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EDITORIAL
Bacteriophages, revitalized after 100 years in the shadow of antibiotics [pubmed]
Hongping Wei
In this issue, readers will not only find that bacteriophage research is a booming field but also learn about the diverse applications currently being explored for bacteriophages. The biggest driving force behind these applications is the serious threat of bacterial antibiotic resistance that is emerging in the current era.
REVIEWS
Bacteriophage secondary infection [pubmed]
Stephen T Abedon
Phages are credited with having been first described in what we now, officially, are commemorating as the 100th. anniversary of their discovery. Those one-hundred years of phage history have not been lacking in excitement, controversy, and occasional convolution. One such complication is the concept of secondary infection, which can take on multiple forms with myriad consequences. The terms secondary infection and secondary adsorption, for example, can be used almost synonymously to describe virion interaction with already phage-infected bacteria, and which can result in what are described as superinfection exclusion or superinfection immunity. The phrase secondary infection also may be used equivalently to superinfection or coinfection, with each of these terms borrowed from medical microbiology, and can result in genetic exchange between phages, phage-on-phage parasitism, and various partial reductions in phage productivity that have been termed mutual exclusion, partial exclusion, or the depressor effect. Alternatively, and drawing from epidemiology, secondary infection has been used to describe phage population growth as that can occur during active phage therapy as well as upon phage contamination of industrial ferments. Here primary infections represent initial bacterial population exposure to phages while consequent phage replication can lead to additional, that is, secondary infections of what otherwise are not yet phage-infected bacteria. Here I explore the varying meanings and resultant ambiguity that has been associated with the term secondary infection. I suggest in particular that secondary infection, as distinctly different phenomena, can in multiple ways infl uence the success of phage-mediated biocontrol of bacteria, also known as, phage therapy.
Bacteriophage therapy against Enterobacteriaceae [pubmed]
Youqiang Xu, Yong Liu, Yang Liu, Jiangsen Pei, Su Yao, Chi Cheng
The Enterobacteriaceae are a class of gram-negative facultative anaerobic rods, which can cause a variety of diseases, such as bacteremia, septic arthritis, endocarditis, osteomyelitis, lower respiratory tract infections, skin and soft-tissue infections, urinary tract infections, intra-abdominal infections and ophthalmic infections, in humans, poultry, animals and fi sh. Disease caused by Enterobacteriaceae cause the deaths of millions of people every year, resulting in enormous economic loss. Drug treatment is a useful and effi cient way to control Enterobacteriaceae infections. However, with the abuse of antibiotics, drug resistance has been found in growing number of Enterobacteriaceae infections and, as such, there is an urgent need to find new methods of control. Bacteriophage therapy is an efficient alternative to antibiotics as it employs a different antibacterial mechanism. This paper summarizes the history of bacteriophage therapy, its bacterial lytic mechanisms, and the studies that have focused on Enterobacteriaceae and bacteriophage therapy.
Survival and proliferation of the lysogenic bacteriophage CTXΦ in Vibrio cholerae [pubmed]
Fenxia Fan, Biao Kan
The lysogenic phage CTXΦ of Vibrio cholerae can transfer the cholera toxin gene both horizontally (inter-strain) and vertically (cell proliferation). Due to its diversity in form and species, the complexity of regulatory mechanisms, and the important role of the infection mechanism in the production of new virulent strains of V. cholerae, the study of the lysogenic phage CTXΦ has attracted much attention. Based on the progress of current research, the genomic features and their arrangement, the host-dependent regulatory mechanisms of CTXΦ phage survival, proliferation and propagation were reviewed to further understand the phage’s role in the evolutionary and epidemiological mechanisms of V. cholerae.
Phage lytic enzymes: a history [pubmed]
David Trudil
There are many recent studies regarding the efficacy of bacteriophage-related lytic enzymes: the enzymes of ‘bacteria-eaters’ or viruses that infect bacteria. By degrading the cell wall of the targeted bacteria, these lytic enzymes have been shown to efficiently lyse Gram-positive bacteria without affecting normal fl ora and non-related bacteria. Recent studies have suggested approaches for lysing Gram-negative bacteria as well (Briersa Y, et al., 2014). These enzymes include: phage-lysozyme, endolysin, lysozyme, lysin, phage lysin, phage lytic enzymes, phageassociated enzymes, enzybiotics, muralysin, muramidase, virolysin and designations such as Ply, PAE and others. Bacteriophages are viruses that kill bacteria, do not contribute to antimicrobial resistance, are easy to develop, inexpensive to manufacture and safe for humans, animals and the environment. The current focus on lytic enzymes has been on their use as anti-infectives in humans and more recently in agricultural research models. The initial translational application of lytic enzymes, however, was not associated with treating or preventing a specifi c disease but rather as an extraction method to be incorporated in a rapid bacterial detection assay (Bernstein D, 1997).The current review traces the translational history of phage lytic enzymes-from their initial discovery in 1986 for the rapid detection of group A streptococcus in clinical specimens to evolving applications in the detection and prevention of disease in humans and in agriculture.
RESEARCH ARTICLES
Selection of phages and conditions for the safe phage therapy against Pseudomonas aeruginosa infections [pubmed]
Victor Krylov, Olga Shaburova, Elena Pleteneva, Sergey Krylov, Alla Kaplan, Maria Burkaltseva, Olga Polygach, Elena Chesnokova
The emergence of multidrug-resistant bacterial pathogens forced us to consider the phage therapy as one of the possible alternative approaches to treatment. The purpose of this paper is to consider the conditions for the safe, long-term use of phage therapy against various infections caused by Pseudomonas aeruginosa. We describe the selection of the most suitable phages, their most effective combinations and some approaches for the rapid recognition of phages unsuitable for use in therapy. The benefi ts and disadvantages of the various different approaches to the preparation of phage mixtures are considered, together with the specifi c conditions that are required for the safe application of phage therapy in general hospitals and the possibilities for the development of personalized phage therapy.
Molecular dissection of phage lysin PlySs2: integrity of the catalytic and cell wall binding domains is essential for its broad lytic activity [pubmed]
Yanling Huang, Hang Yang, Junping Yu, Hongping Wei
The novel phage lysin PlySs2, is reported to be highly active against various bacteria, including staphylococci, streptococci and Listeria. However, the molecular mechanisms underlying its broad lytic spectrum remain to be established. In the present study, the lytic activity of the catalytic domain (CD, PlySc) and binding specificity of the cell wall binding domain (CBD, PlySb) of PlySs2 were examined. Our results showed that PlySc alone maintains very limited lytic activity. Enhanced green fluorescent protein (EGFP)-fused PlySb displayed high binding affinity to the streptococcal strains tested, including S. suis, S. dysgalactiae, and S. agalactiae, but not staphylococci, supporting its utility as a good CBD donor for streptococcal-targeted lysin engineering. EGFP-fused intact PlySs2 similarly displayed high affinity for streptococci, but not staphylococci. Notably, four truncated PlySb fragments showed no binding capacity. These fi ndings collectively indicate that integrity of the PlySc and PlySb domains is an essential determinant of the broad lytic activity of PlySs2.
Isolation and characterization of glacier VMY22, a novel lytic cold-active bacteriophage of Bacillus cereus [pubmed]
Xiuling Ji, Chunjing Zhang, Yuan Fang, Qi Zhang, Lianbing Lin, Bing Tang, Yunlin Wei
As a unique ecological system with low temperature and low nutrient levels, glaciers are considered a “living fossil” for the research of evolution. In this work, a lytic cold-active bacteriophage designated VMY22 against Bacillus cereus MYB41-22 was isolated from Mingyong Glacier in China, and its characteristics were studied. Electron microscopy revealed that VMY22 has an icosahedral head (59.2 nm in length, 31.9 nm in width) and a tail (43.2 nm in length). Bacteriophage VMY22 was classifi ed as a Podoviridae with an approximate genome size of 18 to 20 kb. A one-step growth curve revealed that the latent and the burst periods were 70 and 70 min, respectively, with an average burst size of 78 bacteriophage particles per infected cell. The pH and thermal stability of bacteriophage VMY22 were also investigated. The maximum stability of the bacteriophage was observed to be at pH 8.0 and it was comparatively stable at pH 5.0-9.0. As VMY22 is a cold-active bacteriophage with low production temperature, its characterization and the relationship between MYB41-22 and Bacillus cereus bacteriophage deserve further study.
LETTERS
Variation of resistance and infectivity between Pseudomonas fluorescens SBW25 and bacteriophage Ф2 and its therapeutic implications [pubmed]
Hanchen Chen, Guohua Chen
Studies of the coevolutionary dynamics between Pseudomonas fluorescens SBW25 and bacteriophage Ф can explore host resistance and parasite infectivity with applications in the ecological and therapeutic fields.Coevolutionary dynamics determine the efficacy of phage-based therapy. In the study described here, bacterial resistance and phage infectivity fluctuated with culturetime, perhaps resulting from random mutation and temporaladaptation, which reminds us of the necessity toconsider evolutionary mechanisms when applying phageto treat bacterial infections.
A novel transposable Mu-like prophage in Bacillus alcalophilus CGMCC 1.3604 (ATCC 27647) [pubmed]
Junjie Yang, Yimeng Kong, Xuan Li, Sheng Yang
In this letter, we provide evidence for the first transposable prophage BalMu-1 in Bacilli. The transposable prophage (BalMu-1, Genbank No. KP063902 and KP063903) was identified in Bacillus alcalophilus CGMCC 1.3604(ATCC 27647) through high throughput genome sequencing and PCR-dideoxy chain-termination(Sanger) sequencing.
Isolation and characterization of a lytic bacteriophage φKp-lyy15 of Klebsiella pneumoniae [pubmed]
Yinyin Lu, Hongyan Shi, Zhe Zhang, Fang Han, Jinghua Li, Yanbo Sun
In conclusion, the lytic bacteriophage φKp-lyy belonging to the Siphoviridae family specific for K. pneumonia was isolated and characterized. φKp-lyy displayed a short latent period, stability to a wide pH rang, high thermal resistance, and lytic activity toward a relatively broad range of K. pneumonia isolates. Thus, phage φKplyy should be considered as a candidate for inclusion in phage cocktails to control K. pneumoniae-associated nosocomial infections.
Expression and purification of recombinant lyase gp17 from the LSB-1 phage in Escherichia coli [pubmed]
Taiwu Wang, Hui Lin, Lu Zhang, Guorong Huang, Long Wu, Lei Yu, Hongyan Xiong
In this study, we successfully expressed and purified the recombinant gp17 protein from the LSB-1 phage and also confirmed its bacteriostatic effect. Assays also showed that the recombinant enzyme was soluble and had signifi cant lyase effects on the host bacterium, EIEC8401. A preliminary study demonstrated that the enzyme did not have inhibitory effects on other strains (unpublished data), which might indicate that the exclusive antibacterial effect of gp17 on EIEC8401 could have a special significance in practical application in bacterial therapy.
T4-like coliphage φKAZ14 virulent to pathogenic and extended spectrum β-lactamase-producing Escherichia coli of poultry origin [pubmed]
Kaikabo Adamu Ahmad, Abdulkarim Sabo Mohanmmed, Faridah Abas, Sieo Chin Chin
The aim of the present study was to isolate bacteriophages for the pre-harvest biocontrol of APEC 01 and ESBL-producing E. coli in chicken, in order to mitigate the risk of these pathogens to the food chain. Isolation and characterization of the T4-like coliphage KAZ14, lytic to APEC 01 and ESBL-producing E. coli, is reported and discussed.
Isolation and complete genome sequence of a novel virulent mycobacteriophage, CASbig [pubmed]
Tieshan Teng, Junping Yu, Hang Yang, Hongping Wei
In this study, we report the isolation and the complete genome of a novel mycobacteriophage, CASbig, which has an icosahedral head (diameter 50 ± 2 nm) and a long, non-contractile tail (length 160 ± 5 nm) with transverse striations, ending in a small knob. The length of the tail includes the middle of the baseplate, and the head measurements were taken between opposite apices. These characteristics indicate that the phage belongs to the family Siphoviridae morphotypes.
INSIGHT
Experience of the Eliava Institute in bacteriophage therapy [pubmed]
Mzia Kutateladze
The rapid propagation of multidrug resistant bacterial strains is leading to renewed interest in bacteriophage therapy. With challenges in the treatment of bacterial infections, it is essential for people worldwide to understand how alternative approaches, such as bacteriophages, could be used to combat antibiotic resistant bacteria. The Eliava Institute of Bacteriophages, Microbiology and Virology (Tbilisi, Georgia) is arguably the most famous institution in the world focused on the isolation, study, and selection of phages active against a variety of bacterial pathogens.
A Smaller Flea 