Claesson Rolf, Sjögren Ulf, Esberg Anders, Brundin Malin, Granlund Margareta
Department of Odontology, Umeå University, Umeå, Sweden.
Department of Odontology, Umeå University, Umeå, Sweden.
Anaerobe. 2017 Dec;48:19-26. doi: 10.1016/j.anaerobe.2017.06.011. Epub 2017 Jun 21.
There are few reports on the bacterial species Actinomyces radicidentis in the literature. In this study, putative A. radicidentis isolates were collected from 16 root canal samples from 601 examined patients. The isolates were examined by biochemical tests, 16S rRNA gene sequencing, Arbitrarily-primed (AP-) PCR, antibiotic susceptibility testing, and MALDI-TOF analyses. In parallel, two A. radicidentis reference strains and two putative A. radicidentis isolates from United Kingdom were tested. Sixteen of the 18 isolates were confirmed as A. radicidentis. The remaining two isolates, both of which were isolated from root canals (one from Sweden and the other from the UK), but were identified as Actinomyces haliotis by sequencing ∼ 1300 base pairs of the 16S rRNA-gene. This isolates had a divergent, but between them similar, AP-PCR pattern, and a common distribution of sequence signatures in the 16S rRNA gene, but were not identified by MALDI-TOF. A. haliotis is a close relative to A. radicidentis, hitherto only been described from a sea-snail. The identity of A. haliotis was confirmed by a phylogenetic tree based on 16S rRNA gene sequences with species specific sequences included, and by additional biochemical tests. The examined bacteria exhibited similar antibiotic susceptibility patterns when tested for 10 separate antibiotic classes with E-tests (bioMérieux). The MIC for β-lactams (benzylpenicillin and cefuroxime) and vancomycin was 0.5 mg/L, for colistin and ciprofloxacin 8 mg/mL and for the other antibiotic classes ≤ 25 mg/mL The isolation of A. haliotis from infected dental root canals cast doubt on the accepted opinion that all Actinomyces infections have an endogenous source.
文献中关于牙根放线菌的报道较少。在本研究中，从601例受检患者的16份根管样本中收集了疑似牙根放线菌分离株。通过生化试验、16S rRNA基因测序、任意引物（AP-）PCR、药敏试验和基质辅助激光解吸电离飞行时间（MALDI-TOF）分析对分离株进行检测。同时，对两株牙根放线菌参考菌株和两株来自英国的疑似牙根放线菌分离株进行检测。18株分离株中有16株被确认为牙根放线菌。其余两株分离株均从根管中分离得到（一株来自瑞典，另一株来自英国），但通过对16S rRNA基因约1300个碱基对进行测序，鉴定为鲍氏放线菌。这两株分离株具有不同但彼此相似的AP-PCR模式，以及16S rRNA基因中序列特征的共同分布，但未通过MALDI-TOF鉴定。鲍氏放线菌是牙根放线菌的近亲，迄今为止仅在一种海螺中被描述过。通过基于包含物种特异性序列的16S rRNA基因序列构建的系统发育树以及额外的生化试验，证实了鲍氏放线菌的身份。当使用E-test（生物梅里埃公司）对10种不同抗生素类别进行测试时，所检测的细菌表现出相似的药敏模式。β-内酰胺类（苄青霉素和头孢呋辛）和万古霉素的最低抑菌浓度（MIC）为0.5mg/L，黏菌素和环丙沙星为8mg/mL，其他抗生素类别≤25mg/mL。从感染的牙根管中分离出鲍氏放线菌，这对所有放线菌感染均有内源性来源这一公认观点提出了质疑。
