Abstract
The optimal treatment for patients with bacteremia caused by penicillin-susceptible Staphylococcus aureus (PSSA) has not been established; however, recent evidence suggests that penicillin G (PCG) may be useful. Since anti-staphylococcal penicillins are not approved in Japan, cefazolin (CEZ) is the first agent of choice for the treatment of bacteremia caused by methicillin-susceptible S. aureus (MSSA), including PSSA. However, because of problems with the supply of raw materials and a new manufacturing process, it became difficult to maintain a stable supply of CEZ in 2019. The supply system was restored one and a half years later, but the same situation may occur in the future. It is beneficial to use PCG in the β-lactamase production test to confirm PSSA positivity. In this study, we performed penicillin disk zone edge tests on 26 MSSA strains isolated from blood cultures at our hospital over the past 4 years and were determined to be susceptible to PCG with a minimum inhibitory concentration (MIC) of ≤ 0.12 μg/mL. It was found that two strains were detected by the penicillin disc zone edge test. On the other hand, a zone edge test was also performed on 70 strains that had been isolated from materials other than blood, such as sputum, urine, stool, pus, and joint fluid, and could be preserved. None of these strains were detected. β-lactamase production detected by the penicillin disk zone edge test should be confirmed to provide useful information for selecting the appropriate antimicrobial agent before reporting PSSA positivity on the basis of MIC values indicating sensitivity to PCG.
