Burkholderia thailandensis and B. pseudomallei are closely related gram-negative saprophytic microbes. Recently, variant strains of B. thailandensis bearin

Neisseria meningitidis is a pathogenic bacterial agent that causes meningococcal meningitis in humans. Developing a rapid and low-cost N. meningitidis detection method is crucial, especially for developing countries. This study focuses on the development of an efficient loop-mediated isothermal amplification (LAMP) method for accurate N. meningitidis identification. A new LAMP primer set was designed, and a LAMP reaction was optimized. The colorimetric detection method was also applied, and the assay characteristics were evaluated using clinical samples. The results demonstrated a specific LAMP reaction for N. meningitidis detection of genotypes A, B, and C, with a limit of detection of 10² cfu/mL, 100% specificity and sensitivity, and a rapid detection time of only 40 min by colorimetric visual inspection. No cross-reactivity with reference strains of Streptococcus pneumoniae, Staphylococcus aureus, Neisseria lactamica, Mycobacterium tuberculosis, and Haemophilus influenzae type b was observed in the LAMP reaction with the new primer set. This result suggests that the LAMP reaction could be a promising tool for developing a rapid N. meningitidis detection method suitable for use in Vietnam and other developing countries.

ВВЕДЕНИЕ Burkholderia thailandensis и B. pseudomallei филогенетически близкие сапрофитные бактерии. Эти два вида значительно отличаются по патогенности для млекопитающих, в том числе из-за наличия у B. pseudomallei капсульного полисахарида (CPS) — одного из основных факторов вирулентности, вместо которого у B. thailandensis присутствует экзополисахарид (EPS). Недавно были обнаружены вариантные штаммы B. thailandensis (BTCV — Burkholderia thailandensis capsular variant), содержащие кластер генов биосинтеза капсульного полисахарида (Bp-like CPS), который имеет высокое сходство с ортологичным кластером B. pseudomallei. Целью настоящего исследования было выявление BTCV штаммов B. thailandensis в почве южного и центрального Вьетнама. МАТЕРИАЛ И МЕТОДЫ Видовую принадлежность штаммов определяли с использованием мультилокусной ПЦР, идентифицирующей три основных вида комплекса B. pseudomallei, и МЛСТ. Исследовано 87 почвенных изолятов B. thailandensis. РЕЗУЛЬТАТЫ С использованием разработанного набора из шести пар праймеров для детекции генов кластера Bp-like CPS было выявлено 11 BTCV штаммов. Вариантные штаммы в основном росли в виде морщинистых колоний, что более характерно для B. pseudomallei. Обнаружено, что во Вьетнаме среди основной популяции B. thailandensis присутствуют штаммы, которые в отличие от типового штамма B. thailandensis E264 также образуют колонии pseudomallei-подобных морфотипов. ЗАКЛЮЧЕНИЕ Показана ассоциация аминокислотных полиморфизмов L1629S и T1942A в поликетидсинтазе типа I и pseudomallei-подобной морфологии EPS-экспрессирующих штаммов B. thailandensis. Полученные данные свидетельствуют о высокой степени генетической гетерогенности внутри вьетнамской популяции B. thailandensis, сопровождаемой выраженным фенотипическим разнообразием штаммов.

Nghiên cứu tiến hành xây dựng quy trình bào chế viên nang cứng EntVN từ các chủng lợi khuẩn Enterococcus faecium F26BA và F54BA được phân lập từ nguồn thực phẩm Việt Nam. Nồng độ sữa tiệt trùng để tạo sinh khối giống khởi động là 15% (w/w), thời gian tiến hành đông khô sinh khối ướt là 24 giờ, tỷ lệ tá dược độn (bột đậu nành) được trộn với sinh khối probiotic 1:4 (sinh khối:tá dược, w/w), nhiệt độ sấy 40oC trong 4 giờ thu được bột sinh khối probiotic có mật độ khuẩn lạc đạt 4,5x1010CFU/g. Bột sinh khối (460 mg/viên nang) sau khi nghiền mịn trộn với tá dược độn (20 mg/viên nang), tá dược dính (10 mg/viên nang), tá dược trơn chảy (10 mg/viên nang), tiến hành đóng nang. Viên nang EntVN thu được đạt các chỉ tiêu về khối lượng (sai số không quá 7,5%), độ rã (dưới 30 phút), các chỉ tiêu về giới hạn nhiễm khuẩn, hàm lượng kim loại nặng và lượng khuẩn lạc (3,3x1010CFU/g). Viên nang EntVN được bào chế từ các chủng lợi khuẩn bản địa với các đặc điểm dễ dàng thích nghi và phù hợp với người Việt, nguyên liệu bào chế phổ biến, quy trình đơn giản, giá thành vừa phải đáp ứng được nhu cầu thị trường Việt Nam.

The aim of the study was to identify and compare potential determinants of aminoglycoside resistance in gentamicin susceptible Burkholderia pseudomallei strains.Materials and methods. A bioinformatics analysis of whole genome shotgun sequences of three B. pseudomallei strains having different levels of sensitivity to gentamicin was carried out.Results and discussion. B. pseudomallei is intrinsically resistant to aminoglycosides. Such strains, as a rule, are not taken into account in the classical scheme of isolation and identification. At the same time, there were no significant differences in the clinical manifestations of melioidosis during infection with gentamicin-resistant and sensitive strains. In B. pseudomallei strains of different sequence types (ST70, ST948, and ST1566), point missense mutations were found in the genes of three efflux pumps of the RND family: AmrAB-OprA, BpeAB-OprB, BpeEF-OprC, and one with unknown functions, as well as in the gene aminoglycoside-6’-N-acetyltransferase AAC(6’)-III. All three strains had amino acid substitutions in the AmrA periplasmic linker: ARG160SER, Arg116Gln and Gly237Arg, Thr317Lys, respectively. In moderately sensitive strains (ST948 and ST1566), an identical Val222Met substitution was found in the repressor of the AmrAB-OprA operon, AmrR. It is likely that the intermediate level of sensitivity to gentamicin in the studied strains is mediated by the constitutive expression of the AmrAB-OprA operon, which partially compensates for the structural defects. It is also possible that a dinucleotide deletion in the AAC (6’)-III aminoglycoside-6’-N-acetyltransferase gene, as well as detected mutations in the homologues of the periplasmic linker (BPSL2234) of an uncharacterized efflux operon of the RND family, are involved in the loss of resistance to gentamicin.

Background: Neisseria meningitidis (N. meningitidis) is a leading cause of acute meningitis and is classified into 13 serogroups, six of which are predominantly associated with invasive meningococcal disease. This study aimed to investigate the genotype, subgenotype, and antigenic profiles of N. meningitidis serogroup B strains isolated in Vietnam. Methods: Genotyping was performed on 106 N. meningitidis strains isolated from clinical samples from Vietnamese patients and nasopharyngeal swabs of healthy adolescents between 2019 and 2024. The genetic profiles, including the porA, porB, fetA, fHbp, abcZ, adk, aroE, fumC, gdh, pdhC, and pgm genes, were analyzed using Sanger sequencing and bioinformatic methods. Results: We found that 84.9% of the strains carried VR3 families 36 or 35-1, with VR1, VR2, and VR3 families 22-25, 14, and 36 being the most prevalent. Among the 106 serogroup B isolates, 20 variants of the porB allele 3 were identified, with porB 3-1212 being the most frequent (30.2%). Dominant PorB variable loops included L1.6, L4.5, L5.7, L6.6, and L7.13. fHbp variant group 2 was predominant (104/106 strains), and 12 FetA allele variants were identified, with F1-7 being the most common (47.2%). Three clonal complexes were identified, and clonal complex ST-32 was the most predominant. Fifty-five strains (51.9%) belonged to sequence types that have not yet been assigned to any clonal complexes, and 15 strains (14.1%) with allelic profiles were not assigned to STs. The 3-253 and 3-1212 alleles of porB, the F1-7 variant of FetA, the ST-44 and ST-1576 sequence types, and the ST-41/44 complex were observed more frequently in patients compared to asymptomatic carriers, suggesting their association with more virulence. Conclusions: This study showed a high genetic and antigenic diversity of N. meningitidis serogroup B isolates in Vietnam, with VR3 family 36 most common and porB 3-1212 as the predominant allele. fHbp variant group 2 and FetA allele F1-7 were most frequent. ST-32 was the dominant clonal complex, though many strains remained unassigned, highlighting the need for ongoing molecular surveillance.