Methicillin 저항성 포도구균의 β-Lactam계 항생제 함유배지에서의 증식 양상 = Growth Patterns of Methicillin Resistant Staphylococcus aureus in β-Lactam Antibiotic Containing Muller-Hinton Broth

다국어 초록 (Multilingual Abstract)

-Abstract- Methicillin-resistant Staphylococcus aureus(MRSA) has become a major pathogen in patients with nosocomial or community-acquired infections.
In the present study, we examined the minimum inhibitory concentration(MIC) and maximum bactericidal concentration(MBC) of methicillin, oxacillin, cefatrizine and tetracycline on MRSA, then followed growth patterns of MRSA and formation of L-form at the respective MIC for various strains to elucidate the mechanism of paradoxic effect of penicillin antibiotics on MRSA.
Following results were obtained 1. In twenty strains of MRSA, the MBC of methicillin equal to MIC was 15%, the MBC two fold greater than MIC was 60%, the MBC three fold greater than MIC was 20% and the MBC four greater than MIC was 20%.
2. With oxacillin, the MBC with equal to MIC was 10%, the MBC two fold greater than MIC was 50%, the MBC three fold greater than MIC was 20% and the MBC four fold greater than MIC was 20%.
3. With cefatrizine, the MBC with equal to MIC was 10%, the MBC two fold greater than MIC was 60%, the MBC three fold greater than MIC was 20% and the MBC four fold greater than MIC was 10%.
4. With tetracycline, the MBC with equal to MIC was 10%, the MBC two fold greater than MIC was 55%, the MBC three fold greater than MIC was 25% and the MBC four fold greater than MIC was 5%.
5. In all strains of MRSA showing a paradoxical effect of methicillin, growth was significantly more with 0.5xMIC than with 1xMIC in using Muller-Hinton.
6. In some strains of MRSA, the paradoxical effect was observed at 0.5xMIC in the 50% serum containing Muller-Hinton broth.
7. The paradoxical effects of oxacillin and cefatrizine occurred at 1xMIC in Muller-Hinton broth and 0.5xMIC in 50% serum containing Muller-Hinton broth.
8. With tetracycline, the paradoxical effect was not observed both in Muller-Hinton broth and 50% containing Muller-Hinton broth.
9. MRSA strains formed L-form in the media containing 0.5xMIC of methicillin, oxacillin, cefatrizine containing agar, but not in tetracycline containing agar.
These results indicate that in some strains of MRSA paradoxical effects of methicillin, oxacillin, and cefatrizine can be observed at 0.5-1x MIC, and this is due to the formation of L-form bacteria.