Ye Bin Kim

Enterotoxigenic/Shiga toxin-producing hybrid Escherichia coli (ETEC/STEC) strains harbor virulence determinants of both pathotypes and may carry multiple antimicrobial resistance determinants. We characterized the complete genome and antimicrobial resistance profile of the ETEC/STEC hybrid strain GCUHS-1A isolated from a post-weaning pig in Korea. Molecular and bioinformatic analyses identified virulence and antimicrobial resistance genes, plasmid replicons, prophages, serotype, and sequence type, while antimicrobial susceptibility was assessed by minimum inhibitory concentration testing. The 5.64-Mb genome comprised one chromosome and seven plasmids. GCUHS-1A was assigned to sequence type 88 (ST88) and serotype O-untypable:H11. Plasmid-borne eltAB and F18ac fimbrial genes and prophage-encoded stx2e confirmed its ETEC/STEC hybrid profile. The strain was resistant to 16 antimicrobial agents and carried multiple acquired resistance genes and quinolone resistance-associated gyrA substitutions. Despite cephalosporin resistance and a positive extended-spectrum β-lactamase (ESBL) phenotypic confirmatory test, no acquired ESBL or plasmid-mediated ampC genes were detected. To our knowledge, GCUHS-1A is the first completely sequenced porcine-associated ST88 ETEC/STEC hybrid strain reported in Korea. These findings provide a genomic reference for porcine-associated ST88 ETEC/STEC hybrid strains, illustrate the modular coexistence of virulence and multidrug resistance determinants, and highlight the value of integrating phenotype and genomic resistance analyses.

The emergence of multidrug-resistant Shiga toxin-producing Escherichia coli (STEC) poses a major challenge to public health and necessitates the development of alternative antimicrobial strategies. This study aimed to isolate and characterize five lytic bacteriophages belonging to the genus Mosigvirus and evaluate their potential as biocontrol against MDR STEC strains and their biofilms. The five bacteriophages, designated vB_EcoM-pJBB (ΦB), vB_EcoM-pJBC (ΦC), vB_EcoM-pJBJ (ΦJ), vB_EcoM-pJBK (ΦK), and vB_EcoM-pJBL (ΦL), were isolated from sewage treatment plant samples using STEC ATCC 43895 as host. Biological characterization included host range determination against 19 MDR STEC strains, one-step growth analysis, environmental stability assays, bacteriolytic activity assessment, and antibiofilm efficacy testing. Whole-genome sequencing and phylogenetic analyses were performed to determine genomic features and taxonomic classification. The phages demonstrated varying infectious capacities, lysing between six and 12 strains, with ΦL exhibiting the broadest spectrum of activity. All phages showed MOI-independent antibiofilm activity, preventing biofilm formation by approximately 70% and disrupting pre-formed biofilms by up to 80.3%. Genomic analysis revealed the absence of lysogeny markers, virulence factors, and antimicrobial resistance genes, while identifying putative depolymerase genes associated with tail fiber proteins. Phylogenetic analysis confirmed the taxonomic position of these phages within the Mosigvirus genus in the Straboviridae family. Our findings indicate that the newly identified Mosigvirus phages are promising candidates for phage-based biocontrol applications.

Shiga toxin-producing Escherichia coli (STEC) infections have increased in humans, animals, and the food industry, with ready-to-eat (RTE) food products being particularly susceptible to contamination. The prevalence of multidrug-resistant strains has rendered the current control strategies insufficient to effectively control STEC infections. Herein, we characterized the newly isolated STEC phage vB_ESM-pEJ01, a polyvalent phage capable of infecting Escherichia and Salmonella species, and assessed its efficacy in reducing STEC in vitro and food matrices. The phage, belonging to the Tevenvirinae, exhibits effective bacteriolytic activity, a short latent period, large burst size, and stability under a broad pH range and moderate temperatures. Moreover, the phage demonstrated strong anti-biofilm efficacy even at low concentrations. Genomic analysis revealed that the phage was similar to the well-characterized RB49 phage (T4-like phage) but possesses distinct host-specificity-related genes that potentially contribute to its extensive host range. The efficacy of phage vB_ESM-pEJ01 was evaluated in artificially STEC-inoculated green juice samples, where it significantly reduced STEC and the abundance of Shiga toxin-producing genes at 4 and 25 °C. Therefore, these results suggest that the polyvalent phage vB_ESM-pEJ01 is a promising biocontrol agent for foodborne pathogens in RTE foods such as fresh juices.

Acute hepatopancreatic necrosis disease (AHPND) is one of the most important diseases in the global shrimp industry. The emergence of mutant AHPND-associated V. parahaemolyticus (Vp_AHPND) strains has raised concerns regarding potential misdiagnosis and unforeseen pathogenicity. In this study, we report the first emergence of a type II (pirA⁻, pirB⁺) natural mutant, Vp_AHPND (strain 20-082A3), isolated from cultured Penaeus vannamei in Korea. Phenotypic and genetic analyses revealed a close relationship between the mutant strain 20-082A3 and the virulent Korean Vp_AHPND strain 19-021-D1, which caused an outbreak in 2019. Detailed sequence analysis of AHPND-associated plasmids showed that plasmid pVp_20-082A3B in strain 20-082A3 was almost identical (>99.9%) to that of strain 19-021-D1. Moreover, strains 20-082A3 and 19-021-D1 exhibited the same multilocus sequence type (ST 413) and serotype (O1:Un-typeable K-serogroup), suggesting that the mutant strain is closely related to and may have originated from the virulent strain 19-021-D1. Similar to previous reports on the natural mutant Vp_AHPND, strain 20-082A3 did not induce AHPND-related symptoms or cause mortality in the shrimp bioassay. The emergence of a mutant strain which is almost identical to the virulent Vp_AHPND highlights the need for surveillance of the pathogen prevalent in Korea. Further investigations to elucidate the potential relationship between ST 413 and recent Korean Vp_AHPND isolates are needed.

본 연구에서는 북한 지역의 지속가능한 자원개발과 남북 자원교류 협력을 위해 침수 취약성을 고려하여 GIS 기반의 광산-항만 간 교통 연결성을 분석하였다. 북한 지역의 주요 항만 인프라 현황을 파악하고, 광산-항만 간 교통 연결성을 분석해 8개 항만을 중심으로 북한 전체에 대해 권역을 분류한 후, 데이터 취득이 제한적인 북한 지역의 공간적인 침수 취약성을 평가하기 위해 지형적 요인과 기상재해 영향을 고려해 GIS 분석을 수행하였다. 산출된 침수 취약성의 검증을 위해 2020년 8월에 발생한 집중호우 및 태풍 전후의 Sentinel-1B SAR 영상에 대해 전처리를 수행한 후, 수표면 영역을 추출하여 변화를 탐지하였다. 분석 결과, 태풍 및 집중호우 시기 이후의 영상에서 수계 영역 인근으로 수표면 영역이 약 19.4% 확장되었으며, 침수 취약 등급이 높아질수록 침수 영역의 비율 또한 증가했음을 알 수 있었다. 본 연구를 통해 태풍 혹은 집중호우 발생 시 교통 인프라의 예상되는 침수 피해를 정량적으로 파악하였다.