Helicobacter pylori Infection Status and Gastric Tumor Incidence According to the Year of Birth.

Background/Aims: : The prevalence of Helicobacter pylori-naive status is increasing. Nonetheless, biennial gastroscopy is recommended for all Koreans aged 40 to 75 years. This study aimed to determine whether gastric cancer screening guidelines could be changed according to H. pylori infection status and year of birth. Methods: : Koreans who underwent serum assays and gastroscopy for gastric cancer screening between 2010 and 2016 were included if screening tests were followed up for ≥3 times. H. pylori infection was confirmed when invasive tests or 13C-urea breath tests were positive. In the case of negative test findings, eradication history, serologically detected atrophy, and intestinal metaplasia/atrophy were checked for past infection. If all were absent, H. pylori-naive status was confirmed. Results: : Two-thousand and two (256 H. pylori-naive, 743 past-infected, and 1,003 infected) Koreans underwent screening tests for 95.5±28.4 months. The mean year of birth in the naive group (1969±7) differed from those of the past-infected (1957±10, p<0.001) and infected (1958±10, p<0.001) groups. H. pylori-naive status was correlated with recent year of birth (r=0.368, p<0.001). No gastric tumors were observed among the naive participants (p=0.007), whereas 23 adenomas, 18 adenocarcinomas, and two neuroendocrine tumors were detected in 1.9% (14/743) of past-infected and 2.5% (25/1,003) of infected participants, including four infected participants with metachronous tumors. Conclusions: : The prevalence of H. pylori-naive status is increasing in young Koreans, and gastric tumors are rare in this population. Hence, biennial gastroscopy could be waived after the confirmation of naive status.

Changes in the Hepatitis B Surface Antigen Level According to the HBeAg Status and Drug Used in Long-term Nucleos(t)ide Analog-treated Chronic Hepatitis B Patients.

Backgrounds/Aims: The HBsAg levels have been used to monitor the chronic hepatitis B (CHB) treatment response to antiviral therapy. On the other hand, it is unclear if the HBsAg quantification levels at each treatment point differ according to the HBeAg status and drug in CHB patients. This study compared the changes in HBsAg in CHB patients according to the HBeAg status and treatment drugs. Methods: CHB patients with at least 1 year of follow-up treatment with one drug, either entecavir (ETV) or tenofovir (TDF), were enrolled in this study. The mean HBsAg levels were measured annually for up to 6 years. A linear mixed model was used to compare the HBsAg quantification levels during the follow-up period. An independent samples t-test was used to analyze the differences in the HBsAg quantification levels at each treatment time point. Results: Ninety-seven patients were enrolled in this study; 59 among them were HBeAg-positive. Two patients in the TDF group achieved HBsAg seroconversion. The HBsAg level decreased during the follow-up in the ETV and TDF groups. The HBsAg level was lower in the TDF group than the ETV group during the follow-up. On the other hand, subgroup analysis showed that this trend was the same only in the HBeAg-negative patients, not in the HBeAg-positive patients. In the HBeAg-negative patients, HBsAg level in the TDF group was significantly lower than that in the ETV group at 36, 48, and 72 months. The change in HBsAg level from the baseline increased at a decreasing rate during the follow-up in both groups. Furthermore, the change in the HBsAg level in the TDF group was significantly larger than that of the ETV group at 36 months in the HBeAg-negative patients. Conclusions: Although TDF might be more efficient than ETV in reducing the HBsAg level in HBeAg-negative patients in a few years, HBsAg seroconversion occurred very rarely. A further large-scale, long-term study will be needed to confirm the antiviral effects on the HBsAg level.

Molecular analysis of spatial variation of iron-reducing bacteria in riverine alluvial aquifers of the Mankyeong River.

Alluvial aquifers are one of the mainwater resources in many countries. Iron reduction in alluvial aquifers is often a major anaerobic process involved in bioremediation or causing problems, including the release of As trapped in Fe(III) oxide. We investigated the distribution of potential iron-reducing bacteria (IRB) in riverine alluvial aquifers (B1, B3, and B6 sites) at the Mankyeong River, Republic of Korea. Inactive iron reduction zones, the diversity and abundance of IRB can be examined using a clone library and quantitative PCR analysis of 16S rRNA genes. Geobacter spp. are potential IRB in the iron-reducing zone at the B6 (9 m) site, where high Fe(II) and arsenic (As) concentrations were observed. At the B3 (16 m) site, where low iron reduction activity was predicted, a dominant clone (10.6%) was 99% identical in 16S rRNA gene sequence with Rhodoferax ferrireducens. Although a major clone belonging to Clostridium spp. was found, possible IRB candidates could not be unambiguously determined at the B1 (18 m) site. Acanonical correspondence analysis demonstrated that, among potential IRB, only the Geobacteraceae were well correlated with Fe(II) and As concentrations. Our results indicate high environmental heterogeneity, and thus high spatial variability, in thedistribution of potential IRB in the riverine alluvial aquifersnear the Mankyeong River.