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Gebru, Elias,Lee, Joong-Su,Chang, Zhi-Qiang,Hwang, Mi-Hyun,Cheng, Henrique,Park, Seung-Chun American Society for Microbiology 2009 Antimicrobial Agents and Chemotherapy Vol.53 No.7
<B>ABSTRACT</B><P>The pharmacokinetics (PK) and pharmacodynamics (PD) of orbifloxacin were studied in beagle dogs after intravenous (i.v.) and intramuscular (i.m.) administration at a dose of 2.5 mg/kg body weight. An absolute bioavailability of 100.1% ± 4.76%, a terminal half-life of 4.23 ± 0.2 h and 3.95 ± 0.15 h after i.v. and i.m. administration, a steady-state volume of distribution of 1.61 ± 0.13 liters/kg, and clearance of 0.31 ± 0.03 liters/h/kg were observed. Orbifloxacin showed rapid, concentration-dependent killing against the <I>Escherichia coli</I>, <I>Staphylococcus aureus</I>, <I>Staphylococcus intermedius</I>, and <I>Proteus mirabilis</I> clinical isolates. Computations based on PK-PD analysis indicated that the recommended dose is unlikely to be clinically effective against some strains like <I>S. intermedius</I>. Therefore, a higher dose of orbifloxacin would be worthy of consideration for treatment of certain bacterial infections in dogs.</P>
Gebru, Elias,Damte, Dereje,Choi, Myung-Jin,Lee, Seung-Jin,Kim, Young-Hoan,Park, Seung Chun Elsevier 2012 Veterinary microbiology Vol.154 No.3
<P><B>Abstract</B></P><P>The antibacterial activity, selection of <I>Escherichia coli</I> (<I>E. coli</I>) mutants and mechanisms of fluoroquinolone resistance were investigated by integrating the minimum inhibitory concentration (MIC), mutant prevention concentration (MPC) and <I>in vitro</I> dynamic model approaches. Difloxacin and orbifloxacin, for which the above information has been scarce, were used. A range of area under curve over a 24h interval (AUC<SUB>24h</SUB>)/MIC ratios and selected <I>E. coli</I> strains were investigated using the dynamic models. Continuous incubation for three days in the presence of difloxacin or orbifloxacin resulted in losses in <I>E. coli</I> susceptibility. An AUC<SUB>24h</SUB>/MIC (AUC<SUB>24h</SUB>/MPC)-dependent fluoroquinolone activity and selection of <I>E. coli</I> mutants was confirmed. Maximum losses in susceptibility occurred at AUC<SUB>24h</SUB>/MIC ratios of 54 (orbifloxacin) and 57.3 (difloxacin). AUC<SUB>24h</SUB>/MIC ratios of 169.8 (orbifloxacin) and 199.5 (difloxacin) were estimated to be protective against the selection of <I>E. coli</I> mutants, and the corresponding ratios based on AUC<SUB>24h</SUB>/MPC predictions were 34 (orbifloxacin) and 36.3 (difloxacin). When integrating our <I>in vitro</I> data with pharmacokinetic data in dogs, the conventional clinical doses of both drugs were found to be inadequate to attain the above protective values for 90% of the mutant subpopulation (AUC<SUB>24h</SUB>/MPC<SUB>90</SUB>). Both target mutations, esp. at codon 83 (Ser to Leu) of <I>gyrA</I>, and overexpression of efflux pumps contributed to resistance development, with mutants also showing decreased susceptibility to enrofloxacin and marbofloxacin. Additional studies would determine the role of mutations found outside the QRDR, at codon 24 of <I>gyrA</I>, and at codon 116 of <I>parC</I>, and establish the significance of these observations <I>in vivo</I>.</P>
Elias gebru,Seungjin Lee,Dereje Damte,Woosik Jo,Seungchun Park 한국버섯학회 2010 한국버섯학회지 Vol.8 No.4
Phellinus gilvus(PG) is a medicinal mushroom belonging to the Hymenochaetaceae basidiomycetes, and has advantages over many Phellinus species due to its short growth period (3 mo), making it cheaper to produce. In the current investigation, we determined the major components of the ethyl acetate extract of PG responsible for its biological activities and further compared the magnitude of the antioxidant/anti-inflammatory activities of components with the various fractional extracts of PG. As the results, the average total DPPH radical scavenging activities of both Fd and Fc of PG was 10 mg/mL, > 95%. Among the fractional extracts of PG, Fd had the greatest inhibitory activity with an IC50 value of 36.70㎍/mL, whereas Fb showed the lowest activity. PCA had even greater activity of NO inhibition than Fd with an IC50 value of 19.46㎍/mL. The mRNA expression of iNOS or COX-2 was nearly undetectable in the absence of LPS. However, LPS- stimulation markedly increased the expression of both iNOS and COX-2 genes. Fd inhibited the effect of LPS in a concentration-dependent manner. Six major compounds were identified from the ethyl acetate extract of PG, and protocatechualdehyde (PCA) was supposed to be the major phenolic compound of PG responsible for its DPPH free radical scavenging activity and its inhibitory effects on LPS-induced NO production in RAW264.7 cells. Further in vitro and in vivo experiments are currently underway to confirm this observation and to investigate the detailed molecular mechanisms involved in the process as well as the biological activities of other fractions of Fd.
Probiotic properties and adsorption of Enterococcus faecalis PSCT3-7 to vermiculite
김진윤,Elias Gebru Awji,박나혜,박지영,김종춘,이삼빈,서주원,박승춘 대한수의학회 2017 Journal of Veterinary Science Vol.18 No.1
The probiotic properties of Enterococcus (E.) faecalis PSCT3-7, a new strain isolated from the intestines of pigs fed dietary fiber containing 50% sawdust, were investigated. E. faecalis PSCT3-7 tolerated a pH range of 3 to 8 and 0.3% bile salts, and it inhibited the growth of Salmonella Typhimurium in a concentration-dependent manner. In addition, E. faecalis showed resistance to several antibacterial agents. Vermiculite, a nutrient and microbial carrier, increased the bile tolerance of the strain. Scanning electron microscope images revealed good adsorption of E. faecalis PSCT3-7 onto vermiculite. E. faecalis PSCT3-7 represents a potential probiotic candidate to administer with vermiculite to swine.
Yohannes, Sileshi,Awji, Elias Gebru,Lee, Seung-Jin,Park, Seung-Chun Taylor & Francis 2015 Xenobiotica Vol.45 No.3
<P>1. The aim of the present study was to determine the PKs of marbofloxacin in beagle dogs after intravenous (i.v.) and intramuscular (i.m.) administration, the <I>ex vivo</I> and <I>in vitro</I> PK/PD indices of marbofloxacin against clinical isolates of S<I>taphylococcus pseudintermedius</I>, and the <I>ex vivo</I> AUC/MIC ratios associated with different levels of antibacterial activity.</P><P>2. After i.v. of marbofloxacin (2 mg/kg), the mean ± SEM values of AUC, t<SUB>1/2β</SUB>, V<SUB>ss</SUB>, and CL were 8.47 ± 3.51 h µg/mL, 8.08 ± 6.25 h, 2.32 ± 1.00 L/kg and 0.23 ± 0.06 L/kg/h and corresponding values after intramuscular injection were 11.37 ± 3.07 h µg/mL, 7.51 ± 3.70, 1.80 ± 0.90 L/kg and 0.17 ± 0.04 L/kg/h. After i.m. administration, a C<SUB>max</SUB> of 1.76 ± 0.09 µg/mL was achieved at T<SUB>max</SUB> of 0.47 ± 0.08 h. The <I>ex-vivo</I> AUC/MIC ratios required to produce bacteriostasis, bactericidal action and elimination of <I>S. pseudintermedius</I> were 65.03, 97.02 and 136.84 h.</P><P>3. The <I>in vivo</I> AUC/MIC ratios obtained after i.v. and i.m. administration of 2 mg/kg marbofloxacin (67.76 ± 1.23 and 91.18 ± 2.61) were below the <I>ex vivo</I> AUC/MIC ratios required for bactericidal activity and bacterial elimination (97.02 ± 9.24 2 mg/kg and 136.21 ± 7.58), suggesting that the recommended daily dosage (2 mg/kg) may not suffice to kill and eradicate <I>S. pseudintermedius</I> strains encountered in clinical area.</P>
Lee, Seung-Jin,Awji, Elias Gebru,Park, Na-hye,Park, Seung-Chun American Society for Microbiology 2017 Antimicrobial Agents and Chemotherapy Vol.61 No.2
<P>The objectives of this study were to determine pharmacokinetic/pharmacodynamic (PK/PD) indices of fluoroquinolones that minimize the emergence of resistant Salmonella enterica serovar Typhimurium (S. Typhimurium) using in vitro dynamic models and to establish mechanisms of resistance. Three fluoroquinolones, difloxacin (DIF), enrofloxacin (ENR), and marbofloxacin (MAR), at five dose levels and 3 days of treatment were simulated. Bacterial killing-regrowth kinetics and emergence of resistant bacteria after antibacterial drug exposure were quantified. PK/PD indices associated with different levels of antibacterial activity were computed. Mechanisms of fluoroquinolone resistance were determined by analyzing target mutations in the quinolone resistance-determining regions (QRDRs) and by analyzing overexpression of efflux pumps. Maximum losses in susceptibility of fluoroquinolone-exposed S. Typhimurium occurred at a simulated AUC/MIC ratio (area under the concentration-time curve over 24 h in the steady state divided by the MIC) of 47 to 71. Target mutations in gyrA (S83F) and overexpression of acrAB-tolC contributed to decreased susceptibility in fluoroquinolone-exposed S. Typhimurium. The current data suggest AUC/MIC (AUC/mutant prevention concentration [MPC])-dependent selection of resistant mutants of S. Typhimurium, with AUC/MPC ratios of 69 (DIF), 62 (ENR), and 39 (MAR) being protective against selection of resistant mutants. These values could not be achieved in veterinary clinical areas under the current recommended therapeutic doses of the fluoroquinolones, suggesting the need to reassess the current dosing regimen to include both clinical efficacy and minimization of emergence of resistant bacteria.</P>