Susceptibility of Pseudomonas aeruginosa veterinary isolates to Pbunavirus PB1-like phages

In recent years, antimicrobial-resistant Pseudomonas aeruginosa strains have increased in the veterinary field. Therefore, phage therapy has received significant attention as an approach for overcoming antimicrobial resistance. In this context, we isolated and characterized four Pseudomonas bacteriophages. Phylogenetic analysis showed that the isolated phages are novel Myoviridae Pbunavirus PB1-like phages with ØR12 belonging to a different clade compared with the other three. These phages had distinct lytic activity against 22 P. aeruginosa veterinary isolates. The phage cocktail composed from the PB1-like phages clearly inhibited the occurrence of the phage-resistant variant, suggesting that these phages could be useful in phage therapy.     

Diversity among Lactobacillus paracasei phages isolated from a probiotic dairy product plant

Aims:  To evaluate the phage diversity in the environment of a dairy industry which manufactures a product fermented with a probiotic strain of Lactobacillus paracasei .
Methods and Results:  Twenty-two Lact. paracasei phages were isolated from an industrial plant that manufactures a probiotic dairy product. Among them, six phages were selected based on restriction profiles, and two phages because of their notable thermal resistance during sample processing. Their morphology, host range, calcium dependency and thermal resistance were investigated. All phages belonged to the Siphoviridae family (B1 morphotype), were specific for Lact. casei and paracasei strains showing identical host spectrum, and only one phage was independent of calcium for completing its lytic cycle. Some of the phages showed an extraordinary thermal resistance and were protected by a commercial medium and milk.
Conclusions:  Phage diversity in a probiotic product manufacture was generated to a similar or greater extent than during traditional yogurt or cheese making.
Significance and Impact of the Study:  This work emphasizes probiotic phage infections as a new ecological situation beyond yogurt or cheese manufactures, where the balanced coexistence between phages and strains should be directed toward a favourable state, thus achieving a successful fermentation.     

Isolation of Escherichia coli bacteriophages from the stool of pediatric diarrhea patients in Bangladesh

A 3-week coliphage survey was conducted in stool samples from 140 Bangladeshi children hospitalized with severe diarrhea. On the Escherichia coli indicator strain K803, all but one phage isolate had 170-kb genomes and the morphology of T4 phage. In spot tests, the individual T4-like phages infected up to 27 out of 40 diarrhea-associated E. coli, representing 22 O serotypes and various virulence factors; only five of them were not infected by any of these new phages. A combination of diagnostic PCR based on g32 (DNA binding) and g23 (major capsid protein) and Southern hybridization revealed that half were T-even phages sensu strictu, while the other half were pseudo-T-even or even more distantly related T4-like phages that failed to cross-hybridize with T4 or between each other. Nineteen percent of the acute stool samples yielded T4-like phages, and the prevalence was lower in convalescent stool samples. T4-like phages were also isolated from environmental and sewage water, but with low frequency and low titers. On the enteropathogenic E. coli strain O127:K63, 14% of the patients yielded phage, all of which were members of the phage family Siphoviridae with 50-kb genomes, showing the morphology of Jersey- and beta-4 like phages and narrow lytic patterns on E. coli O serotypes. Three siphovirus types could be differentiated by lack of cross-hybridization. Only a few stool samples were positive on both indicator strains. Phages with closely related restriction patterns and, in the case of T4-like phages, identical g23 gene sequences were isolated from different patients, suggesting epidemiological links between the patients.     

Salmonella Enteritidis bacteriophage candidates for phage therapy of poultry

Aims: Salmonella is a worldwide foodborne pathogen causing acute enteric infections in humans. In the recent years, the use of bacteriophages has been suggested as a possible tool to combat this zoonotic pathogen in poultry farms. This work aims to isolate and perform comparative studies of a group of phages active against a collection of specific Salmonella Enteritidis strains from Portugal and England. Also, suitable phage candidates for therapy of poultry will be selected. Methods and Results: The Salm. Enteritidis strains studied were shown to have a significantly high occurrence of defective (cryptic) prophages; however, no live phages were found in the strains. Bacteriophages isolated from different environments lysed all except one of the tested Salm. Enteritidis strains. The bacteriophages studied were divided into different groups according to their genetic homology, RFLP profiles and phenotypic features, and most of them showed no DNA homology with the bacterial hosts. The bacteriophage lytic efficacy proved to be highly dependent on the propagation host strain. Conclusions: Despite the evidences shown in this work that the Salm. Enteritidis strains used did not produce viable phages, we have confirmed that some phages, when grown on particular hosts, behaved as complexes of phages. This is most likely because of the presence of inactive phage‐related genomes (or their parts) in the bacterial strains which are capable of being reactivated or which can recombine with lytic phages. Furthermore, changes of the bacterial hosts used for maintenance of phages must be avoided as these can drastically modify the parameters of the phage preparations, including host range and lytic activity. Significance and Impact of the Study: This work shows that the optimal host and growth conditions must be carefully studied and selected for the production of each bacteriophage candidate for animal therapy.     

Bacteriophage therapy as an alternative biocontrol against emerging multidrug resistant E. coli in broilers

Avian pathogenic Escherichia coli (APEC) is considered a severe issue to both poultry business and health of the general public. In that context, 50 samples from 250 diseased broiler chickens in 10 chicken farms were employed to Escherichia coli isolation. Microbiological techniques were employed to detect isolates of E. coli from 250 diseased broiler chickens which were examined by antimicrobial susceptibility profiles against 11 antimicrobial agents using disc diffusion technique as well as their biofilm forming capacity were detected. In addition to, study the isolation and purification of phages based on spot technique to verify that lytic phages are present in E. coli isolates and plaque assay for titration of bacteriophages. In the present research, we also looked at the ability of bacteriophages to inhibit and dissolve previously formed biofilms by E. coli O78 isolate. Moreover, experimental testing of E. coli O78 bacteriophages for colibacillosis prevention and control in one day old broiler chicks were done. The obtained results showed that twenty-six E. coli isolates out of 50 examined samples were isolated (10.4%). The most prevalent serotypes were O78, O121:H7, O146:H2, O124, O113:H4, O112:H2, O1:H7, O55:H7, O2:H6, O91:H21, O26:H11. Antibiogram results demonstrated the resistance of E. coli isolates with high percentage 100% were against, Ampicillin, Amoxicillin and Tetracycline. Biofilm quantification analysis showed that 24/26 (92.3%) isolates were considered biofilm producer isolates. The characterization and the lytic activity of bacteriophage were performed based on Transmission electron microscopy and showed the greatest lytic activity against the evaluated host strains with effective activity at concentration of 10⁷ at 24 h and strong significant reduction of the established E. coli O 78 biofilm within 12 h. The result of experimental infection showed that the performance indicators of phage in treated and challenged group showed high significant increase in body weight, weight gain and improved FCR than infected –antibiotic treated and infected bacteriophage and antibiotic treated. Total viable cell counts of E. coli in the lungs of birds revealed that there is highly significant difference between the six groups count results. We concluded that phage therapy found to be an attractive option to prevent and control multidrug resistant colibacillosis in broilers.     

Host range and lytic capability of four bacteriophages against bovine and clinical human isolates of Shiga toxin-producing Escherichia coli O157:H7

Aims:  To evaluate host range and lytic capability of four bacteriophages (rV5, wV7, wV8 and wV11) against Escherichia coli O157:H7 (STEC O157:H7) from cattle and humans.
Methods and Results:  Four hundred and twenty-two STEC O157:H7 isolates (297 bovine; 125 human) were obtained in Alberta, Canada. The four phages were serially diluted and incubated for 5 h with overnight cultures of STEC O157:H7 to estimate their multiplicity of infection (MOI). All bovine STEC O157:H7 were subjected to pulsed-field gel electrophoresis (PFGE) and phage typing (PT). Phage wV7 lysed all human and bovine isolates irrespective of PFGE genotype or PT phenotype and exhibited the lowest MOI (0·004–0·006, P  < 0·0001) of all phages. Phages rV5 and wV11 exhibited a lower MOI (0·002–0·04, P  < 0·0001) than did phage wV8 (25–29) and they had a narrower host range than wV7 or wV8. Phages rV5, wV11 and wV8 lysed 342 (81·0%), 321 (76·1%) and 407 (96·4%), respectively, of the 422 isolates. Susceptibility of bovine STEC O157:H7 to rV5, w11 and wV8 was influenced by PFGE genotype and/or PT phenotype.
Conclusions:  Phages exhibited activity against the majority of bovine and human STEC O157:H7 isolates. PFGE genotype and/or PT phenotype of the host-target influenced their vulnerability to phage attack. Susceptibility of bovine STEC O157:H7 to phage may also differ among farms. Both lytic capability and host range should be considered in the selection of therapeutic phage for on-farm control of STEC O157:H7.
Significance and Impact of the Study:  The present work indicates that a four-phage cocktail should be equally effective at mitigating STEC O157:H7 isolates both of bovine and of human origin. Given that some STEC O157:H7 exhibited resistance to some but not all phages, a phage cocktail is the logical approach to efficacious on-farm therapy.     

Identification, cloning and sequencing of Escherichia coli strain χ1378 (O78:K80) iss gene isolated from poultry colibacillosis in Iran

Aims:  To identify, clone and sequence the iss (increased serum survival) gene from E. coli strain χ1378 isolated from Iranian poultry and to predict its protein product, Iss.
Methods and Results:  The iss gene from E. coli strain χ1378 was amplified and cloned into the pTZ57R/T vector and sequenced. From the DNA sequence, the Iss predictive protein was evaluated using bioinformatics. Iss from strain χ1378 had 100% identity with other E. coli serotypes and isolates from different origins and also 98% identity with E. coli O157:H7 Iss protein. Phylogenetic analysis showed no significant different phylogenic groups among E. coli strains.
Conclusions:  The strong association of predicted Iss protein among different E. coli strains suggests that it could be a good antigen to control and detect avian pathogenic E. coli (APEC).
Significance and Impact of the study:  Because the exact pathogenesis and the role of virulence factors are unknown, the Iss protein could be used as a target for vaccination in the future, but further research is required.     

Isolation and characterization of lytic bacteriophages against enterohaemorrhagic Escherichia coli

Aims: The objective of this study was to isolate, identify and characterize a collection of lytic bacteriophages capable of infecting enterohaemorrhagic Escherichia coli (EHEC) serotypes. Methods and Results: Phages were isolated from dairy and cattle feedlot manure using E. coli O157, O26 and O111 strains as hosts. Phages were enriched from faecal slurries by culture in 10× trypticase soy broth at 37°C overnight. Phage plaques were obtained by mixing the filtered culture supernatant with molten tryptone agar containing the phage E. coli host strain, pouring the inoculated agar on top of cooled TS agar and incubating the culture overnight. Phages were purified from plaques and screened against additional E. coli and EHEC strains by the efficiency of plating method (EOP). Phage CEV2, and five other phages previously isolated, were able to lyse all of the 15 O157 strains tested with EOP values consistently above 0·001. Two phages were found to be highly effective against strains of E. coli O157 through EOP tests and against O26 strains through spot tests, but not against the O serogroup 111 strains. A cocktail of eight phage that lyse E. coli O157 strains resulted in >5 log CFU ml^?1 reductions at 37°C. Multiplex‐PCR revealed that none of these eight phages carried stx1, stx2, hlyA or eaeA genes. Conclusions: A cocktail of bacteriophages was capable of lysing most strains of two EHEC serotypes. Significance and Impact of the Study: This collection of phages can be combined and potentially used as an antimicrobial cocktail to inactivate E. coli strains from O serogroups 157 and 26 and reduce their incidence in the food chain.     

Diversity and Geographical Distribution of Flavobacterium psychrophilum Isolates and Their Phages: Patterns of Susceptibility to Phage Infection and Phage Host Range

Flavobacterium psychrophilum is an important fish pathogen worldwide that causes cold water disease (CWD) or rainbow trout fry syndrome (RTFS). Phage therapy has been suggested as an alternative method for the control of this pathogen in aquaculture. However, effective use of bacteriophages in disease control requires detailed knowledge about the diversity and dynamics of host susceptibility to phage infection. For this reason, we examined the genetic diversity of 49 F. psychrophilum strains isolated in three different areas (Chile, Denmark, and USA) through direct genome restriction enzyme analysis (DGREA) and their susceptibility to 33 bacteriophages isolated in Chile and Denmark, thus covering large geographical (>12,000 km) and temporal (>60 years) scales of isolation. An additional 40 phage-resistant isolates obtained from culture experiments after exposure to specific phages were examined for changes in phage susceptibility against the 33 phages. The F. psychrophilum and phage populations isolated from Chile and Denmark clustered into geographically distinct groups with respect to DGREA profile and host range, respectively. However, cross infection between Chilean phage isolates and Danish host isolates and vice versa was observed. Development of resistance to certain bacteriophages led to susceptibility to other phages suggesting that “enhanced infection” is potentially an important cost of resistance in F. psychrophilum, possibly contributing to the observed co-existence of phage-sensitive F. psychrophilum strains and lytic phages across local and global scales. Overall, our results showed that despite the identification of local communities of phages and hosts, some key properties determining phage infection patterns seem to be globally distributed.     

Isolation and characterization of Campylobacter bacteriophages from retail poultry

The ability of phages to survive processing is an important aspect of their potential use in the biocontrol of Campylobacter in poultry production. To this end, we have developed a procedure to recover Campylobacter bacteriophages from chilled and frozen retail poultry and have validated the sensitivity of the method by using a characterized Campylobacter phage (i.e., NCTC 12674). By using this method, we have shown that Campylobacter phages can survive on retail chicken under commercial storage conditions. Retail chicken portions purchased in the United Kingdom were screened for the presence of endogenous Campylobacter phages. Thirty-four Campylobacter bacteriophages were isolated from 300 chilled retail chicken portions, but none could be recovered from 150 frozen chicken portions. The phage isolates were characterized according to their lytic profiles, morphology, and genome size. The free-range products were significantly more likely to harbor phages (P < 0.001 by single-factor analysis of variance) than were standard or economy products. This study demonstrates that Campylobacter bacteriophages, along with their hosts, can survive commercial poultry processing procedures and that the phages exhibited a wide range of recovery rates from chicken skin stored at 4 degrees C.     

Characterization of two bacteriophages specific to Acinetobacter baumannii and their effects on catheters biofilm

Multidrug-resistant strains of Acinetobacter baumannii cause major nosocomial infections. Bacteriophages that are specific to the bacterial species and destroy bacteria can be effectively used for treatment. In this study, we characterized lytic bacteriophages specific to A. baumannii strains. We isolated lytic bacteriophages from environmental water samples and then investigated their morphology, host range, growth characteristics, stability, genome analysis, and biofilm destruction on the catheter surface. Our results showed that the efficacy of the phages varied between 32% and 78%, tested on 78 isolates of A. baumannii; 80 phages were isolated, and two lytic bacteriophages, vB_AbaP_HB01 (henceforth called C2 phage) and vB_AbaM_HB02 (henceforth called K3 phage), were selected for characterization. Electron microscopy scans revealed that the C2 and K3 phages were members of the Podoviridae and Myoviridae families, respectively. Whole-genome sequencing revealed that the sequence of the C2 phage is available in the NCBI database (accession number: OP917929.1), and it was found sequence identity with Acinetobacter phage AB1 18%, the K3 phage DNA sequence is closely related to Acinetobacter phage vB_AbaM_phiAbaA1 (94% similarity). The cocktail of C2 and K3 phages demonstrated a promising decrease in the bacterial cell counts of the biofilm after 4 h. Under a scanning electron microscope, the cocktail treatment destructed the biofilm on the catheter. We propose that the phage cocktail could be a strong alternative to antibiotics to control the A. baumannii biofilm in catheter infections.     

A guard-killer phage cocktail effectively lyses the host and inhibits the development of phage-resistant strains of Escherichia coli

In recent years, after the emergence of a large number of multidrug-resistant bacteria, phages and phage-associated products for the prevention and control of bacterial disease have revealed prominent advantages as compared with antibiotics. However, bacteria are susceptible to becoming phage-resistant, thus severely limiting the application of phage therapy. In this study, Escherichia coli cells were incubated with lytic bacteriophages to obtain mutants that were resistant to the lytic phages. Then, bacteriophages against the phage-resistant variants were isolated and subsequently mixed with the original lytic phage to prepare a novel phage cocktail for bactericidal use. The data showed that our phage cocktail not only had notable bactericidal effects, including a widened host range and rapid lysis, but also decreased the generation and mutation frequency of phage-resistant strains in vitro. In addition, we tested our cocktail in a murine bacteremia model. The results suggested that compared with the single phage, fewer phage-resistant bacteria appeared during the treatment of phage cocktail, thus prolonging the usable time of the phage cocktail and improving its therapeutic effect in phage applications. Importantly, our preparation method of phage cocktail was proved to be generalizable. Because the bacteriophage against the phage-resistant strain is an ideal guard that promptly attacks potential phage resistance, this guard-killer dual-function phage cocktail provides a novel strategy for phage therapy that allows the natural ecology to be sustained.

     

Bacteriophages Isolated in China for the Control of Pectobacterium carotovorum Causing Potato Soft Rot in Kenya

Soft rot is an economically significant disease in potato and one of the major threats to sustainable potato production. This study aimed at isolating lytic bacteriophages and evaluating methods for and the efficacy of applying phages to control potato soft rot caused by Pectobacterium carotovorum. Eleven bacteriophages isolated from soil and water samples collected in Wuhan, China, were used to infect P. carotovorum host strains isolated from potato tubers showing soft rot symptoms in Nakuru county, Kenya. The efficacy of the phages in controlling soft rot disease was evaluated by applying individual phage strains or a phage cocktail on potato slices and tubers at different time points before or after inoculation with a P. carotovorum strain. The phages could lyse 20 strains of P. carotovorum, but not Pseudomonas fluorescens control strains. Among the 11 phages, Pectobacterium phage Wc5 r, interestingly showed cross-activity against Pectobacterium atrosepticum and two phage-resistant P. carotovorum strains. Potato slice assays showed that the phage concentration and timing of application are crucial factors for effective soft rot control. Phage cocktail applied at a concentration of 1 9 109 plaque-forming units per milliliter before or within an hour after bacterial inoculation on potato slices, resulted in C 90%reduction of soft rot symptoms. This study provides a basis for the development and application of phages to reduce the impact of potato soft rot disease.     

Characterization of 4 T1-like lytic bacteriophages that lyse Shiga-toxin Escherichia coli O157:H7

Bacteriophages are associated with reduced fecal shedding of Shiga-toxin-producing Escherichia coli O157:H7 (STEC O157:H7) in cattle. Four phages exhibiting activity against 12 of 14 STEC O157:H7 strains, representing 11 common phage types, were isolated. Phages did not lyse non-O157 E. coli, with 11 of the 12 STEC strains exhibiting extreme susceptibility (average multiplicity of infection (MOI) = 0.0003-0.0007). All phages had icosahedral heads with tapered, noncontractile tails, a morphology indicative of T1-like Siphoviridae. Genome size of all phages was ～44 kb, but EcoR? or HindIII digestion profiles differed among phages. Based on restriction enzyme digestion profiles, phages AHP24, AHS24, and AHP42 were more related (66.7%-82.4%) to each other than to AKS96, while AHP24 and AHS24, isolated from the same feedlot pen, exhibited the highest identity (88.9%-92.3%). Phages AHP24 and AHS24 exhibited the broadest host range and strongest lytic activity against STEC O157:H7, making them strong candidates for biocontrol of this bacterium in cattle.     

Milk Contamination and Resistance to Processing Conditions Determine the Fate of Lactococcus lactis Bacteriophages in Dairies

Milk contamination by phages, the susceptibility of the phages to pasteurization, and the high levels of resistance to phage infection of starter strains condition the evolution dynamics of phage populations in dairy environments. Approximately 10% (83 of 900) of raw milk samples contained phages of the quasi-species c2 (72%), 936 (24%), and P335 (4%). However, 936 phages were isolated from 20 of 24 (85%) whey samples, while c2 was detected in only one (4%) of these samples. This switch may have been due to the higher susceptibility of c2 to pasteurization (936-like phages were found to be approximately 35 times more resistant than c2 strains to treatment of contaminated milk in a plate heat exchanger at 72°C for 15 s). The restriction patterns of 936-like phages isolated from milk and whey were different, indicating that survival to pasteurization does not result in direct contamination of the dairy environment. The main alternative source of phages (commercial bacterial starters) does not appear to significantly contribute to phage contamination. Twenty-four strains isolated from nine starter formulations were generally resistant to phage infection, and very small progeny were generated upon induction of the lytic cycle of resident prophages. Thus, we postulate that a continuous supply of contaminated milk, followed by pasteurization, creates a factory environment rich in diverse 936 phage strains. This equilibrium would be broken if a particular starter strain turned out to be susceptible to infection by one of these 936-like phages, which, as a consequence, became prevalent.     

Bacteriophage therapy to reduce salmonella colonization of broiler chickens

Acute enteric infections caused by salmonellas remain a major public health burden worldwide. Poultry, particularly chickens, are known to be the main reservoir for this zoonotic pathogen. Although some progress has been made in reducing Salmonella colonization of broiler chickens by using biosecurity and antimicrobials, it still remains a considerable problem. The use of host-specific bacteriophages as a biocontrol is one possible intervention by which Salmonella colonization could be reduced. A total of 232 Salmonella bacteriophages were isolated from poultry farms, abattoirs, and wastewater in 2004 and 2005. Three phages exhibiting the broadest host ranges against Salmonella enterica serotypes Enteritidis, Hadar, and Typhimurium were characterized further by determining their morphology and lytic activity in vitro. These phages were then administered in antacid suspension to birds experimentally colonized with specific Salmonella host strains. The first phage reduced S. enterica serotype Enteritidis cecal colonization by > or = 4.2 log10 CFU within 24 h compared with controls. Administration of the second phage reduced S. enterica serotype Typhimurium by > or = 2.19 log10 CFU within 24 h. The third bacteriophage was ineffective at reducing S. enterica serotype Hadar colonization. Bacteriophage resistance occurred at a frequency commensurate with the titer of phage being administered, with larger phage titers resulting in a greater proportion of resistant salmonellas. The selection of appropriate bacteriophages and optimization of both the timing and method of phage delivery are key factors in the successful phage-mediated control of salmonellas in broiler chickens.     

Ten new temperate bacteriophages of<Emphasis Type="Italic">Citrobacter youngae</Emphasis>

In a cross-test, we examined 55 strains of Citrobacter youngae against each other as potential producers of temperate bacteriophages and as potential sensitive indicators for them. Ten strains (18.2 %) showed the production of phages. Seven different strain-specific spectra of activity (from 1 to 11 strains each) were found. Phage production by 6 strains was inducible with mitomycin C, in 4 strains it was not inducible. The plaques of the phages were more or less turbid, without a lytic halo, tiny to small, 0.2-1.3 mm in diameter. Using a polyclonal, specific anti-lambda serum, all 10 phages were found to be clearly distinct from E. coli lambda phage, the phage 31/47 showing the highest neutralization titre of all. Interspecific tests with 15 strains of 8 species of Enterobacteriaceae revealed not a single case of activity of Citrobacter phages towards any of them. Five phage-immune clones lysogenized with 5 of the phages kept their remaining phage sensitivity spectra, though extended by sensitivity to 1-3 phages; 2 of these strains acquired also sensitivity to phage lambda. The phages belong to the morphotypes of Myoviridae (6 phages) and Siphoviridae (4 phages), with head diameters of 51-58 nm and tail length of 97-173 nm. Three strains produced corpuscular bacteriocins.     

Characterization of filamentous bacteriophage PE226 infecting Ralstonia solanacearum strains

Aims: The aim of this study was to isolate and characterize new bacteriophages that infect a wide range of plant pathogenic Ralstonia solanacearum strains. Methods and Results: Fifteen bacteriophages were isolated from pepper, tomato and tobacco plant rhizospheres infected with R. solanacearum. A host specificity analysis of the isolated phages using nine strains of R. solanacearum indicated great phage diversity in a single soil. Two phages, PE226 and TM227, showed clear plaques on all nine bacterial hosts tested and were virtually identical in morphology and genome. PE226, an Inovirus, is a long, flexible, filamentous phage carrying a circular (+) sense single‐strand DNA genome of 5475 nucleotides. DNA sequences of PE226 exhibited nine open reading frames (ORF) that were not highly similar to those of other phages infecting R. solanacearum. The genome organization of PE226 was partially similar to that of p12J of Ralstonia pickettii. One ORF of PE226 showed identity to the zot gene encoding zonula occludens toxin of Vibrio cholera. Orf7 of PE226 was also present in the genome of R. solanacearum strain SL341. However, SL341, a highly virulent strain in tomato, was still sensitive to phage PE226. Conclusions: A new, flexible, filamentous phage PE226 infected wide range of R. solanacearum strains and carried unique circular single‐strand DNA genome with an ORF encoding Zot‐like protein. Significance and Impact of the Study: PE226 may be a new type of temperate phage, based on its lytic nature on a wide range of hosts and the presence of a zot homologue in a host bacterial genome.     

Local bacteriophage isolates showed anti- Escherichia coli O157:H7 potency in an experimental ligated rabbit ileal loop model

Escherichia coli O157:H7 is considered among the most important recently emerged food-borne bacteria causing severe hemorrhagic diarrhea. Antibiotic treatment is not recommended as a prospective curative agent against this pathogen. Therefore, potency assessment of the local lytic phage isolates infecting E. coli O157:H7 as an alternate remedy to antibiotics was the principal concern of this study. Phage isolates against E. coli O157:H7 were checked by polymerase chain reaction for the presence of the virulence genes stx1 and stx2, and the safe phages were further screened in vitro for their capacity as biocontrol agents. Two bacteriophage strains, namely PAH6 and P2BH2, that had expressed potential antibacterial activity (P?< 0.05) in vitro were selected for in vivo testing in ligated rabbit ileal loop models. Both phage isolates were capable of decreasing fluid accumulation in rabbit ileal loops along with reducing bacterial growth (r = 0.992). Combined application of the phages was found most satisfactory, reducing seven?log cycles of bacterial growth. Consistent results in both in vivo and in vitro experiments demonstrate the applicability of bacteriophages as a rapid response tool against E.?coli O157:H7. To our knowledge, this is the first successful application of the rabbit ileal loop test for therapeutic evaluation of bacteriophages.     

Complete Genome Sequence of the Novel Escherichia coli Phage phAPEC8

Bacteriophage phAPEC8 is an Escherichia coli-infecting myovirus, isolated on an avian pathogenic Escherichia coli (APEC) strain. APEC strains cause colibacillosis in poultry, resulting in high mortality levels and important economic losses. Genomic analysis of the 147,737-bp double-stranded DNA phAPEC8 genome revealed that 53% of the 269 encoded proteins are unique to this phage. Its closest relatives include the Salmonella phage PVP-SE1 and the coliphage rv5, with 19% and 18% similar proteins, respectively. As such, phAPEC8 represents a novel, phylogenetically distinct clade within the Myoviridae, with molecular properties suitable for phage therapy applications.