Antibacterial activities of piperacillin for several resistant strains from respiratory infections - In reference to MRSA, PRSP, BLNAR and P. aeruginosa

We investigated antibacterial activities of piperacillin (PIPC) for several resistant strains of bacteria isolated from patients with respiratory infections from 1998 to 1999 in comparison with reference drugs and obtained the following results: 1. The majority of methicillin resistant strains of Staphylococcus aureus (MRSA) showed high resistance to β-lactam antibiotics including PIPC. 2. MIC₉₀ of PIPC was 1 and 4 μg/ml for penicillin intermediate and penicillin resistant strains of Streptococcus pneumoniae (PISp/PRSP), respectively. 3. MIC₉₀ of PIPC was 0.25 μg/ml for β-lactamase negative ampicillin resistant strains of Haemophilus influenzae (BLNAR), showing higher antibacterial activity than the reference drugs. 4. PIPC exhibited the MICs of 8 μg/ml or less in 19 out of 40 IPM resistant (MIC≥16 μg/ml) strains of Pseudomonas aeruginosa. From these results, PIPC is proved to possess extremely favorable antibacterial activities for BLNAR, and it was suggested that PIPC might be a drug of choice even for PISP/PRSP and IPM resistant strains of P. aeruginosa.