacteriophage targeting Alicyclobacillus spp. The Alicyclobacillus phage strain KKP 3916 was isolated from orchard soil against the Alicyclobacillus acidoterrestris strain KKP 3133. The bacterial host's range and the effect of phage addition at different rates of multiplicity of infections (MOIs) on the host's growth kinetics were determined using a Bioscreen C Pro growth analyzer. The Alicyclobacillus phage strain KKP 3916, retained its activity in a wide range of temperatures (from 4 °C to 30 °C) and active acidity values (pH from 3 to 11). At 70 °C, the activity of the phage decreased by 99.9%. In turn, at 80 °C, no activity against the bacterial host was observed. Thirty minutes of exposure to UV reduced the activity of the phages by almost 99.99%. Based on transmission-electron microscopy (TEM) and whole-genome sequencing (WGS) analyses, the Alicyclobacillus phage strain KKP 3916 was classified as a tailed bacteriophage. The genomic sequencing revealed that the newly isolated phage had linear double-stranded DNA (dsDNA) with sizes of 120 bp and 131 bp and 40.3% G+C content. Of the 204 predicted proteins, 134 were of unknown function, while the remainder were annotated as structural, replication, and lysis proteins. No genes associated with antibiotic resistance were found in the genome of the newly isolated phage. However, several regions, including four associated with integration into the bacterial host genome and excisionase, were identified, which indicates the temperate (lysogenic) life cycle of the bacteriophage. Due to the risk of its potential involvement in horizontal gene transfer, this phage is not an appropriate candidate for further research on its use in food biocontrol. To the best of our knowledge, this is the first article on the isolation and whole-genome analysis of the Alicyclobacillus-specific phage.

Genomic Analysis and In Vitro Investigation of the Hop Resistance Phenotype of Two Novel Loigolactobacillus backii Strains, Isolated from Spoiled Beer.

Loigolactobacillus backii is an important beer-spoiling species, exhibiting high hop tolerance. Here, we present the annotated whole genome sequence of two recently isolated strains, Lg. backii KKP 3565 and KKP 3566. Firstly, to study the genetic basis of the persistence of the two isolates in beer, a comprehensive bioinformatic analysis ensued. Their chromosome map was constructed, using whole-genome sequencing and assembly, revealing that the two strains carry genomes with a length of 2.79 Mb with a GC content of 40.68%. An average nucleotide identity (ANI) analysis demonstrated that the novel strains possess unique genomic sequences, also confirming their classification into the Lg. backii species. Their genome harbors numerous insertion sequences and plasmids, originating from other beer-spoiling species. Regarding their adaptation in brewery environment, homologous genes that confer resistance to hop were spotted, while the impact of hop bitters and pure beer on bacterial growth was investigated, in vitro. In brief, low hop concentrations were found to induce the proliferation of strains, while a higher concentration negatively affected their growth. Nonetheless, their ability to survive in pure beer indicated their tolerance to high hop concentrations. These results offer insight into the capacity of Lg. backii KKP 3566 and Lg. backii KKP 3566 to tolerate the extreme conditions prevalent in the brewery environment.

Depiction of the In Vitro and Genomic Basis of Resistance to Hop and High Hydrostatic Pressure of Lactiplantibacillus plantarum Isolated from Spoiled Beer.

Among the beer-spoiling microorganisms, the dominant ones belong to the genera Lactobacillus, Leuconostoc, Oenococcus, and Pediococcus. It is assumed that resistance to hop bitters correlates with resistance to other factors and can significantly impact the brewing industry. Beer preservation with high hydrostatic pressure eliminates the spoiling microorganisms while preserving all desired properties of the beer. Here, we present comprehensive in vitro and genomic analysis of the beer-spoiling Lactiplantibacillus plantarum KKP 3573 capacity to resist hop and high hydrostatic pressure. Lp. plantarum KKP 3573 is a strain isolated from spoiled beer. Our finding suggests that the growth rate of the strain depends on the medium variant, where a small concentration of beer (5 IBU) stimulates the growth, suggesting that the limited concentration has a positive effect on cell growth. At the same time, increased concentrations of 20 IBU, 30 IBU, and pure beer 43.6 IBU decreased the growth rate of the KKP 3573 strain. We observed that higher extract content in the pressurized beer increased microbial survivability. The wort and Vienna Lager beer can stimulate the baroprotective effect. The taxonomy of the novel strain was confirmed after whole genome sequencing (WGS) and comparative genomic analysis. More specifically, it contains a chromosome of 3.3 Mb with a GC content of 44.4%, indicative of the Lp. plantarum species. Accordingly, it possesses high genomic similarity (>98%) with other species members. Annotation algorithms revealed that the strain carries several genes involved in resistance to stress, including extreme temperature, hop bitters and high pressure, and adaptation to the brewing environment. Lastly, the strain does not code for toxins and virulence proteins and cannot produce biogenic amines.

Effectiveness of a Phage Cocktail as a Potential Biocontrol Agent against Saprophytic Bacteria in Ready-To-Eat Plant-Based Food.

This study aimed to evaluate the effectiveness of the phage cocktail to improve the microbiological quality of five different mixed-leaf salads: rucola, mixed-leaf salad with carrot, mixed-leaf salad with beetroot, washed and unwashed spinach, during storage in refrigerated conditions. Enterobacterales rods constituted a significant group of bacteria in the tested products. Selected bacteria were tested for antibiotic resistance profiles and then used to search for specific bacteriophages. Forty-three phages targeting bacteria dominant in mixed-leaf salads were isolated from sewage. Their titer was determined, and lytic activity was assessed using the Bioscreen C Pro automated growth analyzer. Two methods of phage cocktail application including spraying, and an absorption pad were effective for rucola, mixed leaf salad with carrot, and mixed leaf salad with beetroot. The maximum reduction level after 48 h of incubation reached 99.9% compared to the control sample. In washed and unwashed spinach, attempts to reduce the number of microorganisms did not bring the desired effect. The decrease in bacteria count in the lettuce mixes depended on the composition of the autochthonous saprophytic bacteria species. Both phage cocktail application methods effectively improved the microbiological quality of minimally processed products. Whole-spectral phage cocktail application may constitute an alternative food microbiological quality improvement method without affecting food properties.

Increased production of IL-5 and dominant Th2-type response in airways of Churg-Strauss syndrome patients.

OBJECTIVE: Churg-Strauss syndrome (CSS) is a rare systemic vasculitis associated with eosinophilia and asthma. We assessed the local immune response in airways of CSS patients with different activity of the disease. METHODS: Concentration of IL-5, CCL17, CCL22 and CCL26 (ELISA) together with cell expression of T-helper-related genes (real-time PCR array) were measured in bronchoalveolar lavage fluid (BALF) sampled from 11 patients with active CSS, 11 patients with CSS in remission and 9 control subjects with bronchial asthma. RESULTS: In active CSS, both BALF and blood eosinophil counts were increased (P<0.01). BALF cells in active disease were characterized by an increased expression of Th2 and regulatory-type transcripts: STAT6, STAT3, GATA3, IL4, IL5 and IL10 as compared with asthmatics, and STAT5A, CCR4, FOXP3, IL4, IL5 and IL10 when compared with inactive CSS. There was significant increase in BALF concentration of IL-5 and CCL26 in exacerbation of CSS. CCR4-active chemokines were detected more frequently in active disease. We found a strong positive correlation between clinical parameters of disease activity (BVAS, eosinophilia) and expression of IL4, IL5, IL10 and STAT5A. CONCLUSION: These results indicate that as compared with asthma, active-CSS patients have much stronger local Th2 response in the airways. Airway cells may contribute to lung eosinophilia in CSS by producing IL-5 and eosinophil active chemokines.

Two-dimensional speckle-tracking echocardiography reveals systolic abnormalities in granulomatosis with polyangiitis (Wegener's).

BACKGROUND: Two-dimensional speckle-tracking echocardiography (STE) is a novel technique providing accurate assessment of myocardial function. However, its value in granulomatosis with polyangiitis (Wegener's) (WG) has not been studied. OBJECTIVE: To assess the presence and frequency of systolic left ventricular (LV) dysfunction using STE and to determine incremental value of STE over standard echocardiography to detect myocardial abnormalities in WG. METHODS: Twenty-two WG patients (11 males, 11 females, mean age 46.8 ± 12.3 years) and 22 sex- and age-matched healthy subjects underwent standard and STE. Global longitudinal, circumferential, and rotational deformation parameters were calculated. RESULTS: All patients had LV ejection fraction (EF) >50%. LVEF was 65.0 ± 7.5% and LV end-diastolic volume index 44.8 ± 11.8 mL/m(2) . Regional LV wall motion abnormalities were found in 7 (32%), while abnormal global STE determined systolic dysfunction in 16 (73%) subjects (P = 0.008). Global longitudinal, circumferential and radial peak-systolic deformational parameters (strain or strain rate) were decreased in 11 (50%), 9 (41%), and 3 (14%) patients (P = 0.02), respectively. Comparing patients with abnormal and normal STE derived global systolic function, the former had higher cumulative disease extent index (10.6 ± 3.0 vs 7.5 ± 1.8; P = 0.03) and vasculitis damage index (7.9 ± 1.9 vs 6.0 ± 1.7; P = 0.04). CONCLUSIONS: Despite normal LVEF the global systolic LV abnormalities detected by STE are common in WG. They correspond to the extent and severity of WG and are more frequent than regional wall motion abnormalities in standard echocardiography.

The mechanics of left ventricular dysfunction in patients with Churg-Strauss syndrome.

BACKGROUND: Heart is frequently involved in Churg-Strauss syndrome (CSS). However, the mechanics of left ventricular (LV) dysfunction in CSS has not been studied. OBJECTIVE: To assess the mechanics of LV function and to characterize the contribution of longitudinal, circumferential and rotational deformation to LV dysfunction in CSS. METHODS: We enrolled 22 CSS patients (eight males, mean age 43.2 ± 9.5 years) in remission of their disease and 22 sex- and age-matched healthy subjects. All patients underwent conventional and two-dimensional speckle-tracking echocardiography. Global longitudinal, circumferential and rotational deformation parameters were calculated. RESULTS: CSS subjects demonstrated lower LV ejection fraction (EF) than controls (56.6 ± 15.0% vs 63.8 ± 3.4%; P < 0.05). When compared to those with LVEF ≥ 50% (n = 14), CSS patients with LVEF < 50% (n = 7) had decreased global peak-systolic longitudinal and circumferential strain/strain rate (all P < 0.001) and tended to have lower global peak-systolic radial strain (P = 0.05). There were no differences between these two subgroups in global peak-systolic radial strain rate and LV twist/torsion. When comparing individual systolic and diastolic parameters early diastolic longitudinal and circumferential strain rate demonstrated the highest correlation with corresponding global longitudinal and circumferential peak-systolic strain/strain rate (r < -0.80, P < 0.001 for all correlations). CONCLUSIONS: In CSS LV systolic dysfunction strongly correlates with longitudinal and circumferential, but not radial or rotational systolic components, indicating that impaired LV systolic function may result predominantly from impaired contraction of inner and middle, but not outer myocardial fiber layers. The spatial correspondence between systolic and diastolic deformation parameters suggests the similar impact of pathologic process on systolic and diastolic function in CSS.

[Effective application of therapeutic plasma exchange in a case of acute dermatomyositis]. / Skuteczne zastosowanie terapeutycznej wymiany osocza u chorego na ostra postac zapalenia skórno-miesniowego.

We present a case of 22-year-old male with acute dermatomyositis who did not respond to a standard immunosuppressive therapy. Due to rapidly deteriorating clinical status a series of plasmapheresis was performed subsequent to which a quick clinical improvement was observed.

Role of Lactic Acid Bacteria in Food Preservation and Safety.

Fermentation of various food stuffs by lactic acid bacteria is one of the oldest forms of food biopreservation. Bacterial antagonism has been recognized for over a century, but in recent years, this phenomenon has received more scientific attention, particularly in the use of various strains of lactic acid bacteria (LAB). Certain strains of LAB demonstrated antimicrobial activity against foodborne pathogens, including bacteria, yeast and filamentous fungi. Furthermore, in recent years, many authors proved that lactic acid bacteria have the ability to neutralize mycotoxin produced by the last group. Antimicrobial activity of lactic acid bacteria is mainly based on the production of metabolites such as lactic acid, organic acids, hydroperoxide and bacteriocins. In addition, some research suggests other mechanisms of antimicrobial activity of LAB against pathogens as well as their toxic metabolites. These properties are very important because of the future possibility to exchange chemical and physical methods of preservation with a biological method based on the lactic acid bacteria and their metabolites. Biopreservation is defined as the extension of shelf life and the increase in food safety by use of controlled microorganisms or their metabolites. This biological method may determine the alternative for the usage of chemical preservatives. In this study, the possibilities of the use of lactic acid bacteria against foodborne pathogens is provided. Our aim is to yield knowledge about lactic acid fermentation and the activity of lactic acid bacteria against pathogenic microorganisms. In addition, we would like to introduce actual information about health aspects associated with the consumption of fermented products, including probiotics.

Application of Lytic Bacteriophages and Their Enzymes to Reduce Saprophytic Bacteria Isolated from Minimally Processed Plant-Based Food Products-In Vitro Studies.

The aim of this study was to isolate phage enzymes and apply them in vitro for eradication of the dominant saprophytic bacteria isolated from minimally processed food. Four bacteriophages-two Enterobacter-specific and two Serratia-specific, which produce lytic enzymes-were used in this research. Two methods of phage enzyme isolation were tested, namely precipitation with acetone and ultracentrifugation. It was found that the number of virions could be increased almost 100 times due to the extension of the cultivation time (72 h). The amplification of phage particles and lytic proteins was dependent on the time of cultivation. Considering the influence of isolated enzymes on the growth kinetics of bacterial hosts, proteins isolated with acetone after 72-hour phage propagation exhibited the highest inhibitory effect. The reduction of bacteria count was dependent on the concentration of enzymes in the lysates. The obtained results indicate that phages and their lytic enzymes could be used in further research aiming at the improvement of microbiological quality and safety of minimally processed food products.

Bacterial Pathogens in the Food Industry: Antibiotic Resistance and Virulence Factors of Salmonella enterica Strains Isolated from Food Chain Links.

Salmonella is one of the most important foodborne pathogens. Fifty-three strains of Salmonella deposited in the Culture Collection of Industrial Microorganisms-Microbiological Resources Center (IAFB) were identified using molecular and proteomic analyses. Moreover, the genetic similarity of the tested strains was determined using the PFGE method. Main virulence genes were identified, and phenotypical antibiotic susceptibility profiles and prevalence of resistance genes were analyzed. Subsequently, the occurrence of the main mechanisms of ß-lactam resistance was determined. Virulence genes, invA, fimA, and stn were identified in all tested strains. Phenotypic tests, including 28 antibiotics, showed that 50.9% of the strains were MDR. The tet genes associated with tetracyclines resistance were the most frequently identified genes. Concerning the genes associated with ESBL-producing Salmonella, no resistance to the TEM and CTX-M type was identified, and only two strains (KKP 1597 and KKP 1610) showed resistance to SHV. No strains exhibited AmpC-type resistance but for six Salmonella strains, the efflux-related resistance of PSE-1 was presented. The high number of resistant strains in combination with multiple ARGs in Salmonella indicates the possible overuse of antibiotics. Our results showed that it is necessary to monitor antimicrobial resistance profiles in all food chain links constantly and to implement a policy of proper antibiotic stewardship to contain or at least significantly limit the further acquisition of antibiotic resistance among Salmonella strains.