Yuliya N. Kozlova

Staphylococcus aureus is an ESKAPE pathogen, defined by its ability to evade antibacterial treatment, and together with S. epidermidis is a leading Gram-positive cause of wound infection. The emergence of methicillin- and vancomycin-resistant strains further limits conventional antibiotic treatment. The staphylococcal endolysin LysSte134_1 was produced recombinantly, its proper folding confirmed by zymography, and its lytic activity demonstrated against planktonic cultures of both S. aureus and S. epidermidis. The combination of LysSte134_1 with 10% 1,3-propanediol and Zn²⁺ increased CFU reduction in both species relative to LysSte134_1 with Zn²⁺ alone. In a murine wound model, topical application of LysSte134_1 significantly reduced the bacterial burden in wound tissue, achieving a 2–3-log reduction in MRSA and below the detection limit for S. epidermidis. Treatment was accompanied by normalization of peripheral leukocyte counts and a shift in the serum cytokine profile from a sustained pro-inflammatory state with elevated IL-6, IL-17 and IL-10 toward levels comparable to non-infected controls. These results suggest the potential utility of LysSte134_1 as a component of topical antibacterial formulations and support further investigation in models of staphylococcal wound infection.

The global proliferation of multidrug-resistant Pseudomonas aeruginosa stimulates the search for alternatives to conventional therapy. This study developed human serum albumin (HSA)-based hydrogels for the delivery of bacteriophage PA57. Matrices were fabricated via combined thermal- and ethanol-induced gelation. The release kinetic was dependent on protein concentration: 20% (w/v) HSA provided sustained release over 48 h, whereas 10–15% (w/v) HSA exhibited burst release effects. Combined systems effectively suppressed P. aeruginosa growth in vitro during the early and middle stages of incubation, maintaining low culture optical density for up to 28 h. Although late-stage bacterial regrowth was observed, the final bacterial load remained significantly lower than in the control. Furthermore, cytocompatibility assays with HaCaT keratinocytes and MRC-5 fibroblasts demonstrated high cell viability, confirming the safety of the hydrogel matrix for wound healing applications. These results demonstrate the promise of HSA-based hydrogels as a platform for localized phage therapy of infected wounds.

Multidrug resistance (MDR) is a global problem for the healthcare system, complicating the therapy of bacterial infections. It is noted that patients infected with MDR strains often require prolonged hospitalization, have a high risk of mortality, and remain vulnerable to reinfection after recovery. In this study, recombinant phage-encoded depolymerase DepKP144 was produced using the Escherichia coli expression system and purified. The depolymerase DepKP144 protein was able to reduce viable bacterial counts following capsule degradation in 95% of the tested strains of type K1 and 85% of the tested strains of type K2 Klebsiella pneumoniae. The depolymerase DepKP144 was active against K. pneumoniae K1-type and K2-type planktonic cells and destroyed the biofilms formed by clinical MDR strains of K. pneumoniae. In in vivo experiments, DepKP144 at a dose of 180 μg/mouse resulted in a 50% survival of the mice infected with K2-type K. pneumoniae and in a 17% survival of the mice infected with K1-type K. pneumoniae. This depolymerase is promising for further development of prevention and therapeutic candidates against MDR K. pneumoniae.

Considering the therapeutic potential of the Proteus mirabilis PM16 podophage, the interaction between PM16, its host strain, and the mouse immune system was investigated. We evaluated how pre-existing humoral immunity to PM16 influences the immune response against P. mirabilis and the neutralization of the phage itself. Balb/c mice were divided into three groups and immunized two times with (1) 0.9% NaCl, (2) adjuvants, or (3) a mixture of PM16 and an adjuvant. Then, each group was subdivided into three subgroups: mock infection, infection with P. mirabilis, and infection with P. mirabilis followed by model phage therapy with PM16. The obtained results demonstrated that pre-immunization with PM16 enhanced the anti-P. mirabilis IgG antibody response upon bacterial challenge, indicating that the phage potentiates antibacterial immunity. In addition, pre-immunization elicited a significant anti-PM16 antibody response that resulted in in vitro neutralization of phage lytic activity. However, phage-neutralizing antibodies neither decreased the efficacy of phage therapy nor influenced bacteria-specific immune response. Thus, while PM16 can boost the host’s immune response against its bacterial host, the resulting humoral immunity also drives phage clearance through both direct and bacteria-mediated neutralization pathways, revealing a complex immunopharmacological relationship central to phage therapy.

Klebsiella pneumoniae, a member of the ESKAPEE group of priority pathogens, has become one of the most challenging bacterial pathogens in modern clinical practice, largely due to its multidrug resistance and the immune-evasive effect of its capsular polysaccharide (CPS). Phage-encoded depolymerases, which selectively degrade the capsular polysaccharide, have emerged as promising antimicrobial agents capable of restoring bacterial susceptibility to both immune clearance and phage infection. The fragment corresponding to the C-terminal region of a putative depolymerase of bacteriophage KlebP_144, namely DepKP144ΔC, was cloned, expressed in E. coli, and purified using immobilized metal affinity chromatography. DepKP144ΔC displays an enzymatic activity against capsular polysaccharides of 100% K1 capsular-type strains and 85% K2 capsular-type strains, including classical and hypervirulent isolates. It was demonstrated that this protein is capable of inhibiting K. pneumoniae biofilm formation, but it is unable to disrupt mature biofilms. In vivo experiments using a murine K. pneumoniae infection model further confirmed its therapeutic potential: treatment with DepKP144ΔC improved survival rate in mice infected with K2-type K. pneumoniae, indicating significant attenuation of bacterial virulence. Therefore, these results demonstrate the potential role of the C-terminal domain of the bacteriophage KP144 tail-fiber protein in phage entry and show that its carbohydrate-recognition motifs possess enzymatic activity against the Klebsiella capsular polysaccharides.

Bacteriophages, traditionally viewed solely as antibacterial agents, are increasingly being studied for their immunomodulatory properties. In this study, we demonstrate that PM16 phage therapy not only effectively controls subcutaneous Proteus mirabilis infection in mice, but also induces long-term specific humoral immunity against subsequent reinfection. This immunomodulatory effect was dose-dependent. In vitro, PM16 directly activates macrophages, leading to increased production of proinflammatory cytokines (tumor necrosis factor-α and interleukin-1β) and inducible nitric oxide synthase, and enhances macrophage bactericidal activity against P. mirabilis. We assume that the enhancement of the adaptive immune response is mediated not by the phage acting as a classical antigenic adjuvant, but by its ability to prime innate immune cells, specifically macrophages. This priming leads to more efficient bacterial clearance, antigen presentation, and the formation of protective immunological memory.

Coagulase-negative staphylococci, including Staphylococcus capitis and Staphylococcus caprae can be causative agents of various nosocomial infections. A novel Staphylococcus phage StaphC_127, active against both S. caprae and S. capitis, was isolated from the surface of a spoiled tomato. All susceptible Staphylococcus strains were isolated from clinical samples collected from the irritated skin surface. StaphC_127 has low lytic activity against the host strain S. caprae CEMTC 1849 and is possibly a temperate phage as its genome encodes the repressor, antirepressor, and site-specific DNA recombinase. In addition, the StaphC_127 genome was detected in bacteriophage insensitive mutants (BIMs) obtained from at least two sensitive S. caprae strains after StaphC_127 infection. Notably, the StaphC_127 genome encodes the Tad2 protein belonging to the Tad2 phage protein family, which inhibits the Thoeris antiphage defense system. The obtained results of the genome analysis indicated that StaphC_127 is the first member of a new supposed Staphcevirus genus that, in turn, is part of a putative Estebevirinae subfamily containing phages capable of infecting coagulase-negative staphylococci.

The problem of spreading harmful infections through contaminated surfaces has become more acute during the recent coronavirus pandemic. The design of self-cleaning materials, which can continuously decompose biological contaminants, is an urgent task for environmental protection and human health care. In this study, the surface of blended cotton/polyester fabric was functionalized with N-doped TiO₂ (TiO₂-N) nanoparticles using titanium(IV) isopropoxide as a binder to form durable photoactive coating and additionally decorated with Cu species to promote its self-cleaning properties. The photocatalytic ability of the material with photoactive coating was investigated in oxidation of acetone vapor, degradation of deoxyribonucleic acid (DNA) fragments of various lengths, and inactivation of PA136 bacteriophage virus and Candida albicans fungi under visible light and ultraviolet A (UVA) radiation. The kinetic aspects of inactivation and degradation processes were studied using the methods of infrared (IR) spectroscopy, polymerase chain reaction (PCR), double-layer plaque assay, and ten-fold dilution. The results of experiments showed that the textile fabric modified with TiO₂-N photocatalyst exhibited photoinduced self-cleaning properties and provided efficient degradation of all studied contaminants under exposure to both UVA and visible light. Additional modification of the material with Cu species substantially improved its self-cleaning properties, even in the absence of light.

Three novel Aeromonas phages vB_AerVS_332-Yuliya, vB_AerVM_332-Vera, and vB_AerVM_332-Igor and their host Aeromonas veronii CEMTC7594 were found in the same water + sediments sample collected in a freshwater pond. Complete genome sequencing indicated that vB_AerVS_332-Yuliya (43,584 bp) is a siphophage, whereas vB_AerVM_332-Vera (294,685 bp) and vB_AerVM_332-Igor (237,907 bp) are giant phages. The host strain can grow at temperatures from 5 °C to 37 °C with an optimum of 25–37 °C; siphophage vB_AerVS_332-Yuliya effectively reproduced at temperature ≤ 25 °C, the optimal temperature for giant phage vB_AerVM_332-Igor was 25 °C, and giant phage vB_AerVM_332-Vera infected host cells at 5–10 °C. The genomes of these phages differed significantly from known phages; their level of nucleotide identity and values of intergenomic similarity with the corresponding neighboring phages indicated that each of these phages is a member of a new genus/subfamily. Giant phage vB_AerVM_332-Vera is a member of the proposed Chimallinviridae family, which forms Cluster D of giant phages that possibly evolved from phages with shorter genomes. Giant phage vB_AerVM_332-Igor is part of Cluster E, the known members of which preserve the size of genomes. Phages from Cluster F, containing Aeromonas phages among others, show a gradual decrease and/or increase in genomes during evolution, which indicates different strategies for giant phages.

In this study, the impact of the genomic scaffold on the properties of bacteriophages was investigated by swapping the genomic scaffolds surrounding the tailspike genes between two Przondovirus phages, KP192 and KP195, which infect Klebsiella pneumoniae with different capsular types. A yeast-based transformation-associated recombination cloning technique and subsequent “rebooting” of synthetic phage genomes in bacteria were used to construct the phages. Using Klebsiella strains with K2, K64, and KL111 capsular types, it was shown that the capsular specificity of the synthetic phages is fully consistent with that of the tailspike proteins (tsp). However, the efficiency of plating and the lytic efficiency of these phages strongly depended on the genomic scaffold used and the Klebsiella strain used. Synthetic phages with swapped genomic scaffolds demonstrated superior reproduction efficiency using a number of strains compared to wild-type phages, indicating that some elements of the swapped genomic scaffold enhance phage replication efficiency, presumably by blocking some of the host anti-phage defense systems. Our findings demonstrate that even in the case of closely related phages, the selection of the genomic scaffold used for tsp gene transplantation can have a profound impact on the efficiency of phage propagation on target bacterial strains.