Tenri University

In cases of infections caused by multidrug-resistant Gram-negative bacilli (MRGNB), the efficacy of various antimicrobial agents may be limited due to antimicrobial resistance. This study evaluated the antimicrobial activity of various antimicrobials, principally novel beta-lactam beta-lactamase inhibitor combinations, against MRGNB prevalent in the Kinki region of Japan.

A total of 207 strains were utilized in the study, encompassing 108 carbapenemase-producing Enterobacterales (CPE) strains, 9 carbapenemase-non-producing carbapenem-resistant Enterobacterales (non-CP-CRE) strains, 73 carbapenem-resistant Pseudomonas aeruginosa (CRPA) strains, and 17 carbapenem-resistant Acinetobacter spp. (CRA) strains. These strains were obtained from the Study of Bacterial Resistance in the Kinki Region of Japan. Antimicrobial susceptibility testing was assessed via broth microdilution, with MICs determined according to the Clinical and Laboratory Standards Institute standards.

The MIC₅₀/MIC₉₀ values (in μg/mL) for each antimicrobial agent were determined for the CPE, non-CP-CRE, CRPA, and CRA strains. The following agents demonstrated activity: ceftazidime/avibactam (CAZ/AVI) (16/>16, 2/8, 8/16, 16/>16), piperacillin/tazobactam (8/>64, >64/>64, 64/>64, 8/>64), ceftolozane/tazobactam (CTLZ/TAZ) (>32/>32, 16/>32, 8/>32, >32/>32), imipenem/relebactam (IPM/REL) (0.25/4, 1/2, 8/>8, >8/>8), tigecycline (≤0.5/2, 1/8, >8/>8, ≤0.5/1), colistin (1/2, 1/8, 1/1, 1/2), and cefiderocol (0.25/2, 1/16, 1/8, 0.5/32).

The MIC distributions for colistin, tigecycline, and cefiderocol were narrow across resistant strains, indicating consistent activity. Furthermore, the MIC distributions of CAZ/AVI and IPM/REL exhibited a narrow range of concentrations against non-CP-CRE and non-CP-CRPA, respectively. In contrast, CTLZ/TAZ exhibited a similarly narrow distribution against non-CP-CRPA. These findings suggest that these antimicrobials effectively treat infections caused by MRGNB.

We aimed to screen the entire genome for genetic variants associated with passive muscle stiffness, which has been suggested as a risk factor for muscle strain injury.

This genome-wide association study (GWAS) on passive muscle stiffness included 350 physically active young Japanese individuals. Three hamstring constituents were measured using ultrasound shear wave elastography. Skeletal muscle transcriptomes were compared across the genotypes of GWAS-identified variants in 48 healthy Japanese individuals. Association between GWAS-identified variants and history of muscle strain injury was examined in 1428 Japanese athletes.

Two loci on chromosome 11 demonstrated a genome-wide significant association with passive muscle stiffness of the biceps femoris long head (rs12807854 T/C: P = 5.19 × 10−10, rs78405694 T/C: P = 2.09 × 10−8; linear regression analysis adjusted for sex, age, and stretching exercise habits). Skeletal muscle RNA sequencing revealed significantly elevated expression of extracellular matrix-related genes in muscles carrying stiffness-increasing alleles of these variants. Among athletes, rs12807854 T/C was significantly associated with a history of muscle strain injury (P = 0.0254; logistic regression analysis adjusted for age, sex, competitive level, and main sport). Carriers of the C allele, associated with increased muscle stiffness, exhibited a heightened risk of muscle strain injury (odds ratio = 1.62; 95% confidence interval = 1.06–2.47 per C allele increase). By contrast, rs78405694 did not show a significant association with muscle strain injury in this population.

A novel locus associated with passive muscle stiffness and muscle strain injury was identified. Elucidating the detailed mechanisms linking the identified locus to passive muscle stiffness may lead to the development of new strategies to prevent muscle strain injuries.

Five strains related to the genus Rodentibacter were isolated from five pet hamsters kept in Japan. Isolates were genotypically and phenotypically distinct from previously described species within the genus Rodentibacter (family Pasteurellaceae). The five strains were the most genetically similar to Rodentibacter haemolyticus 1625-19T, exhibiting a 16S rRNA gene sequence similarity of 96.5%, an average nucleotide identity value of 90.8% and a digital DNA–DNA hybridization value of 42.7%. Phenotypic characteristics further distinguish the isolated strains from other Rodentibacter species. Although they share β-haemolysis capacity with R. haemolyticus, the novel strains are differentiated by their positive reactions for α-glucosidase, l-arabinose and trehalose, as well as negative reactions for β-glucuronidase, mannose, inositol and glycerol. Genotypic and phenotypic differences between the novel strains and closely related known strains suggested that we have identified a new Rodentibacter species. We propose the name Rodentibacter abscessus sp. nov. The type strain is THUN1654T with a G+C DNA content of 40.6 mol%, and it is deposited in the DSMZ Germany (DSM 118002T), KCTC Korea (KCTC 8595T) and JCM Japan (JCM 37054T).