| Nara Lim | 2 Articles |
<b>Objectives</b><br/>
<i>Mycobacterium intracellulare</i> is the major causative agent of nontuberculous mycobacteria-related pulmonary infections. The strain typing of <i>M. intracellulare</i> is important for the treatment and control of its infections. We compared the discrimination capacity and effective value of four different molecular typing methods.<br/><b>Methods</b><br/>
Antibiotic susceptibility testing, <i>hsp65</i> and <i>rpoB</i> sequencing, pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), mycobacteria interspersed repetitive-unit-variable-number tandem-repeat analysis (MIRU-VNTR), and VNTR assay targeting 44 <i>M. intracellulare</i> isolates obtained from patients with pulmonary infections were performed.<br/><b>Results</b><br/>
All the antibiotic susceptibility patterns had no association with the molecular and sequence types tested in this study; however, the molecular and sequence types were related with each other. PFGE gave best results for discriminatory capacity, followed by VNTR, MLST, and MIRU-VNTR.<br/><b>Conclusion</b><br/>
The high discriminatory power of PFGE, VNTR, and MLST is enough for differentiating between reinfection and relapse, as well as for other molecular epidemiological usages. The MLST could be regarded as a representative classification method, because it showed the clearest relation with the sequence types.
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<b>Objectives</b><br/>
Enteroaggregative <i>Escherichia coli</i> (EAEC) was recently reported as a major diarrheagenic pathogen in infant and adult travelers, both in developing and developed countries. EAEC strains are known to be highly resistant to antibiotics including quinolones. Therefore in this study we have determined the various mechanisms of quinolone resistance in EAEC strains isolated in Korea.<br/><b>Methods</b><br/>
For 26 EAEC strains highly resistant to fluoroquinolone, minimal inhibitory concentrations for fluoroquinolones were determined, mutations in the quinolone target genes were identified by PCR and sequencing, the presence of transferable quinolone resistance mechanism were identified by PCR, and the contribution of the efflux pump was determined by synergy tests using a proton pump inhibitor. The expression levels of efflux pump-related genes were identified by relative quantification using real-time PCR.<br/><b>Results</b><br/>
Apart from two, all tested isolates had common mutations on GyrA (Ser83Leu and Ser87Gly) and ParC (Ser80Gln). Isolates EACR24 and EACR39 had mutations that have not been reported previously: Ala81Pro in ParC and Arg157Gly in GyrA, respectively. Increased susceptibility of all the tested isolates to ciprofloxacin and norfloxacin in the presence of the pump inhibitor implies that efflux pumps contributed to the resistance against fluoroquinolones. Expression of the efflux pump-related genes, <i>tolC</i>, <i>mdfA</i>, and <i>ydhE</i>, were induced in isolates EACR 07, EACR 29, and EACR 33 in the presence of ciprofloxacin.<br/><b>Conclusion</b><br/>
These results indicate that quinolone resistance of EAEC strains mainly results from the combination of mutations in the target enzyme and an increased expression of efflux pump-related genes. The mutations Ala81Pro in ParC and Arg157Gly in GyrA have not been reported previously the exact influence of these mutations should be investigated further.
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