• Korean Journal of Poultry Science
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• v.24 no.2
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• pp.67-72
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• 1997

In order to investigate the effect of feeding live yeast (Sacckaromyces cerevisiae) on the growth performance and changes of intestinal microorganism (E. coli), a growth assay was conducted with 144 broiler chicks. Treatments were consisted of corn-soybean meal control, 0.05% live yeast, and 0.05% dead yeast. Most of the chick protein of the live yeast was in the pure protein form, and had a high amino acid composition with 47% of essential amino acids and 53% of non-essential amino acids. No differences in growth performance were shown among dietany treatments. Total number of E. coli in the small intestine of chicks fed either live or dead yeast was significantly reduced compared to chicks fed the control diet. Although the changes of E. coli in the cecum were not identical to differences in the small intestine, the changes of E. coli in the cecurn had a similar trend.

• The Journal of the Korean Society for Microbiology
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• v.17 no.1
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• pp.35-41
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• 1982

Enterotoxigenk E. coli is one of the major causative agents of the infantile diarrhea and traveler's diarrhea. The heat-labile enterotoxin is thought to be a virulence factor in the pathogenesis of the diarrhea and to be a marker for identification of the enterotoxigenic E. coli from non pathogenic E. coli. Therefore knowledge about the heat-labile enterotoxin is essential not only for understanding the pathogenesis but also for the diagnosis of the diarrhea. However the in-vitro heat-labile enterotoxin production is reported to be greatly affected by the cultural condition. In this regards, this study was designed to know the optimal conditions for the production of the heat-labile enterotoxin by assaying the permeability factor in the 18 hours culture supernatant of E. coli 08K25(B2) H9 and of E. coli 015 H11. Results obtained were summerized as follows: 1. Amounts of heat-labile enterotoxin produced were greater at initial pH 8.5 than at 7.0 of CYES-2 broth culture. However, the bacterial growth itself was more abundant at 7.0 than at 8.5. 2. Heat-labile enterotoxin per unit volume of culture supernatant was greater at shaking culture than at standing culture condition, but ratio of the enterotoxin produced over the unit mass of E. coli calculated was greater at standing culture than shaking culture condition, indicating that the greater yields of the toxin produced at shaking culture was due to increase in E. coli cell mass compared to the standing culture condition: 3. The enterotoxin produced in the lincomycin(128 microgram/ml) supplemented media was 5 or 11 times greater on the basis of enterotoxin per unit mass of E. coli, compared to the lincomycin-non-supplemented media, indicating that lincomycin itself increases the enterotoxin production. 4. Treatment of 18 hours culture of E. coli with polymyxin B(0.2 mg/ml) for 1 hour increased the yields of enterotoxin amounting to 2 or 5 times of the non-treated control cultures.

• Journal of Veterinary Science
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• v.23 no.2
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• pp.23.1-23.15
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• 2022

Background: Antibacterial agents play important roles in the treatment of bacterial infections. However, the development of antimicrobial resistance (AMR) and carry-over of substances into the environment are several problems arising during oral treatment of bacterial infections. We assessed AMR development in commensal Escherichia coli (E. coli) in enrofloxacin treated and untreated animals. In addition, we examined fluoroquinolone in the plasma and urine of treated and untreated animals, and in sedimentation dust and aerosol. Methods: In each trial, six pigs were treated with enrofloxacin via powder, granulate or pellet forms in two time periods (days 1-5 and 22-26). Four pigs served as untreated controls. The minimum inhibitory concentration (MIC) was determined to evaluate AMR development. Analysis of enro- and ciprofloxacin was performed with high performance liquid chromatography. Results: Non-wildtype E. coli (MIC > 0.125 ㎍/mL) was detected in the pellet treated group after the first treatment period, whereas in the other groups, non-wildtype isolates were found after the second treatment period. E. coli with MIC > 4 ㎍/mL was found in only the pellet trial. Untreated animals showed similar susceptibility shifts several days later. Bioavailability differed among the treatment forms (granulate > pellet > powder). Enro- and ciprofloxacin were detected in aerosols and sedimentation dust (granulate, powder > pellet). Conclusions: This study indicates that the kind of the oral dosage form of antibiotics affects environmental contamination and AMR development in commensal E. coli in treated and untreated pigs.

• Korean Journal of Clinical Laboratory Science
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• v.52 no.4
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• pp.342-348
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• 2020

Uropathogenic Escherichia coli (UPEC) is a major cause of urinary tract infections (UTIs), which is one of the most common infectious diseases in humans worldwide. Since UPEC is increasingly gaining resistance to many antimicrobial agents, antibiotic therapy of UTI has recently become a great concern. This study examined the epidemiological relationship, and antimicrobial resistance patterns of 84 UPEC isolates obtained from UTI patients in Daejeon, from March to December 2017. Molecular epidemiology was investigated by multilocus sequence typing (MLST), and an antimicrobial susceptibility test was determined using an E-test. In this study, UTI was more common in females (73.8%) than in males (26.2%), and the highest incidence of UTI was observed in the age group in their 70s. Among the 84 UPEC isolates, 59 isolates (70.2%) were multidrug-resistant (MDR), and the major sequence type was ST131 (44 isolates, 52.4%). Interestingly, the rates of MDR in non-ST131 isolates (72.5%) were higher compared to ST131 isolates (68.2%). These results indicate the possibility of the development and spread of MDR in non-ST131 isolates. Effective surveillance networks and continuous research need to be conducted globally to prevent the emergence and international spread of MDR non-ST131 isolates.

• Korean Journal of Microbiology
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• v.27 no.3
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• pp.176-180
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• 1989

There are three pseudourdine ($Psi$)bases in the E. coli $tRNA^{phe}$ In order to study the function of the pseudouridine bases in the $tRNA^{phe}$, changes of bases $tRNA^{phe}$ gene to other bases were undertaken by the site-specific mutagenesis. Site-specific mutagenesis of T in the pheW gene, a $tRNA^{phe}$ gene of E. coli, corresponding to the baseat the No.32 position to C and also T corresponding to the base at the No.39 position to C were performed using Kunkel's uracil-containing template method. Identification of mutants were undertaken by the KNA sequencing techniques of the mutated pheW genes and activities of the mutated pheW genes complementing to E. coli NP37 mutant($pheS^{-ts}$) using the recombinant plasmid containing the mutated genes. Neither NP37 harboring pheW gene mutated at No.32 position nor NP37 harboring pheW gene mutated at No.39 position can be grown at non-permissive temperature. The result means that both mutated pheW genes can not complement to E. coli NP37, and that the pseudouridine bases are essential to the activity of the E. coli $tRNA^{phe}$ in vivo.

• Journal of Food Hygiene and Safety
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• v.6 no.3
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• pp.147-155
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• 1991

Enterotoxigenic E. coli is one of the major causative agents of the infantile diarrhea and traveler's diarrhea. The heat-stable enterotoxin(ST) is thought to be a virulence factor in the pathogenesis of the diarrhea and to be a maker for identification of the enterotoxingeic E. coli from non pathogenic E. coli. The isolate of enterotoxigenlc E. coli was isolated from swine during 1989 year(from 5 to 10 month) in the Kyong-gi and Chung-Cheong provinces, and three strains(KM-4, KM-7 and KM-12) was selected from 189 isolates of ST producing E. coli. The detection of a ST produced of the isolated E. coli was performed by the infant mouse assay(IMA). This study was designed to know optimal conditions for the production of the ST and the molecular properties of plasmids of the enterotoxigenic E. coli. Amount of ST produced were the most at initial pH 8.5~9.0 of succinate salts medium culture. The cultural time of the same medium was accumulated the highest level of ST was at the 14 to 16 hours, and then stationary phase was at the 20 hours. From this experiment the KM-7 strain was selected among ST producing strains by IMA. Partial plasmid-curing experiment was done to select plasmid encoding for ST among other plasmids and then comparing the plasmid pattern of ST producing strain(KM-7) with those of other ST non-producing strains, it is found that ST gene exists on the about 80 Kbp plasmid. Each fragment of this plasmid digested with EcoRl was ligated to vector pBR 322 and transformed into E. coli K-12. A clone producing ST(eKT 53) was selected by IMA. The EcoRl digestion pattern of the isolated plasmid(pKD 37) from the ST producing clone it is indicated that the size of the inserted fragment in eKT 53 strain is 16 Kbp. The cultured supernatant of eKT 53 strain was positive result of ST production in IMA.

• Korean Journal of Veterinary Research
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• v.12 no.1
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• pp.133-139
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• 1972

Estrous and non-estrous rabbits were inoculated with E. coli or Streptococcus pyogenes, and the mixture of the two organisms, and bacterial count and histopathological studies of uterine horns were made to observe the effects of estrogen on the resistance of the uterus to bacterial infection. The results obtained were summarized as followings; 1. Four hours after inoculation of bactoria into uterine horn, the number of organisms was significantly lower in estrous rabbits than in non-estrous regardless of the kind of organisms inoculated. 2. The highest reduction rate of the organisms among the three bacterial inoculation groups was found in estrous rabbits inoculated with E. coli, and the lowest reduction rate was with Streptococcus pyogenes. 3. Histopathological changes of uterine horns induced five days after bacterial inoculation were observed. In estrous rabbits, a mild inflammatory reaction was found in Streptococcus pyogenes group, but a slight inflammatory reaction and only a negligible inflammatory reaction were observed in mixed bacteria group, and in E. coli group respectively. In non-estrous group, however, a marked inflammatory reaction was observed in Streptococcus pyogenes group, a moderate inflammatory reaction and a slight inflammatory reaction were observed in the mixed bacterial group and E. coli group, respectively.

• Korean Journal of Microbiology
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• v.40 no.3
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• pp.232-236
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• 2004

We investigated hydrogen peroxide resistance of Escherichia coli possessing acetyl xylan esterase(AxeA) of Streptomyces coelicolor A3(2). The induction of AxeA production by isopropyl-$\beta$-thiogalactoside was confirmed by SDS-polyacrylamide gel electrophoresis. The differences in growth between induced and non-induced E. coli were determined by the changes in optical density of cultures after hydrogen peroxide treatment The lethal effect of hydrogen peroxide was observed for non-induced cultures at all concentrations tested in this study (lmM, 2.5mM and 5mM). However, cultures induced for AxeA production resisted the lethal effect, except at 5mM where cells were killed irrespective of the AxeA production. The axeA induction increased survival against 1.5mM hydrogen peroxide from 59% to 74%. In addition, AxeA producing E. coli showed increased survival at $45^{\circ}C$, near maximum growth temperature. Therefore, it was concluded that AxeA conferred a cross-resistance upon the bacterium against both oxidative- and heat stress.

• Journal of Food Hygiene and Safety
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• v.18 no.3
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• pp.118-124
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• 2003

For the rapid detection of various pathogenic microorganisms from food sample, various kinds of kits have been developed and commercially available in the markets. With the advantages of speed, accuracy and easiness, the market of these kits has gradually increased for the QC and QA field of food company as well as testing facilities or laboratories. In this study, the characteristics such as the detection limit and the sensitivity of immunochromatographic type of rapid detection kit (Donga Co, Korea, D-kit) for E. coli 0157:H7 developed by monoclonal antibody were examined and also the possibility of application of the kit to food samples was evaluated. The reference kits used for comparison study were Reveal E. coli 0157:H7 (Neogen Co., USA, R-kit) and VIP EHEC kit (Biocontrol Inc., USA, V-kit) occupying major market share. In the detection limit test with the E. coli 0157:H7 reference, both R-kit and D-kit showed a distinct positive reaction in $10^4$/ml and weak positive reaction in $10^3$/ml, whereas V-kit showed a same reaction in 105/ml. Also, it was identified that the culture treated with heat showed more sensitivity than no heat treated culture. The sensitivity test was conducted against 22 isolates of E. coli 0157:H7, 7 strains of non-O157:H7 verotoxin-producing E. coli, 40 strains of E. coli with different O and H antigen type, and 38 strains of non-E. coli Enterobacteriaceae, and all of the test strains except three were showed exactly three were showed exactly the same reaction against three kinds of the tested kits. All the three kinds of kits showed a positive reaction against E. coli O157:H19, E. coli O148:H18 and Salmonella galinarium. We suppose that there might be a similarity in serological property between these three strains and O157:H7. From the test results, it can be concluded that there is (was) no difference between the D-kit developed in this study and R-kit or V-kit based on the detection limit and sensitivity.

• Food Science and Biotechnology
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• v.15 no.4
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• pp.511-515
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• 2006

Antibiotic resistance of foodborne pathogens adapted to garlic (Allium sativum Linn.) was determined in order to understand the relationship between antibiotic resistance and garlic. The Gram (-) strains of Escherichia coli and Salmonella typhimurium and the Gram (+) strains of Bacillus cereus and Staphylococcus aureus were subcultured consecutively in a garlic broth, and the surviving colonies on the agar were selected as the adapted strains. Minimal inhibitory concentrations (MIC) for 15 antibiotics on the adapted strains were determined on Muller-Hinton Infusion agar. Adaptation to 1.3%(v/v) garlic juice increased MIC for vancomycin, aminoglycoside, and erythromycin on B. cereus, and for ampicillin and erythromycin on E. coli O157:H7. MIC of aminoglycosides, chloramphenicol, and vancomycin on the adapted S. aureus increased. The adapted S. typhimurium was more resistant to penicillin and vancomycin than the non-treated strain. The adapted S. typhimurium and S. aureus lost their antibiotic resistance in non-garlic stress conditions. However, the adapted B. cereus was still resistant to erythromycin and vancomycin, and the adapted E. coli was also resistant to erythromycin. Antibacterial garlic might increase the antibiotic resistance of E. coli, B. cereus, S. aureus, and S. typhimurium and this resistance can continue even without the stress of garlic. Therefore, garlic as a food seasoning could influence the resistance of such pathogens to these antibiotics temporarily or permanently.