Endolysin-based therapeutics are promising antibacterial agents and can successfully supplement the existing antibacterial drugs array. It is specifically important in the case of Gram-negative pathogens, e.g., ESKAPE group bacteria, which includes Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species, and are highly inclined to gain multiple antibiotic resistance. Despite numerous works devoted to the screening of new lytic enzymes and investigations of their biochemical properties, there are significant breaches in some aspects of their operating characteristics, including safety issues of endolysin use. Here, we provide a comprehensive study of the antimicrobial efficacy aspects of four Gram-negative bacteria-targeting endolysins LysAm24, LysAp22, LysECD7, and LysSi3, their in vitro and in vivo activity, and their biological safety. These endolysins possess a wide spectrum of action, are active against planktonic bacteria and bacterial biofilms, and are effective in wound and burn skin infection animal models. In terms of safety, these enzymes do not contribute to the development of short-term resistance, are not cytotoxic, and do not significantly affect the normal intestinal microflora in vivo. Our results provide a confident base for the development of effective and safe candidate dosage forms for the treatment of local and systemic infections caused by Gram-negative bacterial species.

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Abscess formation is a common complication of severe life-threatening infections caused by obligate anaerobes. Fusobacterium necrophorum is among the frequently detected anaerobic pathogens from clinical specimens associated with liver abscesses, skin and soft tissue infections, or oral abscesses. The antimicrobial therapy for this kind of infection needs to be optimized. Here, we examined the possibility of treating F. necrophorum-induced abscess wound infections with candidate therapeutics based on three endolysins with activity against a broad spectrum of aerobe Gram-negative pathogens. Antibacterial gel containing three Gram-negative bacteria-targeting endolysins, LysAm24, LysAp22, and LysECD7, was formulated for topical use. Abscess formation was induced in rabbits with F. necrophorum and caused systemic infection. The survival and lifespan of the animals, general parameters, and biochemical and hematological blood tests were analyzed to assess the effectiveness of the gel treatment for the wound infection. The administration of the investigated gel twice per day for 5 days resulted in less acute inflammation, with decreased leukocytes and segmented neutrophils in the blood, retardation of infection progression, and an almost two-fold increase in the lifespan of the animals compared to the placebo group. The results indicate that endolysin-based therapy is an effective approach to treat anaerobic bacterial infections. The use of endolysins as independent pharmaceuticals, or their combination with antibiotics, could significantly reduce the development of complications in infectious diseases caused by sensitive bacterial species.

The presence of IgG and IgM antibodies in the venous blood of 76 patients with confirmed COVID-19 infection was determined by ELISA using Russian test systems. Different levels of IgM antibodies to N-protein and receptor binding domain of the Spike protein (RBD) were revealed. The dynamics of IgG antibodies to the whole virion antigen and recombinant antigens showed high values on weeks 4-5 of the disease. The level of IgG antibodies to Nprotein remained low throughout the observation period. The characteristic dynamics of IgG measured using test systems with sorbed whole virion or recombinant spike proteins reflects the duration of the disease.

Introduction. Infectious otitis externa and middle ear can cause hearing loss, which significantly reduces the quality of life of patients. The main causative agents of acute bacterial otitis media are Pseudomonas aeruginosa and Staphylococcus aureus. This article is devoted to the development and study of a novel dosage form for treatment of infectious diseases of the external ear containing bacteriophages that lyse bacterial strains of Pseudomonas aeruginosa. Ear drops were considered as a promising dosage form for instillation into the ear canal.Aim. The aim of the work is to develop a dosage form of Pseudomonas aeruginosa bacteriophages for the local treatment of infectious otitis media.Materials and Methods. The active substances of the developed drug are bacteriophages that lyse bacterial strains of Pseudomonas aeruginosa: PA5 and PA10, which were obtained by growing on a solid growth medium in mattress flasks with subsequent sterilizing filtration through a membrane filter (0,22 µm) and elimination of endotoxins on a chromatographic column. To obtain experimental compositions, excipients that do not cause a drop in the titer of bacteriophages were used – purified water as the solvent, viscosity modifiers: glycerol (CHIMMED, Russia) and a mix of macrogol 6 and glyceryl caprilocaprate brand Softigen 767 (Cremer, Germany), antioxidant Ethylenediaminetetraacetic acid (EDTA), preservatives nipagin and nipazole. The obtained samples were standardized according to pharmacopoeial indicators, recommended for the dosage form "drops" – density, pH, viscosity. For all experimental compositions, the stability of the titer of bacteriophages was studied by the Gratia method for 6 months. The local irritation and systemic effects were also studied on five chinchilla male rabbits.Results and discussion. As a result of the conducted research, four experimental compositions of ear drops with a cocktail of bacteriophages PA5 and PA10 were obtained. The optimal technological characteristics were observed in the composition containing glycerol as a viscosity modifier at a concentration of 10,0 %. For optimal composition, the stability of the bacteriophages cocktail titer, local irritating and systemic effects were analyzed. The study revealed stability of the bacteriophages PA5 and PA10 titers in the composition of dosage form, and absence of local irritating and systemic effects of ear drops.Conclusion. The dosage form can be recommended for preclinical studies.