Characterization and the host specificity of Pet-CM3-4, a new phage infecting Cronobacter and Enterobacter strains

Amino acid residues in the tail fiber differentiate the host specificity of Cronobacter sakazakii bacteriophage

Cronobacter sakazakii is a Gram-negative pathogen that causes severe infections such as neonatal meningitis and sepsis. Bacteriophages (phages) rely on tail fibers for host recognition and infection, but the mechanisms of how phages recognize their bacterial hosts are not completely elucidated. In this study, two lytic C. sakazakii phages belonging to the Drexlerviridae family, CRES7 and CRES9, were isolated from sewage in South Korea. The genomes of both phages are almost the same, with only two nucleotide differences in the gene encoding a putative tail fiber, causing two amino acid differences at amino acid residues 400 and 550 of the tail fiber. The predicted structure of the tail fiber revealed that the two amino acid residues are located on the surface of the tail fiber, suggesting that these two amino acid residues may affect receptor binding. These amino acid differences resulted in differential host ranges, adsorption rates, and burst sizes of CRES7 and CRES9; CRES7, which could infect only the C. sakazakii serotype O1 strain, exhibited a higher adsorption rate and larger burst size compared to CRES9, whereas CRES9 could infect both serotypes O1 and O3 strains. These findings provide insights into how the mutations in the tail fiber gene contribute to the fitness of phages within natural environments and help develop phage-based strategies with expanded host range or enhanced specificity for targeted biocontrol of C. sakazakii.IMPORTANCEAccurate recognition and attachment to the bacterial host, mediated by tail fibers, are crucial for successful phage infection. Understanding the mechanisms underlying host specificity of phages is essential for developing targeted biocontrol applications. This study identified specific amino acid residues responsible for host specificity in the tail fibers of two newly isolated Cronobacter sakazakii phages, CRES7 and CRES9. Differences in these residues showed variation in O serotype recognition, leading to differences in host range, adsorption efficiency, and burst size. These findings provide valuable insights into tail fiber-mediated host specificity, facilitating the development of more effective phage-based strategies against C. sakazakii.

Impact of Metabolites from Foodborne Pathogens on Cancer

Foodborne pathogens are microorganisms that cause illness through contamination, presenting significant risks to public health and food safety. This review explores the metabolites produced by these pathogens, including toxins and secondary metabolites, and their implications for human health, particularly concerning cancer risk. We examine various pathogens such as Salmonella sp., Campylobacter sp., Escherichia coli, and Listeria monocytogenes, detailing the specific metabolites of concern and their carcinogenic mechanisms. This study discusses analytical techniques for detecting these metabolites, such as chromatography, spectrometry, and immunoassays, along with the challenges associated with their detection. This study covers effective control strategies, including food processing techniques, sanitation practices, regulatory measures, and emerging technologies in pathogen control. This manuscript considers the broader public health implications of pathogen metabolites, highlighting the importance of robust health policies, public awareness, and education. This review identifies research gaps and innovative approaches, recommending advancements in detection methods, preventive strategies, and policy improvements to better manage the risks associated with foodborne pathogens and their metabolites.

Characterization and genomic analysis of the lytic bacteriophage vB_EclM_HK6 as a potential approach to biocontrol the spread of Enterobacter cloacae contaminating food

BACKGROUND

Increased prevalence of Enterobacter cloacae within food products underscores food as an underexplored reservoir for antibiotic resistance, thus requiring particular intervention. Bacteriophages have been explored as a promising approach for controlling bacterial growth in different matrices. Moreover, their specific interaction and self-replication, put them apart from traditional methods for controlling bacteria in different matrices.

METHODS

Sixteen Enterobacter cloacae strains were recovered from raw chicken. These strains were used to isolate bacteriophages using enrichment protocol. The broad-spectrum bacteriophage was evaluated in terms of thermal, pH, shearing stress and storge. Moreover, its infection kinetics, in vitro antibacterial activity, cytotoxicity were also assessed. Genomic sequencing was performed to exclude any potential virulence or resistance genes. Finally, the capability of the isolated phages to control bacterial growth in different chicken samples was assessed alone and in combination with sodium nitrite.

RESULTS

The lytic bacteriophage vB_EclM_HK6 was isolated and showed the broadest spectrum being able to infect 8/16 E. cloacae strains with a lytic activity against its host strain, E. cloacae EC21, as low as MOI of 10-6. The phage displays a latent period of 10 min and burst size of 115 ± 44 and resistance frequency of 5.7 × 10-4 ± 3.0 × 10-4. Stability assessment revealed a thermal tolerance up to 60 ˚C, wide range pH stability (3-10) and the ability to withstand shearing stress up to 250 rpm. HK6 shows no cytotoxicity against oral epithelial cells up to 1012 PFU/ml. Genomic analysis revealed a Strabovirus with total size of 177,845 bp that is free from known resistance and virulence genes. Finally, HK6 pretreatment of raw chicken, chicken nuggets and ready-made cheese salad shows a reduced bacterial count up to 4.6, 2.96 and 2.81 log-units, respectively. Moreover, combing HK6 with sodium nitrite further improved the antibacterial activity in both raw chicken and chicken nuggets without significant enhancement in case of cheese salad.

CONCLUSION

Enterobacter bacteriophage vB_EclM_HK6 presents a safe and effective approach for controlling E. cloacae contaminating stored chicken food samples. Moreover, they could be combined with a reduced concentrations of sodium nitrite to improve the killing capacity.

Genomic and biological characterization of bacteriophages against Enterobacter cloacae, a high-priority pathogen

Enterobacter cloacae is a clinically significant pathogen due to its multi-resistance to antibiotics, presenting a challenge in the treatment of infections. As concerns over antibiotic resistance escalate, novel therapeutic approaches have been explored. Bacteriophages, characterized by their remarkable specificity and ability to self-replicate within target bacteria, are emerging as a promising alternative therapy. In this study, we isolated and partially characterized nine lytic bacteriophages targeting E. cloacae, with two selected for comprehensive genomic analysis based on their host range and bacteriolytic activity. All identified phages exhibited a narrow host range, demonstrated stability within a temperature range of 30-60 °C, displayed pH tolerance from 3 to 10, and showed an excellent bacteriolytic capacity for up to 18 h. Notably, the fully characterized phage genomes revealed an absence of lysogenic, virulence, or antibiotic-resistance genes, positioning them as promising candidates for therapeutic intervention against E. cloacae-related diseases. Nonetheless, translating this knowledge into practical therapeutic applications mandates a deeper understanding of bacteriophage interactions within complex biological environments.

Characterization of bacteriophages infecting multidrug-resistant uropathogenic Escherichia coli strains

Uropathogenic Escherichia coli (UPEC) is the most common causative agent of urinary tract infections, and strains that are resistant to antibiotics are a major problem in treating these infections. Phage therapy is a promising alternative approach that can be used to treat infections caused by polyresistant bacterial strains. In the present study, 16 bacteriophages isolated from sewage and surface water were investigated. Phage host specificity was tested on a collection of 77 UPEC strains. The phages infected 2-44 strains, and 80% of the strains were infected by at least one phage. The susceptible E. coli strains belonged predominantly to the B2 phylogenetic group, including strains of two clones, CC131 and CC73, that have a worldwide distribution. All of the phages belonged to class Caudoviricetes and were identified as members of the families Straboviridae, Autographiviridae, and Drexlerviridae and the genera Kagunavirus, Justusliebigvirus, and Murrayvirus. A phage cocktail composed of six phages - four members of the family Straboviridae and two members of the family Autographiviridae - was prepared, and its antibacterial activity was tested in liquid medium. Complete suppression of bacterial growth was observed after 5-22 hours of cultivation, followed by partial regrowth. At 24 hours postinfection, the cocktail suppressed bacterial growth to 43-92% of control values. Similar results were obtained when testing the activity of the phage cocktail in LB and in artificial urine medium. The results indicate that our phage cocktail has potential to inhibit bacterial growth during infection, and they will therefore be preserved in the national phage bank, serving as valuable resources for therapeutic applications.

Therapeutic Potential of a Novel Lytic Phage, vB_EclM_ECLFM1, against Carbapenem-Resistant Enterobacter cloacae

The global rise of multidrug-resistant Enterobacter cloacae strains, especially those that are resistant to carbapenems and produce metallo-β-lactamases, poses a critical challenge in clinical settings owing to limited treatment options. While bacteriophages show promise in treating these infections, their use is hindered by scarce resources and insufficient genomic data. In this study, we isolated ECLFM1, a novel E. cloacae phage, from sewage water using a carbapenem-resistant clinical strain as the host. ECLFM1 exhibited rapid adsorption and a 15-min latent period, with a burst size of approximately 75 PFU/infected cell. Its genome, spanning 172,036 bp, was characterized and identified as a member of Karamvirus. In therapeutic applications, owing to a high multiplicity of infection, ECLFM1 showed increased survival in zebrafish infected with E. cloacae. This study highlights ECLFM1's potential as a candidate for controlling clinical E. cloacae infections, which would help address challenges in treating multidrug-resistant strains and contribute to the development of alternative treatments.

Isolation and Characterization of Bacteriophage VA5 against Vibrio alginolyticus

Bacteriophages, or phages, can be used as natural biological control agents to eliminate pathogenic bacteria during aquatic product cultivation. Samples were collected from seafood aquaculture water and aquaculture environmental sewage, and phage VA5 was isolated using the double-layer agar plate method, with Vibrio alginolyticus as the host bacteria. The purified phage strain was subjected to genome sequencing analysis and morphological observation. The optimal multiplicity of infection (MOI), the one-step growth curve, temperature stability, and pH stability were analyzed. Phage VA5 was observed to have a long tail. Whole-genome sequencing revealed that the genome was circular dsDNA, with 35,866 bp length and 46% G+C content. The optimal MOI was 1, the incubation period was 20 min, the outbreak period was 30 min, and the cleavage amount was 92.26 PFU/cell. The phage showed good activity at -20 °C, 70 °C, and pH 2-10. Moreover, the phage VA5 exhibited significant inhibitory effects on V. alginolyticus-infected shrimp culture. The isolated phage VA5 has a wide range of host bacteria and is a good candidate for biological control of pathogenic bacteria.