Browsing by Author "Cheng, HH"

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Colonization of human immunodeficiency virus-infected outpatients in Taiwan with Candida species
(2005-04-01)
Hung, CC
;
Yang, YL
;
Lauderdale, TL
;
McDonald, LC
;
Hsiao, CF
To understand the Candida colonization of human immunodeficiency virus (HIV)-infected outpatients in Taiwan, we have conducted a prospective cohort study of Candida colonization and its risk factors at the National Taiwan University Hospital from 1999 to 2002. More than 50% of the patients were colonized with Candida species, and 12% developed symptomatic candidiasis. Patients colonized with fluconazole-resistant strains of Candida species had a higher prevalence of candidiasis than those colonized with susceptible strains. Our analysis found that antibiotic treatment and lower CD4(+) counts (< 200 cells/mm(3)) increased the rate of oropharyngeal candidiasis in HIV-infected patients, while antiretroviral therapy protected patients from the development of candidiasis.
Distribution and susceptibility to amphotericin B and fluconazole of Candida spp. isolated from Taiwan
(2005-04-01)
Yang, YL
;
Ho, YA
;
Cheng, HH
;
Lo, HJ
;
生物科技學系
Susceptibilities to amphotericin B and fluconazole of 628 clinical yeast strains collected from 22 hospitals in Taiwan were determined. A total of 53 isolates (8.4%) were resistant to fluconazole. Each hospital had different resistance rate to fluconazole ranging from 0 % to 24 %. None of the 186 isolates from eight of the 22 hospitals was resistant to fluconazole. In contrast, isolates from nine of the remaining 14 hospitals had greater than 10 % resistance rate to fluconazole. Consistently, 88.9 % (8/9) fluconazole-resistant C. albicans isolates were from hospitals having a high resistance rate to fluconazole. The prevalence of various Candida spp. in each hospital was different. A positive association was found between the prevalence of C. tropicalis and the resistance rate to fluconazole for individual hospitals. Although only three isolates (0.5 %) were resistant to amphotericin B, a co-resistance to both amphotericin B and fluconazole was observed, which highlights the emerging problem of drug resistance.
Exciton relaxation in Ga1-xInxAs/GaAs self-organized quantum dots
(1999-01-01)
Shen, JX
;
Oka, Y
;
Cheng, HH
;
Tsai, FY
;
Lee, CP
The exciton dynamics in Ga1-xInxAs/GaAs self-organized quantum dots grown on GaAs (1 1 1)B substrates are studied by the time-resolved photoluminescence (PL). We have found the intra-dot exciton relaxation by the reduction of the linewidth and peak energy and also by the energy-dependent PL rise time in the transient PL spectra. Compared with the energy relaxation in the reference quantum wells, we have confirmed that the exciton relaxation in three-dimensionally confined quantum dots is slower than in the quantum wells, (C) 1999 Academic Press.
In vitro activity of voriconazole against Candida species isolated in Taiwan
(2004-09-01)
Yang, YL
;
Cheng, HH
;
Lo, HJ
;
生物科技學系
;
Department of Biological Science and Technology
The activity of voriconazole was determined against 285 Candida species consisting of 53 resistant isolates, 43 susceptible-dose dependent and 189 isolates susceptible to fluconazole. The MIC50 and MIC90 to fluconazole were 8 and 64 mg/l, respectively. The range of minimum inhibitory concentrations (MICs) to voriconazole was from 0.0325 to 2 mg/l and the MIC50 and MIC90 were 0.125 and 0.5 mgA, respectively. Only 3 of 285 tested isolates had MICs to voriconazole equal to 2 mg/l. A total of 38 isolates, consisted of 3 Candida albicans, 5 Candida krusei, 7 Candida tropicalis and 21 Candida glabrata, had MICs greater than or equal to 0.5 mg/l to voriconazole. There was correlation between the susceptibility to fluconazole and voriconazole. (C) 2004 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.
Magneto-luminescence of quasi-zero dimensional In0.25Ga0.75As/GaAs quantum dots
(1998-12-01)
Cheng, HH
;
Nicholas, RJ
;
Priest, A
;
Tsai, FY
;
Lee, CP
We report photoluminescence measurements on In0.25Ga0.75As/GaAs quantum well and dots grown on (1 1 1)B GaAs substrate in high magnetic fields up to 45 Tesla. A well-defined PL line with full width at half maximum of approximately 5.5 meV is observed. From an analysis of the zero field transition energy, we point out the importance of an internal piezoelectric field. By analyzing the diamagnetic shift of the PL in both Faraday and Voigt configurations, the optical characteristics of a quasi-zero dimensional exciton are discussed. (C) 1998 Elsevier Science B.V. All rights reserved.
Molecular epidemiology of long-term colonization of Candida albicans strains from HIV-infected patients
(2006-04-01)
Li, SY
;
Yang, YL
;
Chen, KW
;
Cheng, HH
;
Chiou, CS
Twenty-one Candida albicans isolates from three HIV-infected patients were collected over a period of 3 years and characterized for fluconazole susceptibility, infectivity and genetic relatedness. Fluconazole resistance was found in five isolates, four exhibited dose-dependent susceptibility and the remainder were fully susceptible to this agent. Pulsed-field gel clectrophoresis of SfiI restriction digests of the genomic DNA from the isolates revealed that isolates from the same swab specimen were identical despite differences in Susceptibility to fluconazole and isolates recovered over time from the three patients retained clonally related DNA fingerprints within each patient. This small-scale study confirms the persistence of oral colonization of C. albicans strains in HIV-infected patients. Clinical data also suggests that the primary infecting strain may become a persistent colonist in the oral cavity once the immune function of the patient has been restored.
On the equivalence between magnetic-field-induced phase transitions in the integer quantum Hall effect
(2003-04-01)
Huang, CF
;
Chang, YH
;
Cheng, HH
;
Yang, ZP
;
Wang, SY
Magnetic-field-induced phase transitions in the two-dimensional electron system in a AlGaAs/InGaAs/GaAs heterostructure are studied. Two kinds of magnetic-field-induced phase transitions, plateau-plateau (P-P) and insulator-quantum Hall conductor (I-QH) transitions, are observed in the integer quantum Hall effect regime at high magnetic fields. In the P-P transition, both the semicircle law and the universality of critical conductivities are broken and we do not observe the universal scaling. However, the P-P transition can still be mapped to the I-QH transition by the Landau-level addition transformation, and as the temperature decreases the critical points of these two transitions appear at the same temperature. Our observations indicate that the equivalence between P-P and I-QH transitions can be found by the suitable analysis even when some expected universal properties are invalid. (C) 2003 Elsevier Science Ltd. All rights reserved.
Susceptibilities of Candida species to amphotericin B and fluconazole: The emergence of fluconazole resistance in Candida tropicalis
(2004-01-01)
Yang, YL
;
Ho, YA
;
Cheng, HH
;
Ho, M
;
Lo, HJ
OBJECTIVE: To determine the susceptibilities of Candida species isolated from Taiwan to amphotericin B and fluconazole. DESIGN: Prospective surveillance study. METHODS: Each hospital was asked to submit up to 10 C. albicans and 40 non-albicans Candida species during the collection period, from April 15 to June 15, 1999. One isolate was accepted from each episode of infection. The broth microdilution method was used to determine susceptibilities to amphotericin B and fluconazole. RESULTS: Only 3 of 632 isolates, one each of C. famata, C. krusei, and C. tropicalis, were resistant to amphotericin B. A total of 53 (8.4%) of 632 clinical yeast isolates, consisting of 4% C. albicans, 8% C. glabrata, 15% C. tropicalis, and 70% C. krusei, were resistant to floconnzole. In contrast. no C. Parapsilosis isolate was resistant to fluconazole. Isolates from tertiary-care medical centers had higher rates of resistance to fluconazole than did those from regional and local hospitals (11.4% vs 6.6%). Isolates from different sources showed different levels of susceptibility to fluconazole. All of the isolates with the exception of C. tropicalis and C. krusei isolated from blood were susceptible to fluconazole. A pattern of co-resistance to both amphotericin B and fluconazole was observed. CONCLUSIONS: Non-albicans Candida species had higher rates of resistance to fluconazole than did C. albicans (44 of 395 [11.2%] vs 9 of 237 [3.8%]; P = .002). The increasing rate of fluconazole resistance in C. tropicalis (15%) is important because C. tropicalis is one of the most commonly isolated non-albicans Candida species.
Susceptibilities to amphotericin B and fluconazole of Candida species in TSARY 2002
(2005-03-01)
Yang, YL
;
Li, SY
;
Cheng, HH
;
Lo, HJ
;
生物科技學系
Susceptibilities to amphotericin B and fluconazole of 909 Candida species collected during the Taiwan Surveillance of Antimicrobial Resistance of Yeasts (TSARY) in 2002 were determined by the broth microdilution method. There were 395 (43.5%) Candida albicans, 244 (26.8%) C. tropicalis, 187 (20.6%) C. glabrata, 63 (6.9%) C. parapsilosis, 9 (1%) C. krusei, and 11 (1.2%) others. Among them, 23 (2.5%) isolates were resistant to amphotericin B. They consisted of 10 C. glabrata, 6 C. krusei, 3 C. albicans, 1 C. tropicalis, 1 C. parapsilosis, and 2 others. The resistance rate to amphotericin B has increased compared with that of TSARY 1999 (2.5% versus 0.5%). There were 7 C. krusei, 5 C. albicans, 3 C. glabrata, and 2 others isolates resistant to fluconazole. The resistance rate to fluconazole has decreased from 8.4% in 1999 to 1.9% in 2002. A pattern of coresistance to both amphotericin B and fluconazole was observed. (c) 2005 Elsevier Inc. All rights reserved.
The trend of susceptibilities to amphotericin B and fluconazole of Candida species from 1999 to 2002 in Taiwan
(2005-11-03)
Yang, YL
;
Li, SY
;
Cheng, HH
;
Lo, HJ
;
生物科技學系
Background: Candida species have various degrees of susceptibility to common antifungal drugs. The extent of resistance to amphotericin B and fluconazole of Candida glabrata isolates causing candidemia has been reported. Active surveillance may help us to monitor the trend of susceptibility to antifungal drugs and to determine if there is an emerging co-resistance to both drugs of Candida species, specifically, of C. glabrata in Taiwan. Methods: The susceptibilities to amphotericin B and fluconazole of Candida species collected in 1999 and 2002 of the Taiwan Surveillance of Antimicrobial Resistance of Yeasts (TSARY) were determined by the microdilution method. Results: The antifungal susceptibilities of 342 and 456 isolates collected from 11 hospitals participating in both TSARY 1999 and TSARY 2002, respectively, have been determined. The resistance rate to amphotericin B has increased from 0.3% in the TSARY1999 to 2.2% in the TSARY 2002. In contrast, the resistance rate to fluconazole has decreased from 8.8% to 2.2%. Nevertheless, significantly more C. glabrata isolates were not susceptible to fluconazole in the TSARY 2002 (47.4%) than that in the TSARY 1999 (20.8%). There were 9.8% and 11% of C. glabrata isolates having susceptible-dose dependent and resistant phenotype to fluconazole in the TSARY 1999, verse 45.3% and 2.1% in the TSARY 2002. Conclusion: There was an increase of resistance rate to amphotericin B in C. glabrata. On the other hand, although the resistance rate to fluconazole has decreased, almost half of C. glabrata isolates were not susceptible to this drug. Hence, continuous monitoring the emerging of coresistance to both amphotericin B and fluconazole of Candida species, specifically, of C. glabrata, will be an important early-warning system.
Time-resolved photoluminescence study of InGaAs/GaAs quantum wells on (111)B GaAs substrates
(1999-04-01)
Tsai, FY
;
Lee, CP
;
Shen, JX
;
Oka, Y
;
Cheng, HH
The exciton dynamics in In0.15Ga0.85As/GaAs quantum wells grown on (111)B and (100)GaAs substrates are studied by the time-resolved photoluminescence (PL). We have found that the piezoelectric fields in (111)B samples affect the transient behavior of PL spectra. Compared with the reference (100) samples, we have confirmed that the piezoelectric effect induces slower exciton relaxation in (111)B strained quantum wells. (C) 1999 Elsevier Science Ltd. All rights reserved.
Time-resolved photoluminescence study of InGaAs/GaAs quantum wells on (111)B GaAs substrates under magnetic fields
(2001-06-15)
Tsai, FY
;
Lee, CP
;
Voskoboynikov, O
;
Cheng, HH
;
Shen, JX
The exciton dynamics in InxGa1-xAs/GaAs quantum wells grown on (111)B and (100) GaAs substrates were studied by time-resolved photoluminescence (PL) under magnetic fields in a Faraday configuration. We have found that the piezoelectric fields in (111)B samples affect the transient behavior of the PL spectra. Compared with the reference (100) sample, we have found that the strong piezoelectric fields, as well as the magnetic fields, cause a slower spin-flip process in (111)B strained quantum wells. (C) 2001 American Institute of Physics.