Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) is a gram-positive bacterium, and the treatment of patients with MRSA has induced microbial substitution. Regarding antibiotics used for treatment, vancomycin (VCM) has an antibacterial action only against gram-positive bacteria, while arbekacin (ABK) has an antibacterial action against both gram-positive and gram-negative bacteria. In view of this, we supposed that there would be a difference in gram-negative bacteria occurrence rates between patients administered VCM and those administered ABK and tested this supposition by comparing the appearance of gram-negative bacteria in these two patient groups. While gram-negative bacteria were newly detected in 45% of patients after receiving VCM, no patients receiving ABK showed any new gram-negative bacteria. On the other hand, gram-negative bacteria were still detected after administering ABK in patients who had gram-negative bacteria beforehand. This finding suggests that ABK may not be a superior agent when gram-negative bacteria are already present.
