Isolation and Characterization of a Novel Phage Collection against Avian-Pathogenic Escherichia coli

Application of a novel lytic phage to control enterotoxigenic Escherichia coli in dairy food matrices

A novel Escherichia coli phage designated as EC BD was isolated from cattle dung samples. Transmission electron microscopy demonstrated that the morphology of phage EC BD belongs to the family Myoviridae. The efficiency of plating (EOP) and scanning electron microscopy revealed the strong lytic activity of phage EC BD with a large burst size and a short latent period. Whole genome data analysis suggested that phage EC BD was inclined towards being completely lytic and revealed the absence of toxins, virulence and antibiotic resistance genes. Phylogenomic analysis of phage EC BD receptor binding proteins (RBPs) showed 74-100 % similarity with sixteen Enterobacter phages, representing their broad host range. The phage genome contains 262 ORFs, of which 107 displayed a unique pattern and additionally, the presence of a tRNA gene directed their fast replication and high stability. Comparative genome analysis suggested phage EC BD as a novel member of the genus Duplodnaviria and family Myoviridae. The efficiency of phage EC BD was determined in dairy food matrices (milk, cheese and paneer) artificially contaminated with enterotoxigenic E. coli strains ETEC H10407, ETEC K 12S and ETEC PB 176 with a significant reduction of 4.8, 6.0 and 5.3 log CFU/mL in milk and a substantial 4.9, 5.8 and 4.6 log CFU/mL reduction in cheese samples after 6 days at low storage temperature (4 °C); furthermore, within the similar conditions, paneer samples showed 4, 5.1 and 3.5 log CFU/mL reduction. EC BD phage treatment represents the complete eradication of three ETEC strains in liquid and semisolid dairy food matrices. This study suggested that phage EC BD might have potential as a biocontrol approach against ETEC foodborne infections.

Avian Pathogenic Escherichia coli: An Overview of Infection Biology, Antimicrobial Resistance and Vaccination

Avian Pathogenic Escherichia coli (APEC) is an extraintestinal pathotype of E. coli that leads to a range of clinical manifestations, including respiratory, systemic and reproductive infections of chickens in both egg and meat production. Unlike most E. coli pathotypes, APEC is not defined by specific virulence genes but rather is a collection of several distinct genotypes that can act as both primary and secondary pathogens leading to colibacillosis. Recent measures to reduce antimicrobials both as growth promoters and as flock-level therapeutics are considered to have led to increased numbers of animals affected. Nevertheless, antimicrobial resistance is a considerable problem in APEC, with resistance to third and fourth-generation cephalosporins via extended-spectrum beta-lactamases (ESBLs), fluoroquinolones and colistin seen as a particular concern. The need to control APEC without antimicrobial use at the flock level has seen an increased focus on vaccination. Currently, a few commercial vaccines are already available, and a range of approaches are being applied to develop new vaccines, and other controls, such as bacteriophage or probiotics, are attracting interest. The lack of a single defined APEC genotype presents challenges to these approaches.

Isolation and characterization of a phage collection against Pseudomonas putida

The environmental bacterium, Pseudomonas putida, possesses a broad spectrum of metabolic pathways. This makes it highly promising for use in biotechnological production as a cell factory, as well as in bioremediation strategies to degrade various aromatic pollutants. For P. putida to flourish in its environment, it must withstand the continuous threats posed by bacteriophages. Interestingly, until now, only a handful of phages have been isolated for the commonly used laboratory strain, P. putida KT2440, and no phage defence mechanisms have been characterized. In this study, we present a new Collection of Environmental P. putida Phages from Estonia, or CEPEST. This collection comprises 67 double-stranded DNA phages, which belong to 22 phage species and 9 phage genera. Our findings reveal that most phages in the CEPEST collection are more infectious at lower temperatures, have a narrow host range, and require an intact lipopolysaccharide for P. putida infection. Furthermore, we show that cryptic prophages present in the P. putida chromosome provide strong protection against the infection of many phages. However, the chromosomal toxin-antitoxin systems do not play a role in the phage defence of P. putida. This research provides valuable insights into the interactions between P. putida and bacteriophages, which could have significant implications for biotechnological and environmental applications.

In vitro evaluation of two novel Escherichia bacteriophages against multiple drug resistant avian pathogenic Escherichia coli

BACKGROUND

In recent years, there has been a growing interest in phage therapy as an effective therapeutic tool against colibacillosis caused by avian pathogenic Escherichia coli (APEC) which resulted from the increasing number of multidrug resistant (MDR) APEC strains.

METHODS

In the present study, we reported the characterization of a new lytic bacteriophage (Escherichia phage AG- MK-2022. Basu) isolated from poultry slaughterhouse wastewater. In addition, the in vitro bacteriolytic activity of the newly isolated phage (Escherichia phage AG- MK-2022. Basu) and the Escherichia phage VaT-2019a isolate PE17 (GenBank: MK353636.1) were assessed against MDR- APEC strains (n = 100) isolated from broiler chickens with clinical signs of colibacillosis.

RESULTS

Escherichia phage AG- MK-2022. Basu belongs to the Myoviridae family and exhibits a broad host range. Furthermore, the phage showed stability under a wide range of temperatures, pH values and different concentrations of NaCl. Genome analysis of the Escherichia phage AG- MK-2022. Basu revealed that the phage possesses no antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and any E. coli virulence associated genes. In vitro bacterial challenge tests demonstrated that two phages, the Escherichia phage VaT-2019a isolate PE17 and the Escherichia phage AG- MK-2022. Basu exhibited high bactericidal activity against APEC strains and lysed 95% of the tested APEC strains.

CONCLUSIONS

The current study findings indicate that both phages could be suggested as safe biocontrol agents and alternatives to antibiotics for controlling MDR-APEC strains isolated from broilers.

Fighting Salmonella Infantis: bacteriophage-driven cleaning and disinfection strategies for broiler farms

Introduction

Salmonella is a bacterium that can cause food-borne infections and is responsible for the most common gastrointestinal illnesses. The emergence of multi-drug resistant (MDR) strains worldwide is a major threat, representing a major challenge in public health. To reduce its incidence, the One Health approach is required, and the development of new biocontrol protocols will help prevent or eliminate the spread of Salmonella. Prevention measures, such as on-farm cleaning and disinfection protocols, are a crucial step in reducing infection to new flocks and eliminating bacteria that remain in the facilities. However, MDR Salmonella species, such as S. Infantis, are highly resistant to conventional cleaning and disinfection protocols, with an increased ability to persist in the broiler farm environment. The need for alternative biocontrol methods has led to the use of bacteriophages or phages, viruses that target bacteria, as promising tools. Thus, the aim of this study was to evaluate the efficacy of phages as a biocide against S. Infantis isolates in combination with cleaning and disinfection protocols in 10 commercial poultry farms.

Methods

All commercial farms selected in this study had persistent Salmonella, even after the routinely used cleaning and disinfection procedures. In addition, Salmonella isolated before treatment were phenotypically characterized by antimicrobial resistance patterns.

Results

The results showed that 100% of S. Infantis were resistant to at least one antibiotic, and > 70% were MDR. Phages were then isolated against the in-farm bacteria, purified, and multiplied for each poultry farm. The cleaning and disinfection protocols included the application of the lytic phages (vB_Si_CECAV_FGS009; vB_Si_CECAV_FGS017; vB_Si_CECAV_FGS029 and vB_Si_CECAV _FGS030) twice at 24-h intervals between cleaning and disinfection. Following the cleaning and disinfection procedures, Salmonella detection was reduced from 100% after cleaning to 36% after applying the phages and dropped to 0% after the final step of disinfection, thus eliminating Salmonella from the farm facilities.

Discussion

This study demonstrates that bacteriophage application after cleaning and before disinfection enhances the removal of MDR Salmonella Infantis in commercial broiler farms, suggesting their use as biocontrol agents to reduce Salmonella, a major public health concern.

Bacteriophage Therapy in Companion and Farm Animals

Bacteriophages, which are viruses with restricted tropism for bacteria, have been employed for over a century as antimicrobial agents; they have been largely abandoned in Western countries but are constantly used in Eastern European countries with the advent of antibiotics. In recent decades, the growing spread of multidrug-resistant bacteria, which pose a serious threat to worldwide public health, imposed an urgent demand for alternative therapeutic approaches to antibiotics in animal and human fields. Based on this requirement, numerous studies have been published on developing and testing bacteriophage-based therapy. Overall, the literature largely supports the potential of this perspective but also highlights the need for additional research as the current standards are inadequate to receive approval from regulatory authorities. This review aims to update and critically revise the current knowledge on the application of bacteriophages to treat bacterial-derived infectious diseases in animals in order to provide topical perspectives and innovative advances.

Control of Escherichia coli in Poultry Using the In Ovo Injection Technique

Pathogens, such as Escherichia coli (E. coli), have been identified as significant causes of poultry mortality. Poultry can serve as potential sources of E. coli transmission, even when asymptomatic, posing a substantial threat to food safety and human health. The in ovo administration of antimicrobials is crucial for preventing and/or effectively combating acute and chronic infections caused by poultry pathogens. To achieve this goal, it is critical that antimicrobials are properly injected into embryonic fluids, such as the amnion, to reach target tissues and trigger robust antimicrobial responses. Several protocols based on antimicrobials were evaluated to meet these requirements. This review analyzed the impacts of antimicrobial substances injected in ovo on the control of E. coli in poultry. The reduction in infection rates, resulting from the implementation of in ovo antimicrobials, combined with efforts aimed at hygienic-sanitary action plans in poultry sheds, reinforces confidence that E. coli can be contained before causing large scale damage. For example, antimicrobial peptides and probiotics have shown potential to provide protection to poultry against infections caused by E. coli. Issues related to the toxicity and bacterial resistance of many synthetic chemical compounds represent challenges that need to be overcome before the commercial application of in ovo injection protocols focused on microbiological control.

Development of carrageenan-immobilized lytic coliphage vB_Eco2571-YU1 hydrogel for topical delivery of bacteriophages in wound dressing applications

Bacteriophages are employed as cost-effective and efficient antibacterial agents to counter the emergence of antibiotic-resistant bacteria and other host bacteria in phage therapy. The increasing incidence of skin wounds is a significant concern in clinical practice, especially considering the limitations of antibiotic therapy. Furthermore, the lack of an effective delivery system that preserves the stability of bacteriophages hampers their clinical implementation. In recent years, there has been a growing amount of research on bacteriophage applications in veterinary and biomedical sciences. In our study, lytic coliphage vB_Eco2571-YU1 was isolated against pathogenic Escherichia coli host bacteria, and hydrogel wound dressing materials were fabricated with marine polysaccharide carrageenan (carr-vB_Eco2571-YU1) for their antibacterial activity. Transmission electron microscopy (TEM) morphology identified it as a Myoviridae coliphage with an icosahedral head length and width of approximately 60 and 56.8 nm, respectively, and a tail length of 119.7 nm. The one-step growth curve of coliphage revealed a latent period of 10 min, a rise period of 15 min, and a burst size of 120 virions per cell. The bacteriolytic activity of unimmobilized coliphages was observed within 2 h; however, strain-specific phage resistance was acquired after 9 h. In contrast, carr-vB_Eco2571-YU1 showed a sharp decline in the growth of bacteria in the log phase after 2 h and did not allow for the acquisition of phage resistance by the E. coli strain. The stability of coliphage under different pH, temperature, osmolarity, detergents, and organic solvents was evaluated. We also studied the long-term storage of carr-vB_Eco2571-YU1 hydrogels at 4 °C and found that the titer value decreased during a time-dependent period of 28 days. These hydrogels were also found to be hemocompatible using a hemolysis assay. The addition of plasticizer (0.6 % (w/v)) to the carrageenan (2 % (w/v)) to prepare carr-vB_Eco2571-YU1 hydrogels showed a decrease in compressive strength with enhanced elasticity. This phage therapy using polymeric immobilization of bacteriophages is a promising next-generation wound dressing biomaterial alternative to conventional wound and skin care management.

Comparative genomics and proteomics analysis of phages infecting multi-drug resistant Escherichia coli O177 isolated from cattle faeces

The increasing prevalence of antimicrobial-resistant (AMR) pathogens has become a major global health concern. To address this challenge, innovative strategies such as bacteriophage therapy must be optimised. Genomic characterisation is a crucial step in identifying suitable phage candidates for combating AMR pathogens. The aim of this study was to characterise seven phages that infect the Escherichia coli O177 strain using a whole genome sequencing. The analysis of genome sequences revealed that these phages had linear dsDNA, with genome sizes spanning from 136, 483 to 166,791 bp and GC content varying from 35.39 to 43.63%. Taxonomically, the phages were classified under three different subfamilies (Stephanstirmvirinae, Tevenvirinae, and Vequintavirinae) and three genera (Phapecoctavirus, Tequatrovirus, and Vequintavirus) within the class Caudoviricetes. In silico PhageAI analysis predicted that all the phages were virulent, with confidence levels between 96.07 and 97.26%. The phage genomes contained between 66 and 82 ORFs, which encode hypothetical and putative functional proteins. In addition, the phage genomes contained core genes associated with molecular processes such as DNA replication, transcription modulation, nucleotide metabolism, phage structure (capsid and tail), and lysis. None of the genomes carried genes associated with undesirable traits such as integrase, antimicrobial resistance, virulence, and toxins. The study revealed high genome and proteome homology among E. coli O177 phages and other known Escherichia phages. The results suggest that the seven phages are new members of the genera Phapecoctavirus, Tequatrovirus, and Vequintavirus under the subfamilies Stephanstirmvirinae, Tevenvirinae, and Vequintavirinae, respectively.

In ovo administration of a phage cocktail partially prevents colibacillosis in chicks

Avian pathogenic Escherichia coli (APEC) causes colibacillosis, the main bacterial disease in poultry leading to significant economic losses worldwide. Antibiotic treatments favor the emergence of multidrug-resistant bacteria, and preventive measures are insufficient to control the disease. There is increasing interest in using the potential of bacteriophages, not only for phage therapy but also for prevention and biocontrol. This study aimed to evaluate the efficacy of a phage cocktail administered in ovo to prevent avian colibacillosis in chicks. When 4 different phages (REC, ESCO3, ESCO47, and ESCO58), stable under avian physiological conditions, were combined and inoculated at 17 embryogenic days (ED), they were transmitted to the newly hatched chicks. In a second trial, the 4-phage cocktail was inoculated into the allantoic fluid at ED16 and after hatch 1-day-old chicks were challenged with the O2 APEC strain BEN4358 inoculated subcutaneously. Two phages (REC and ESCO3) were still detected in the ceca of surviving chicks at the end of the experiment (7-days postinfection). Chicks that received the phages in ovo did not develop colibacillosis lesions and showed a significant decrease in intestinal BEN4358 load (8.00 × 107 CFU/g) compared to the challenged chicks (4.52 × 108 CFU/g). The majority of the reisolated bacteria from the ceca of surviving chicks had developed full resistance to ESCO3 phage, and only 3 were resistant to REC phage. The partially or complete resistance of REC phage induced a considerable cost to bacterial virulence. Here, we showed that phages inoculated in ovo can partially prevent colibacillosis in 1-wk-old chicks. The reduction in the APEC load in the gut and the decreased virulence of some resistant isolates could also contribute to control the disease.