• Journal of Microbiology and Biotechnology
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• v.29 no.9
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• pp.1460-1469
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• 2019

The extensive distribution of multidrug-resistant (MDR) methicillin-resistant Staphylococcus aureus (MRSA) poses a threat to healthcare worldwide. This study aimed to investigate the MDR and molecular patterns of MRSA isolates in children admitted to the two biggest tertiary care pediatric hospitals in northern and southern Vietnam. A total of 168 MRSA strains were collected to determine antibiotic susceptibility by minimum inhibitory concentration tests. Antibiotic-resistant genes, pulsed-field gel electrophoresis, staphylococcal cassette chromosome mec (SCCmec) typing, and multilocus sequence typing were used for the molecular characterization of MRSA. Among the total strains, the MDR rate (51.8%) was significantly higher in the northern hospital than in the southern hospital (73% vs. 39%, p < 0.0001). The MDR-MRSA with the highest rates were "ciprofloxacin-erythromycin-gentamicintetracyclines" (35.6%), followed by "erythromycin-tetracycline-chloramphenicol" (24.1%), and "ciprofloxacin-erythromycin-gentamicin" (19.5%), showing an accumulative total of 79.3%. The most susceptible antibiotics were rifampicin (100%) and vancomycin (100%), followed by doxycycline (94.0%), meropenem (78.0%), and cefotaxime (75.0%). The SCCmecII strains showed greater resistance to gentamicin, ciprofloxacin, tetracycline, meropenem and cephalosporins compared with the other strains. The SCCmecII strains exhibited the highest rate in the tested genes (aacA/aphD: 55.2%, ermA/B/C: 89.7%, and tetK/M: 82.8%). ST5-SCCmecII was the predominant clone in the northern hospital, whereas SCCmecIVa was more pronounced in the southern hospital. In conclusion, our results raised concerns about the predominant MDR-MRSA strains in the pediatric hospitals in Vietnam. The north-south difference in the antibiotic resistance patterns and genetic structure of MRSA suggests different MRSA origins and various uses of antimicrobial agents between the two regions.

• Animal Bioscience
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• v.35 no.1
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• pp.138-146
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• 2022

Objective: The objective of the current study was to investigate the influences of conventional (CO) and deep litter (DE) systems on antimicrobial resistance in fecal Escherichia coli (E. coli). Methods: A cross-sectional study was carried out to detect antimicrobial resistance to E. coli in swine fecal samples in CO and DE systems located in western and northeastern Thailand. Individual rectal swab samples were taken only from healthy pigs. A total of 215 individual and healthy pigs were randomly selected for isolation and antimicrobial susceptibility test of E. coli by the disc diffusion method. The test panel included amoxicillin (AMX), colistin, doxycycline (DOX), enrofloxacin, gentamicin (GEN), kanamycin, neomycin (NEO), and trimethoprim-sulfamethoxazole (SXT). Results: There were significant (p<0.05) lower resistance levels for GEN, NEO, and SXT in the DE farms compared to those in the CO farms. There was a lower number of antimicrobial resistance agents (p<0.001) in the DE farms compared to those in the CO farms. This result was consistent with those in western (p<0.01) and northeastern (p<0.01) Thailand. Overall, antibiograms of AMX-SXT and AMX-DOX-SXT were found in the CO (19.09% and 20.91%, respectively) and the DE (16.19% and 24.76%, respectively) farms. No antimicrobial resistance (5.71%) was found and AMX (13.33%) resistant pigs in the DE farms, whereas the pattern of AMX-GEN-SXT (6.36%) and AMX-DOX-GEN-SXT (11.82%) resistant pigs was found in the CO farms. Conclusion: The DE system for pig farming was superior to conventional pig farming by lowering the resistance level of fecal E. coli to GEN, NEO, and SXT, with decreasing the number of antimicrobial resistance agents and inducing a small proportion of pigs to be free from antimicrobial resistance.

• Journal of fish pathology
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• v.10 no.2
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• pp.125-135
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• 1997

The possibility of identification of families of antibacterial agent residues in fish tissue was studied by disk assay using three test organisms, Bacillus subtilis BGA, Micrococcus luteus ATCC 9341, and Bacillus cereus var. mycoides ATCC 11778. In the present method, a simple clean-up procedure was performed to obtain the aqueous solution from homogenized flounder muscle sample(10g) in Mcilvaine buffer. Then, aqueous solution was fractionated into A and B to be used in disk assay by choloroform and Sep-Pak $C_{18}$ cartridge column after being defatted in hexane. The chloroform layer of fraction A was used for the analysis of macrolide antibiotics(ML), sulfa drugs(SA), chloramphenicol(CP), and quinolone antibiotics(QN). Adsorbed materials to Sep-Pak $C_{18}$ of fraction B were also employed for the analysis of penicillins(PC), tetracyclines(TC), and nitrofuran derivatives(NF) Minimun-detectable concentrations by the present method were, $0.1{\mu}g$/g for oxytetracycline, tetracycline, doxycycline, spiramycin and ciprofloxacin, $0.025{\mu}g$/g for erythromycin and ampicillin, $1.0{\mu}g$/g for sodium nifurstyrenate and florfenical, $0.25{\mu}g$/g for sulfamonomethoxie and sulfadimethoxine, $2.5{\mu}g$/g for oxolinic acid and flumequine, and $15{\mu}g$/g for piromidic acid, respectively. Three test organisms showed different sensitivity patterns for each family of antibacterial agent. Sensitivity patterns were B. cereus > B. subtilis > M. luteus for TC and NF, M. luteus > B, subtilis > B. cereus for ML and PC, B. cereus = B. subtilis > M. luteus for CP and QN, and B. subtilis > B. cereus＝M. luteus for SA. The present method utilizing these characteristics could be useful as a routine screening test for the determination of family of antibacterial agent residues in fish tissue.

• Korean Journal of Poultry Science
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• v.36 no.2
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• pp.177-186
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• 2009

It is well-known that unregulated over-expression of foreign gene may have unwanted physiological or toxic effects in transgenic animals. To circumvent these problems, we constructed retrovirus vector designed to express the foreign gene under the control of the tetracycline-inducible promoter. However, gene expressions in the tetracycline-inducible expression system (Tet system) are not completely regulated but a little leaky due to the inherent defects in conventional Tet-based systems. A more tightly controllable regulatory system can be achieved when the advanced versions ($rtTA2^SM2$) of rtTA and a minimal promoter in responsive components (pTRE-tight) are used in combination therein. In this study, we tried to produce human thrombopoietin (hTPO) from various target cells and transgenic chickens using the retrovirus vector combined with Tet system. hTPO is the primary regulator of platelet production and has an important role in the survival and expansion of hematopoietic stem cells. In a preliminary experiment in vitro, higher hTPO expression and tighter expression control were observed in chicken embryonic fibroblast (CEF) cells. We also measured the biological activity of the hTPO using Mo7e cells whose proliferation is dependant on hTPO. The biological activity of the recombinant hTPO from CEF was higher than both its commercial counterpart and hTPO from other target cells. The recombinant retrovirus was injected beneath the blastoderm of non-incubated chicken embryos (stage X). Out of 138 injected eggs, 15 chicks hatched after 21 days of incubation. Among them, 8 hatched chicks were hTPO positive. When the Go transgenic chicken was fed doxycycline (0.5 mg per 1 gram of feed), a tetracycline derivative, hTPO concentration of the transgenic chicken blood was 200 ng/mL. Germline transmission of the transgene was confirmed in sperm of the Go transgenic roosters. These results are informative to establish transgenic chickens as bioreactors for the mass production of commercially valuable and biological active human cytokine proteins.

• Pediatric Infection and Vaccine
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• v.9 no.2
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• pp.175-181
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• 2002

Purpose : Scrub typhus(tsutsugamushi disease) is a febrile disease characterized by fever, rash, eschar, lymphadenopathy. Therapy with tetracycline(doxycycline) or chloramphenicol is currently recommended for the treatment for scrub typhus. But there are limitations in usage a tetracycline(doxycycline) for scrub typhus in the children. Recently, there was a report that azithromycin, a macrolide antibiotic was used for scrub typhus in pregnant woman successfully. So we evaluated the effectiveness of the Clarithromycin, other a macrolide antibiotic, for scrub typhus. Methods : Seven patients with scrub typhus at department of internal medicine and three patients with scrub typhus at department of pediatrics Masan Fatima Hospital were involved for this study. A serologic diagnosis for scrub typhus were performed by use of passive hemagglutination test. Clarithromycin(Abbott Laboratories, North Chicago, IL, USA) was administrated orally in a daily dose of 500 mg for adult patients and 15 mg/kg/bid/day for pediatric patients. Results : There were 7 cases of adult patients, varying from 28 to 76 years of age and 3 cases of pediatirc patients, varying from 4 to 7 years of age with scrub typhus. All of cases had fever, myalgia, headache, rash, eschar. Seven cases had positive passive hemagglutination test and eight cases had abnormal liver function. Mean duration for the removal of fever after medication was 1.3 day(1~2 days) and all cases were recovered without complications. Conclusion : Our results suggest that Clarithromycin therapy may be effective for scrub typhus.

• Pediatric Infection and Vaccine
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• v.31 no.1
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• pp.25-36
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• 2024

Purpose: Tetracycline is not recommended for children under 12 by guideline due to the risk of tooth discoloration. We aimed to assess the incidence of dental discoloration in Korean children prescribed tetracyclines and investigate whether its risk was greater in tetracycline-exposed children than in the general population. Methods: This population-based cohort study using the Health Insurance Review and Assessment service database included children aged 0-12 years exposed to tetracyclines for at least 1 day between January 2008 and December 2020. The primary outcome was the incidence rate of dental discoloration ≥6 months after prescription, and the standardized incidence ratio (SIR) was evaluated as secondary outcome. Results: 56,990 children were included-1,735 and 55,255 aged <8 and 8-12 years, respectively. 61% children were prescribed tetracycline for <14 days with mostly second-generation tetracyclines, doxycycline (61%) and minocycline (35%). The 5- and 10-year cumulative incidence rates of dental discoloration were 4.1% (95% confidence interval [CI], 3.0-5.7%) and 5.7% (95% CI, 4.1% to 7.8%), respectively, in the 0-7 years age group and 0.8% (95% CI, 0.7% to 0.9%) and 1.3 (95% CI, 1.1% to 1.4%), respectively, in the 8-12 years age group. Tetracycline exposure did not increase such risk compared to that in the general population (SIR, 1.08; 95% CI, 0.69 to 1.60). Conclusions: The incidence of dental discoloration was lower than previously suggested. Relieving the age restriction for prescribing tetracyclines may be considered.

• Pediatric Infection and Vaccine
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• v.8 no.2
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• pp.213-221
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• 2001

Propose : Tsutsugamushi fever is a acute febrile disease, which is caused by O. tsutsugamushi. Recently, this disease is increasingly reported in children. This study was undertaken to investigate clinical features of tsutsugamushi fever in children. Methods : This study involved 17 children with tsutsugamushi fever who were admitted to Masan Samsung hospital between September 1997 and December 2000. We investigated the age, sex ratio, clinical manifestations, laboratory findings, response of therapy and prognosis. Results : The age of patients was $6.9{\pm}3.6$ years, ranging from 6 months to 12 years and male predilection(58.8%) was noted and all cases of patients occured in October or November. The most common symptoms were fever in all cases and headache in 8(47.1%). The most common signs were skin rash in all cases, eschar in 14(82.4%) and lymphadenopathy 8(47.1%). Locations of the eschars were back and inguinal area in each 3 cases, neck and chest in each 2, popliteal area in 2, scalp and thigh in each 1. Laboratory findings included anemia in 1 case, leukopenia and thrombocytopenia in each 5, hematuria and proteinuria in each 1, ESR elevation in 2 and positive CRP in 12, AST elevation in 9 and ALT elevation in 7. Serologic diagnosis was made by passive hemagglutination assay(PHA) in 8 cases(47%) on admission, 4 cases in initial negative group were performed follow-up test at 2nd or 3rd weeks of illness and then all cases of 4 were converted to positive reaction. Clinical improvement was noticed in all cases after treatment to chloramhenicol or doxycycline. Mean duration for defervescence after treatment was $1.4{\pm}0.8$ days. Complications were interstitial pneumonia in 1 case and aseptic meningitis in 3, but all cases of patients were recovered without sequelae or recurrence. Conclusions : Tsutsugamushi fever in children was similiar to adult in the clinical features except male predilection. Early diagnosis and empirical treatment based on clinical manifestations such as fever, skin rash, eschar, lymphadenopathy is important and serologic diagnosis need to perform follow-up test at 2nd or 3rd weeks of illness.

• Journal of Periodontal and Implant Science
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• v.29 no.1
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• pp.233-249
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• 1999

Primary fixation is one of the most important factor in establishing adequate osseointegration between implant and bone. To evaluate the initial healing response of bone around implants without primary bone contact, this study was designed to create considerable space between implant and bone in 5 mongrel dogs, about 1-year old. After 3 holes of 6.0mm in diameter were prepared at the femur neck of the dogs, commercially pure titanium thread type implants(STERI-$OSS^{(R)}$), 8mm in length and 3.8mm, 5.0mm and 6.0mm in diameter, were inserted. Implants were supported by only nonresorbable membrane($Teflon^{(R)}$), and the penetration of upper soft tissue into the gap was inhibited by it. The each implant was positioned in the center of the drilled hole. 9 implants with different diameters were inserted in 3 dogs for histologic observation, and 12 were inserted in 2 dogs for mobility test and removal torque test.Fluorescent dyes were injected in order of Doxycycline, Alizarin Red S, and Calcein at intervals of 2 weeks. At 4-, 8-, and 12-week after placement, 3 dogs were sacrificed for histologic observation, and at 8- and 12-week after placement, 2 dogs were sacrificed for mobility test using $Periotest^{(R)}$ (Simens AG, Bensheim, Germany) and torque test using Autograph AGS-1000D $series^{(R)}$(Japan). The result were as follows: 1. The wider the gap between bone and implant was, the less bone maturity was, and the later osseointegration was occurred. Trabecular direction of new bone around implant was changed from parallel to perpendicular to the implant, and the gap was filled with new bone, over time. 2. There was a decreasing tendency over time in the mobility of all implants, but the wider gap between bone and implant was, the smaller decrease of the mobility was. 3. There was a increasing tendency over time in the removal torque gauge of all implants, and the wider gap was, the smaller increase of the removal torque gauge was. The results suggest that osseointegration in case of implant without primary bone contact may be obtained by guided bone regeneration technique with prolonged healing period, but the time of second surgery should be considered carefully.

• Journal of Food Hygiene and Safety
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• v.22 no.4
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• pp.370-374
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• 2007

An analytical method for the simultaneous determination of four tetracycline (oxytetracycline, tetracycline, chlortetracycline, doxycycline) in egg samples was developed and validated using liquid chromatography with ultraviolet detection. Egg samples were extracted by the liquid-liquid extraction based on acetonitrile. The chromatographic separation was achieved on a reverse phase C8 column with gradient elution using a mobile phase of 20 mM oxalic acid (pH 1.5)/acetonitrile. The procedure was validated according to the Food Drugs Administration guideline determining accuracy, precision, and limit of detection. Mean recovery of tetracyclines from spiked egg samples (50, 100, 200, 400, and $800{\mu}g/kg$) were 78.8-109.3%. Linearity in concentration range of $50-800{\mu}g/kg$ was obtained with the correlation coefficient $(r^2)$ of 0.994-0.999. The intra- and inter-day precision (relative standard deviation; RSD) was between 0.3-12.8 and 0.2-11.7%, respectively. Limit of detection (LOD) and limit of quantification (LOQ) for the investigated tetracyclines were 30 and $50{\mu}g/kg$ depending on egg samples, respectively. This method was reliable, sensitive, economical and suitable for routine monitoring of tetracycline residues in dairy egg.

• Tuberculosis and Respiratory Diseases
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• v.70 no.5
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• pp.405-415
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• 2011

Background: In an effort to find alternative therapeutic agents to prevent excessive fibrosis as a sequela to complicated parapneumonic effusion or empyema, we examined the effect of tissue plasminogen activator (tPA) as a fibrinolytic agent combined with talc or transforming growth factor (TGF)-${\beta}1$ in a human pleural mesothelial cell line, MeT-5A. Methods: MeT-5A cells were stimulated with various doses of talc, doxycycline or TGF-${\beta}1$ for 24 h and then were treated with tPA for an additional 24 h. Cell viability was measured by MTT assay. The production of interleukin (IL)-8 and vascular endothelial growth factor (VEGF) in the culture supernatants was measured by ELISA. Real-time PCR was carried out for measurement of type I collagen mRNA. Results: MeT-5A cells treated with talc showed a dose-dependent increase in production of IL-8. Talc also increased production of type I collagen mRNA at low doses, but talc did not influence the induction of VEGF. Addition of tPA to talc-stimulated cells showed further increases in the production of IL-8, but tPA did not influence the production of VEGF or type I collagen mRNA. TGF-${\beta}1$ increased the production of both VEGF and collagen type I mRNA, both of which were effectively inhibited by additional tPA treatment in MeT-5A cells. Conclusion: TGF-${\beta}1$ is a potent inducer of collagen synthesis without induction of IL-8 in MeT-5A cells. Addition of tPA after TGF-${\beta}1$ stimulation inhibited further fibrosis by direct inhibition of collagen mRNA synthesis as well as by inhibition of VEGF production.