研究一株對ceftazidime具有抗藥性的Aggregatibacter paraphrophilus的抗藥性機轉

To study the antibiotic-resistant mechanisms of an isolate of ceftazidime-resistant Aggregatibacter paraphrophilus

南部的某區域醫院，在2014年4月18日，自一位罹患上頷竇鼻竇炎的55歲男性病人分離出一株對ceftazidime 具有抗藥性的Aggregatibacter paraphrophilus。根據抗生素敏感性試驗的結果顯示，此菌株對於大部分的測試抗生素都具有敏感性，但是卻對ceftazidime具有抗藥性，而E-test的結果顯示，此菌株對於ceftazidime的最低抑菌濃度為12 mg/ml。分子生物學實驗顯示，此菌株不存在任何β-lactamase基因，但是卻存在penicillin-binding protein 3 (PBP3)發生突變。因此，我們認為此菌株對ceftazidime產生抗藥性的機轉可能是 PBP3 突變的結果。在此，我們主張臨床上一旦自臨床檢體分離出HACEK菌群，包括Haemophilus spp.（除了 H. influenzae之外），Aggregatibacter spp.，Cardiobacterium spp.，Eikenella spp.及 Kingella spp.，應該常規做抗生素敏感性試驗，如此可以使病人得到較適當的抗生素治療。

A ceftazidime-resistant Aggregatibacter paraphrophilus strain was isolated from a 55-year-old male patient with maxillary sinusitis at a regional hospital in southern Taiwan, on 18 April 2014. Antimicrobial susceptibility testing revealed the isolate was susceptible to most antibiotics tested, but resistant to ceftazidime. E-test revealed the minimal inhibitory concentration to ceftazidime was 12 μg/ml. Molecular methods revealed no detectable β-lactamase genes were present, however, the mutation in penicillin-binding protein 3 (PBP3) gene was found. Therefore, the potential mechanism of the isolate resistant to ceftazidime might be due to PBP3 mutation. Herein, we suggest that once HACEK group, including Haemophilus spp. except H. influenzae, Aggregatibacter spp., Cardiobacterium spp., Eikenella spp., and Kingella spp. are isolated from clinical samples, antimicrobial susceptibility testing should be routinely performed to offer more appropriate antibiotic treatment regimens for patients.