武汉市丙酸杆菌对红霉素耐药与23SrRNA点突变和携带erm基因相关

Erythromycin resistance in propionibacteria isolated from patients with acne in Wuhan city is associated with mutations in 23S rRNA gene and presence of erm genes

目的探讨武汉市耐红霉素丙酸杆菌23SrRNA有无点突变以及携带ermX基因的Tn5432转座子是否转入了丙酸杆菌。方法从痤疮患者皮损中分离丙酸杆菌，E—test法检测分离株对红霉素和克林霉素的MIC值。PCR扩增耐药株23SrRNA、ermX、ermX（ei）、ISl249a、ISl249b并测序，并在基因库中比较。结果19株痤疮丙酸杆菌（P．acnes）和10株卵白丙酸杆菌（P．avidum）对红霉素均表现为高度耐药（MIC均〉256μg／ml）。19株P．acnes中，16株对克林霉素高度耐药（MIC〉256μg／ml），3株敏感；10株P．avidum对克林霉素高度耐药（MIC〉256μg／ml）。19株P．acnes耐药株中，7株在相当于E．co／i23SrRNA2058位点发现由A—G点突变，均对红霉素和克林霉素高度耐药；4株在相当于E．coli23SrRNA2059位点发现由A—G点突变，其中1株对克林霉素耐药，3株敏感；另外8株P．acnes扩增errnX阳性，其序列与基因库中P．acnesermX基因100％同源。10株P．avidum中，2株ermX扩增阳性，其序列与P．aenesermX基因100％同源；另外8株扩增ermX（ei）得到预期片段PCR产物，与基因库中CorynebacteriumjeikeiumermX（ei）序列99％同源，而与P．acnesermX基因仅有94％的同源性。10株扩增ermX基因阳性的菌株扩增IS1249a和IS1249b均阳性，而其余菌株均阴性。结论武汉市耐红霉素丙酸杆菌分别由相当于E．co／i23SrRNA2058、2059由A-G点突变、携带ermX的Tn5432传人以及ermX（cj）传人丙酸杆菌引起。

Objective To determine whether erythromycin-resistant propionibacteria isolated from patients with acne in Wuhan city harbor 23S rRNA gene mutations as well as the transposon Tn5432 carrying ermX genes. Methods Twenty-nine Propionibacterium strains isolated from outpatients with acne in Wuhan city were included in this study. The E-test method was used to determine the susceptibility of these strains to erythromycin and clindamycin. PCR was performed to amplify the 23S rRNA, ermX, ermX （cj）, IS1249a and IS1249b genes from resistant strains followed by DNA sequencing and nucleotide alignment. Results Among the 29 Propionibacterium strains, 19 were identified as P. acnes and 10 as P. avidum. All of these Propionibacterium strains were resistant to erythromycin （MIC 〉 256μg/ml） and clindamycin （MIC 〉 256 μg/ml）, except for 3 P. acnes strains sensitive to clindamycin. Seven P. aches strains resistant to both antibiotics exhibited an A→G transition at a position cognate with Escheerchia coli 23S rRNA 2058. An A→G transition at a position cognate with E.coli 23S rRNA 2059 was identified in one clindamycin-resitant and three clindamycin-sensitive P. acnes isolates. The ermX gene was found in the remaining 8 P. aches isolates and 2 P. avidum isolates, with the sequence 100% identical to the reference sequence of the ermX gene of P. acnes in Genbank. Meanwhile, the ermX （cj） gene was successfully amplified from the other 8 P. avidum isolates, which showed 99% sequence homology with the ermX （cj） gene of Corynebacteriam jeikeium, but 94% homology with the ermX gene of P. aches in Genbank. Both IS1249a and IS1249b genes were amplified in the 10 ermX gene-positive Propionibacterium strains, but not in the other ermX gene-negative strains. Conclusions The erythromyein resistance in Propionibacterium isolates from Wuhan city may be associated with the A→G transition at the E.coli equivalent bases 2058 and 2059 of the 23S rRNA gene, as well as the presence of the erm X （transferred through the transposon Tn5432） and ermX （cj） genes.