Background: Tuberculosis (TB) is a preventable and usually curable disease. Yet in 2022, TB was the world’s second leading cause of death from a single infectious agent, after coronavirus disease (COVID-19)1. Aim: By reviving strains isolated at specific years over a 10-year interval and performing next-generation sequencing, we can analyze their strain genotype, epidemiology, drug resistance, and dynamicsTherefore, this study was conducted to examine the historical trends and dynamics of strain genotype, variants, and drug resistance of tuberculosis preserved in the culture bank. Materials and Methods:: Using a retrospective, laboratory-based research approach, 200 strains were randomly selected from over 1,000 diagnostic isolates preserved in the NTRL culture collection from 2010 and 2020. Whole-genome sequencing (WGS) was performed using GridION from Oxford Nanopore Technologies (ONT, Oxford, UK) to analyze these strains. The FastQ file was submitted to the International Mycobacterial Database. Strain genotypes, subtypes, gene mutations of drug resistance, and resistance profiles were identified using TBprofiler, MTBseq, IQ-Tree (version 1.6.12), and EPI2me software. Results: Of the tuberculosis strains selected for the study, 66.5% were from eight out of nine districts of Ulaanbaatar, while 33.5% were sampled from 16 out of 21 provinces. Out of the strains analyzed, 83.9% (95% CI 78.7–89.1) belonged to lineage 2 or the Beijing genotype, while 16.1% (95% CI 10.9–21.3) were lineage-4 or Euro-American genotype. While the proportion of Beijing lineage strains was slightly higher and the Euro-American lineage strains slightly lower in rural populations compared to urban populations, the difference in strain distribution between urban and rural areas was not statistically significant (p=0.485). Among the Beijing lineage strains, only the modern Beijing sublineage (100%) was identified. In contrast, the Euro-American lineage exhibited various sublineages: 4 (0.5%), 4.5 (1%), 4.1.2.1 (Haarlem, 3%), Latin American-Mediterranean (LAM, 7.5%), mainly T (3.5%), and S type (0.5%). Notably, the proportion of Lineage 2 strains increased from 80% in 2010 to 86% in 2020. The overlap of the confidence intervals for 2010 (72.16%–87.84%) and 2020 (79.20%–92.80%) indicates that there has been no significant change in the distribution of Mycobacterium tuberculosis lineages over time. The study revealed that among the selected Mycobacterium tuberculosis strains, resistance rates to first-line anti-tuberculosis drugs were as follows: isoniazid (39%), rifampicin (21%), ethambutol (19%), and streptomycin (34%). Genotypic analysis indicated that the Beijing lineage was predominantly associated with drug-resistant tuberculosis cases, including multidrug-resistant (MDR), poly-drug-resistant, and mono-drug-resistant TB. Notably, the Beijing lineage accounted for 100% of pre-extensively drug-resistant (pre-XDR) TB cases. Within the Haarlem lineage, 33% were MDR-TB. In the Latin American-Mediterranean (LAM) lineage, 13.3% were MDR-TB, 6.6% were poly-drug-resistant, and 13.3% were mono-drug-resistant. Among the mainly T lineage, 42.8% exhibited mono-drug resistance. These findings suggest that the distribution of M. tuberculosis lineages in the Mongolian population has remained relatively stable over time, with no significant temporal changes. Conclusion The distribution of M. tuberculosis genotypes circulating among the population of Mongolia has remained relatively stable over time, with no significant time-dependent changes. Additionally, no mutations associated with resistance to newly introduced anti-TB drugs were detected.

Background: Chronic hepatitis C virus (HCV) infection remains a major global health concern. Approximately 55–85% of individuals with acute HCV infection progress to chronic disease, which is often asymptomatic. Therefore, early diagnosis and treatment are crucial to prevent long-term complications. This provided the rationale for our study to evaluate the clinical characteristics, diagnosis, and treatment outcomes of chronic HCV patients using direct-acting antivirals (DAAs), with comparisons by viral genotype. Aim: To compare the clinical features, diagnosis, and treatment outcomes of chronic hepatitis C according to viral genotypes. Materials and Methods: A total of 1203 chronic HCV patients attending the outpatient department of Arkhangai Provincial General Hospital were included in this prospective and retrospective cohort study. HCV genotyping was performed, and patients received DAA therapy. Clinical manifestations, laboratory findings, HCV RNA levels, and fibrosis scores (APRI and FIB-4) were assessed at baseline, at week 4 of treatment, and at 12 weeks post-treatment. Statistical analysis was conducted using SPSS version 26.0. Results: : Among all patients, 6.7% had liver cirrhosis, and 1.4% had previously received interferon-based therapy. Patients with cirrhosis more frequently reported fatigue, abdominal discomfort, insomnia, right upper quadrant pain and loss of appetite (p<0.001). Virologic response at week 4 was 98.9%, and sustained virologic response at 12 weeks post-treatment was 99.3%. The mean APRI score decreased from 0.71±0.67 to 0.31±0.54, and FIB-4 from 1.61±0.41 to 1.16±0.26 (p<0.001). The most common adverse events were fatigue, headache, and nausea. Conclusion Treatment outcomes were 99.5% in patients with genotype 1b, 100% in genotype 1a, and 75% in genotype 2, with statistically significant differences (p<0.001). Both APRI and FIB-4 scores significantly decreased after treatment, confirming the effectiveness of DAA therapy in improving liver fibrosis (p<0.001).

Background: Globally, gastric cancer accounts for 1,089,000 new cases and 769,000 deaths annually, ranking fifth in overall cancer incidence and third in cancer-related mortality. The aim to determine HER2 expression in patients with gastric cancer and to evaluate its correlation with clinical and immunological biomarkers, as well as the need for further laboratory diagnostics. Aim: To determine HER2 expression in patients with gastric cancer and to evaluate its association with clinical and immunological biomarkers, as well as the potential need for further laboratory diagnostics. Materials and Methods: A retrospective study was conducted using archived materials from patients with gastric cancer at the Clinical Pathology, Molecular Genetics, and Pathology Laboratories of the National Cancer Center of Mongolia, covering the period from 2019 to June 2025. HER2 protein expression in tumor tissue was assessed using immunohistochemistry (IHC), and chromogenic in situ hybridization (CISH-HER2) was employed to confirm gene amplification. Statistical analysis was performed using the Prisma-10 software. Results: In our study, among 210 cases of gastric cancer evaluated by IHC for HER2, 46 (21.9%) were HER2-positive and 164 (78.1%) were HER2-negative. When comparing patients with gastric cancer stratified into HER2 1+ (negative) and HER2 3+ (positive) groups, no statistically significant differences (p < 0.05) were observed in age, sex, tumor location (surgically resected tissue), morphology, or disease stage. However, a higher proportion of males was noted in the HER2 3+ group (80.9%), though this did not reach statistical significance (p = 0.0879). Significant associations were found with tumor markers. Elevated serum CA-72-4 (>5 ng/mL) was more frequent in the HER2 3+ group (58.8%; p = 0.0069). In contrast, elevated CA-19-9 (>35 U/mL) was more common in the HER2 1+ group (93.5%; p = 0.0117), and elevated CEA (>6.9 U/mL) was also predominant in the HER2 1+ group (90.6%; p = 0.002). These findings suggest that HER2 3+ status predominates in cases with elevated CA-72-4, which may influence diagnostic strategies and HER2-targeted therapies (e.g., trastuzumab). Conversely, elevated CA-19-9 and CEA were more associated with HER2 1+ status, indicating a need for further detailed investigation of these markers in relation to HER2 expression. In patients evaluated by CISH for HER2 expression, stratification into HER2-positive and HER2-negative groups revealed no statistically significant differences (p < 0.05) in age, sex, tumor location, morphology, stage, or serum tumor markers (CA-72-4, CA-19-9, CEA). This suggests that HER2 status (positive/negative) may be independent of these variables. Although HER2 positivity was higher in poorly differentiated tumors (48% vs. 30.6% negative; p=0.1414) and in stage IV disease (50% vs. 39.3% negative; p=0.2607), these differences were not statistically significant. Elevated serum markers (CA-72-4, CA-19-9, CEA) were observed but showed no significant correlation with HER2 status. Conclusion Determining the molecular profile of gastric cancer patients can significantly contribute to refining clinical diagnosis, developing treatment strategies, enhancing therapeutic outcomes, and improving patients’ quality of life.

Background: The continuous annual increase in the prevalence of diabetes mellitus (DM) poses significant challenges not only within our nation but also globally in the control and management of tuberculosis. Aim: This study aimed to determine the incidence of pulmonary tuberculosis among individuals with type 2 diabetes mellitus (T2DM) residing in six central districts of Ulaanbaatar and to investigate associated factors. Materials and Methods: A cross-sectional study design was employed. Participants aged 18 years and older diagnosed with T2DM and receiving care at endocrinology clinics in six central districts of Ulaanbaatar were selected using systematic random sampling. Presumptive TB cases were identified through a structured questionnaire and chest X-ray. Sputum specimens were collected and subjected to smear microscopy and Xpert MTB/RIF assay for tuberculosis detection. Cases confirmed by laboratory diagnosis, currently undergoing tuberculosis treatment and previously treated cases as per questionnaire data were classified as tuberculosis cases, and prevalence was calculated. Results: A total of 1,644 individuals with T2DM were enrolled in the study, of whom 836 (50.9%) were female, with a mean age of 58 years (range 19–89). The overall prevalence of presumptive TB cases was 10.5% (n=172; 95% CI, 9.0–12.0). Among 112 suspected cases from whom sputum samples were obtained, 10 (8.9%; 95% CI, 4.9–15.7) were laboratory-confirmed for M.tuberculosis. Notably, 7.2% (6 cases; 95% CI, 3.4–14.9) of asymptomatic individuals with abnormal X-ray findings were diagnosed with tuberculosis. According to questionnaire responses, 9 participants (0.5%; 95% CI, 0.3–1.0) were undergoing tuberculosis treatment, and 53 (3.2%; 95% CI, 2.5–4.2) reported a previously treated TB cases. The overall prevalence of tuberculosis among individuals with diabetes was 4.4% (n=72; 95% CI, 3.5–5.5). Stratification by age and sex revealed a significantly higher prevalence among males (5.9%; n=48; 95% CI, 4.5–7.8) compared to females (2.9%; 95% CI, 1.2–4.2) (p=0.002), indicating a twofold increased risk of tuberculosis in males. Although no statistically significant differences in tuberculosis prevalence were observed across age groups (p>0.05), a declining trend in prevalence with older age was noted. Conclusion The prevalence of tuberculosis among individuals with type 2 diabetes was 4.4% (n=72; 95% CI, 3.5–5.5), with a significantly higher rate in males (p=0.002) and a decreasing trend with increasing age. Among asymptomatic individuals exhibiting radiographic abnormalities, 7.2% were confirmed to have tuberculosis via laboratory testing

Background: To prevent and combat the spread of the COVID-19 pandemic, the Government of Mongolia has implemented measures such as movement and time restrictions, social distancing and isolation, closure of schools, kindergartens and public places, immunization, and others. It has caused adverse consequences for people, social relations, and the economy, causing health, social, economic, and humanitarian crises. Not only does this situation, medical students, as frontline healthcare workers, are more susceptible to virus infection. Vaccines against COVID-19 have been researched quickly due to the pandemic and are being used under emergency use authorization. In our country the approach of mixing vaccine doses from different manufacturers was used (fractional doses). Therefore, there is no study on the exposure of medical students to the COVID-19 infection and the adverse effects after receiving a dose of a heterologous vaccine. Objective: To study the exposure to the COVID-19 infection and vaccination status of medical students. Methods: The survey was conducted from November 2023 to December 2023 using a cross-sectional study design, and 170 students who study at ASUSU and live in the dormitory were included. Results: A total of 170 students participated in the study. 55.9% (n=95) of them were in the first year, 22.4% (n=38) were in the second year, 10% (n=17) were in the third year, 7.6% (n=13) were in the fourth year, 2.4% (n=4) were from the 5th year and 1.8% (n=3) were from the 6th year students. 88.2% (n=150) of students were female and 11.8% (n=20) were male. In this study, 37.1% of the students were infected by COVID-19 infection previously. Among them, 50% of the students were infected from family members, 16.7% from the school environment, and 15.2% did not know about the source of infection. 76.2% of the respondents were diagnosed with COVID-19 in a medical institution, and forty-one students answered that they were treated at the hospital. 83% of the cases were treated at home and were cured within 14 days. In contrast, 93.8% of the hospitalized students were treated within four months to 1 year. The current study demonstrates neurological, respiratory, sensory, cardiovascular, psychiatric, digestive, and dermatological symptoms were in 37.6%, 24.1%, 27.6%, 17.6%, 11.8%, 11.2%, and 10% of the students who participated in the study, respectively. For a year or more, symptoms of all organ systems were present, but neurological symptoms appeared to be the highest. 55.9% (n=115) of the enrolled students received 3 or 4 doses of the vaccine, 3.5% (n=6) did not receive the vaccine. In total, 35% (n=60) of the enrolled students experienced side effects and 65% (n=106) had no side effects. Conclusion In this study, 37.1% of the students were infected by COVID-19 infection previously. According to the current study, symptoms related to the nervous system was the most prevalent and 55.9% (n=115) of the enrolled students received 3 or 4 doses of the vaccine. In total, 35% (n=60) of the enrolled students experienced side effects.