Objective To investigate the genotype and epidemiology of plasmid‐mediated AmpC β‐lactamases produced by the clinical strains of Escherichia coli and Klebsiella pneumoniae .Methods A total of 176 clinical nonrepetitive cefoxitin non‐sensitivity isolates of Escherichia coli and Klebsiella pneumoniae was collected from July 2011 to August 2012 .Polymerase chain reaction (PCR) for AmpC enzyme gene amplification and DNA sequencing were carried out for genotype of AmpC beta‐lactamases .Results The results of PCR showed that the positive rate of ampC of the 176 strains of Escherichia coli and Klebsiella pneumoniae AmpC was 18 .2% ,mainly DHA type ,counting for 59 .4% ,CIT counting for 37 .5% ,EBC counting for 3 .1% .The positive rate of ampC of Escherichia coli was 11 .4% ,mainly CIT type ,counting for 77 .8% ,the positive rates of DHA type and EBC type both were 11 .1% .The positive rate of ampC of Klebsiella pneumoniae were 23 .7% ,mainly DHA type ,counting for 78 .3% ,CIT type count‐ing for 21 .7% .The results of DNA sequencing showed that there were 18 strains DHA‐1 type and 1 strain ampC gene type of Morganella morganii in DHA type strains ,the concordance rate was 97 .0% ,10 CIT type strains was CMY‐2 type ,1 strain was CMY‐42 ,one strain was CMY‐4 type ,EBC type was ampC gene type of Enterobacter cloacae ,the concordance rate was 99 .0% .A total of 32 strains of gene sequencing were registered as KJ127248 - KJ127279 in GenBank .Conclusion The main genotypes of plasmid‐mediated ampC enzyme produced by Escherichia coli and Klebsiella pneumoniae were CMY‐2 and DHA‐1 respectively .

MicroRNA (miRNA) are a class of small non-coding single-stranded RNA that exert their biological effects by binding to target messenger RNA (mRNA). There is new evidence that miRNA may play an important role in regulating the growth and development of mandibular condylar cartilage. In this paper, the production and mechanism of miRNA are reviewed, and the progress of studies on the growth and development of mandibular condylar cartilage, which is helpful to further study the growth and development of mandibular condylar cartilage.

Objective:To study the alveolar bone remodeling of maxillary anterior teeth after extraction treatment and 2-year recovery period in adolescent patients with maxillary anterior arch protrusion.Methods:15 adolescent patients with maxillary anterior arch protru-sion were included,2 maxillary first premolars were extracted and implant anchorage combined with sliding method were used to close the extraction gap.CBCT images were taken before treatment(T0),after treatment(T1)and 2 years of recorvery period(T2),respectively.After multi-plane reconstruction with Dophin Imaging,the alveolar bone area(ABA)changes of maxillary central incisor,lateral incisor and canine at cementoenamel junction(CEJ-3 mm),root neck,central part,and root tip were measured and recorded as TAC,TA1,TA2 and TA3 respectively.The labial palatal alveolar crest to CEJ bone height(BH)of each tooth was recorded as BCL,BCP respectively.The data were analyzed by IBM SPSS statistics 25.0.Results:In T0-T2 phase,TA1 of each tooth was reduced.In T0-T1 phase,the horizontal adsorption of teeth was significantly correlated with ΔBCP,followed by ΔTA3.In T0-T2 phase,ΔBCP,ΔTA2,ΔTA3 and the horizontal adsorption of teeth showed low negative correlation.In T0-T1 phase,the vertical reduction of teeth was significantly positively correlated with ΔTAC,followed by low correlation with ΔTA3 and ΔTA1.Conclusion:In the treatment of anterior arch protrusion after extraction correction in adolescent patients the more the vertical reduction and horizontal adsorption of teeth in the treatment phase,the more the alveolar bone thickness and height around the tooth root in the maintenance phase,which were significantly positively correlated.Reasonable control of the vertical move-ment of teeth in the alveolar bone can improve the periodontal condition around the teeth to a certain extent.