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Background: This study aimed to analyze the distribution of pathogens and antimicrobial resistance in bone and joint infections (BJIs) among children under four years old., Methods: A retrospective analysis was conducted on the clinical data of children under four years old who received inpatient treatment for BJIs at the Children's Hospital of Soochow University between January 2016 and December 2022. Results of bacterial culture and antimicrobial resistance were analyzed., Results: Among the 131 patients, 52 (39.7%) showed positive bacterial culture results. There were Gram-positive (G+) bacteria detected in 38 strains (73.07%), Gram-negative (G-) bacteria in 12 strains (23.08%), and fungi in 2 strains (3.85%). Thirty-one strains of Staphylococcus aureus (S. aureus) were detected (59.62%), including 7 MRSA strains (22.58%). The resistance rate of G+ bacteria to penicillin was 72.97%, while resistance to erythromycin and clindamycin was approximately 50%. No resistance was found against linezolid, vancomycin, and teicoplanin. G- bacteria showed a sensitivity of 100% to carbapenems, including meropenem, ertapenem, and imipenem, a resistance rate of 91.67% to ampicillin-sulbactam, and relatively high resistance rates to compound sulfamethoxazole, ampicillin/sulbactam, and piperacillin., Conclusions: Regional variations existed in the distribution of pathogens and antimicrobial resistance in children under four years old with BJIs. In our hospital, the most common pathogen is S. aureus, with MRSA accounting for approximately one-fourth of all S. aureus patients. Additionally, extended-spectrum β-lactamase (ESBL)-producing G- bacteria have been identified, underscoring the importance of careful consideration during empirical antibiotic therapy.

D-amino acid oxidase (DAAO) can catalyze the dehydrogenation of D-amino acids, such as D-alanine, to the corresponding amino acids and is then reoxidized by molecular oxygen to yield hydrogen peroxide, a reactive oxygen species, which reacts with DNA, lipids and protein, inducing cell death. This study investigated whether rat glioma 9L cells infected with the recombinant retrovirus containing the DAAO cDNA fragment can be induced in order to undergo cytotoxic oxidative stress by D-alanine. The recombinant retroviral vector, plzrus-DAAO-FLAG-GFP (pl-Dfg), was constructed and used to transfect packaged phoenix cells. The supernatant containing recombinant retroviral particles from the transfected phoenix cells was harvested and utilized to infect target 9L cells. The cytotoxic oxidative stress of infected 9L cells was induced by the DAAO substrate, D-alanine. The plasmid pl-Dfg was successfully constructed. The high titer retroviral supernatant was obtained from the transfected phoenix cells. Infected 9L cells were less viable after exposure to D-alanine compared to the control group. Anti-apoptotic proteins significantly inhibited cell death. The DAAO/D-alanine system has a potential utility for gene therapy and may be an effective strategy for the treatment of brain cancer and other malignant tumors.