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KMID : 0370220070510020108
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Yakhak Hoeji
2007 Volume.51 No. 2 p.108 ~ p.114
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Molecular Analysis of Spontaneous Mutations in erm(A) and erm(C) Selected In vitro as a Constitutive MLS[B] Resistant Staphylococci
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Yun Eun-Jeong
Shim Mi-Ja
Jin Sung-Hye
Choi Eung-Chil
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Abstract
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The predominant Macrolides-Lincosamide-Streptogramin B (MLS_B) antibiotics resistance genes in staphylococci are erm(A) and erm(C). There is the phenomenon that the ratio of constitutively MLS_B antibiotics resistance (cMLS) in erm(A) is much higher than in erm(C). Thus, we confirmed that the difference of the mutation ratio between erm(A) and erm(C) makes the phenomenon. We examined 8 staphylococci carrying inducibly expressed (iMLS) erm(A) or erm(C) genes. After overnight incubation in the presence of the non-inducer MLS_B antibiotics, spontaneous mutants constitutively expressed MLS_B resistance were selected. Against our expectation, the mutation ratio of erm(A) was lower than erm(C). Therefore, possibilities of other factors determining the ratio of cMLS phenotype might be concerned. All the mutants showed sequence alterations in translational attenuator and all the alterations seemed to give rise to change the second structure of mRNA to express constitutively. For erm(A), 4 different types of sequence deletions ranging from 72 bp to 122 bp and 3 different types of duplications ranging 24 bp to 93 bp were detected. Also, there were 9 different types of duplications ranging 15bp to 154bp in erm(C).
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KEYWORD
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MLS[B] resistance, Staphylococcus aureus, coagulase-negative staphylococci, erm(A), erm(C)
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