- Alterations of gyrA, gyrB, and parC and Activity of Efflux Pump in Fluoroquinolone-resistant Acinetobacter baumannii
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Sunok Park, Kyeong Min Lee, Yong Sun Yoo, Jung Sik Yoo, Jae Il Yoo, Hwa Su Kim, Yeong Seon Lee, Gyung Tae Chung
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Osong Public Health Res Perspect. 2011;2(3):164-170. Published online December 31, 2011
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DOI: https://doi.org/10.1016/j.phrp.2011.11.040
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 Abstract
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- Objectives
This study investigated the fluoroquinolone-resistant mechanism of 56 clinical cases of A baumannii infection from 23 non-tertiary hospitals, collected between 2004 and 2006.
Methods
Susceptibility testing was performed by broth microdilution and Epsilometer test. Analyses of quinolone resistance-determining region (QRDR) were done by sequencing. The activity of the efflux pump was measured using inhibitors.
Results
The sequences from selected 56 isolates were divided into seven groups (I-VII) on the basis of mutations in gyrA (S83L), parC (S80L, S80W and S84K) and gyrB (containing the novel mutations E679D, D644Y and A677V). The 27 isolates with triple mutations in gyrA, gyrB and parC (groups IV-VII) showed higher levels of resistance to ciprofloxacin (minimal inhibitory concentration [MIC] of 16-256 μg/mL) than the 26 isolates with double mutations in gyrA and parC (groups II and III, MIC of 8-64 μ g/mL; p < 0.05). Alterations in the efflux pump were observed in four isolates with the parC S80L mutation (group II) or E84K mutation (group VII), but no effect was observed in an isolate with the parC S80 W mutation (group III).
Conclusion
These results suggest that triple mutations in clinical isolates of A baumannii contribute to the development of high levels of resistance to fluoroquinolones and that mutations in parC S80L or E84K (groups II and VII) may contribute to alterations in efflux pump activity in A baumannii.
- Gene Expression and Identification Related to Fluconazole Resistance of Candida glabrata Strains
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Jae Il Yoo, Chi Won Choi, Kyeong Min Lee, Yeong Seon Lee
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Osong Public Health Res Perspect. 2010;1(1):36-41. Published online December 31, 2010
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DOI: https://doi.org/10.1016/j.phrp.2010.12.009
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1,584
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8
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Abstract
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- Objectives
Candida glabrata has become one of the most common causes of Candida bloodstream infections worldwide. Some strains of C. glabrata may be intermediately resistant to all azoles. The several possible mechanisms of azole resistance have been reported previously, but the exact resistant mechanism is not clear. In this study, we identified differentially expressed genes (DEGs) of fluconazole-resistant C. glabrata and compared the gene expression of fluconazole-resistant strains with that of fluconazole-susceptible strains to identify gene corresponding to fluconazole resistance.
Methods
Using antifungal susceptibility test, several C. glabrata strains were selected and used for further study. The expression of CgCDR1 and CgCDR2 genes was investigated by slot hybridization against fluconazole-susceptible, -resistant, and resistant-induced strains. In addition, ERG3 and ERG11 genes were sequenced to analyze DNA base substitution. DEGs were identified by reverse transcription-polymerase chain reaction using DEG kit composed of 120 random primers.
Results
In slot hybridization, CgCDR1 gene was expressed more than CgCDR2 gene in resistant strains. Though base substitution of ERG11 and ERG3 genes was observed in several base sequences, just one amino acid change was identified in resistant strain. In the results of reverse transcription-polymerase chain reaction, 44 genes were upregulated and 34 genes were downregulated. Among them, adenosine triphosphate-binding cassette transporter-related genes, fatty acid desaturase, lyase, and hypothetical protein genes were upregulated and aldehyde dehydrogenase, oxidoreductase, and prohibitin-like protein genes were downregulated. Other DEGs were also identified.
Conclusion
This study showed that CgCDR1 gene was more closely related to fluconazole resistance of C. glabrata than CgCDR2 gene. In addition, several other genes related with fluconazole resistance of C. glabrata were identified.
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