| Autor: |
Funashima Y; Department of Medical Technology and Science, Faculty of Fukuoka Health Care, International University of Health and Welfare. Medical Laboratory Science, Graduate School of Health and Welfare Sciences, International University of Health and Welfare., Nagasawa Y; Medical Departments, Self Defense Force Kumamoto Hospital., Narita T; Department of Clinical Laboratory, Medical Kouhoukai Takagi Hospital., Hanaiwa H; Department of Clinical Laboratory, Medical Kouhoukai Takagi Hospital., Nagasawa Z; Department of Medical Technology and Science, Faculty of Fukuoka Health Care, International University of Health and Welfare. Medical Laboratory Science, Graduate School of Health and Welfare Sciences, International University of Health and Welfare. Department of Clinical Laboratory, Medical Kouhoukai Takagi Hospital. |
| Abstrakt: |
There are several problems associated with antimicrobial susceptibility testing (AST) of Haemophilus influenzae . β-Lactamase-negative ampicillin-resistant H. influenzae (BLNAR) isolates with minimum inhibitory concentration (MIC) of ampicillin (ABPC) <4 mg/l will be classified as susceptible according to the MIC breakpoint of the CLSI M100 criteria, in spite of harboring penicillin-binding protein (PBP) mutations that cause ABPC resistance. A total of 103 isolates were collected from clinical materials for analysis. The genotypes of the PBP mutations were analyzed by polymerase chain reaction. The WalkAway 96 Plus (WALKAWAY), dry plate Eiken (DP-EIKEN), and RAISUS S4 systems (RAISUS) were used for AST. HTM broth was used as the culture medium for WALKAWAY, Mueller‒Hinton broth with 5% lysed horse blood for DP-EIKEN, and HTM with 5% horse serum for RAISUS. The MIC concordance rates of ABPC for g-BLNAR, for RAISUS vs. DP-EIKEN, RAISUS vs. WALKAWAY, and DP-EIKEN vs. WALKAWAY were 96.1, 86.4, and 85.4%, respectively. WALKAWAY had a low correlation with the other two systems. Moreover, concordance rates of ABPC MIC ≥4 mg/l, which is considered as resistant, of 69 g-BLNAR isolates for the RAISUS, DP-EIKEN, and WALKAWAY systems were 68.1, 58.0, and 37.7%, respectively. Therefore, in Japan, where the BLNAR strain is isolated at a high frequency, it is necessary to understand the characteristics of the measuring systems to appropriately interpret the test results. |
