Explore the vast range of titles available.

Bacteriophages are the main vehicle for gene swapping in bacteria, notoriously of pathogenicity islands and antibiotic resistance genes. Chen et al. noticed that the Staphylococcus aureus prophages do not excise from their host's genome until very late in their life cycles (see the Perspective by Davidson). Thus, the phage DNA is amplified while embedded in the bacterial chromosome. The resulting concatemers are processively packed into virus capsules while still integrated in the host chromosome. Each virion is only set loose when the capsule has reached physical capacity—a process called “headful” packaging. In situ amplification maximizes viral replication, and the headful mechanism means adjacent bacterial-host DNA also gets grabbed to fill the capsule. This process ensures that host genes are transmitted along with the phage. Science , this issue p. 207 ; see also p. 152 Staphylococcus aureus phages amplify and package while chromosomally integrated such that host DNA becomes incorporated in the virus particle. Genetic transduction is a major evolutionary force that underlies bacterial adaptation. Here we report that the temperate bacteriophages of Staphylococcus aureus engage in a distinct form of transduction we term lateral transduction. Staphylococcal prophages do not follow the previously described excision-replication-packaging pathway but instead excise late in their lytic program. Here, DNA packaging initiates in situ from integrated prophages, and large metameric spans including several hundred kilobases of the S. aureus genome are packaged in phage heads at very high frequency. In situ replication before DNA packaging creates multiple prophage genomes so that lateral-transducing particles form during normal phage maturation, transforming parts of the S. aureus chromosome into hypermobile regions of gene transfer.

Bacteriophages, viruses that only kill specific bacteria, are receiving substantial attention as nontraditional antibacterial agents that may help alleviate the growing antibiotic resistance problem in medicine. We describe the design and preclinical development of AB-SA01, a fixed-composition bacteriophage product intended to treat Staphylococcus aureus infections. AB-SA01 contains three naturally occurring, obligately lytic myoviruses related to Staphylococcus phage K. AB-SA01 component phages have been sequenced and contain no identifiable bacterial virulence or antibiotic resistance genes. In vitro, AB-SA01 killed 94.5% of 401 clinical Staphylococcus aureus isolates, including methicillin-resistant and vancomycin-intermediate ones for a total of 95% of the 205 known multidrug-resistant isolates. The spontaneous frequency of resistance to AB-SA01 was ≤3 × 10−9, and resistance emerging to one component phage could be complemented by the activity of another component phage. In both neutropenic and immunocompetent mouse models of acute pneumonia, AB-SA01 reduced lung S. aureus populations equivalently to vancomycin. Overall, the inherent characteristics of AB-SA01 component phages meet regulatory and generally accepted criteria for human use, and the preclinical data presented here have supported production under good manufacturing practices and phase 1 clinical studies with AB-SA01.

Past work has seen over-representation of Staphylococcus aureus clinical isolates in genome and biology studies on staphylococci. Here, we show by a selective plating analysis of municipal wastewater that independent isolates representing seven other species of Staphylococcus were recovered ( S. cohnii , S. equorum , S. lentus , S. nepalensis , S. sciuri, S. shinii, and S. xylosus ), as readily identified in the samples. Genome sequence analysis revealed some species-specific antibiotic resistance profiles across the strains, and a bacteriophage was isolated that had a cross-species host range. Using this broad biological approach to analyze staphylococci has identified a phage with a broad killing range, and this phage is morphologically distinct from the three known types of tailed phages.

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) infection is one of the global healthcare concerns. Here, we report the phenotypic and genotypic characterization of a novel multi-host Staphylococcus phage RuSa1, isolated from wastewater samples derived from a spotted sambar deer ( Rusa unicolor ) enclosure located at Mangalore, India. Clinical MRSA strains ( n  = 18) susceptible to RuSa1 were genetically and phenotypically diverse as determined by DNA fingerprinting and in vitro culture assays. RuSa1 displayed a latent period and burst size of 10 min and 50 PFU, respectively, and exhibited efficient biofilm removal activities against S. aureus ATCC BAA-44. The phage exhibited moderate UV stability (3 min) and high titre at 4–37 °C and pH 5‒9. RuSa1 possessed a linear double-stranded genomic DNA with a length of 140 kb. The genome contained 30.18% GC composition and shared 82.0‒94.9% sequence similarity with eleven authentic species of Kayvirus recognized by the International Committee on Taxonomy of Viruses based on VIRIDIC analysis. RuSa1 established distinct phyletic lineage in the maximum likelihood phylogenetic analysis of DNA encoding structural proteins and lacked genes that confer lysogeny. Based on the genotypic, phylogenetic and phenotypic data, RuSa1 is proposed to be a lytic phage and a new species of Kayvirus with a potential therapeutic ability against staphylococcal infections.

Bovine mastitis is a considerable challenge within the dairy industry, causing significant financial losses and threatening public health. The increased occurrence of methicillin-resistant Staphylococcus aureus (MRSA) has provoked difficulties in managing bovine mastitis. Bacteriophage therapy presents a novel treatment strategy to combat MRSA infections, emerging as a possible substitute for antibiotics. This study evaluated the therapeutic potency of a novel bacteriophage cocktail against MRSA mastitis. Two new bacteriophages (vB_SauR_SW21 and vB_SauR_SW25) with potent lytic activity against MRSA were isolated and characterized. The one-step growth curve displayed a rapid latent period (20–35 min) and substantial burst size (418 and 316 PFU/ cell). In silico analyses have confirmed the absence of antimicrobial resistance or virulence factor-encoding genes within their genomes. According to the results, combining these phages augmented their host range and virulence. The phage cocktail significantly reduced bacterial burden in a BALB/c mastitis model, demonstrating efficacy comparable to antibiotic treatment. Moreover, its administration led to decreased concentrations of IL-1β and TNF-α compared to the negative control group. The bacteriophage cocktail (SW21-SW25) exhibits a promising profile for therapeutic applications and may represent a novel substitute to antibiotics for managing MRSA bovine mastitis.

Methicillin-resistant Staphylococcus aureus (MRSA), a leading cause of chronic and post-surgical wound infections, is a hard-to-treat pathogen. In this study, we isolated and characterized a lytic MRSA bacteriophage, vB_SauM-MUHD-1, and evaluated its therapeutic potential in a murine wound infection model. Among 107 clinical wound samples, MRSA was reported in 48.6% of cases. Phage vB_SauM-MUHD-1, isolated from sewage, demonstrated lytic activity against 70.6% of the tested MRSA isolates. The phage exhibited efficient replication kinetics and remained stable under physiologically relevant conditions. Whole-genome sequencing identified a ~ 134 kb dsDNA genome (~ 30.45% GC) lacking detectable lysogeny-associated, virulence, or antimicrobial-resistance genes. In a BALB/c excisional wound model infected with MRSA, topical phage treatment significantly reduced bacterial burden, accelerated wound closure, and improved clinical severity scores compared to untreated controls, performing comparably to phage-linezolid combination therapy and outperforming linezolid monotherapy in bacterial clearance. These findings support that our phage vB_SauM-MUHD-1 has potential for treating MRSA-infected wounds and should be further investigated for efficacy in more challenging chronic or biofilm-rich wound environments. Key Points • This study provides a newly kayvirus, strictly lytic anti-MRSA phage vB_SauM-MUHD-1. • Phage exhibited favorable replication kinetics, physical stability and genomic safety. • Topical phage therapy reduced bacterial burden and accelerated wound healing.

A novel lytic phage with a broad host range was isolated from pig faeces and the complete genome was subsequently sequenced. The phage was found to lyse Staphylococcus hyicus , S. pseudintermedius , S. schleiferi and S. warneri , generating approximately 27 PFU per infected S. hyicus cell. The phage has an isometric head of 42 ± 2 nm in diameter and a noncontractile tail of 114 ± 9 nm long. The genome is 53,660 bp in size and consists of 79 predicted ORFs and one tRNA Arg gene. The phage has been classified within the Caudoviricetes, specifically the Chaseviridae family. Its broad host range and absence of harmful genes make it suitable for use in phage therapy. In addition, a novel temperate phage was discovered that was spontaneously released from a S. hyicus isolate Pel11 from a pig with exudative epidermitis. This novel temperate phage differs from the known temperate phages in S. hyicus strains NCTC10350, MM2101 or 83/7-1B, representing a novel pathogenicity element in the S. hyicus genome.

Livestock-associated Staphylococcus aureus ST398 is a highly pathogenic species that causes infections in a wide variety of animals, including humans. The bacteriophage (phage) vB_SauS_S1 was isolated originally using a ST398 strain as its “isolating host”, then the spot tests showed it was able to infect 73.33% (22/30) ST398 isolates. Phage S1 was assigned as a temperate phage based on genome analysis and phenotypic validation. Phylogenetic analysis showed that S1 was closely related to temperate phages tp310-2 and SA137ruMSSAST121PVL. Following infection of ST398 by phage S1, the lysogenic strain showed enhanced biofilm forming ability compared to the wildtype strain, and the invasion rate of MAC-T cells increased by 10.39%. The minimum inhibitory concentration showed that phage S1 did not change the antibiotic sensitivity of the lysogen strain, and the virulence of the lysogen strain did not change significantly in the injection models of Galleria mellonella ( G. mellonella ) and mice. The lysogen demonstrated superinfection immunity and reduced sensitivity to virulent phage infection. Thus, this study contributes to understanding the co-evolutionary relationships between temperate phages and the multi-host zoonotic pathogen S. aureus ST398.

Lytic phages are potential therapeutic options, based on their ability to lyse bacteria in vitro. Although many infection-types for which phage therapy is being considered involve biofilms, in vitro anti-biofilm activity of phage is poorly defined, in part due to a lack of standardized methods for assessment. Here, phages SaMD07phi1 and SaRBI05030phi5 were evaluated against Staphylococcus aureus SaMD07 and SaRBI05030, respectively, in biofilms formed in 96-well plates and on glass beads, and planktonically, in TSB and PBS, with endpoints including by CFUs and Biolog Omnilog hold times. The bead biofilm assay in TSB using the Omnilog (BBTO) was employed to test eight staphylococcal phages against S. aureus , Staphylococcus epidermidis , and Staphylococcus lugdunensis from periprosthetic joint infection. Biofilms on beads in TSB showed better eradication than in microtiter wells, with no significant changes with PBS in either format. CFU counts and Omnilog units correlated linearly through 8 h of testing. In the bead assay, CFU counts showed that phage SaMD07phi1 eliminated growth at 4 h, while SaRBI05030phi5 achieved a ~ 3-log reduction at 8 h; with Omnilog hold times of 37 and 28 h, respectively. Diverse activity and good reproducibility of the BBTO was observed among 8 phages, with SaMD07phi1 showing the highest activity. In conclusion the BBTO is a promising potential method for biofilm susceptibility testing.

The emergence of life-threatening methicillin-resistant Staphylococcus aureus (MRSA) has led to increased interest in the use of bacteriophages as an alternative therapy to antibiotics. The success of phage therapy is greatly dependent on the selected phage possessing a wide host range. This study describes phage ɸMR003 isolated from sewage influent at a municipal wastewater treatment plant in Tokyo, Japan. ɸMR003 could infect 97% of 104 healthcare- and community-associated MRSA strains tested, compared with 73% for phage ɸSA012, which has a broad host range against bovine mastitis S. aureus . Genome analysis revealed that ɸMR003 belongs to the genus Silviavirus which has not been studied extensively. ɸMR003 recognizes and binds to wall teichoic acid (WTA) of S. aureus during infection. In silico comparisons of the genomes of ɸMR003 and ɸSA012 revealed that ORF117 and ORF119 of ɸMR003 are homologous to the putative receptor-binding proteins ORF103 and ORF105 of ɸSA012, with amino acid similarities of 75% and 72%, respectively. ORF104, which is an N -acetylglucosaminidase found in the ɸMR003 tail, may facilitate phage's infection onto the WTA-null S. aureus RN4220. The differences in tail and baseplate proteins may be key contributing factors to the different host specificities of ɸMR003 and ɸSA012. ɸMR003 showed strong adsorptivity, but not infectivity, against S. aureus SA003, which may be influenced by the bacterium’s restriction modification system. This study expands our knowledge of the genomic diversity and host specificity of Silviavirus , which is a potential phage therapy candidate for MRSA infections.