Linear Double-stranded DNA Research Articles

Characterization of bacteriophage vB_AbaS_SA1 and its synergistic effects with antibiotics against clinical multidrug-resistant Acinetobacter baumannii isolates.

Acinetobacter baumannii is a major cause of nosocomial infections globally. The increasing prevalence of multidrug-resistant (MDR) A. baumannii has become an important public health concern. To combat drug resistance, alternative methods such as phage therapy have been suggested. In total, 30 MDR A. baumannii strains were isolated from clinical specimens, and their antibiotic susceptibilities were determined. The Acinetobacter phage vB_AbaS_SA1, isolated from hospital sewage, was characterized. In addition to its plaque size, particle morphology, and host range, its genome sequence was determined and annotated. Finally, the antibacterial effects of phage alone, antibiotics alone, and phage/antibiotic combinations were assessed against the A. baumannii strains. Phage vB_AbaS_SA1 had siphovirus morphology, showed a latent period of 20 minutes, and a 250 PFU/cell (plaque forming unit/cell) burst size. When combined with antibiotics, vB_AbaS_SA1 (SA1) showed a significant phage-antibiotic synergy (PAS) effect and reduced the overall effective concentration of antibiotics in time-kill assessments. The genome of SA1 is a linear double-stranded DNA of 50,108bp in size with a GC content of 39.15%. Despite the potent antibacterial effect of SA1, it is necessary to perform additional research to completely elucidate the mechanisms of action and potential constraints associated with utilizing this bacteriophage.

Isolation and evaluation of bacteriophage cocktail for the control of colistin-resistant Escherichia coli

The frequent emergence of colistin-resistant E. coli worldwide drives the exploration of alternative therapies, and bacteriophages (phages) have emerged as promising candidates to tackle this challenge. In this study, three E. coli phages were isolated, screened, and evaluated against 96 colistin-resistant strains obtained from diverse sources. The combined recognition rate for these strains was 43.6%, while individually it ranged from 17.0% to 24.5%. Notably, among the tested phages (FJ3-79, SD1-92L, and FJ4-63), FJ4-63 demonstrated exceptional characteristics in regulating host population dynamics upon infection by exhibiting a shorter latent period (20 min) and a larger burst size (95.99 ± 3.61 PFU/cell). Furthermore, it exhibited relative stability at pH 3-11 and below 60°C. Transmission electron microscopy and genomic analysis classified phage FJ4-63 belongs to the Dhakavirus genus within the Straboviridae family. Its genome comprised a linear double-stranded DNA measuring 169,669 bp (containing 272 coding sequences) with a GC content of 39.76%, of which 93 (34.2%) had known functions, and the remaining 177 were annotated as hypothetical proteins. Additionally, two tRNAs were recognized, possess the “holin-endolysin” lytic system, and no resistance or virulence genes were detected. The phylogenetic tree and average nucleotide identity (ANI) analysis revealed that phage FJ4-63 exhibited the highest similarity to Escherichia phage C6 (679410.1), indicating a consistent close relationship within the same branch. The cocktail comprising three phages exhibits enhanced in vitro bactericidal efficacy compared to a single phage. At high doses with MOI = 100, it rapidly and completely eradicates bacteria within 1 h while significantly reducing bacterial biofilms. All this evidence suggests that lytic phages offer an effective solution for clinical treatment, with a phage cocktail demonstrating greater potential in the alternative management of colistin-resistant E. coli infections.

Characterization of a novel lytic phage against methicillin resistance Staphylococcus aureus in Hainan island

Methicillin resistance Staphylococcus aureus (MRSA) is currently threatening global public health, and a similar issue was encountered in Hainan. For establishing a promising alternative therapeutic option, a phage with the capacity of lysing 18 out of 35 MRSA clinical isolates was recovered from domestic natural sources, which was termed as vB_SauP_L1 due to its morphology and genomic similarity with Rountreeviridae. Satisfactory proliferation rate and environmental tolerance were demonstrated by subsequent infectious properties tests and stability assessments. Sequencing revealed that its genome consisted of a linear double-stranded DNA of 17,114 bp, in which neither virulent nor resistant gene was detected, indicating its potential in MRSA prevention and treatment.

High Nucleotide Skew Palindromic DNA Sequences Function as Potential Replication Origins due to their Unzipping Propensity.

Locations of DNA replication initiation in prokaryotes, called "origins of replication", are well-characterized. However, a mechanistic understanding of the sequence dependence of the local unzipping of double-stranded DNA, the first step towards replication initiation, is lacking. Here, utilizing a Markov chain model that was created to address the directional nature of DNA unzipping and replication, we model the sequence dependence of local melting of double-stranded linear DNA segments. We show that generalized palindromic sequences with high nucleotide skews have a low kinetic barrier for local melting near melting temperatures. This allows for such sequences to function as potential replication origins. We support our claim with evidence for high-skew palindromic sequences within the replication origins of mitochondrial DNA, bacteria, archaea and plasmids.

Genome microsatellite signature analysis in Adenoviridae family of viruses

Simple sequence repeats (SSRs) are present across both coding & non-coding regions of the genomes of all organisms with diversity in incidence, complexity, and repetition. The present study is focused on Adenoviridae which are non-enveloped viruses consisting of linear double-stranded DNA genome. The members of Adenoviridae are known to cause respiratory illnesses like the common cold (cough, runny nose, mild fever), pneumonia (occasionally), keratoconjunctivitis (infection in the eye known as pink eye), croup and cystitis (inflammation of the bladder). Our investigation aims to extract and analyse SSRs from 68 Adenoviridae genomes. Virus genome sequences were retrieved from NCBI and SSRs extracted from MISA. ETE3 and iTOL were used for the phylogenetic tree construction, annotation and visualization. The genome length of Adenoviridae genomes ranged from 26163 bp to 45667 bp while GC content varied from 33.6 % to 66.9 %. Genome wide analysis revealed a total incidence of 9861 SSRs and 793 cSSRs. The minimum and maximum range of SSR incidence is 112 (A67) to 203 (A61) respectively. The most prevalent mono, di and tri-SSR motif is “A”, “GC/CG” and “GAG/CTC” comprised of 1177, 1859 and 201 occurrences respectively. About 78 % SSRs are present in the coding region in the studied genomes. In terms of protein specific distribution, DNA polymerase enzyme had the highest incidence of 485 SSRs. The presence of mono-SSRs in the A/T region is a marker for host determination and divergence. The average mono-SSRs present in A/T region is 67.14 % and it ranged from 16.22 % to 99.11 %. The high prevalence of mono-SSRs in the A/T region was associated with human and related species as hosts. Further, the clustering of viruses as per their hosts was observed in the phylogenetic tree suggesting the role of host in viral evolution. The presence of unique and conserved cSSRs as genome markers has also been highlighted.

A Novel Dhillonvirus Phage against Escherichia coli Bearing a Unique Gene of Intergeneric Origin.

Antibiotics resistance is expanding amongst pathogenic bacteria. Phage therapy is a revived concept for targeting bacteria with multiple antibiotics resistances. In the present study, we isolated and characterized a novel phage from hospital treatment plant input, using Escherichia coli (E. coli) as host bacterium. Phage lytic activity was detected by using soft agar assay. Whole-genome sequencing of the phage was performed by using Next-Generation Sequencing (NGS). Host range was determined using other species of bacteria and representative genogroups of E. coli. Whole-genome sequencing of the phage revealed that Escherichia phage Ioannina is a novel phage within the Dhillonvirus genus, but significantly diverged from other Dhillonviruses. Its genome is a 45,270 bp linear double-stranded DNA molecule that encodes 61 coding sequences (CDSs). The coding sequence of CDS28, a putative tail fiber protein, presented higher similarity to representatives of other phage families, signifying a possible recombination event. Escherichia phage Ioannina lytic activity was broad amongst the E. coli genogroups of clinical and environmental origin with multiple resistances. This phage may present in the future an important therapeutic tool against bacterial strains with multiple antibiotic resistances.

Characterization and Anti-Biofilm Activity of Lytic Enterococcus Phage vB_Efs8_KEN04 against Clinical Isolates of Multidrug-Resistant Enterococcus faecalis in Kenya.

Enterococcus faecalis (E. faecalis) is a growing cause of nosocomial and antibiotic-resistant infections. Treating drug-resistant E. faecalis requires novel approaches. The use of bacteriophages (phages) against multidrug-resistant (MDR) bacteria has recently garnered global attention. Biofilms play a vital role in E. faecalis pathogenesis as they enhance antibiotic resistance. Phages eliminate biofilms by producing lytic enzymes, including depolymerases. In this study, Enterococcus phage vB_Efs8_KEN04, isolated from a sewage treatment plant in Nairobi, Kenya, was tested against clinical strains of MDR E. faecalis. This phage had a broad host range against 100% (26/26) of MDR E. faecalis clinical isolates and cross-species activity against Enterococcus faecium. It was able to withstand acidic and alkaline conditions, from pH 3 to 11, as well as temperatures between -80 °C and 37 °C. It could inhibit and disrupt the biofilms of MDR E. faecalis. Its linear double-stranded DNA genome of 142,402 bp contains 238 coding sequences with a G + C content and coding gene density of 36.01% and 91.46%, respectively. Genomic analyses showed that phage vB_Efs8_KEN04 belongs to the genus Kochikohdavirus in the family Herelleviridae. It lacked antimicrobial resistance, virulence, and lysogeny genes, and its stability, broad host range, and cross-species lysis indicate strong potential for the treatment of Enterococcus infections.

Isolation and Characterization of Novel Bacteriophages to Target Carbapenem-Resistant Acinetobacter baumannii.

The spread of multidrug-resistant Acinetobacter baumannii in hospitals and nursing homes poses serious healthcare challenges. Therefore, we aimed to isolate and characterize lytic bacteriophages targeting carbapenem-resistant Acinetobacter baumannii (CRAB). Of the 21 isolated A. baumannii phages, 11 exhibited potent lytic activities against clinical isolates of CRAB. Based on host spectrum and RAPD-PCR results, 11 phages were categorized into four groups. Three phages (vB_AbaP_W8, vB_AbaSi_W9, and vB_AbaSt_W16) were further characterized owing to their antibacterial efficacy, morphology, and whole-genome sequence and were found to lyse 37.93%, 89.66%, and 37.93%, respectively, of the 29 tested CRAB isolates. The lytic spectrum of phages varied depending on the multilocus sequence type (MLST) of the CRAB isolates. The three phages contained linear double-stranded DNA genomes, with sizes of 41,326-166,741 bp and GC contents of 34.4-35.6%. Genome-wide phylogenetic analysis and single gene-based tree construction revealed no correlation among the three phages. Moreover, no genes were associated with lysogeny, antibiotic resistance, or bacterial toxins. Therefore, the three novel phages represent potential candidates for phage therapy against CRAB infections.

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.

Rapid and highly sensitive colorimetric LAMP assay and integrated device for visual detection of monkeypox virus

BackgroundThe monkeypox virus (MPXV) is a linear double-stranded DNA virus with a large genome that causes tens of thousands of infections and hundreds of deaths in at least 40 countries and regions worldwide. Therefore, timely and accurate diagnostic testing could be an important measure to prevent the ongoing spread of MPXV and widespread epidemics. ResultsHere, we designed multiple sets of primers for the target region of MPXV for loop-mediated isothermal amplification (LAMP) detection and identified the optimal primer set. Then, the specificity in fluorescent LAMP detection was verified using the plasmids containing the target gene, pseudovirus and other DNA/RNA viruses. We also evaluated the sensitivity of the colorimetric LAMP detection system using the plasmid and pseudovirus samples, respectively. Besides, we used monkeypox pseudovirus to simulate real samples for detection. Subsequent to the establishment and introduction of a magnetic beads (MBs)-based nucleic acid extraction technique, an integrated device was developed, characterized by rapidity, high sensitivity, and remarkable specificity. This portable system demonstrated a visual detection limit of 137 copies/mL, achieving sample-to-answer detection within 1 h. SignificanceThe device has the advantages of integration, simplicity, miniaturization, and visualization, which help promote the realization of accurate, rapid, portable, and low-cost testing. Meanwhile, this platform could facilitate efficient, cost-effective and easy-operable point-of-care testing (POCT) in diverse resource-limited settings in addition to the laboratory.

Biocontrol characteristics and application of phage SEP4 against multidrug-resistant Salmonella biofilm on food matrix

The emergence of antibiotic resistance and biofilm formation among Salmonella strains, especially in chicken meat, poses substantial risks to economic and public health. To mitigate these challenges, we explored interventions and biofilm inhibition strategies against multidrug-resistant serovars (B, C1, and D groups), by Salmonella phage SEP4, an isolate with broad host-spectrum. The morphological and genomic analyses classified it as a member of the Siphoviridae family with an icosahedral head of 124.56 ± 8.9 nm diameter and 66.28 ± 2.01 nm tail length, respectively. Phage SEP4 displayed robust survivability over a pH range of 3–10 and temperatures from 30 °C to 60 °C. Phage adsorption peaked at 73.20% in 15 min, with a burst size of 119 PFU/CFU at optimal MOI-1. Moreover, a linear double-stranded DNA genome of 41,828 bp, characterized by 49.84% GC content and putative 57 open reading frames (ORFs), and lacked antibiotic or virulence factor genes. Anti-Salmonella phage efficacy demonstrated a significant reduction in viable cell counts at 25 °C compared to 4 °C against tested MDR strains in food models. The bactericidal activity of phage SEP4 ranged from 14% to 46% and 25%–33.8% against host at MOI-1 and 100, while 22%–37% for other MDR strains. Simultaneously, SEP4 inhibited the growth of matured biofilms on lettuce leaves and chicken surfaces, achieving complete reduction within 4–6 h. SEM images confirmed the drastic destruction of cohesive biofilm architectures by phage treatment. The findings show that phage SEP4 has promising potential as a biocontrol agent, ensuring food safety by controlling MDR Salmonella contaminations and associated biofilms.

Isolation and characterization of Bacillus cereus virulent phage CA1

Infection of Bacillus cereus can lead to massive mortality of Chinese soft- shelled turtles (Pelodiscus sinensis). Phage has shown promising effects in the treatment of bacterial infections. A virulent phage CA1 was obtained from pond water of a P. sinensis aquaculture farm. The characteristics of CA1 and its protective effect on P. sinensis were analyzed, and whole genome were sequenced. The phage CA1, with a long tail and a hexagonal head could specifically lyse B. cereus. The CA1 latent phase was 40 min, and the rise phase was 40–160 min. The optimal growth temperature for CA1 was 45 °C, the optimal pH was 7.0, and the multiplicity of infection (MOI) was 0.1. Its whole genome was 45,902 bp linear double-stranded DNA molecule with an average GC of 38.30%, and contained 74 predicted open reading frames. After infection of P. sinensis with B. cereus (1.0 × 107 CFU/g), the protection rate was 54% at the phage MOI of 0.1. The above findings demonstrate that CA1 exhibits typical traits of phage-based disinfectants, suggesting its potential application in the prevention and management of B. cereus contamination within aquaculture environments.

Isolation and characterisation of a novel Silviavirus bacteriophage promising antimicrobial agent against methicillin-resistant Staphylococcus aureus infections

The increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) emphasises the urgent need for novel antimicrobial agents as alternatives to antibiotics. Bacteriophage therapy is one of the most promising antimicrobial strategies. Here, we isolated and comprehensively characterized a novel Staphylococcus phage, vB_SauM_VL10 (VL10), from urban sewage. The VL10 genome displays 141,746 bp of linear double-stranded DNA, containing 193 open reading frames and lacking tRNA, virulence, or antibiotic resistance genes. Phylogenetic analysis categorizes VL10 as a novel species within the Silviavirus genus, Twortvirinae subfamily. VL10 exhibits lytic behaviour characterized by efficient adsorption, a short latent period, and substantial burst size, with environmental stability. It demonstrates lytic activity against 79.06% of tested S. aureus strains, highlighting its species specificity. Additionally, VL10 effectively targets MRSA biofilms, reducing biomass and viable cells. In MRSA-infected G. mellonella larvae, VL10 enhances survival rates, supporting its potential for phage therapy applications. Moreover, the emergence of VL10-resistant S. aureus strains associated with fitness trade-offs, including reduced growth, biofilm formation, and virulence. Altogether, these findings emphasize VL10 as a promising candidate for developing therapeutic agents against MRSA infections, providing insights into phage biology and resistance dynamics.

Research progress on the effect of hepatitis B virus DNA integration on antiviral therapy

Hepatitis B virus (HBV) DNA integration occurs during the reverse transcription process of HBV replication, which develops in the early stages of HBV infection and accompanies the entire disease course. The integration of HBV DNA is detrimental to the attainment of clinical cure goals and also raises the risk of developing liver cancer. Theoretically, nucleos(t)ide analogs can reduce the synthesis of new double-stranded linear DNA, but there is no clearance function for hepatocytes that have already integrated HBV. Therefore, patients with serum HBV DNA-negative conversions still have the risk of developing liver cancer. As an immunomodulatory drug, interferon can not only inhibit viral replication but also inhibit or even eliminate existing clonally amplified hepatocytes carrying integrated HBV DNA fragments. However, there are currently few studies on the effects of nucleos(t)ide analogues and interferon therapy on HBV DNA integration. Thus, large-scale clinical studies are urgently needed for further clarification.

Characteristics and whole-genome analysis of a novel Pseudomonas syringae pv. tomato bacteriophage D6 isolated from a karst cave

Pseudomonas syringae is a gram-negative plant pathogen that infects plants such as tomato and poses a threat to global crop production. In this study, a novel lytic phage infecting P. syringae pv. tomato DC3000, named phage D6, was isolated and characterized from sediments in a karst cave. The latent period of phage D6 was found to be 60 min, with a burst size of 16 plaque-forming units per cell. Phage D6 was stable at temperatures between 4 and 40 °C but lost infectivity when heated to 70 °C. Its infectivity was unaffected at pH 6–10 but became inactivated at pH ≤ 5 or ≥ 12. The genome of phage D6 is a linear double-stranded DNA of 307,402 bp with a G + C content of 48.43%. There is a codon preference between phage D6 and its host, and the translation of phage D6 gene may not be entirely dependent on the tRNA library provided by the host. A total of 410 open reading frames (ORFs) and 14 tRNAs were predicted in its genome, with 92 ORFs encoding proteins with predicted functions. Phage D6 showed low genomic similarity to known phage genomes in the GenBank and Viral sequence databases. Genomic and phylogenetic analyses revealed that phage D6 is a novel phage. The tomato plants were first injected with phage D6, and subsequently with Pst DC3000, using the foliar spraying and root drenching inoculum approach. Results obtained after 14 days indicated that phage D6 inoculation decreased P. syringae-induced symptoms in tomato leaves and inhibited the pathogen’s growth in the leaves. The amount of Pst DC3000 was reduced by 150- and 263-fold, respectively. In conclusion, the lytic phage D6 identified in this study belongs to a novel phage within the Caudoviricetes class and has potential for use in biological control of plant diseases.

Isolation and characteristic of Bacillus cereus phage Z3 and its application in rice and milk

Bacillus cereus is a foodborne pathogen that widely exists in various food products. In this study, a new B. cereus phage, named Z3, was isolated from the soil and characterized. Transmission electron microscopy (TEM) observations revealed that Z3 had an icosahedral head and a retractable tail, belonging to myxovirus. The double-stranded linear DNA of Z3 was 159,116 bp in length with a CG% content of 39.96%. Genomic analysis indicated that Z3 represented a new species belonging to the Caeruleovirus genus. Z3 showed broad lytic spectrum, as it could lyse 10 out of 13 tested strains of B. cereus. The in vitro phage killing assay and the one-step growth curve showed that Z3 could effectively inhibit the bacteria growth within 10 h and it had a short latent period and fast multiplication speed. Besides, stability tests showed that Z3 was tolerant to a wide range of temperature (4 °C–55 °C) and pH levels (4–10), and was UV-resistant for 100 min. Furthermore, the applications of Z3 in rice and milk demonstrated its effective antimicrobial properties against B. cereus in food matrix. These findings suggested that Z3 may be a promising biocontrol agent against B. cereus in food industry.

Bacillus phage phi18-2 is a novel temperate virus with an unintegrated genome present in the cytoplasm of lysogenic cells as a linear phage-plasmid.

Bacillus subtilis is a Gram-positive bacterium that is widely used in fermentation and in the pharmaceutical industry. Phage contamination occasionally occurs in various fermentation processes and causes significant economic loss. Here, we report the isolation and characterization of a temperate B. subtilis phage, termed phi18-2, from spore powder manufactured in a fermentation plant. Transmission electron microscopy showed that phi18-2 has a symmetrical polyhedral head and a long noncontractile tail. Receptor analysis showed that phi18-2 recognizes wall teichoic acid (WTA) for infection. The phage virions have a linear double-stranded DNA genome of 64,467 bp with identical direct repeat sequences of 309 bp at each end of the genome. In lysogenic cells, the phage genome was found to be present in the cytoplasm without integration into the host cell chromosome, and possibly as a linear phage-plasmid with unmodified ends. Our data may provide some insight into the molecular basis of the unique lysogenic cycle of phage phi18-2.

Two Novel Bacteriophage Species Against Hybrid Intestinal Pathogenic Escherichia coli/Extraintestinal Pathogenic Escherichia coli Strains.

Colibacillosis caused by Escherichia coli is one of the main problems in the swine industry. In addition, the emergence of antimicrobial resistance and the combination of virulence genes among pathotypes have led to the emergence of more virulent pathogenic E. coli strains. Phage therapy has become a promising approach to address these issues. Virulence genes for intestinal pathogenic E. coli (IPEC) and extraintestinal pathogenic E. coli (ExPEC) were investigated in pathogenic E. coli isolated from pigs. In addition, two potential phages, vB_EcoM-RPN187 and vB_EcoM-RPN226, isolated in our previous study, were further characterized in this study. Both phages were lytic and were highly effective at 20-37°C. Interestingly, they infected the hybrid IPEC/ExPEC strains. vB_EcoM-RPN187 and vB_EcoM-RPN226 possess 167 kbp of linear double-stranded DNA without virulence or antibiotic resistance genes and may be classified as new phage species in the genera Mosigvirus and Tequatrovirus, respectively. Both phages could be promising candidates for phage therapy against pathogenic E. coli.

Isolation and characterization of coliphages from different water sources and their biocontrol application combined with electron beam irradiation for elimination of E. coli in domestic wastewater

BackgroundAntibiotic-resistant bacteria, including Escherichia coli (E. coli), are high-risk waterborne pathogens that pose a vital threat to the general public’s health. Therefore, this study aims to develop alternative and affordable treatment approaches. Coliphage treatment is an economically and environmentally sustainable method for eliminating pathogenic bacteria. A significant step toward improving germicidal effectiveness might be to combine coliphage with electron beam treatment.ResultsTwelve isolated E. coli were used as host bacteria. In addition, eleven coliphages were isolated and characterized to determine their suitable host range and lytic activities. Antibiotic resistance was tested to detect the most antimicrobial-resistant E. coli isolates. Results indicated that E. coli-2 and E. coli-10 were the most resistant bacterial isolates. Both somatic coliphage-3 (S3) and F-specific coliphage-3 (F3) were the most active lytic coliphages. Based on transmission electron microscope analysis, S3 was classified as a member of the Myoviridae family, while F3 belonged to the Leviviridae family. Genome types were detected; the S3 genome was a linear double-stranded DNA virus, while the F3 genome was a single-strand RNA virus. The adjustment of pH to 7 and temperature to 38 °C increased coliphage activity by 32.2% for S3 and 14% for F3. The optimum multiplicity of infection (MOI) for S3 was 1:1 and 2:1 for F3. From the one-step growth curve, both the latent periods of S3 and F3 were estimated to be 30 and 20 min, and the burst sizes showed 5.8 and 4.6 (PFU)/infected cells, respectively. The D10 values of the most two antimicrobial-resistant strains (E. coli-2 and E. coli-10) were calculated, showing nearly identical values (0.37 and 0.38 kGy), respectively. Both coliphages were used, either alone or in combination with electron beam irradiation (EBI), to eradicate the most multidrug-resistant E. coli in domestic wastewater. EBI reduced the counts of E. coli-2 and -10 by 59% and 65%, respectively. While the combination of coliphages and EBI completely eradicated these microbes.ConclusionsCombination of each individual coliphage and EBI decreased the growth of E. coli in domestic wastewater to an undetectable level.Graphical

A broad host phage, CP6, for combating multidrug-resistant Campylobacter prevalent in poultry meat

Campylobacter is a major cause of bacterial foodborne diarrhea worldwide. Consumption of raw or undercooked chicken meat contaminated with Campylobacter is the most common causative agent of human infections. Given the high prevalence of contamination in poultry meat and the recent rise of multi-drug-resistant (MDR) Campylobacter strains, an effective intervention method of reducing bird colonization is needed. In this study, the Campylobacter-specific lytic phage CP6 was isolated from chicken feces. Phage CP6 exhibited a broad host range against different MDR Campylobacter isolates (97.4% of strains were infected). Some biological characteristics were observed, such as a good pH (3-9) stability and moderate temperature tolerance (<50 ℃). The complete genome sequence revealed a linear double-stranded DNA (178,350 bp, group II Campylobacter phage) with 27.51% GC content, including 209 predicted open reading frames, among which only 54 were annotated with known functions. Phylogenetic analysis of the phage major capsid protein demonstrated that phage CP6 was closely related to Campylobacter phage CPt10, CP21, CP20, IBB35, and CP220. CP6 phage exerted good antimicrobial effects on MDR Campylobacter in vitro culture and reduced CFUs of the host cells by up to 1-log compared with the control in artificially contaminated chicken breast meat. Our findings suggested the potential of CP6 phage as a promising antimicrobial agent for combating MDR Campylobacter in food processing.