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Background The host-unrestricted, non-typhoidal Salmonella enterica serovar Enteritidis (S. Enteritidis) and the serovar Typhimurium (S. Typhimurium) are major causative agents of food-borne gastroenteritis, and the host-restricted Salmonella enterica serovar Gallinarum (S. Gallinarum) is responsible for fowl typhoid. Increasing drug resistance in Salmonella contributes to the reduction of effective therapeutic and/or preventive options. Bacteriophages appear to be promising antibacterial tools, able to combat infectious diseases caused by a wide range of Salmonella strains belonging to both host-unrestricted and host-restricted Salmonella serovars. Methods In this study, five novel lytic Salmonella phages, named UPWr_S1-5, were isolated and characterized, including host range determination by plaque formation, morphology visualization with transmission electron microscopy, and establishment of physiological parameters. Moreover, phage genomes were sequenced, annotated and analyzed, and their genomes were compared with reference Salmonella phages by use of average nucleotide identity, phylogeny, dot plot, single nucleotide variation and protein function analysis. Results It was found that UPWr_S1-5 phages belong to the genus Jerseyvirus within the Siphoviridae family. All UPWr_S phages were found to efficiently infect various Salmonella serovars. Host range determination revealed differences in host infection profiles and exhibited ability to infect Salmonella enterica serovars such as Enteritidis, Gallinarum, Senftenberg, Stanley and Chester. The lytic life cycle of UPWr_S phages was confirmed using the mitomycin C test assay. Genomic analysis revealed that genomes of UPWr_S phages are composed of 51 core and 19 accessory genes, with 33 of all predicted genes having assigned functions. UPWr_S genome organization comparison revealed 3 kinds of genomes and mosaic structure. UPWr_S phages showed very high sequence similarity to each other, with more than 95% average nucleotide identity. Conclusions Five novel UPWr_S1-5 bacteriophages were isolated and characterized. They exhibit host lysis range within 5 different serovars and are efficient in lysis of both host-unrestricted and host-restricted Salmonella serovars. Therefore, because of their ability to infect various Salmonella serovars and lytic life cycle, UPWr_S1-5 phages can be considered as useful tools in biological control of salmonellosis.

Extended-spectrum β-lactamases (ESBLs) and AmpC β-lactamases are plasmid (but also chromosomally) encoded enzymes found in Enterobacteriaceae, determining resistance to a variety of important antibiotics including penicillins, cephalosporins, and monobactams. In recent decades, the prevalence of ESBL/AmpC-producing bacteria has increased rapidly across the world. Here, we evaluate the potential use of bacteriophages in terms of a reduction of antibiotic-resistant bacteria in healthy animals. The aim of our studies was to isolate bacteriophages capable of destroying ESBL/AmpC-producing Escherichia coli isolated from livestock habitats. The efficacy of isolated phages against ESBL/AmpC E. coli strains varies, but creation of a phage cocktail with broad activity spectrum is possible. This may indicate that the role of phages may not be limited to phage therapy, but bacterial viruses may also be applied against spread of bacteria with antibiotic resistance genes in the environment. We also addressed the hypothesis, that phages, effective for therapeutic purposes may be isolated from distant places and even from different environments other than the actual location of the targeted bacteria. This may be beneficial for practical purposes, as the construction of effective phage preparations does not require access to disease outbreaks.

Infectious diseases pose a significant threat to both human and animal populations. Intracellular bacteria are a group of pathogens that invade and survive within the interior of eukaryotic cells, which in turn protect them from antibacterial drugs and the host immune system. Limited penetration of antibacterials into host cells results in insufficient bacterial clearance and treatment failure. Bacteriophages have, over the decades, been proved to play an important role in combating bacterial infections (phage therapy), making them an important alternative to classical antibiotic strategies today. Phages have been found to be effective at killing various species of extracellular bacteria, but little is still known about how phages control intracellular infections. With advances in phage genomics and mechanisms of delivery and cell uptake, the development of phagebased antibacterial strategies to address the treatment of intracellular bacteria has general potential. In this review, we present the current state of knowledge regarding the application of bacteriophages against intracellular bacteria. We cover phage deployment against the most common intracellular pathogens with special attention to therapeutic and preventive strategies.

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Salmonella enterica serovar Enteritidis (S. Enteritidis) is the major contaminant of poultry products, and its ability to form biofilms on produced food and poultry farm processing surfaces contributes to Salmonella transmission to humans. Bacteriophages have come under increasing interest for anti-Salmonella biofilm control. In this study, we used the three previously sequenced and described phages UPWr_S1, UPWr_S3, and UPWr_S4 and a phage cocktail, UPWr_S134, containing these three phages to degrade biofilms formed by two S. Enteritidis strains, 327 lux and ATCC 13076, in vitro. It was found that treatment with bacteriophages significantly reduced biofilm on a 96-well microplate (32–69%) and a stainless steel surface (52–98%) formed by S. Enteritidis 327 lux. The reduction of biofilm formed by S. Enteritidis ATCC 13076 in the 96-well microplate and on a stainless steel surface for bacteriophage treatment was in the range of 73–87% and 60–97%, respectively. Under laboratory conditions, an experimental model utilizing poultry drinkers artificially contaminated with S. Enteritidis 327 lux and treated with UPWr_S134 phage cocktail was applied. In in vitro trials, the phage cocktail significantly decreased the number of Salmonella on the surface of poultry drinkers. Moreover, the phage cocktail completely eradicated Salmonella from the abundant bacterial load on poultry drinkers in an experimentally infected chickens. Therefore, the UPWr_S134 phage cocktail is a promising candidate for Salmonella biocontrol at the farm level.

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The emerging global crisis of antibiotic resistance demands new alternative antibacterial solutions. Although bacteriophages have been used to combat bacterial infections for over a century, a dramatic boost in phage studies has recently been observed. In the development of modern phage applications, a scientific rationale is strongly required and newly isolated phages need to be examined in detail. In this study, we present the full characterization of bacteriophages BF9, BF15, and BF17, with lytic activity against extended-spectrum β-lactamases (ESBLs)- and AmpC β-lactamases (AmpC)-producing Escherichia coli, the prevalence of which has increased significantly in livestock in recent decades, representing a great hazard to food safety and a public health risk. Comparative genomic and phylogenetic analysis indicated that BF9, BF15, and BF17 represent the genera Dhillonvirus, Tequatrovirus, and Asteriusvirus, respectively. All three phages significantly reduced in vitro growth of their bacterial host and retained the ability to lyse bacteria after preincubation at wide ranges of temperature (−20–40 °C) and pH (5–9). The results described herein indicate the lytic nature of BF9, BF15, and BF17, which, along with the absence of genes encoding toxins and bacterial virulence factors, represents an undoubted asset in terms of future phage application.