Journal of the Korean Pediatric Society 1998;41(9):1224-1233.
Published online September 15, 1998.
Interaction of the mec Regulator Genes in Methicillin Resistant Staphylococcus
Young Choi1, In Seok Lim1, Tae Sub Shim2, Mi Kyung Lee3, Ae Ja Park3
1Department of Pediatrics, College of Medicine, Chung-Ang University, Seoul, Korea
2Department of Pediatrics, College of Medicine, Chung-Ang University, Seoul, Korea
3Department of Clinical Pathology, College of Medicine, Chung-Ang University, Seoul, Korea
메티실린 내성 포도구균에서 mec 조절 유전자들의 상호작용
최영1, 임인석1, 심태섭2, 이미경3, 박애자3
1중앙대학교 의과대학 소아과학교실
2중앙대학교 의과대학 소아과학교실
3중앙대학교 의과대학 임상병리과학교실
Correspondence: 
Young Choi, Email: 1
Abstract
Purpose
: Low-affinity penicillin-binding protein PBP 2a encoded by mecA is closely related to methicillin resistance in staphylococci, and the expression of PBP 2a is controlled by regulator elements encoded by mecR1 and mecI. Deletion or mutation which occurred in mecI is considered to be associated with constitutive production of PBP 2a. We investigated the distribution of mec regulator genes and the presence of the mutations in mecI among mecA gene-positive methicillin-resistant Staphylococcus aureus(MRSA) and methicillin-resistant coagulase negative Staphylococcus(MRCNS) strains.
Methods
: A total of 28 MRSA and 26 MRCNS clinical strains were isolated at Chung-Ang University Hospital. The distribution of mec regulator genes and the presence of mutations in mecI were analyzed using polymerase chain reaction and direct sequencing.
Results
: In 28 MRSA and 26 MRCNS, only mecR1A-positive pattern(type Ⅲ) was detected in 53.6% of MRSA and 46.4% of MRCNS. The mecR1(mecR1A and mecR1B) and mecI-positive pattern(type Ⅰ) were detected in 42.3% of MRSA and 38.5% of MRCNS. In 19.2% of MRCNS was type Ⅳ in which no mec regulator genes were detected. Our results showed that a greater genomic variation existed in MRCNS than a MRSA. Results in direct sequencing of mecI revealed that mecI gene tested in our study did not harbour mutations and deletions. There was no correlation between the level of resistance and the presence or absence of mec regulator genes.
Conclusion
: The induction of methicillin resistance and the variability of phenotypic expression of methicillin resistance suggested that additional factors on the chromosome are involved.
Key Words: Methicillin resistant Staphylococcus., mec regulator genes(mecI and mecR1)


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