Hydroxymethylcytosine (hmC) is a natural nucleobase, which is converted from methylcytosine (mC) by tet methylcytosine dioxygenase (TET) family (TET1-3) enzymes. Decrease of genomic hmC is postulated to confer a risk for myeloid-lineage as well as T-cell neoplasms, based on the fact that loss-of-function mutations in the TET2 gene were frequently identified in these diseases. The relationship between hmC and aging remains to be elucidated. Here, we demonstrated that hmC content decreased with age in the peripheral blood T cells of 53 human volunteers. We further identified that the mRNA expression levels of TET1 and TET3 decreased with age, while those of TET2 were not influenced by age. The genomic hmC content was correlated with the mRNA expression level of TET3, but not those of TET1 and TET2. Our study suggests the presence of new epigenetic regulatory mechanisms in aging T cells.

Background: MBiliary tract infection is a common cause of bacteremia with high morbidity and mortality, particularly in older patients with co-morbid disease or when there is a delay in diagnosis and treatment. This study is undertaken to determine the microbiological pattern and antibiotic resistance in biliary tract infection at Cho Ray Hospital in 2021.Subbjects and methods: NA retrospective study was conducted from January 2021 to Demcember 2021 at Cho Ray hospital. Bile samples were cultured on Blood agar, Mac-conkey agar. Bacterial strains were identified by the MALDI-TOF MS system and made susceptibility testing on the VITEK 2-compact system of Biomerieux. The antibiotic susceptibility were determined by mininum inhibitory concentration(MIC) according to CLSI.Results: Out of 595 bile samples sent for aerobic culture and susceptibility testing, 203 (34.1%) weresterile and 392 (65.9%) were found to be culture positive. Of the bile culture positives, 129 (21.7%)were polymicrobial. The most prevalent bacteria isolates were Escherichia coli 33.8% (102), Klebsiella pneumoniae 22.2% (67), Enterococcus spp. 16.6% (50), Pseudomonas aeruginosa 7.9% (24). The ESBL rate of Escherichia coli was 42.2%, while this rate of Klebsiella pneumoniae was 9%. The vancomycin resistant rate of Enterococcus spp. was 8.3%. In Pseudomonas aeruginosa, among beta-lactams, imipenem had the highest resistant rate (45.8%). No resistance to colistin had been reported.Conclusion: In biliary tract infections, about one-third cases had negative-culture results and about onefifth cases had polymicrobial infection. The common pathogens in biliary tract infections were Escherichia coli, Klebsiella pneumoniae, Enterococcus spp. and Pseudomonas aeruginosa. The resistance rate to commonly used antibiotics in treatment was quite high.