MDPI AG Acta Medica Okayama 2076-2607 14 4 2026 The Role of Nitrate-Reducing Bacteria Isolated from Helicobacter pylori-Infected Individuals in Gastric Cancer Development 760 EN Serika Kuwagi Department of Bacteriology, Academic Field of Health Sciences, Okayama University Kazuyoshi Gotoh Department of Bacteriology, Academic Field of Health Sciences, Okayama University Marina Komatsubara Department of Bacteriology, Academic Field of Health Sciences, Okayama University Shuma Tsuji Department of Bacteriology, Academic Field of Health Sciences, Okayama University Shyoutarou Okanoue Department of Gastroenterology and Hepatology, Academic Field of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Hiroyuki Okada Himeji Red Cross Hospital Jumpei Uchiyama Department of Bacteriology, Academic Field of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Akari Watanabe Department of Oral Health Care and Rehabilitation, Institute of Biomedical Sciences, Graduate School, Tokushima University Kenji Yokota Department of Bacteriology, Academic Field of Health Sciences, Okayama University Helicobacter pylori is a Gram-negative bacterium that inhabits the gastric mucosa, with a global prevalence in humans of approximately 40%. It is likely the cause of 90% of gastric cancer (GC) cases and thus considered the most prominent driver of GC development. However, during gastric mucosal atrophy, other bacteria such as nitrate-reducing bacteria (NRB) also proliferate. In this study, we isolated NRB from patients with gastritis and GC to examine their effects on the epithelial cell cycle and production of various cytokines in monocytic cell lines. Bacterial counts (excluding H. pylori and NRB) increased with the progression of gastric mucosal atrophy and were significantly higher in patients with GC. Gastric epithelial cell lines were stimulated with isolated NRB, and the proportion of cells in each cell cycle was measured. Strains from patients with open-type gastritis progressed more rapidly through cell cycles than those from patients with GC. NRB isolated from gastric cancer had high nitrate-reducing activity. Thus, NRB may contribute to GC progression during H. pylori-induced carcinogenesis. Therefore, evaluating gastric atrophy and microbiota may be important for managing the risk of GC. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 1746-6148 22 1 2026 Genetic and phenotypic identities of Staphylococcus coagulans isolated from pustules of dogs with superficial bacterial folliculitis 98 EN Takafumi Osumi Animal Medical Center, Faculty of Agriculture, Tokyo University of Agriculture and Technology Yuuki Shinomiya Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology Thamonwan Wanganuttara Department of Bacteriology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Ichiro Imanishi Kimberly and Eric J. Waldman Department of Dermatology, Icahn School of Medicine at Mount Sinai Yotaro Shimazaki Animal Medical Center, Faculty of Agriculture, Tokyo University of Agriculture and Technology Keita Iyori 1sec Co. Ltd. Yoichi Toyoda 1sec Co. Ltd. Kaori Ide Animal Medical Center, Faculty of Agriculture, Tokyo University of Agriculture and Technology Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Koji Nishifuji Animal Medical Center, Faculty of Agriculture, Tokyo University of Agriculture and Technology Background Staphylococcus coagulans, formerly called Staphylococcus schleiferi subsp. coagulans is the second most common isolate from skin lesions of dogs with superficial bacterial folliculitis (SBF). However, the clinical significance of S. coagulans in pustules of canine SBF remains uncertain. This study aimed to investigate the prevalence and genotypic and phenotypic diversity of S. coagulans isolated from pustules in two dogs with SBF. Results Two dogs with SBF were included in this study. S. schleiferi/coagulans was isolated as the sole organism from three pustules in case #1, whereas it coexisted with S. pseudintermedius in two of seven pustules in case #2. S. pseudintermedius was the sole organism in the remaining five pustules in case #2. Whole genome sequences revealed that all isolates tested were annotated as S. coagulans. The isolates from the same pustules exhibited identical genotypic and phenotypic profiles, indicating clonal multiplication. S. coagulans isolated from different pustules exhibited similar yet distinct genotypic and phenotypic profiles. Conclusions S. coagulans with identical genetic and phenotypic profiles can be identified as the sole pathogen or coexist with S. pseudintermedius in the pustules of the same dogs with SBF. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 1349-4147 54 1 2026 Mycobacterium mageritense-associated refractory cutaneous infection and lymphadenitis in an immunocompetent adult: insights from genomic sequencing 19 EN Shinnosuke Fukushima Department of Bacteriology, Dentistry and Pharmaceutical Sciences, Okayama University Graduate School of Medicine Jumpei Uchiyama Department of Bacteriology, Dentistry and Pharmaceutical Sciences, Okayama University Graduate School of Medicine Yoshio Kawakami Department of Dermatology, Okayama University Hospital Yoshiko Matsuura Konohana Dermatology Clinic Satoru Sugihara Department of Dermatology, Okayama University Hospital Shin Morizane Department of Dermatology, Okayama University Hospital Poowadon Muenraya Department of Bacteriology, Dentistry and Pharmaceutical Sciences, Okayama University Graduate School of Medicine Hideharu Hagiya Department of Infectious Diseases, Okayama University Hospital Background Nontuberculous mycobacteria are increasingly recognized as causes of chronic and refractory skin and soft tissue infections, even in individuals without immunodeficiency. Among them, Mycobacterium mageritense is a rare, rapidly growing species that can lead to persistent lesions requiring prolonged antimicrobial therapy. Reports of M. mageritense infections involving both the skin and regional lymph nodes are limited, and this case adds new clinical and genomic insights. Case presentation A 48-year-old previously healthy man presented with a slowly enlarging cutaneous lesion on his lower leg and ipsilateral inguinal lymphadenitis. Empirical antibacterial therapy with β-lactams and macrolides was ineffective. Wound cultures subsequently grew M. mageritense, confirmed by whole-genome sequencing. Several antimicrobial regimens were attempted, and the final successful therapy consisted of oral levofloxacin and minocycline for 4 months, leading to complete clinical resolution. Genomic analysis identified resistance-related genes, including erm(40), aac(2′)-Ib, tet(V), and RbpA, although in vitro minimum inhibitory concentrations showed variable susceptibility. Phylogenetic comparison revealed that the isolate was closely related to previously reported M. mageritense strains from Japan. Conclusions This case demonstrates that M. mageritense can cause cutaneous infection with secondary lymphadenitis in an immunocompetent host. Accurate species identification using molecular or genomic methods and selection of appropriate combination antibiotic therapy based on susceptibility testing are crucial for successful management of such infections. No potential conflict of interest relevant to this article was reported.

Elsevier BV Acta Medica Okayama 0014-4800 145 2026 Assessing the role of folate syntrophy and folate cross-feeding in the pathobiology of infectious-inflamed milieu caused by Fusobacterium nucleatum 105021 EN Darab Ghadimi Department of Microbiology and Biotechnology, Max Rubner-Institut Sophia Blömer Faculty of Medicine, Christian-Albrechts-University of Kiel Aysel Şahin Kaya Department of Nutrition and Dietetics, Faculty of Health Sciences, Antalya Bilim University Sandra Krüger Institute of Pathology, Kiel University, University Hospital, Schleswig-Holstein Christoph Röcken Institute of Pathology, Kiel University, University Hospital, Schleswig-Holstein Heiner Schäfer Laboratory of Molecular Gastroenterology & Hepatology, Christian-Albrechts-University & UKSH Campus Kiel Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Shigenobu Matsuzaki Department of Medical Laboratory Science, Faculty of Health Sciences, Kochi Gakuen University Wilhelm Bockelmann Department of Microbiology and Biotechnology, Max Rubner-Institut Diet and nutrition affect almost every biological process, including multiple chronic diseases, diabetes, and some cancers. However, there are still significant gaps in our understanding of the importance of nutrition and healthy diets in syntrophy with respect to cross-feeding of the microbe-microbe and the microbe-host in the pathobiology of the infectious-inflamed intestinal milieu caused by anaerobic opportunistic bacteria such as Fusobacterium nucleatum (F. nucleatum). We examined the immune outcomes of three-member folate syntrophy and cross-feeding between F. nucleatum bacteria, endogenous folate-producing gut bacteria, and host cells at the host-pathogen interface using a triple co-culture model. T84, THP-1, and Huh7 cells were inoculated with F. nucleatum for 6 h in regular DMEM, DMEM with 9.5 μM folic acid, or with/without a mixture of Bifidobacterium longum subsp. infantis (B. infantis) and Escherichia coli Nissle 1917 (EcN). Cytokine secretion, cometabolite levels (ammonia, indoles), cell viability, and barrier integrity were assessed. F. nucleatum-induced folate depletion was associated with increased IL-1β and IL-6 and decreased IL-22, along with reduced transepithelial electrical resistance (TEER) and cell viability in T84 cells. Folate supplementation mitigated these effects. The mixture of B. infantis and EcN reduced F. nucleatum-induced pro-inflammatory cytokines, increased IL-22, and improved TEER and cell viability. These protective effects were enhanced by the addition of folate. F. nucleatum also elevated ammonia and reduced indoles, effects reversed by B. infantis and EcN. In addition to the intrinsic pathogenicity of harmful bacteria, folate deprivation, microbe–microbe folate syntrophy, and microbe–host folate cross-feeding contribute to the pathobiology of anaerobic opportunistic bacteria and influence the physiological fate of host cells. A combination of B. infantis and EcN modulates the infectious-inflamed interface through a cytoprotective effect and mechanical competitive extrusion of pathogenic F. nucleatum. These results provide potential insights into the mechanisms of early-onset colorectal cancer, and evidently, require future studies using patient-derived organoids and in vivo systems to improve clinical relevance. No potential conflict of interest relevant to this article was reported.

Frontiers Media SA Acta Medica Okayama 1663-9812 16 2025 Regulatory considerations for developing phage therapy medicinal products for the treatment of antimicrobial resistant bacterial infections 1713471 EN Ai Fukaya-Shiba Office of Regulatory Science Coordination, Pharmaceuticals and Medical Devices Agency Akiko Ogata Office of Regulatory Science Coordination, Pharmaceuticals and Medical Devices Agency Ryosuke Kuribayashi Office of Cellular and Tissue-based Products, Pharmaceuticals and Medical Devices Agency Akira Sakurai Office of Cellular and Tissue-based Products, Pharmaceuticals and Medical Devices Agency Kanako Suzuki Office of Regulatory Science Coordination, Pharmaceuticals and Medical Devices Agency Shunsuke Takadama Office of New Drug IV, Pharmaceuticals and Medical Devices Agency Jihei Nishimura Office of New Drug IV, Pharmaceuticals and Medical Devices Agency Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Hiroki Ohge Department of Infectious Diseases, Hiroshima University Hospital Takamasa Takeuchi Pathogen Genomics Center, National Institute of Infectious Diseases, Japan Institute for Health Security Hideyuki Tamaki Biomanufacturing Process Research Center, National Institute of Advanced Industrial Science and Technology Tetsuya Matsumoto Department of Infectious Diseases, International University of Health and Welfare Kotaro Kiga Department of Drug Development, National Institute of Infectious Diseases, Japan Institute for Health Security Hidetomo Iwano Laboratory of Veterinary Biochemistry, Rakuno Gakuen University School of Veterinary Medicine Recently, there have been growing expectations that treatment of infections with bacteriophages (phages), viruses which specifically infect bacteria, can be used as a treatment option for antimicrobial resistant bacterial infections. In Europe and the United States, in addition to phage therapy as a form of personalized medicine, development of pre-defined phage therapy medicinal products (PTMPs) is progressing, and clinical trials are underway. From October 2024 to July 2025, the Pharmaceuticals and Medical Devices Agency exchanged opinions on trends and points to consider in drug development of PTMPs used for antimicrobial resistant bacterial infections with external experts. Development of PTMPs for regulatory approval requires quality control strategies, establishment of manufacturing methods, non-clinical evaluations, and clinical trial plans based on the characteristics of the phage. In this document, based on the regulatory and development trends in Europe and the United States, the current considerations on quality, non-clinical evaluation, and clinical trial planning including the Cartagena Act in the development of PTMPs in Japan are summarized. The basic concepts presented here are intended to be applied to antimicrobial resistant bacterial infections targeted by PTMPs but can be mostly applicable to bacterial infections in general. We hope that these findings will further accelerate more active development of PTMPs towards timely patient access to innovative products. No potential conflict of interest relevant to this article was reported.

Elsevier BV Acta Medica Okayama 0040-8166 98 2026 The vicious cycle between nutrient deficiencies and antibiotic-induced nutrient depletion at the host cell-pathogen interface: Coenzyme Q10 and omega-6 as key molecular players 103224 EN Darab Ghadimi Department of Microbiology and Biotechnology, Max Rubner-Institut Sophia Blömer Faculty of Medicine, Christian-Albrechts-University of Kiel Aysel Şahi̇n Kaya Department of Nutrition and Dietetics, Faculty of Health Sciences, Antalya Bilim University Sandra Krüger Institute of Pathology, Kiel University, University Hospital, Schleswig-Holstein Christoph Röcken Institute of Pathology, Kiel University, University Hospital, Schleswig-Holstein Heiner Schäfer Laboratory of Molecular Gastroenterology & Hepatology, Christian-Albrechts-University & UKSH Campus Kiel Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Shigenobu Matsuzaki Department of Medical Laboratory Science, Faculty of Health Sciences, Kochi Gakuen University Wilhelm Bockelmann Department of Microbiology and Biotechnology, Max Rubner-Institut The increasing prevalence of antibiotic resistance and pathological inflammation underscores the importance of understanding the underlying biochemical and immune processes that govern the host-pathogen interface. Nutrient deficiency, compounded by antibiotic-induced nutrient depletion, forms a vicious cycle of overt inflammation, contributing to bacterial toxin translocation in human inter-organ and intra-organs milieus. Coenzyme Q10 (CoQ10) and omega-6 linoleic acid (LA 18:2ω6) are integral to cellular membrane integrity and immune defense. However, the complex enzymatic steps at the host cell-pathogen interface remain poorly understood. This study is particularly timely, as it explores these knowledge gaps, which can inform the development of nutritional and therapeutic strategies that modulate or target these mechanisms. Using an infectious-inflamed cell co-culture model of the gut-liver axis, we exposed triple cell co-cultures of human intestinal epithelial cells (T84), macrophage-like THP-1 cells, and hepatic cells (Huh7) to linoleic acid-producing Lactobacillus casei (L. casei) and Pseudomonas aeruginosa strain PAO1 (PAO1). The cultures were incubated for 6 h in medium with or without ceftazidime antibiotic. PAO1 and L. casei exerted opposing effects on the secretion of Th1 cytokines IL-1β, IL-6, and the Th 2-type cytokine IL-10. Inoculation with PAO1 decreased CoQ10 and linoleic acid levels compared to uninfected controls. L. casei restored cellular health and biofunctionality impaired by PAO1, indicating its benefit to the host's well-being. The antibiotic ceftazidime exerted dual effects, alleviating PAO1 toxicity while marginally disrupting the beneficial effects of L. casei. Our results show how the vicious cycle of nutrient deficiency and antibiotic-induced nutrient loss reinforces pathological inflammation at the host cell-pathogen interface and highlights the need for more appropriate targeted antibiotic use that preserves essential nutrients like CoQ10 and omega-6 fatty acids. Inflammatory responses driven by opportunistic pathogens and LA-producing bacteria represent opposing immunometabolic pathways that may provide insights into novel approaches for treating infection and reducing antibiotic resistance. No potential conflict of interest relevant to this article was reported.

Oxford University Press (OUP) Acta Medica Okayama 1365-2672 136 10 2025 Gut dysbiosis allows foodborne salmonella colonization in edible crickets: a probiotic strategy for enhanced food safety lxaf217 EN Shuma Tsuji Department of Medical Laboratory Science, Okayama University Graduate School of Health Sciences Osamu Matsushita Department of Bacteriology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Jumpei Uchiyama Department of Bacteriology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Kenji Yokota Department of Medical Laboratory Science, Okayama University Graduate School of Health Sciences Tetsuya Bando Department of Cytology and Histology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Hideyo Ohuchi Department of Cytology and Histology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Kazuyoshi Gotoh Department of Medical Laboratory Science, Okayama University Graduate School of Health Sciences Aims: Edible insects, including crickets, represent a promising protein source, yet concerns over foodborne pathogens limit consumer acceptance. This study investigated whether gut microbiota modulates colonization by Salmonella enterica subsp. enterica serovar Enteritidis (SE) in the two-spotted cricket (Gryllus bimaculatus). Methods and Results: Under standard conditions, SE was undetectable in crickets despite prolonged exposure; however, antibiotic-induced dysbiosis enabled stable SE colonization. Long-read 16S rRNA sequencing revealed significant microbiota shifts, notably a reduction in Lactococcus garvieae. In vitro assays showed strong inhibitory effects of L. garvieae against SE, and supplementation of dysbiotic crickets with L. garvieae reduced SE colonization by ∼1000-fold. Conclusions: The native cricket gut microbiota, especially L. garvieae, plays a protective role against SE colonization. Enhancing beneficial gut bacteria could mitigate pathogen risks and promote edible insects as a sustainable protein. No potential conflict of interest relevant to this article was reported.

Elsevier BV Acta Medica Okayama 0014-4800 142 2025 Cross-feeding between beneficial and pathogenic bacteria to utilize eukaryotic host cell-derived sialic acids and bacteriophages shape the pathogen-host interface milieu 104967 EN Darab Ghadimi Department of Microbiology and Biotechnology, Max Rubner-Institut Regina Fölster-Holst Clinic of Dermatology, Venerology und Allergology, University Hospital Schleswig-Holstein Sophia Blömer Clinic of Dermatology, Venerology und Allergology, University Hospital Schleswig-Holstein Michael Ebsen Städtisches MVZ Kiel GmbH (Kiel City Hospital), Department of Pathology Christoph Röcken Institute of Pathology, Kiel University, University Hospital, Schleswig-Holstein Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Shigenobu Matsuzaki Department of Medical Laboratory Science, Faculty of Health Sciences, Kochi Gakuen University Wilhelm Bockelmann Department of Microbiology and Biotechnology, Max Rubner-Institut Under an inflamed-intestinal milieu, increased free sialic acids are associated with the overgrowth of some pathogenic bacterial strains. Recently, the protective immunomodulatory activity of gut bacteriophages (phages) has also been highlighted. However, the role of phages in triple reciprocal interactions between pathogenic bacteria, beneficial bacteria, and their host cell sialic acids has not been studied so far. We established a sialidase-explicit model in which beneficial and pathogenic bacteria interact through cross-feeding and competition for free sialic acid using a human triple co-culture cell model incorporating colonocytes (T84 cells), monocytes (THP-1 cells), and hepatocytes (Huh7 cells). Triple co-cultured cells were challenged with Gram-positive Bifidobacterium bifidum (B. bifidum) and Gram-negative Pseudomonas aeruginosa PAO1 (P. a PAO1) in the absence or presence of its KPP22 phage in two different cell culture mediums: 1) standard Dulbecco's Modified Eagle Medium (DMEM) and 2) DMEM with 2,3-dehydro-2-deoxy-N-acetylneuraminic acid (DANA). Changes in physiological, functional, and structural health markers of stimulated cocultured cells were evaluated. The concentrations of sialic acid and pro-inflammatory cytokines in the cell culture supernatants were quantified. P. a PAO1 triggered the release of interleukin 6 and 8 (IL-6 and IL-8), accompanied by increased levels of free sialic acid, reduced viability of co-cultured cells, and disrupted the integrity of the cellular monolayer. These disruptive effects were markedly attenuated by KPP22 phage and B. bifidum. In addition to well-documented differences in the structure and composition of the bacterial cell walls of Gram-negative pathogenic bacteria and bifidobacteria, two distinct factors seem to be pivotal in modulating the pathogen-host interface milieu: (i) the presence of phages and (ii) the utilization of free sialic acids secreted from host cells by bifidobacteria. No potential conflict of interest relevant to this article was reported.

Association for Research in Vision and Ophthalmology (ARVO) Acta Medica Okayama 2164-2591 13 12 2024 Disruption of the Enterococcus faecalis–Induced Biofilm on the Intraocular Lens Using Bacteriophages 25 EN Tatsuma Kishimoto Department of Ophthalmology and Visual Science, Kochi Medical School, Kochi University Ken Fukuda Department of Ophthalmology and Visual Science, Kochi Medical School, Kochi University Waka Ishida Department of Ophthalmology and Visual Science, Kochi Medical School, Kochi University Aozora Kuwana Department of Ophthalmology and Visual Science, Kochi Medical School, Kochi University Daisuke Todokoro Department of Ophthalmology, Gunma University Graduate School of Medicine Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Shigenobu Matsuzaki Department of Medical Laboratory Science, Faculty of Health Sciences, Kochi Gakuen University Kenji Yamashiro Department of Ophthalmology and Visual Science, Kochi Medical School, Kochi University Purpose: To compare the effects of bacteriophages (phages) and vancomycin on Enterococcus faecalis–induced biofilms on the intraocular lens. Methods: E. faecalis strains EF24, GU02, GU03, and phiEF14H1 were used. The expression of the enterococcus surface protein (esp) gene was analyzed using polymerase chain reaction. Phages or vancomycin was added to the biofilms formed on culture plates or acrylic intraocular lenses. The biofilms were quantified after staining with crystal violet. The structure of the biofilms was analyzed using scanning electron microscopy. Results: E. faecalis strains EF24, GU02, and GU03 formed biofilms on cell culture plates; however, the esp-negative GU03 strain had a significantly lower biofilm-forming ability than the esp-positive strains EF24 and GU02. The addition of phiEF14H1 resulted in a significant reduction in biofilm mass produced by both EF24 and GU02 compared with the untreated control. However, the addition of vancomycin did not degrade the biofilms. Phages significantly degraded biofilms and reduced the viable EF24 and GU02 bacteria on the intraocular lens. Conclusions: Phages can degrade biofilms formed on the intraocular lens and destroy the bacteria within it. Thus, phage therapy may be a new treatment option for refractory and recurrent endophthalmitis caused by biofilm-forming bacteria. Translational Relevance: Phage therapy, a novel treatment option for refractory and recurrent endophthalmitis caused by biofilm-forming bacteria, effectively lyses E. faecalis–induced biofilms. No potential conflict of interest relevant to this article was reported.

MDPI AG Acta Medica Okayama 1660-3397 23 5 2025 Novel Anti-MRSA Peptide from Mangrove-Derived Virgibacillus chiguensis FN33 Supported by Genomics and Molecular Dynamics 209 EN Namfa Sermkaew School of Pharmacy, Walailak University Apichart Atipairin School of Pharmacy, Walailak University Phetcharat Boonruamkaew School of Pharmacy, Walailak University Sucheewin Krobthong Center of Excellence in Natural Products Chemistry (CENP), Department of Chemistry, Faculty of Science, Chulalongkorn University Chanat Aonbangkhen Center of Excellence in Natural Products Chemistry (CENP), Department of Chemistry, Faculty of Science, Chulalongkorn University Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Yodying Yingchutrakul National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency Nuttapon Songnaka School of Pharmacy, Walailak University Antimicrobial resistance (AMR) is a global health threat, with methicillin-resistant Staphylococcus aureus (MRSA) being one of the major resistant pathogens. This study reports the isolation of a novel mangrove-derived bacterium, Virgibacillus chiguensis FN33, as identified through genome analysis and the discovery of a new anionic antimicrobial peptide (AMP) exhibiting anti-MRSA activity. The AMP was composed of 23 amino acids, which were elucidated as NH3-Glu-Gly-Gly-Cys-Gly-Val-Asp-Thr-Trp-Gly-Cys-Leu-Thr-Pro-Cys-His-Cys-Asp-Leu-Phe-Cys-Thr-Thr-COOH. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for MRSA were 8 µg/mL and 16 µg/mL, respectively. FN33 AMP induced cell membrane permeabilization, suggesting a membrane-disrupting mechanism. The AMP remained stable at 30–40 °C but lost activity at higher temperatures and following exposure to proteases, surfactants, and extreme pH. All-atom molecular dynamics simulations showed that the AMP adopts a β-sheet structure upon membrane interaction. These findings suggest that Virgibacillus chiguensis FN33 is a promising source of novel antibacterial agents against MRSA, supporting alternative strategies for drug-resistant infections. No potential conflict of interest relevant to this article was reported.

MDPI AG Acta Medica Okayama 2079-6382 13 9 2024 Unveiling a New Antimicrobial Peptide with Efficacy against P. aeruginosa and K. pneumoniae from Mangrove-Derived Paenibacillus thiaminolyticus NNS5-6 and Genomic Analysis 846 EN Namfa Sermkaew School of Pharmacy, Walailak University Apichart Atipairin School of Pharmacy, Walailak University Sucheewin Krobthong Center of Excellence in Natural Products Chemistry (CENP), Department of Chemistry, Faculty of Science, Chulalongkorn University Chanat Aonbangkhen Center of Excellence in Natural Products Chemistry (CENP), Department of Chemistry, Faculty of Science, Chulalongkorn University Yodying Yingchutrakul National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Nuttapon Songnaka School of Pharmacy, Walailak University This study focused on the discovery of the antimicrobial peptide (AMP) derived from mangrove bacteria. The most promising isolate, NNS5-6, showed the closest taxonomic relation to Paenibacillus thiaminolyticus, with the highest similarity of 74.9%. The AMP produced by Paenibacillus thiaminolyticus NNS5-6 exhibited antibacterial activity against various Gram-negative pathogens, especially Pseudomonas aeruginosa and Klebsiella pneumoniae. The peptide sequence consisted of 13 amino acids and was elucidated as Val-Lys-Gly-Asp-Gly-Gly-Pro-Gly-Thr-Val-Tyr-Thr-Met. The AMP mainly exhibited random coil and antiparallel beta-sheet structures. The stability study indicated that this AMP was tolerant of various conditions, including proteolytic enzymes, pH (1.2–14), surfactants, and temperatures up to 40 °C for 12 h. The AMP demonstrated 4 µg/mL of MIC and 4–8 µg/mL of MBC against both pathogens. Time-kill kinetics showed that the AMP acted in a time- and concentration-dependent manner. A cell permeability assay and scanning electron microscopy revealed that the AMP exerted the mode of action by disrupting bacterial membranes. Additionally, nineteen biosynthetic gene clusters of secondary metabolites were identified in the genome. NNS5-6 was susceptible to various commonly used antibiotics supporting the primary safety requirement. The findings of this research could pave the way for new therapeutic approaches in combating antibiotic-resistant pathogens. No potential conflict of interest relevant to this article was reported.

MDPI AG Acta Medica Okayama 1422-0067 26 16 2025 Synergistic Antimicrobial Activity of BrSPR20-P1 Peptide and Silver Nanoparticles Against Pathogenic Bacteria 7832 EN Thanyamai Thongin School of Pharmacy, Walailak University Somchai Sawatdee School of Pharmacy, Walailak University Nuttapon Songnaka School of Pharmacy, Walailak University Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University Theanchai Wiwasuku School of Science, Walailak University Teerapol Srichana Drug Delivery System Excellence Center and Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, Prince of Songkla University Titpawan Nakpheng Drug Delivery System Excellence Center and Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, Prince of Songkla University Apichart Atipairin School of Pharmacy, Walailak University Bacterial infection is a cause of life-threatening diseases. The emergence of antimicrobial-resistant bacteria exacerbates this situation, highlighting the need for the discovery of new antimicrobial agents. Our previous study identified a novel antimicrobial peptide, BrSPR20-P1 (P1), which showed potential activity against MRSA. Additionally, silver nanoparticles (AgNPs) exhibit broad-spectrum antibacterial activity, capable of killing multidrug-resistant bacteria. The combination of antimicrobial agents presents a novel strategy for combating these pathogens. This study aimed to evaluate the antibacterial activity of the combination of P1 and AgNPs. It revealed that the combinations showed synergy. The P1 and AgNP mixture at a concentration of 1 and 8 µg/mL (1:8) doubled the activity against S. aureus and MRSA, while that combination of 64 and 64 µg/mL (64:64) exhibited broad-spectrum activity, expanding to E. coli with a 32-fold increase. These combinations exhibited a bactericidal effect, showing the rapid killing of tested bacteria at 10× MIC, with killing rates during the first 3 h ranging from 4.04 ± 0.01 to 4.31 ± 0.03 h−1. The P1 and AgNP mixtures caused a low risk of antibacterial resistance up to 30 passages. It was demonstrated that the synergistic activity of P1 and AgNPs occurred through the disruption of cell walls and membranes, leakage of intracellular materials, and cell lysis. Additionally, the mixtures appeared to interact with bacterial genomic DNA, as indicated by a gel retardation assay. These activities of the combinations were concentration-dependent. The 1:8 µg/mL mixture caused low hemolysis and cytotoxicity and did not impede the wound healing process. In contrast, although the 64:64 µg/mL mixture showed excellent antibacterial efficacy, it was toxic to erythrocytes and mammalian cells. It implies that dose optimization is required to balance its efficacy and toxicity. Therefore, the P1 and AgNP combinations exhibit synergistic antimicrobial activity and have the potential to resolve bacterial infections. No potential conflict of interest relevant to this article was reported.

Oxford University Press (OUP) Acta Medica Okayama 1460-2725 2025 Disseminated Mycobacterium chelonae infection predominantly involving the facial region of an immunocompromised elderly patient hcaf176 EN Yosuke Sazumi Department of General Medicine, Okayama University Hospital Hideharu Hagiya Department of Infectious Diseases, Okayama University Hospital Shinnosuke Fukushima Department of Infectious Diseases, Okayama University Hospital Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Poowadon Muenraya Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Satoru Sugihara Department of Dermatology, Okayama University Hospital Yoshio Kawakami Department of Dermatology, Okayama University Hospital Shin Morizane Department of Dermatology, Okayama University Hospital Kohei Oguni Department of General Medicine, Okayama University Hospital Fumio Otsuka Department of General Medicine, Okayama University Hospital No potential conflict of interest relevant to this article was reported.

Public Library of Science Acta Medica Okayama 1932-6203 19 10 2024 Examination of yield, bacteriolytic activity and cold storage of linker deletion mutants based on endolysin S6_ORF93 derived from Staphylococcus giant bacteriophage S6 e0310962 EN Sosuke Munetomo Department of Public Health, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Iyo Takemura-Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Thamonwan Wanganuttara Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Yumiko Yamamoto Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Toshihiro Tsukui Nippon Zenyaku Kogyo Co. Ltd. Hideharu Hagiya Department of Infectious Diseases, Okayama University Hospital Shuji Kanamaru School of Life Science and Technology, Tokyo Institute of Technology Hideyuki Kanda Department of Public Health, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Osamu Matsushita Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Methicillin-resistant Staphylococcus spp. present challenges in clinical and veterinary settings because effective antimicrobial agents are limited. Phage-encoded peptidoglycan-degrading enzyme, endolysin, is expected to be a novel antimicrobial agent. The enzymatic activity has recently been shown to be influenced by the linker between functional domains in the enzyme. S6_ORF93 (ORF93) is one of the endolysins derived from previously isolated Staphylococcus giant phage S6. The ORF93 was speculated to have a catalytic and peptidoglycan-binding domain with a long linker. In this study, we examined the influence of linker shortening on the characteristics of ORF93. We produce wild-type ORF93 and the linker deletion mutants using an Escherichia coli expression system. These mutants were designated as ORF93-Delta 05, ORF93-Delta 10, ORF93-Delta 15, and ORF93-Delta 20, from which 5, 10, 15, and 20 amino acids were removed from the linker, respectively. Except for the ORF93-Delta 20, ORF93 and its mutants were expressed as soluble proteins. Moreover, ORF93-Delta 15 showed the highest yield and bacteriolytic activity, while the antimicrobial spectrum was homologous. The cold storage experiment showed a slight effect by the linker deletion. According to our results and other studies, linker investigations are crucial in endolysin development. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 1869-2044 73 1 2023 Exploratory study of volatile fatty acids and the rumen-and-gut microbiota of dairy cows in a single farm, with respect to subclinical infection with bovine leukemia virus 31 EN Takehito Suzuki School of Veterinary Medicine, Azabu University Hironobu Murakami School of Veterinary Medicine, Azabu University Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Reiichiro Sato Faculty of Agriculture, University of Miyazaki Iyo Takemura-Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Masaya Ogata School of Veterinary Medicine, Azabu University Kazuyuki Sogawa School of Veterinary Medicine, Azabu University Hiroho Ishida School of Veterinary Medicine, Azabu University Apichart Atipairin School of Pharmacy, Walailak University Osamu Matsushita Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Makoto Nagai School of Veterinary Medicine, Azabu University Background Subclinical infection with bovine leukemia virus (BLV) in cows can cause economic losses in milk and meat production in many countries, as BLV-related negative effects. The volatile fatty acids (VFAs) and microbiota present in the digestive tracts of cows can contribute to cow health. Here, we exploratorily investigated the VFAs and microbiota in the rumen and gut with respect to subclinical BLV infection using cows housed at a single farm. Results We analyzed a herd of 38 cows kept at one farm, which included 15 uninfected and 23 BLV-infected cows. First, the analysis of the VFAs in the rumen, gut, and blood revealed an absence of statistically significant differences between the uninfected and BLV-infected groups. Thus, BLV infection did not cause major changes in VFA levels in all tested specimens. Next, we analyzed the rumen and gut microbiota. The analysis of the microbial diversity revealed a modest difference between the uninfected and BLV-infected groups in the gut; by contrast, no differences were observed in the rumen. In addition, the investigation of the bacteria that were predominant in the uninfected and BLV-infected groups via a differential abundance analysis showed that no significant bacteria were present in either of the microbiota. Thus, BLV infection possibly affected the gut microbiota to a small extent. Moreover, bacterial associations were compared between the uninfected and BLV-infected groups. The results of this analysis suggested that BLV infection affected the equilibrium of the bacterial associations in both microbiota, which might be related to the BLV-related negative effects. Thus, BLV infection may negatively affect the equilibrium of bacterial associations in both microbiota. Conclusions Subclinical BLV infection is likely to affect the rumen and gut microbiota, which may partly explain the BLV-related negative effects. No potential conflict of interest relevant to this article was reported.

American Society for Microbiology Acta Medica Okayama 2165-0497 11 3 2023 Metataxonomic Analysis of the Uterine Microbiota Associated with Low Fertility in Dairy Cows Using Endometrial Tissues Prior to First Artificial Insemination e04764-22 EN Takuya Yagisawa Hokkaido Agriculture Mutual Aid Association Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Iyo Takemura-Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Shun Ando Hokkaido Agriculture Mutual Aid Association Osamu Ichii Laboratory of Anatomy, Department of Basic Veterinary Sciences, Faculty of Veterinary Medicine, Hokkaido University Hironobu Murakami Laboratory of Infectious Diseases, School of Veterinary Medicine, Azabu University Osamu Matsushita Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Seiji Katagiri Laboratory of Theriogenology, Department of Clinical Sciences, Faculty of Veterinary Medicine, Hokkaido University The deterioration in reproductive performance in association with low fertility leads to significant economic losses on dairy farms. The uterine microbiota has begun to attract attention as a possible cause of unexplained low fertility. We analyzed the uterine microbiota associated with fertility by 16S rRNA gene amplicon sequencing in dairy cows. First, the alpha (Chao1 and Shannon) and beta (unweighted and weighted UniFrac) diversities of 69 cows at four dairy farms that had passed the voluntary waiting period before the first artificial insemination (AI) were analyzed with respect to factors including farm, housing style, feeding management, parity, and AI frequency to conception. Significant differences were observed in the farm, housing style, and feeding management, except parity and AI frequency to conception. The other diversity metrics did not show significant differences in the tested factors. Similar results were obtained for the predicted functional profile. Next, the microbial diversity analysis of 31 cows at a single farm using weighted UniFrac distance matrices revealed a correlation with AI frequency to conception but not with parity. In correlation with AI frequency to conception, the predicted function profile appeared to be slightly modified and a single bacterial taxon, Arcobacter, was detected. The bacterial associations related to fertility were estimated. Considering these, the uterine microbiota in dairy cows can be varied depending on the farm management practices and may become one of the measures for low fertility. No potential conflict of interest relevant to this article was reported.

Japanese Society of Veterinary Science Acta Medica Okayama 0916-7250 84 7 2022 Screening of bacterial DNA in bile sampled from healthy dogs and dogs suffering from liver- or gallbladder-associated disease 1019 1022 EN Sakurako NEO School of Veterinary Medicine, Azabu University Iyo TAKEMURA-UCHIYAMA Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Jumpei UCHIYAMA Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Hironobu MURAKAMI School of Veterinary Medicine, Azabu University Ayaka SHIMA Anicom Specialty Medical Institute Inc. Hideki KAYANUMA School of Veterinary Medicine, Azabu University Taiki YOKOYAMA School of Veterinary Medicine, Azabu University Satoshi TAKAGI School of Veterinary Medicine, Azabu University Eiichi KANAI School of Veterinary Medicine, Azabu University Masaharu HISASUE School of Veterinary Medicine, Azabu University Although the biliary system is generally aseptic, gallbladder microbiota has been reported in humans and some animals apart from dogs. We screened and analyzed the bacterial deoxyribonucleic acid in canine gallbladders using bile sampled from 7 healthy dogs and 52 dogs with liver- or gallbladder-associated disease. PCR screening detected bacteria in 17.3% of diseased dogs (9/52) and none in healthy dogs. Microbiota analysis of PCR-positive samples showed that the microbial diversity differed between liver- and gallbladder-associated disease groups. Thus, a specific bacterial community appears to occur at a certain frequency in the bile of diseased dogs. No potential conflict of interest relevant to this article was reported.

Oxford University Press Acta Medica Okayama 0266-8254 75 6 2022 Characterization of the oral and fecal microbiota associated with atopic dermatitis in dogs selected from a purebred Shiba Inu colony 1607 1616 EN Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Takafumi Osumi Laboratory of Veterinary Internal Medicine, Division of Animal Life Science, Graduate School, Tokyo University of Agriculture and Technology Keijiro Mizukami School of Veterinary Medicine, Azabu University Tomoki Fukuyama School of Veterinary Medicine, Azabu University Ayaka Shima Anicom Specialty Medical Institute Inc. Asaka Unno School of Veterinary Medicine, Azabu University Iyo Takemura‐Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Yumi Une Faculty of Veterinary Medicine, Okayama University of Science Hironobu Murakami School of Veterinary Medicine, Azabu University Masahiro Sakaguchi School of Veterinary Medicine, Azabu University Atopic dermatitis (AD) is a chronic and relapsing multifactorial inflammatory skin disease that also affects dogs. The oral and gut microbiota are associated with many disorders, including allergy. Few studies have addressed the oral and gut microbiota in dogs, although the skin microbiota has been studied relatively well in these animals. Here, we studied the AD-associated oral and gut microbiota in 16 healthy and nine AD dogs from a purebred Shiba Inu colony. We found that the diversity of the oral microbiota was significantly different among the dogs, whereas no significant difference was observed in the gut microbiota. Moreover, a differential abundance analysis detected the Family_XIII_AD3011_group (Anaerovoracaceae) in the gut microbiota of AD dogs; however, no bacterial taxa were detected in the oral microbiota. Third, the comparison of the microbial co-occurrence patterns between AD and healthy dogs identified differential networks in which the bacteria in the oral microbiota that were most strongly associated with AD were related with human periodontitis, whereas those in the gut microbiota were related with dysbiosis and gut inflammation. These results suggest that AD can alter the oral and gut microbiota in dogs. No potential conflict of interest relevant to this article was reported.

Elsevier BV Acta Medica Okayama 0168-1702 319 2022 Phylogenic analysis of new viral cluster of large phages with unusual DNA genomes containing uracil in place of thymine in gene-sharing network, using phages S6 and PBS1 and relevant uncultured phages derived from sewage metagenomics 198881 EN Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Iyo Takemura-Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Kazuyoshi Gotoh Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Shin-ichiro Kato Research Institute of Molecular Genetics, Kochi University Yoshihiko Sakaguchi Department of Microbiology, Kitasato University School of Medicine Hironobu Murakami School of Veterinary Medicine, Azabu University Tomoki Fukuyama School of Veterinary Medicine, Azabu University Mao Kaneki School of Veterinary Medicine, Azabu University Osamu Matsushita Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Shigenobu Matsuzaki Department of Medical Laboratory Science, Faculty of Health Sciences, Kochi Gakuen University Bacteriophages (phages) are the most diverse and abundant life-form on Earth. Jumbophages are phages with double-stranded DNA genomes longer than 200 kbp. Among these, some jumbophages with uracil in place of thymine as a nucleic acid base, which we have tentatively termed "dU jumbophages" in this study, have been reported. Because the dU jumbophages are considered to be a living fossil from the RNA world, the evolutionary traits of dU jumbophages are of interest. In this study, we examined the phylogeny of dU jumbophages. First, tBLASTx analysis of newly sequenced dU jumbophages such as Bacillus phage PBS1 and previously isolated Staphylococcus phage S6 showed similarity to the other dU jumbophages. Second, we detected the two partial genome sequences of uncultured phages possibly relevant to dU jumbophages, scaffold_002 and scaffold_007, from wastewater metagenomics. Third, according to the gene-sharing network analysis, the dU jumbophages, including phages PBS1 and S6, and uncultured phage scaffold_002 formed a cluster, which suggested a new viral subfamily/family. Finally, analyses of the phylogenetic relationship with other phages showed that the dU jumbophage cluster, which had two clades of phages infecting Gram-negative and Gram-positive bacteria, diverged from the single ancestral phage. These findings together with previous reports may imply that dU jumbophages evolved from the same origin before divergence of Gram-negative and Gram-positive bacteria. No potential conflict of interest relevant to this article was reported.

Oxford University Press (OUP) Acta Medica Okayama 1574-6968 369 1 2022 Heterogeneous IgE reactivities to Staphylococcus pseudintermedius strains in dogs with atopic dermatitis, and the identification of DM13-domain-containing protein as a bacterial IgE-reactive molecule fnac019 EN Iyo Takemura-Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Hiroki Tsurui School of Veterinary Medicine, Azabu University, Fuchinobe 1-17-71 Hidekatsu Shimakura School of Veterinary Medicine, Azabu University Tadahiro Nasukawa School of Veterinary Medicine, Azabu University Ichiro Imanishi School of Veterinary Medicine, Azabu University Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama Universty Tomoki Fukuyama School of Veterinary Medicine, Azabu University Shuji Sakamoto Science Research Center, Kochi Medical School Keiko Morisawa Science Research Center, Kochi Medical School Masato Fujimura Fujimura Animal Hospital Hironobu Murakami School of Veterinary Medicine, Azabu University Shuji Kanamaru Department of Life Science and Technology, Tokyo Institute of Technology Kenji Kurokawa Faculty of Pharmaceutical Sciences, Nagasaki International University Keiko Kawamoto School of Veterinary Medicine, Azabu University Keita Iyori Vet Derm Tokyo, Dermatological and Laboratory Service for Animals Masahiro Sakaguchi School of Veterinary Medicine, Azabu University Staphylococcus pseudintermedius is one of the major pathogens causing canine skin infection. In canine atopic dermatitis (AD), heterogeneous strains of S. pseudintermedius reside on the affected skin site. Because an increase in specific IgE to this bacterium has been reported, S. pseudintermedius is likely to exacerbate the severity of canine AD. In this study, the IgE reactivities to various S. pseudintermedius strains and the IgE-reactive molecules of S. pseudintermedius were investigated. First, examining the IgE reactivities to eight strains of S. pseudintermedius using 141 sera of AD dogs, strain variation of S. pseudintermedius showed 10–63% of the IgE reactivities. This is different from the expected result based on the concept of Staphylococcus aureus clonality in AD patients. Moreover, according to the western blot analysis, there were more than four proteins reactive to IgE. Subsequently, the analysis of the common IgE-reactive protein at ∼15 kDa confirmed that the DM13-domain-containing protein was reactive in AD dogs, which is not coincident with any S. aureus IgE-reactive molecules. Considering these, S. pseudintermedius is likely to exacerbate AD severity in dogs, slightly different from the case of S. aureus in human AD. No potential conflict of interest relevant to this article was reported.

American Society for Microbiology Acta Medica Okayama 2165-0497 9 1 2021 Use of Recombinant Endolysin to Improve Accuracy of Group B Streptococcus Tests e00077-21 EN Hidehito Matsui Ōmura Satoshi Memorial Institute, Kitasato University Jumpei Uchiyama Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Masaya Ogata School of Veterinary Medicine, Azabu University, Sagamihara Tadahiro Nasukawa School of Veterinary Medicine, Azabu University, Sagamihara Iyo Takemura-Uchiyama School of Veterinary Medicine, Azabu University, Sagamihara Shin-ichiro Kato Kochi University Hironobu Murakami School of Veterinary Medicine, Azabu University, Sagamihara Masato Higashide Kotobiken Medical Laboratories, Inc., Tsukuba Hideaki Hanaki Ōmura Satoshi Memorial Institute, Kitasato University Group B Streptococcus (GBS) causes serious neonatal infection via vertical transmission. The prenatal GBS screening test is performed at the late stage of pregnancy to avoid risks of infection. In this test, enrichment culture is performed, followed by GBS identification. Selective medium is used for the enrichment; however, Enterococcus faecalis, which is a potential contaminant in swab samples, can interfere with the growth of GBS. Such bacterial contamination can lead to false-negative results. Endolysin, a bacteriophage-derived enzyme, degrades peptidoglycan in the bacterial cell wall; it is a promising antimicrobial agent for selectively eliminating specific bacterial genera/species. In this study, we used the recombinant endolysin EG-LYS, which is specific to E. faecalis; the endolysin potentially enriched GBS in the selective culture. First, in the false-negative model (coculture of GBS and E. faecalis, which disabled GBS detection in the subsequent GBS identification test), EG-LYS treatment at 0.1 mg/ml improved GBS detection. Next, we used 548 vaginal swabs to test the efficacy of EG-LYS treatment in improving GBS detection. EG-LYS treatment (0.1 mg/ml) increased the GBS-positive ratio to 17.9%, compared to 15.7% in the control (phosphate-buffered saline [PBS] treatment). In addition, there were an increased number of GBS colonies under EG-LYS treatment in some samples. The results were supported by the microbiota analysis of the enriched cultures. In conclusion, EG-LYS treatment of the enrichment culture potentially improves the accuracy of the prenatal GBS screening test. No potential conflict of interest relevant to this article was reported.