Sun-Hee Cho

Clinical features and risk factors for striae distensae in Korean adolescents

Background  Despite the high prevalence of striae distensae, clinical studies are few in number, and their pathophysiology still obscure.

Molecular epidemiology of Newcastle disease in Republic of Korea

Twenty-three strains of Newcastle disease virus (NDV) isolated between 1988 and 1999 in Republic of Korea were studied by partial nucleotide sequencing of fusion (F) gene and phylogenetic analysis. Most of Korean strains formed a distinctive cluster in genotype VI and they were genetically distant (4.0-8.7%) from other subtypes (a, b, c, d, and e), and termed provisionally VIf. Some Korean strains isolated in 1995 were grouped into genotype VIIa and they were closer to Taiwan strains than western Europe. The results suggest that the genotype VIf strains have been maintained by enzootic infections during the past decade, while genotype VIIa appears to be introduced more recently in Republic of Korea.

Chronological Study of Antibiotic Resistances and Their Relevant Genes in Korean Avian Pathogenic Escherichia coli Isolates

ABSTRACT Antibiograms and relevant genotypes of Korean avian pathogenic Escherichia coli (APEC) isolates (n = 101) recovered between 1985 and 2005 were assessed via disc diffusion test, PCR, restriction enzyme analysis, and sequencing. These isolates were highly resistant to tetracycline (84.2%), streptomycin (84.2%), enrofloxacin (71.3%), and ampicillin (67.3%), and most of the tetracycline, streptomycin, enrofloxacin, and ampicillin resistances were associated with tetA and/or tetB, aadA and/or strA-strB, mutations in gyrA and/or parC, and TEM, respectively. Class 1 integrons were detected in 40 isolates (39.6%), and a variety of gene cassettes conferring streptomycin (aadA), gentamicin (aadB), and trimethoprim (dfr) resistances were identified: aadA1a (27.5%), dfrV-orfD (2.5%), aadB-aadA1a (2.5%), dfrI-aadA1a (47.5%), dfrXVII-aadA5 (12.5%), and dfrXII-orfF-aadA2 (7.5%). In addition, several types of common promoters (Pant) of the gene cassettes (hybrid P1, weak P1, or weak P1 plus P2) and single-nucleotide polymorphisms in aadA1a were identified. The results of a chronological analysis demonstrated significant and continuous increases in the frequencies of resistances to several antibiotics (tetracycline, streptomycin, enrofloxacin, ampicillin, and trimethoprim-sulfamethoxazole) and of the relevant resistance genes (tetA, strA-strB, and TEM), mutations in gyrA and parC, and multidrug-resistant APEC strains during the period 2000 to 2005.

Variation of a Newcastle Disease Virus Hemagglutinin-Neuraminidase Linear Epitope

ABSTRACT Fifty-six Newcastle disease virus strains collected from 2000 to 2006 could be grouped into subgenotype VIId. However, they displayed cumulative mutations in and around the linear epitope of hemagglutinin-neuraminidase (residues 345 to 353) with time. The antigenicities of the variants that became predominant in Korea differ from each other and from the wild type.

Pathogenicity of SG 9R, a rough vaccine strain against fowl typhoid.

SG 9R, a rough vaccine strain of Salmonella gallinarum, has been used for the prevention of fowl typhoid and paratyphoid in the world despite the presence of residual virulence. SG 9R-like rough strains have been recently isolated from fowl typhoid cases; however, molecular markers to differentiate SG 9R from field strains are not well-characterized and the molecular mechanisms of SG 9R residual virulence are unclear. Therefore, we analyzed LPS biosynthesis (rfa gene cluster) and virulence genes (spv, SPI-2) of both SG 9R and S. gallinarum rough field strains. SG 9R carried a unique nonsense mutation in rfaJ (TCA to TAA) and a shared rfaZ mutation (G-deletion) by rough and smooth S. gallinarum strains. SG 9R also carried intact SPI-2 and spvC, B, A, and R (except deleted spvD). SG 9R-like rough strains (n=10) carried identical mutations in virulence-related genes to SG 9R. SG 9R and SG 9R-like rough strains did not demonstrate significant mortality or liver lesions under normal conditions. However, fowl typhoid was successfully reproduced in the present study by SG 9R inoculation to 1-day-old male brown layer chicks per os following starvation. Therefore, the LPS defect may be one of the major mechanisms of SG 9R attenuation, and the possession of intact SPI-2, spvC, B, A, and R virulence genes may be associated with residual SG 9R virulence.

Characterization of a T7-like lytic bacteriophage (φSG-JL2) of Salmonella enterica serovar gallinarum biovar gallinarum

ABSTRACT φSG-JL2 is a newly discovered lytic bacteriophage infecting Salmonella enterica serovar Gallinarum biovar Gallinarum but is nonlytic to a rough vaccine strain of serovar Gallinarum biovar Gallinarum (SG-9R), S. enterica serovar Enteritidis, S. enterica serovar Typhimurium, and S. enterica serovar Gallinarum biovar Pullorum. The φSG-JL2 genome is 38,815 bp in length (GC content, 50.9%; 230-bp-long direct terminal repeats), and 55 putative genes may be transcribed from the same strand. Functions were assigned to 30 genes based on high amino acid similarity to known proteins. Most of the expected proteins except tail fiber (31.9%) and the overall organization of the genomes were similar to those of yersiniophage φYeO3-12. φSG-JL2 could be classified as a new T7-like virus and represents the first serovar Gallinarum biovar Gallinarum phage genome to be sequenced. On the basis of intraspecific ratios of nonsynonymous to synonymous nucleotide changes (Pi[a]/Pi[s]), gene 2 encoding the host RNA polymerase inhibitor displayed Darwinian positive selection. Pretreatment of chickens with φSG-JL2 before intratracheal challenge with wild-type serovar Gallinarum biovar Gallinarum protected most birds from fowl typhoid. Therefore, φSG-JL2 may be useful for the differentiation of serovar Gallinarum biovar Gallinarum from other Salmonella serotypes, prophylactic application in fowl typhoid control, and understanding of the vertical evolution of T7-like viruses.

Characterization of a Recombinant Newcastle Disease Virus Vaccine Strain

ABSTRACT A recombinant La Sota strain (KBNP-C4152R2L) in which fusion (F) and hemagglutinin-neuraminidase (HN) genes were replaced with those of a contemporary genotype VIId virus, KBNP-4152, has been developed. To attenuate the virulence of the recombinant strain, the F cleavage motif was mutated from 112RRQKR116 to 112GRQAR116, and to reduce pathogenic instability, a codon which does not allow changes to basic amino acids by single point mutation was inserted at codon 115. In addition a six-nucleotide sequence was inserted into the intergenic region between matrix protein and F genes for attenuation without breaking the “rule-of-six.” The HN protein length was increased from 571 to 577 as a marker. Serological tests revealed that the antigenicity of KBNP-C4152R2L was similar to that of KBNP-4152 but distinct from that of the La Sota strain. KBNP-C4152R2L was avirulent (intracerebral pathogenicity index, 0.0; mean death time, >168 h) and stable in pathogenicity through in vivo passages. The killed oil emulsion of and live KBNP-C4152R2L were completely protective against mortality and egg drop caused by virulent strains, and KBNP-C4152R2L was applicable to in ovo vaccination. Therefore, KBNP-C4152R2L is a promising vaccine strain and viral vector in terms of antigenicity, productivity, safety, and pathogenic stability.

Reproduction of Fowl Typhoid by Respiratory Challenge with Salmonella Gallinarum

Abstract Fowl typhoid is a disease of adult chickens and is caused by Salmonella Gallinarum infection via the alimentary tract. The experimental reproduction of fowl typhoid per os (PO) requires artificial conditions to minimize the effect of gastric acid, and several Salmonella serovars have been known to be transmitted via the respiratory route. Therefore, we have hypothesized the existence of a respiratory route for Salmonella Gallinarum infection and have attempted to reproduce fowl typhoid via intratracheal challenge. In accordance with our hypothesis, the intratracheal challenges of Salmonella Gallinarum reproduced exactly same lesions as fowl typhoid and induced higher mortality and morbidity than those of the PO challenge. Therefore, this study represents the first reproduction of fowl typhoid via respiratory route, and our findings may be useful for understanding the transmission of Salmonella Gallinarum in the field.

Presence of human mycoplasma DNA in gastric tissue samples from Korean chronic gastritis patients

We aimed to determine whether mycoplasmas are present in Korean chronic gastritis, and to understand their roles in gastric cancer tumorigenesis, because mycoplasmas resemble Helicobacter pylori in terms of ammonia production and induction of inflammatory cytokines in immune and non‐immune cells. The presence and identity of mycoplasmas were assessed by semi‐nested PCR and sequencing, and the results were compared with pathologic data. Fifty‐six samples collected from Korean chronic gastritis patients were used for this study. Twenty‐three (41.1%) were positive for mycoplasmas. Eighteen sequenced samples contained a single human mycoplasma or two mycoplasmas, which were identified as Mycoplasma faucium (13/18), M. fermentans (3/18), M. orale (1/18), M. salivarium (2/18), and M. spermatophilum (1/18). Mycoplasma‐infected chronic gastritis samples showed significantly more severe neutrophil infiltration than non‐infected samples (P=0.0135). Mycoplasma profiles in the oral cavity (M. salivarium is major) and stomach were different, and the presence of significant proinflammatory responses in mycoplasmapositive patients suggests that the mycoplasmas are not simply contaminants. Further studies are required to understand whether mycoplasmas play a role in gastric tumorigenesis.

High-dose squalene ingestion increases type I procollagen and decreases ultraviolet-induced DNA damage in human skin in vivo but is associated with transient adverse effects

Background.  Evidence for beneficial effects of squalene on ultraviolet (UV)‐induced photoageing of the skin is lacking.