Journal of Microbiology

Journal Article

NOTE] Comparison of the Genetic Structures Surrounding qnrA1 in Korean Enterobacter cloacae and Chinese Escherichia coli Strains Isolated in the Early 2000s: Evidence for qnrA Mobilization via Inc HI2 Type Plasmid: Sang Hoon Han , Young Ah Kim , Minggui Wang , Yangsoon Lee , Hae-Sun Chung , Jong Hwa Yum , Dongeun Yong , Kyungwon Lee , June Myung Kim; J. Microbiol. 2012;50(1):166-169. Published online February 27, 2012; DOI: https://doi.org/10.1007/s12275-012-1350-z

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Abstract: The flanking genetic structure of qnrA1 in Korean Enterobacter cloacae was identical to that of the Chinese Escherichia coli strain, the first qnrA1-carrying strain reported in Asia. Analysis of restriction enzyme sites and Southern blot hybridization results showed that qnrA1 was transferred between E. cloacae and E. coli via Inc HI2 type plasmid.

Research Support, Non-U.S. Gov'ts

Isolation of Multidrug-Resistant Salmonella typhimurium DT104 from Swine in Korea: Ki Eun Lee , Yeonhee Lee; J. Microbiol. 2007;45(6):590-592.; DOI: https://doi.org/2603 [pii]

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Abstract: We report the isolation of Salmonella enterica serotype Typhimurium phage type DT104 (CCARM 8104) from swine in Korea. The CCARM 8104 isolate was resistant to nalidixic acid and showed reduced susceptibility to quinolones. The CCARM 8104 isolate had a missense mutation, Asp87Asn, in the quinolone resistance-determining region in gyrA and produced PSE-1. The CCARM 8104 isolate carried two different class 1 integrons, and the PSE-1 β-lactamase gene was inserted into a 1,200 bp class 1 integron. The presence of DT104 with pse-1 in an integron located in a plasmid and reduced susceptibility to quinolone in swine pose a significant threat of possible horizontal spread between swine and humans.

Isolation of Quinolone-Resistant Escherichia coli Found in Major Rivers in Korea: Dahye Jung , Min Young Lee , Jung Min Kim , Je Chul Lee , Dong Taek Cho , Yeonhee Lee; J. Microbiol. 2006;44(6):680-684.; DOI: https://doi.org/2456 [pii]

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Abstract: Twenty isolates resistant to seven quinolones were isolated from major rivers in Korea. All isolates had three mutations, Ser83→Leu and Asp87→Asn in GyrA and Ser80→Ile or Ser80→Arg in ParC and three isolates had an additional mutation Glu84→Gly or Glu84→Val in ParC. In addition, a clonal spread was not found in these isolates.

Fluoroquinolone Resistance and gyrA and parC Mutations of Escherichia coli Isolated from Chicken: Young-Ju Lee , Jae-Keun Cho , Ki-Seuk Kim , Ryun-Bin Tak , Ae-Ran Kim , Jong-Wan Kim , Suk-Kyoung Im , Byoung-Han Kim; J. Microbiol. 2005;43(5):391-397.; DOI: https://doi.org/2285 [pii]

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Abstract: Escherichia coli is a common inhabitant of the intestinal tracts of animals and humans. The intestines of animals also represent an ideal environment for the selection and transfer of antimicrobial resistance genes. The aim of this study was to investigate the resistance of E. coli isolated from chicken fecal samples to fluoroquinolones and to analyze the characterization of mutations in its gyrA and parC gene related resistance. One hundred and twenty-eight E. coil isolates showed a high resistance to ciprofloxacin (CIP; 60.2%), enrofloxacin (ENO; 73.4%) and norfloxacin (NOR; 60.2%). Missense mutation in gyrA was only found in the amino acid codons of Ser-83 or Asp-87. A high percentage of isolates (60.2%) showed mutations at both amino acid codons. Missense mutation in parC was found in the amino acid codon of Ser-80 or Glu-84, and seven isolates showed mutations at both amino acid codons. Isolates with a single mutation in gyrA showed minimal inhibitory concentrations (MIC) for CIP (≤0.5 to 0.75 ug/ml), ENO (1 to 4 ug/ml) and NOR (0.75 to 4 ug/ml). These MIC were level compared to isolates with two mutations, one in gyrA and one in parC, and three mutations, one in gyrA and two in parC (CIP, ≤0.5 to 3 ug/ml; ENO, 2 to 32< ug/ml; NOR, 1.5 to 6 ug/ml). However, the isolates with two mutation in gyrA regardless of whether there was a mutation in parC showed high MIC for the three fluoroquinolones (CIP, 0.75 to 32 ≤ug/ml; ENO, 3 to 32 ≤ug/ml; NOR, 3 to 32 ≤ug/ml ). Interestingly, although the E. coil used in this study was isolated from normal flora of chicken, not clinical specimens, a high percentage of isolates showed resistance to fluoroquinolones and possessed mutations at gyrA and parC associated with fluoroquinolone resistance.

Laboratory Developed fluoroquinolone Resistant Escherichia coli Has a new Missense Mutation in QRDR of PartC: Lee, Soon Deuk , Lee, Yeon Hee; J. Microbiol. 1998;36(2):106-110.

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Abstract: The fluoroquinolone resistance mechanism of four laboratory developed fluorquinolone resistant strains of Escherichia coli was studied. Fluoroquinolone concentrations inside the resistant cells were similar to the concentrations in the susceptible cells. DNA sequencing of the quinolone resistance determining regions (QRDR) in gyrA and parC revealed the presence of Ser 83Leu and Asp87Gly mutations in GyrA, and Gly78Cys and Ser80Arh mutations in ParC of the ofloxacin, norfloxacin, and HK3140 resistant strains, while the ciprofloxacin resistant strain had Ser83Leu and Aasp87Tyr mutations in GyrA, and Gly78Cys and Ser80Ile mutations in ParC. A Gly78Cys substitution in ParC was newly detected in this work and seemed to be responsible for the extremely high MICs to fluroquinolones.

Concentration of CCCP Should Be Optimized to Detect the Efflux System in Quinolone-Susceptible Escherichia coli: Hyengun Cho , Yoojung Oh , Seohyung Park , Yeonhee Lee; J. Microbiol. 2001;39(1):62-66.

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Abstract: Unlike eukaryotic efflux pumps energized by ATPase, bacterial efflux pumps are energized by the proton motive force. That is the reason why CCCP, an inhibitor of proton motive force, is widely used to study the bacterial efflux pump. In many cases, efflux systems have been observed only in quinoloneresistant bacteria. Most of the quinolone-susceptible strains have been found to maintain little efflux pump. However, some susceptible bacteria showed the increased intracellular quinolone concentration only at a low concentration (0.01 or 0.1 mM) but not at a high concentration (1 mM) of CCCP. If bacterial cells were killed at high concentrations of CCCP and lost the integrity of their membranes, the intracellular quinolone would leak out from cells with no efflux system. The efflux pump system in the quinolone-susceptible strains could not be detected at the same concentration used for sistant bacteria. To test this hypothesis, the intracellular quinolone concentration in the quinolone-susceptible and -resistant strains of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus was assayed at various concentrations of CCCP. Since the effect of CCCP is very rapid, the survival of bacteria was observed by assaying the DNA synthesis in 5 min. In the case of E. coli, but not P. aeruginosa or S. aureus, the quinolone susceptible strain was more susceptible to CCCP than the quinolone resistant ones, especially when the incubation with CCCP was extended. Decrease of the intracellular quinolone concentration resulted in a false result-no or weak efflux system in the quinolone susceptible strains. Results suggested that the concentration of CCCP should be optimized in order to detect the efflux system in the quinolone susceptible strains of E. coli.

Isolation of Norfloxacin Resistant Escherichia coli from the Han River and Characterization of Resistance Mechanism: Yoosun Jung , Hyunjin Hong , Hyeran Nam , Yeonhee Lee; J. Microbiol. 2002;40(1):63-69.

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Abstract: A total of twenty-five norfloxacin resistant Escherichia coli were isolated from Joongrang-chun stream, a branch of the Han River in Seoul, Korea from May to July in 2000 and their norfloxacin resistance mechanism was characterized for target site mutation, permeability, and efflux pump. Fourteen isolates contained the same three mutations, Ser83->Leu and Asp87->Asn in GyrA and Ser90->Ile in ParC. Six isolates had Ser83->Leu and Asp87->Tyr in GyrA and Ser80->Ile in ParC while one isolate had Ser83->Leu and Val103->Ala in GyrA and Ser80->Ile in ParC. Two isolates had mutation(s) in GyrA without any mutation in ParC. Two isolates had Ser80->Arg in ParC instead of the commonly found Ser80->Ile. Every norfloxacin resistant isolate had an efflux system but the correlation between the efflux activity and MIC was not observed. The amount of OmpF for norfloxacin permeability decreased in resistant isolates compared to the susceptible strains. When amplified polymorphic DNA (RAPD) and pulse field gel electrophoresis (PFGE) were performed, these isolates showed no similarity to each other or clinical isolates.

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