• Journal of Microbiology and Biotechnology
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• 제29권8호
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• pp.1273-1280
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• 2019

Edwardsiella piscicida is the causative agent of edwardsiellosis, which has caused enormous economic losses worldwide. In our previous research, an attenuated live vaccine known as WED and based on the virulent strain E. piscicida EIB202 can effectively protect turbots against edwardsiellosis via intraperitoneal injection, while vaccination by immersion exhibits a weaker effect. During the development of the immersion vaccine, we surprisingly found the counts of ${\Delta}pEIB202/EIB202$ colonized on zebrafish were 100 times lower than those of EIB202. However, pEIB202 carries 53 predicted ORFs and has several copies in E. piscicida EIB202, impeding the study of its function. Thus, the replication region is located at a 1,980 bp fragment (from 18,837 to 20,816 bp), containing a transcriptional repressor and a replication protein. Moreover, the minimal replication plasmid, named pRep-q77, has low copies in both E. coli and E. piscicida, but is more stable in E. piscicida than in E. coli. This work lays a foundation for further examination of the function of the virulence plasmid pEIB202.

• 대한미생물학회지
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• 제34권6호
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• pp.513-518
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• 1999

A total of 113 Vibrio sp. strains were examined for plasmid content which were subjected to digestion with restriction enzymes. About the 55% Vibrio spp. have the plasmid more than one. Most of these plasmid various derivatives ranged from $2.4\;kb{\sim}23\;kb$, especially two strains of V. mimicus and one strain of V. furnissii carried one high-molecular weight plasmid (molecular weight ranging between $70\;kb{\sim}100\;kb$). Results of restriction analysis for plasmid of this three strains were by no means the rule. For detection of tdh and ctx gene, the virulence factor involved in the pathogenesis, we carried out the TDH and CT assay, PCR amplification, and hybridization. A total 11 strains were produced TDH, involved in 9 strains of V. parahaemolyticus and 1 strain of V. alginolyticus from clinical isolates and 1 strains of V. mimicus from environmental isolates. In the experiments of tdh gene detection, in all, 3 strains of V. parahaemolyticus from clinical isolates and 2 strains from environmental isolates could be successfully amplified in 400 bp by PCR. The PCR results were consistent with DNA hybridization tests. In the experiments of CT assay, in all, 3 strains of V. cholerae from clinical isolate and 1 strain of V. cholerae from environmental isolates were observed CT-producing. These CT-producing strains amplified in 302 bp by PCR for the detection of ctx gene. All CT-producing strains hybridized with digoxigenin-labeled DNA probe, while CT-negative strains did not hybridize. Also hybridization tests results for detection of ctx gene consistent with PCR.

• 한국미생물·생명공학회지
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• 제51권4호
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• pp.390-402
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• 2023

Salmonella are Gram-negative pathogenic bacteria commonly found in food animals such as poultry and swine and potentially constitute risks and threats to food safety and public health through transmissible virulence and antimicrobial resistance (AMR) genes. Although there are previous studies in the Philippines regarding genotypic and phenotypic AMR in Salmonella, there are very few on virulence and their associations. Hence, this study collected 700 Salmonella isolates from swine samples in abattoirs and wet markets among four districts in Metro Manila and characterized their genotypic virulence and β-lactam AMR profiles. Gene frequency patterns and statistical associations between virulence and bla genes and comparisons based on location types (abattoirs and wet markets) and districts were also determined. High prevalence (>50%) of virulence genes was detected encompassing Salmonella pathogenicity islands (SPIs) 1-5 suggesting their pathogenic potential, but none possessed plasmid-borne virulence genes spvR and spvC. For bla, bla_TEM was detected with high prevalence (>45%) and revealed significant associations to four SPI genes, namely, avrA, hilA, mgtC, and spi4R, which suggest high resistance potential particularly to β-lactam antibiotics and relationships with pathogenicity that remain mechanistically unestablished until now. Lastly, comparisons of location types and districts showed variations in gene prevalence suggesting effects from environmental factors throughout the swine production chain. This study provides vital data on the genotypic virulence and AMR of Salmonella from swine in abattoirs and wet markets that suggest their pathogenicity and resistance potential for policymakers to implement enforced surveillance and regulations for the improvement of the Philippine swine industry.

• Journal of Microbiology and Biotechnology
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• 제20권1호
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• pp.5-14
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• 2010

Enterohemorrhagic Escherichia coli O157:H7 is a major foodborne pathogen causing severe disease in humans worldwide. Healthy cattle are a reservoir of E. coli O157:H7, and bovine food products and fresh produce contaminated with bovine waste are the most common sources for disease outbreaks in the United States. E. coli O157:H7 also survives well in the environment. The abilities to cause human disease, colonize the bovine gastrointestinal tract, and survive in the environment require that E. coli O157:H7 adapt to a wide variety of conditions. Three major virulence factors of E. coli O157:H7 have been identified including Shiga toxins, products of the pathogenicity island called the locus of enterocyte effacement, and products of the F-like plasmid pO157. Among these virulence factors, the role of pO157 is least understood. This review provides a board overview of E. coli O157:H7 with an emphasis on pO157.

• Animal cells and systems
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• 제3권4호
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• pp.399-405
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• 1999

Characteristics of the food isolates and the clinical specimens isolates of E. coli harboring virulence factor and their correlations were analyzed. The predominant serogroup were 08 and 027 in the food isolates and 06 and 018 in the clinical isolates, respectively, showing the different patterns in serogrouping between them. In the test of antibiotic susceptibility, the food isolates were resistant to cephalothin, streptomycin, tetracycline and minocycline, and the clinical isolates were resistant to ampicillin, carbenicillin, streptomycin, cephalothin, trimethoprim/sulfamethoxazole, tetracyclino and minocycline, respectively. It shows that E.coli isolated from food sources and clinical specimens might be correlated. Plasmid profile in the food and clinical isolates showed wide diversity. Especially, large sized plasmid DNA such as 60 MDa, 90 MDa and 120 MDa were observed. The plasmid DNA (60 MDa) containing a gene encoding hemolysin was found in 43% of the food isolates and 35% of the clinical isolates. To study chromosomal homology, PFGE analysis was performed, showing different restriction patterns by Xbal. This result indicates that there were no genetic correlations between the foods and the clinical isolates.

• Journal of Microbiology
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• 제44권1호
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• pp.98-105
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• 2006

Yersinia enterocolitica induces a broad range of gastrointestinal syndromes, including acute enteritis. We previously reported that the clinical isolate, Y. enterocolitica KU14, which lacks pYV, was still capable of causing clinical infection. The present study demonstrated that KU14 did not trigger the death of macrophages in vitro, unlike WA-314 (ATCC51871, which harbors the pYV virulence plasmid). However, the intracellular growth of KU14 in the macrophages was greater than that of WA-C (ATCC51872, a non-plasmid harboring the derivative pYV plasmid). Treatment with a cholesterol-binding drug $(\beta-cyclodextrin)$ that affected lipid rafts resulted in a dramatic reduction in the inracellular growth of KU14. These data clearly indicate that the enhanced inracellular growth of KU14 is related to lipid raft-mediated infection.

• Fisheries and Aquatic Sciences
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• 제16권4호
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• pp.221-227
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• 2013

In total, 131 Escherichia coli isolates from surface seawater of the Gomso Bay, of Korea, were analyzed for their susceptibility to 22 different antimicrobials and for genes associated with antimicrobial resistance and virulence. According to the disk diffusion susceptibility test, the resistance to tetracycline was most prevalent (33.6%), followed by that to ampicillin (22.1%), ticarcillin (22.1%), and trimethoprim (16.8%). More than 46.6% of the isolates were resistant to at least one antimicrobial, and 22.9% were resistant to three or more classes of antimicrobials; these were consequently defined as multidrug resistant. We further found that 29 ampicillin-resistant isolates possessed genes encoding TEM-type (93.1%) and SHV-type (6.9%) ${\beta}$-lactamases. Among the 44 tetracycline-resistant isolates, tetA and tetC were found in 35 (79.5%) and 19 (43.2%), respectively, whereas tetB was detected in only three isolates (6.8%). With regard to virulence genes, merely 0.8% (n = 1) and 2.3% (n = 3) of the isolates were positive for the enteroaggregative E. coli-associated plasmid (pCVD432) gene and the enteropathogenic E. coli-specific attaching and effacing (eae) gene, respectively. Overall, these results not only provide novel insight into the necessity for seawater sanitation in Gomso Bay, but they help reduce the risk of contamination of antimicrobial-resistant bacteria.

• 대한수의학회지
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• 제60권3호
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• pp.163-171
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• 2020

This study examined the prevalence of adherence factors, toxin genes, antimicrobial resistance phenotypes, and resistance genes in Escherichia coli (E. coli) isolated from piglets with diarrhea before and after the ban on antibiotic growth promoters (AGPs) in Korea from 2007 to 2018. In this period, pathogenic 474 E. coli isolates were obtained from diarrheic piglets. The virulence factors and antimicrobial resistance genes were assayed using a polymerase chain reaction, and the susceptibility to antibiotics was tested according to the Clinical and Laboratory Standards Institute guidelines. After the ban on AGPs, the frequency of F4 (12.5% to 32.7%) increased significantly, and LT (31.9% to 20.3%) and EAST-I (46.5% to 35.2%) decreased significantly. In addition, the resistance to streptomycin (45.8% to 67.9%), cephalothin (34.0% to 59.4%), and cefazlin (10.4% to 28.8%) increased significantly. Colistin resistance plasmid-mediated genes, mcr-1 and mcr-3, were detected after the ban on AGPs. The results of this study can provide useful data for analyzing the impact of the ban on AGPs on the virulence profiles and antimicrobial resistance of E. coli isolated from piglets with diarrhea in Korea.

• Journal of Microbiology and Biotechnology
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• 제27권11호
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• pp.1983-1993
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• 2017

Salmonella enterica subsp. enterica serovar Typhimurium, one of the most common foodborne pathogens, is transmitted mainly through contaminated food derived from infected animals. In this study, S. Typhimurium ST1120, an isolate from pig feces in Korea, was subjected to whole-genome analysis to understand its genomic features associated with virulence. The genome of ST1120 was found to have a circular chromosome of 4,855,001 bp (GC content 52.2%) and a plasmid of 6,863 bp (GC content 46.0%). This chromosome was predicted to have 4,558 open reading frames (ORFs), 17 pseudogenes, 22 rRNA genes, and 86 tRNA genes. Its plasmid was predicted to have three ORFs. Comparative genome analysis revealed that ST1120 was phylogenetically close to S. Typhimurium U288, a critical isolate in piggery farms and food chains in Europe. In silico functional analysis predicted that the ST1120 genome harbored multiple genes associated with virulence and stress resistance, including Salmonella pathogenicity islands (SPIs containing SPI-1 to SPI-5, SPI-13, and SPI-14), C63PI locus, ST104 prophage locus, and various antibiotic resistance genes. In accordance with these analysis results, ST1120 showed competence in invasion and survival abilities when it was added to host cells. It also exhibited robust resistance against antibiotics in comparison with other S. Typhimurium strains. This is the first report of the complete genome sequence of S. Typhimurium isolated from swine in Korea. Comparative genome analysis between ST1120 and other Salmonella strains would provide fruitful information toward understanding Salmonella host specificity and developing control measures against S. Typhimurium infection.

• Journal of Microbiology and Biotechnology
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• 제33권3호
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• pp.329-338
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• 2023

Enterohemorrhagic Escherichia coli (EHEC) is a foodborne pathogen that produces attaching and effacing lesions on the large intestine and causes hemorrhagic colitis. It is primarily transmitted through the consumption of contaminated meat or fresh produce. Similar to other bacterial pathogens, antibiotic resistance is of concern for EHEC. Furthermore, since the production of Shiga toxin by this pathogen is enhanced after antibiotic treatment, alternative agents that control EHEC are necessary. This study aimed to discover alternative treatments that target virulence factors and reduce EHEC toxicity. The locus of enterocyte effacement (LEE) is essential for EHEC attachment to host cells and virulence, and most of the LEE genes are positively regulated by the transcriptional regulator, Ler. GrlA protein, a transcriptional activator of ler, is thus a potential target for virulence inhibitors of EHEC. To identify the GrlA inhibitors, an in vivo high-throughput screening (HTS) system consisting of a GrlA-expressing plasmid and a reporter plasmid was constructed. Since the reporter luminescence gene was fused to the ler promoter, the bioluminescence would decrease if inhibitors affected the GrlA. By screening 8,201 compounds from the Korea Chemical Bank, we identified a novel GrlA inhibitor named Grlactin [3-[(2,4-dichlorophenoxy)methyl]-4-(3-methylbut-2-en-1-yl)-4,5-dihydro-1,2,4-oxadiazol-5-one], which suppresses the expression of LEE genes. Grlactin significantly diminished the adhesion of EHEC strain EDL933 to human epithelial cells without inhibiting bacterial growth. These findings suggest that the developed screening system was effective at identifying GrlA inhibitors, and Grlactin has potential for use as a novel anti-adhesion agent for EHEC while reducing the incidence of resistance.