• Journal of Microbiology and Biotechnology
• /
• v.27 no.8
• /
• pp.1449-1456
• /
• 2017

The prevalence and toxin characteristics of Bacillus thuringiensis isolated from 39 organic vegetables were investigated. B. thuringiensis was detected in 30 out of the 39 organic vegetables (76.9%) with a mean value of 2.60 log CFU/g. Twenty-five out of the 30 B. thuringiensis isolates (83.3%) showed insecticidal toxicity against Spodoptera exigua. The hblCDA, nheABC, and entFM genes were found to be the major toxin genes, but the ces gene was not detected in any of the tested B. thuringiensis isolates. The hemolysin BL enterotoxin was detected in all 30 B. thuringiensis isolates (100%). The non-hemolytic enterotoxin complex was found in 27 out of 30 B. thuringiensis isolates (90.0%). The B. thuringiensis tested in this study had similar toxin gene characteristics to B. cereus, which possessed more than one toxin gene. B. thuringiensis could have the potential risk of foodborne illness based on the toxin genes and toxin-producing ability.

• Korean Journal of Microbiology
• /
• v.9 no.2
• /
• pp.86-93
• /
• 1971

Escherichiae-like organisms were isolated from rectal specimens of 56 children who were either in preschool age or in elementary school. The isolated strains were subjected to tests to screen enteropathogens producing heat-labile enterotoxin and susceptibility test to various antibiotics by disc diffusion method on agar plates. Production of heat-labile enterotoxin by the strains was assyed in the sensitive and reproducible cultured adrenal tumor cell system. The assay was sterodogenesis of the cell in the presence of heat-labile enterotoxin. Among 56 strains, gave positive reaction in the test of toxin production. This meant that about 10% of the children population objected to the study harbored the toxigenic strain of enteropathogenes. Some of these toxigenic strains were resistant to the antibiotics employed in the test. This study suggested that considerable population in Korea may harbor entertoxigenic E. coli as a part of intestinal normal flora. The toxigenic strains which are resistant to antibiotics may bring issue of public health in the future.

• Korean Journal of Veterinary Research
• /
• v.53 no.4
• /
• pp.199-205
• /
• 2013

Avian pathogenic Escherichia coli (APEC) is a causative agent for a number of extra intestinal diseases and account for significant losses to the poultry industry. Since protective immunity against APEC is largely directed to virulence antigens, we have individually expressed four different viulence antigens, papA, papG, IutA, and CS31A, using an attenuated Salmonella Typhimurium and a plasmid pBB244. Following oral immunization of mice with combination of two or four of these strains, serum IgG and mucosal IgA responses were elicited against each antigen represented in the mixture. The antigen-specific mucosal IgA responses were significantly higher in the group of mice immunized with the heat-labile Escherichia coli enterotoxin B subunit (LTB) strain than those in the group of mice immunized without the LTB strain. While, there was no significant difference between these two groups in antigen-specific serum IgG responses. The results showed that LTB could act as mucosal immune adjuvant. To assess the nature of immunity, the distribution of antigen-specific IgG isotypes was analyzed. All groups promoted Th1-type immunity as determined by the IgG2a/IgG1 ratio. Thus, our findings provided evidence that immunization with a combination of several vaccine strains is one of the strategies of developing effective vaccines against APEC.

• Journal of Microbiology and Biotechnology
• /
• v.27 no.4
• /
• pp.709-717
• /
• 2017

Mucosal tissues are the initial site through which most pathogens invade. As such, vaccines and adjuvants that modulate mucosal immune functions have emerged as important agents for disease prevention. Herein, we investigated the immunomodulatory mechanisms of the B subunit of Escherichia coli heat-labile enterotoxin type IIa ($LT-IIa-B_5$), a potent non-toxic mucosal adjuvant. Alternations in gene expression in response to $LT-IIa-B_5$ were identified using a genome-wide transcriptional microarray that focused on dendritic cells (DC), a type of cell that broadly orchestrates adaptive and innate immune responses. We found that $LT-IIa-B_5$ enhanced the homing capacity of DC into the lymph nodes and selectively regulated transcription of pro-inflammatory cytokines, chemokines, and cytokine receptors. These data are consistent with a model in which directional activation and differentiation of immune cells by $LT-IIa-B_5$ serve as a critical mechanism whereby this potent adjuvant amplifies mucosal immunity to co-administered antigens.

• Korean Journal of Veterinary Research
• /
• v.27 no.2
• /
• pp.259-267
• /
• 1987

Enterotoxigenic E. coli (ETEC) cause an acute diarrhea (white scour) in both animals and humans. The disease process initially involves the adherence and colonization of the mucosal surface of the small intestine, followed by the elaboration of a heat-labile enterotoxin (LT) and/or heat-stable enterotoxin (ST). Intestinal adherence or colonization by ETEC is generally mediated by a specific surface-associated pilus (fimbrial) antigen that endows the bacteria with the capacity to adhere to epitherial cell surface. Fourteen monoclonal antibodies (MAbs) directed against pili antigens of ETEC were obtained by cell fusion/hybridoma technique. They were characterized by indirect immunofluorescence assay (IFA), and divided into four groups: specific to K99 antigen (group 1), cross-reactive with K99 and F41 antigens (group 2), specific to K88 antigen (group 3) and specific to 987P and K88 antigens (group 4), respectively. These MAbs demonstrated the distinct pili (K) antigens on the surface of ETEC by IFA, and could be utilized as diagnostic reagent for the identification of ETEC. When eighty-seven field isolates of E. coli from piglet with diarrhea were tested by group 3 MAb, fourty-two strains (48.3%) has K88 pilus antigen suggesting that this is one of the major pilus antigen of ETEC present in fifeld.

• Journal of Microbiology and Biotechnology
• /
• v.22 no.7
• /
• pp.894-901
• /
• 2012

Based on their respective antitumor and thrombolytic activities, the superantigen staphylococcal enterotoxin C2 (SEC2) and staphylokinase (Sak) were chosen for the construction of the novel chimeric proteins Sak-linker-SEC2 and SEC2-linker-Sak using a linker composed of nine Ala residues. Both chimeric proteins possessed nearly the same PBMC proliferation stimulating activity and antitumor activity as SEC2 and thrombolytic activity as Sak. Neither the SEC2 or Sak component of each chimeric protein affected the activity of the other component. The results presented in this study provide a possible strategy to prevent and cure tumor thrombus.

• The Journal of the Korean Society for Microbiology
• /
• v.22 no.2
• /
• pp.131-137
• /
• 1987

The incidnce of enterotoxigenic Esherichia coli(ETEC) was investigated in E. coli strains isolated from Korean infants less than two years old. Over a period of 12 months, ETEC strains have been isolated from 45(45.0%) of 100 children with acute diarrhea and from 9(20.5%) of 44 children without diarrhea. In the group with diarrhea, 41(41.0%) strains produced heat-stable toxin, 3(3.1%) produced heat-labile toxin, and 1(1.0%) produced both heat-stable and heat-labile toxins. In the control group, 7(15.9%) released heat-stable toxin, 2(4.5%) released heat-labile toxin and none released both. A statistical association of strains releasing heat-stable toxin was significant(P<0.025).

• Korean Journal of Veterinary Service
• /
• v.29 no.2
• /
• pp.97-102
• /
• 2006

A total of 1,848 samples was taken from bovine and porcine from January 2003 to November 2005. They were examined for the presence of Clostridiuml perfringens. The properties of the isolates were characterized for Gram staining, biochemical features and enterotoxin production. Forty-one strains (2.2%) of C perfringens were isolated from the 1,848 bovine and porcine carcass using selective media. 30 (3.2%) C perfringens were isolated from the 925 of bovine cacasses, and 11(1.2%) were isolated from the 923 of porcine cacasses. In TSC agar, all isolates showed lecithinase activity. The isolation rate was higher in spring and summer than in autumn and winter. Among 41 isolates, only 1 isolate detected the cpe gene in PCR. The PCR amplified band was observed 233 bp.

• Food Science and Preservation
• /
• v.19 no.5
• /
• pp.757-766
• /
• 2012

The SSH100-10 bacterial strain, which exhibits strong antifungal (anti-mold and anti-yeast) activity, was isolated from traditional korean soysauce aged 100 years. The strain was identified as Bacillus velezensis based on Gram-staining, the biochemical properties and 16S rRNA gene sequence determination. B. velezensis SSH100-10 showed strong proteinase activity and NaCl tolerance, but did not produce enterotoxin. Two-antifungal compounds from B. velezensis SSH100-10 were purified using SPE, preparative HPLC, and reverse phase-HPLC. The purified antifungal compounds were identified as $C_{14}$ and $C_{15}$ iturin through MALDI-TOF-MS and amino acid composition analysis. The stability characteristics of the antifungal compounds after temperature, pH, and enzyme treatments suggested that B. velezensis SSH100-10 produced more than two antifungal compounds; pH-stable $C_{14}$ iturin A and $C_{15}$ iturin A, and unidentified pH-unstable compounds. The results suggested that B. velezensis SSH100-10 can be used in soybean fermentation as a starter. Moreover it has potential as a biopreservative in the food and feed industry and as a biocontrol agent in the field of agriculture.

• Journal of Microbiology and Biotechnology
• /
• v.19 no.5
• /
• pp.502-510
• /
• 2009

Although the Escherichia coli heat-labile enterotoxin B subunit (LTB) has already been expressed in several different systems, including prokaryotic and eukaryotic organisms, studies regarding the synthesis of LTB into oligomeric structures of pentameric size in the budding yeast Saccharomyces cerevisiae have been limited. Therefore, this study used a functional signal peptide of the amylase 1A protein from rice to direct the yeast-expressed LTB towards the endoplasmci reticulum to oligomerize with the expected pentameric size. The expression and assembly of the recombinant LTB were confirmed in both the cell-free extract and culture media of the recombinant strain using a Western blot analysis. The binding of the LTB pentamers to intestinal epithelial cell membrane glycolipid receptors was further verified using a GM1-ganglioside enzyme-linked inmmunosorbent assay (GM1-ELISA). On the basis of the GM1-ELISA results, pentameric LTB proteins comprised approximately 0.5-2.0% of the total soluble proteins, and the maximum quantity of secreted LTB was estimated to be 3 mg/l after a 3-day cultivation period. Consequently, the synthesis of LTB monomers and their assembly into biologically active aligomers in a recombinant S. cerevisiae strain demonstrated the feasibility of using a GRAS microorganism-based adjuvant, as well as the development of carriers against mucosal disease.