Methicillin 내성 Staphylococcus aureus의 검출을 위한 분자유전학적 기법에 관한 연구

Comparison between Dot Blot Hybridization and Southern Blot Hybridization in Detecting Methicillin Resistant Staphylococcus aureus

Thirty strains of methicillin resistant Staphylococcus aureus were obtained from the clinical isolates. In order to investigate the pursuit of the pathogens of nosocomial infection, these strains were studied for antibiotic sensitivity as well as its resistant pattern. Among the methods of hybridization which directly confirm the specific antibiotic resistant genes by means of the recently developed specific probe DNA, dot blot hybridization and southern blot hybridization were performed and these two methods were compared in their sensitivity and specificity. Strains that is sensitive to cephalothin to the subject of methicillin resistant Staphylococcus aureus were in 43%. Those that are sensitive to cefoperazone and cefuroxime were 26% and 23%, respectively. In case of MIC, MIC50 of cefoperazone was 8 $\mu\textrm{g}$/$m\ell$, and MIC90 was 128 $\mu\textrm{g}$/$m\ell$ to be the lowest. As the results of plasmid DNA electrophoresis, most of methicillin resistant Staphylococcus aureus strains had more than 4 plasmids. These plasmids digested by BamHI, methicillin resistant Staphylococcus aureus is distributed as 10 fragments with the size of 65 kb to 1.5 kb. Dot blot hybridization were performed to examine the existence of mecA gene to show the detection rate of 50%. Southern blot hybridization were done to see if DNA bands which amplify the activity of digoxigenium-labeled probe by PCR were actually PCR products of mecA gene and it showed the detection rate of 53%. It can be concluded that the southern blot hybridization seemed to be better in sensitivity and specificity when it is compared with the results of dot blot hybridization.