Multidrug-resistant Acinetobacter baumannii (MDRAB) is a pathogen recognized as antimicrobial-resistant bacteria involved in healthcare-associated infections. Resistance to antibiotics has made alternative therapies necessary. Bacteriophage therapy is considered a potential solution to treat MDRAB. In this study, we isolated and characterized the phage vB_AbaS_TCUP2199 (TCUP2199), which can infect MDRAB. Morphological analysis revealed that TCUP2199 belongs to the Siphoviridae family. TCUP2199 has a wide host range, can adsorb rapidly (68.28% in 2 min), and has a burst size of 196 PFU/cell. At least 16 distinct structural proteins were visualized by SDS polyacrylamide gel electrophoresis. A stability test showed that TCUP2199 was stable at 37 °C and pH 7. Genome analysis of TCUP2199 showed that it consists of a double-stranded DNA genome of 79,572 bp with a G+C content of 40.39%, which contains 98 putative open reading frames, none of which is closely related to the bacteriophage genome sequence that was found in the public database. TCUP2199 shows similarity in genomic organization and putative packaging mechanism with Achromobacter phage JWF and Pseudoalteromonas phage KB12-38 based on protein BLAST and phylogenetic analysis. Because of those unique characteristics, we consider TCUP2199 to be a novel phage that is suitable for inclusion in a phage cocktail to treat A. baumannii infection.

The global rise of multidrug-resistant Enterobacter cloacae strains, especially those that are resistant to carbapenems and produce metallo-β-lactamases, poses a critical challenge in clinical settings owing to limited treatment options. While bacteriophages show promise in treating these infections, their use is hindered by scarce resources and insufficient genomic data. In this study, we isolated ECLFM1, a novel E. cloacae phage, from sewage water using a carbapenem-resistant clinical strain as the host. ECLFM1 exhibited rapid adsorption and a 15-min latent period, with a burst size of approximately 75 PFU/infected cell. Its genome, spanning 172,036 bp, was characterized and identified as a member of Karamvirus. In therapeutic applications, owing to a high multiplicity of infection, ECLFM1 showed increased survival in zebrafish infected with E. cloacae. This study highlights ECLFM1’s potential as a candidate for controlling clinical E. cloacae infections, which would help address challenges in treating multidrug-resistant strains and contribute to the development of alternative treatments.

Neutralizing anti–interferon-γ (IFN-γ) autoantibodies (nAIGAs) impair IFN-γ–mediated immunity, predisposing patients with nAIGAs to infection by nontuberculous mycobacteria, Talaromyces marneffei , and other intracellular pathogens. Current clinical management relies on continuous antimicrobial therapy, with no treatment offering sustained benefits. Here, we developed human chimeric autoantibody receptor (CAAR) T cells targeting autoreactive B cells expressing nAIGA B cell receptors (BCRs) using an IFN-γ receptor–irresponsive IFN-γ variant as bait. By exploiting a mouse model of nAIGA BCR-expressing B cell leukemia, we found that IFN-γ CAAR T cells lack off-target toxicity, including IFN-γ receptor cross-reactive toxicity and Fc-redirected toxicity. IFN-γ CAAR T cells substantially reduced circulating AIGAs secreted from target cells in vivo. Further, IFN-γ CAAR T cells effectively eliminated autoreactive B cells in ex vivo cultures of peripheral blood mononuclear cells from patients with nAIGAs. Together, these results demonstrate that IFN-γ CAAR T cells may be a promising strategy to ameliorate nAIGA-associated infections by eliminating autoreactive B cells.

The rise of carbapenem-resistant Klebsiella pneumoniae (CRKP) presents a significant global challenge in clinical and healthcare settings, severely limiting treatment options. This study aimed to utilize a bacteriophage as an alternative therapy against carbapenem-resistant K. pneumoniae. A novel lytic N4-like Klebsiella phage, vB_kpnP_KPYAP-1 (KPYAP-1), was isolated from sewage. It demonstrated efficacy against the K62 serotype polysaccharide capsule of bla_OXA-48-producing K. pneumoniae. KPYAP-1 forms small, clear plaques, has a latent period of 20 min, and reaches a growth plateau at 35 min, with a burst size of 473 plaque-forming units (PFUs) per infected cell. Phylogenetic analysis places KPYAP-1 in the Schitoviridae family, Enquatrovirinae subfamily, and Kaypoctavirus genus. KPYAP-1 employs an N4-like direct terminal repeat mechanism for genome packaging and encodes a large virion-encapsulated RNA polymerase. It lacks integrase or repressor genes, antibiotic resistance genes, bacterial virulence factors, and toxins, ensuring its safety for therapeutic use. Comparative genome analysis revealed that the KPYAP-1 genome is most similar to the KP8 genome, yet differs in tail fiber protein, indicating variations in host recognition. In a zebrafish infection model, KPYAP-1 significantly improved the survival rate of infected fish by 92% at a multiplicity of infection (MOI) of 10, demonstrating its potential for in vivo treatment. These results highlight KPYAP-1 as a promising candidate for developing phage-based therapies targeting carbapenemase-producing K. pneumoniae.

Multidrug-resistant (MDR) Enterobacter cloacae is a growing public health issue worldwide, highlighting the urgent need for alternative antimicrobial strategies. This study reports on a lytic phage, designated B1, isolated from sewage, which exhibits specificity and lytic efficiency against MDR E. cloacae. Morphological observation revealed that B1 possesses an icosahedral head (~54 nm) and a short tail (~13 nm). Phage B1 showed a narrow host range, demonstrated stability within a temperature range of 4–37 °C, tolerance to pH values between 5 and 11, and showed an excellent bacteriolytic capacity with a short latent period of less than 10 min and a burst size of approximately 150 PFU/initially infected cell, indicating a rapid lytic cycle and efficient replication capability. Whole-genome sequencing revealed that the phage genome consists of 40,163 base pairs of double-stranded DNA containing 52 open reading frames (ORFs) with a GC content of 52%. Comparative genome-wide analysis using VIRIDIC revealed that B1 shares 75% to 92% similarity with Escherichia phage IMM-002 (accession: NC_048071), Citrobacter phage SH4, and Cronobacter phage Dev2 (accession: NC_023558), but shares less than 70% similarity with other Enterobacter phages. According to ICTV criteria, B1 represents a new species within the same genus as T7-like phages belonging to Autographiviridae, subfamily Studiervirinae, genus Kayfunavirus. In addition, B1 lacks lysogeny-associated or virulence genes and exhibits potent lytic activity against multidrug-resistant E. cloacae, making it a promising candidate for phage therapy. These findings opened up our understanding of the diversity of T7-like phages and provided insights into their evolutionary adaptability and therapeutic potential.