Objective The purpose of the study is to understand the epidemiology,distribution and molecular characteristics of oxacillin susceptible mecA positive Staphylococcus aureus (S.aureus).Methods Totally 1588 S.aureus isolates collected from 12 hospitals in 10 cities of China between 2010 and 2012 were retrospectively characterized.The isolates were characterized by antimicrobial susceptibility test of 20antimicrobial drugs.Three different methods (cefoxitin disc diffusion,agar dilution for oxacillin and cefoxitin) to detect oxacillin susceptible and mecA positive S.aureus were also compared.All the strains were confirmed to be S.aureus by detecting S.aureus specific genes by PCR (including nuc,femB,and mecA gene),which was viewed as the golden standard of MRSA.The molecular typing methods included SCCmec and spa typing.The statistical analyses were carried out in statistical product and service solutions (SPSS),Version 18.0.The significance level P was set at 0.05.Results According to the MICs of cefoxitin and oxacillin,a total of 60 isolates were oxacillin susceptible methicilin resistance Staphylococcus aureus (MRSA).Based on the differences of the specimen collection date,it is found that oxacillin susceptible MRSA have increased from 2010 to 2012 (P =0.05,95％ CI 0.045-0.056,X2 =6.099).These isolates were distributed in 9 major cities,and the highest prevalence is 30.0％ (18/60) in Guangzhou,followed by Beijing (18.3％,11/60),Wuhan (15.0％,9/60),Hangzhou (13.3％,8/60).Most of the isolates were from skin soft tissue infection (35％,21/60),blood stream infection (30％,18/60) and respiratory infection specimens (18.3％,11/60).The resistance rate to cefoxitin,erythromycin,clindamycin and tetracycline was 100％ (60/60),86.7％ (52/60),66.7％ (40/60) and 50％ (30/60),respectively.The molecular characterization showed that 21 spa and 5 SCCmec types were detected.The most predominant clone was spa t437-SCCmec Ⅳ (25.0％,15/60),followed by spa t437-SCCmecV (13.3％,8/60).Conclusions The detection rate of oxacillin susceptible MRSA is significantly higher from 2010 to 2012.The major clone is t437-SCCmec Ⅳ.The use of cefoxitin should replace oxacillin in detecting this type of MRSA.Further study is needed to confirm whether beta lactam antimicrobial agents should be used in the treatment of oxacillin susceptible mecA positive S.aureus.

Objective To investigate the effect of LY294002 on proliferation of cultured human glomerular mesan-gial cells, and to study on the mechanism underlying this proliferation. Methods Different concentrations of LY294002 (0.02,0.2,2,20,100 mg/L) were administrated to the cultured human glomerular mesangial cells. The effects of mesangial cell proliferation were measured using CCK-8 colorimetric assay. Under appropriate concentrations, proliferation of cultured mesangial cells were measured using CCK-8 at 0.5, 1, 24, 48 hours of drug administration time. Results LY294002(0.02 mg/L)didn’t obviously inhibited the growth of mesangial cells(P>0.05), the inhibition rate was 5.05%. The effect of LY294002 on the cells decreased with rising concentration (0.2 to 20 mg/L) in a dose-dependent manner (P<0.05). Mesan-gial cells would stop growing with the increasing concentration. LY294002 didn’t obviously inhibited the growth of mesan-gial cells at 2 mg/L during 0 to 1 h(P>0.05), but inhibited proliferation gradually from 1 to 48 h (P<0.05). Conclu-sion Within the certain range of concentration and time, the LY294002 inhibits the proliferation of human glomerular me-sangial cells, and PI3K/Akt/mTOR signaling pathway may regulate the proliferation of human mesangial cell.

Objective To investigate the effect of 1,25-dihydroxyvitamin D3 on proliferation and apoptosis of glomerular mesangial cells via the PI3K/Akt/mTOR signal pathway. Methods The normal control group, 1,25-dihydroxyvitamin D3 (10-8 mol/L) group, rapamycin (0.1 μg/mL) group and the rapamycin in combination with 1,25-dihydroxyvitamin D3 group. The cell proliferation was measured by cell counting kit-8 assay. The cell cycle and cell apoptosis were detected by flow cytometry assay , respectively. Results Compared with the normal control group, the proliferation of glomerular mesangial cells was significantly inhibited in the 1 ,25-dihydroxyvitamin D3 group, in the rapamycin group and in the rapamycin in combination with 1,25-dihydroxyvitamin D3 group. The cells at G1 phase were significantly increased, but the cells at S phase were significantly decreased, with significant increase of cell apoptosis rate. Compared with the 1,25-dihydroxyvitamin D3 group, the proliferation of human glomerular mesangial cells was significantly inhibited in the rapamycin group and in the rapamycin in combination with 1,25-dihydroxyvitamin D3 group. Compared with the rapamycin group, the cells at G1 phase were significantly increased and the cells at S phase were significantly decreased in the rapamycin in combination with 1,25-dihydroxyvitamin D3 Group. Conclusions 1,25-dihydroxyvitamin D3 inhibits cell proliferation and promotes human glomerular mesangial cell apoptosis of human glomerular mesangial through the PI3K/Akt/mTOR signal pathway. 1,25-dihydroxyvitamin D3 and rapamycin can synergistically inhibit the proliferation of human glomerular mesangial cells.

Objective To identify critical genes in evolution of Staphylococcus aureus (S.aureus).Methods A total of 2457 genes from two whole genomes of S.aureus strains were amplified for fabricating whole genome microarray,which was employed for comparative genome hybridization (CGH) analysis of 23 strains of divergent MRSA clones,including ST239-spa t037 and ST239-spa t030.Representatives of differential genes were confirmed by PCR.Results Four gene clusters were identified to be associated with evolution of major epidemic MRSA clones.The four gene clusters were specific to ST239-spa t030,and belonged to three known genomic islands (vSa4,prophage ΦSa1 and ΦSa3).Eight genes were variable expressed in ST239-spa t030 MRSA from different coutries.Conclusion The acquisition of genomic islands vSa4,prophage ΦSa1 and ΦSa3 enhanced the virulence and resistance of ST239-spa t030 MRSA,and contributed to its rapid replacement of ST239-spa t037 MRSA in China.

Objective To analyze the molecular epidemiology and resistant mechanisms ofmacrolide-nonsusceptible Moraxella catarrhalis.Methods A total of 383 strains of Moraxella camrrhaliswere collected from nasopharynx of children under 2 years old.The minimum inhibition concentration (MIC)values were determined by Etest method,and the production of β-lactamase was examined by using anitrocefin-based test.The pulsed-field gel electrophoresis (PFGE) method was used to analyze the type ofdifferent isolates.Polymerase chain reaction (PCR) and sequencing were performed for the resistancemechanism of macrolide resistance in Moraxella catarrhalis.The non-susceptibility rates of six cities( Beijing,Shanghai,Jinan,Nanjing,Wuhan and Dongguan) were compared byx2 test.ResultsAccording to Clinicaland Laboratory Standards Institute (CLSI) breakpoints,the non-susceptibility rates for erythromycin andazithromycin in 383 strdns of Moraxella catarrhalis were 40％ and 23％,respectively.Whereas,the non-susceptibility rates were 59％and 60％based on pharmacokinetics/pharmacodynamics(PK/PD)breakpoints.Significant differences in non-susceptibility rates to macrolide were observed in different cities,and the higher non-susceptibility rates were determined in relatively northern cities,such as Beijing andJinan.Among the 383 strains of Moraxella catarrhalis,92％ (353/383) of isolates produced β-lactamase.Atotal of 14 patterns of groups were generated by PFGE in 37 high-level macrolide resistant Moraxella catarrhalis,and 43％ ( 16/37 ) of isolates could be considered to be related or indistinguishable to group A.In this study,the ermA,ermB,mefA,and merE genes were not detected,while the A2982T,A2796T,A2983T mutations in 23S rRNA gene may be related to macrolide resistance in Moraxella catarrhalis.The A2982T and A2796T mutations conferred high-level macrolide resistance,while the A2983T mutation conferred low-level resistance.ConclusionsA large number of macrolide-nonsusceptible Moraxella catarrhalis isolates are detected in the study.The macrolide resistance is probably related to the mutations in 23S rRNA gene,and the relationship between MIC values of macrolide and mutations has been determined.

Objective To investigate the factors affecting the susceptibility of tigecycline and assess the testing methods.Methods The 116 isolates of Acinetobacter baumanaii and Klebsiella pneumoniae were collected in 13 hospitals from January to December,2010,to evaluate the effects on the tigecycline susceptibility of the overnight medium,medium brand and lot number,respectively.The 56 isolates of Acinetobacter baumannii and the 47 isolates of Klebsiella pneumoniae were selected randomly according to the MIC distribution proportion in 2010 and 2012.The broth microdilution was taken as the reference method to evaluate the effects of the agar dilution,disk diffusion,MIC Test Strip (MTS) and Vitek2 (GN16) on the susceptibility of tigecycline.Results The essential agreement (EA) of Acinetobacter baumannii and Klebsiella pneumoniae is 89.7％ (52/58)and 87.9％ (51/58) using overnight medium and fresh medium respectively.Both EA and categorical agreement (CA) of the different brands (BBL and Oxoid) and lot numbers are 100％ using agar dilution.According to the FDA break point criteria,the CA/EA is 77.7％ (80/103)/99.0％ (102/103),87.4％ (90/103)/98.1％ (101/103),64.1％ (66/103)/76.7％ (79/103) using agar dilution,MTS,Vitek (GN16) with respect to broth microdilution.The CA is 79.6％ (82/ 103,S≥14 mm,R≤10 mm),69.9％ (72/103,S≥ 16 mm,R≤ 12 mm),34.0％ (35/103,S≥19 mm,R≤14 mm)using disk diffusion method compared with broth microdilution (FDA break point criteria).Conclusions The susceptibility of tigecycline must be tested using fresh medium.The medium brands and lot numbers used in this test have no effects on the tigecycline susceptibility to Acinetobacter baumannii and Klebsiella pneumoniae.There exist the better correlations on MIC using agar dilution and MTS than the disk diffusion and Vitek(GN16) compared with broth microdilution.It is expected that the consistency can be improved by adjusting the break point of disk diffusion.

In order to improve the precision and robustness in determination of soluble solids content ( SSC) of ‘Fuji ’ apple by NIR spectroscopy and eliminate the effect of origin variability on the accuracy of NIR calibration models for the SSC, sample set partitioning based on joint x-y distances ( SPXY) was used to select representative subset from the apple samples of 4 different origins. As a comparison, partial least square ( PLS) was used to establish local origin and hybrid origin models for the prediction of SSC in apple. Competitive adaptive reweighted sampling ( CARS ) and successive projections algorithm ( SPA ) were implemented to select effective variables of the NIR spectroscopy of SSC of apple. The results indicated that the PLS model established based on the 4 origin apple samples performed better than local origin and other hybrid origin models. The model could be effectively simplified using 16 characteristic variables selected by CARS-SPA method from full-spectrum which had 3112 wavelengths. The correlation coefficient (Rp) and root mean square error of prediction (RMSEP) were 0. 978 and 0. 441 oBrix, respectively for SSC. It was found that the model developed by more samples of different origins combined with effective wavelengths showed good prediction ability for apple sample of unknown origin, which indicated that it could significantly reduce the origin effect on the robustness of NIR models for SSC of apple.

Objective To elucidate the resistance mechanisms of clinical colistin-resistant Klebsiella pneumoniae and Escherichia coli isolates in China.Methods A total of 964 K.pneumoniae and 1 389 E. coli isolates were retrospectively collected from national surveillance programs from 2011 to 2014 in China. Antimicrobial susceptibility testing was determined by the microdilution method.The PCR amplification followed by sequencing was used to detect the mcr-1 gene and colistin-resistance genes, including mgrB, pmrB and phoQ.Real-time quantitative PCR was performed to examine the relative transcriptional levels of pmrB, pmrC, pmrD, pmrK and pmrE genes in K.pneumoniae, and pmrA, pmrB, pmrC, phoP and phoQ genes in E.coli.Conjugation experiment was used to detect the transferability of the resistance plasmid carrying the mcr-1 gene.Statistical analyses were performed using IBM SPSS Statistics (version 16.0) and a P value <0.05 was considered statistically significant. Results The colistin-resistant rates of K. pneumoniae and E.coli were 0.62% ( 6/964 ) and 1.66% ( 23/1 389 ) , respectively.No amino acids substitutions were identified in mgrB genes among colistin-resistant isolates.Among six colistin-resistant K. pneumoniae isolates, five isolates were identified to have point mutations in pmrB gene, but no point substitution was detected in phoQ gene.One to four point mutations had been found in pmrB and phoQ genes in colistin-resistant E.coli isolates, respectively.The expression level of pmrB, pmrC, pmrD, pmrK and pmrE genes showed no significant difference between colistin-resistant and colistin-susceptible isolates [pmrB, (1.04 ±1.12) vs.(0.94 ±0.67), P=0.945; pmrC, (1.39 ±2.01) vs.(0.16 ±0.27), P=0.101;pmrD, (1.59 ±2.43) vs.(0.88 ±0.34),P=0.445;pmrK, (0.64 ±0.62) vs.(0.04 ±0.10), P=0.051;pmrE, (3 492 833 388.83 ±8 478 977 986.85) vs.(20 771 428.93 ±38 000 732.85), P=0.445].However, the transcriptional level of pmrB genes in colistin-resistant group was 9.5-fold higher than that of the colistin-susceptible group in E.coli isolates.Four in six colistin-resistant K.pneumoniae isolates possessed mcr-1 gene, whereas all of the colistin-resistant E. coli had the mcr-1 gene. The conjugation verified the transferability rate of the plasmid carrying mcr-1 gene was 5.78 ×10-6 , and the MIC value of colistin of the conjugant increased 21-fold than the recipient strain.Conclusions Plasmid-mediated mcr-1 gene was the major reason for colistin resistance in clinical isolates of K.pneumoniae and E.coli. Some other resistance mechanisms such as transcriptional up-regulated pmrB gene also involved in colistin resistance.

ObjectiveTo investigate the prevalence,antibiotic characteristics as well as molecular background of community-associated methicillin-sensitive Staphylococcus aureus (CA-MRSA) from patients with skin and sofi tissue infections from 4 different hospitals in Beijing.MethodsFive hundred and one patients were enrolled from 4 hospitals prospectively.Patients with skin and soft tissue infections and no risk factors for healthcare-associated acquisition were included.Sample from the infection sites were collected for culture.Case report form was filled out for each patient.Antibiotic susceptibility test and molecular analysis was performed for each Staphylococcus aureus isolate.ResultsTotally 164 Staphylococcus aureus isolates were cultured from the patients with skin and soft tissue infections.Of them 5 isolates were CA-MRSA.These 5 CA-MRSA isolates harbored SCCmec Ⅰ, SCCmec Ⅲ, SCCmec Ⅳ,SCCmec Ⅴ and untypable,respectively.CA-MRSA was highly resistant to β-lactamase,levofloxacin,erythromycin and clindamycin,but susceptible to vancomycin,teicoplanin,linezolid,daptomycin,and trimethoprim/sulfamethoxazole.Prevalence of PVL in community-associated methicillin sensitive Staphylococcus aureus(CA-MSSA) and CA-MRSA were 41.9％ and 2/5.Other toxins expressed similarly between them.Combined with multilocus sequence typing (MLST) and spa typing,the major clones of CA-MSSA were ST398-t034,ST7-t796,ST398-t571,ST1t127,and ST188-t189,while in CA-MRSA were ST239-t037-SCCmec Ⅰ,ST239-t632-SCCmecⅢ,ST59-t437-SCCmecV,ST8-t008-SCCmecⅣ,and ST6-t701-NT.ConclusionsThe low prevalence of CA-MRSA in Beijing and complexity of the genetic background in CA-MRSA were observed.Clone spread is not found among CA-MRSAisolates.CA-MRSAexhibithigher resistancecomparedwithmethicillinsensitive Staphylococcus aureus (MSSA).Rational drug use scheme is called in the clinical practice to prevent development of high level resistance.

Objective:By studying the gait changes of patients with knee osteoarthritis (KOA), the study provided a theoretical basis for the quantitative indicators obtained from gait analysis to the diagnosis of KOA. And it provided a gait reference for the clinical diagnosis, treatment, rehabilitation, prevention and efficacy evaluation of KOA.Methods:A total of 30 patients (KOA group) with KOA hospitalized in our hospital from May 2021 to October 2021 and 30 healthy people (control group) were compared for gait changes. The t test, Mann-Whitney U test and Fisher′s exact test were used to compare differences between groups. Results:The KOA group were greater than the control group in terms of step time [(642±81) ms and (548±62) ms, t=-5.01, P<0.001], gait cycle [(1 284±168) ms and (1 076±114) ms, t=-5.61, P<0.001], double support time [(531±125) ms and (331±51) ms, t=-8.10, P<0.001], double support time period proportion (0.417±0.063 and 0.309±0.023, t=-8.50, P<0.001), total support time [(914±135) ms and (678±107) ms, t=-7.52, P<0.001], total support time period proportion (0.711±0.027 and 0.627±0.044, t=-8.87, P<0.001), and left static standing time (55.7±8.4 and 51.5±2.2, t=-2.65, P=0.012), for which the differences were statistically significant. The KOA group were lower than the control group in terms of single support time period proportion (0.287±0.030 and 0.334±0.013, t=7.80, P<0.001), right static standing time (44.3±8.4 and 48.5±2.3, t=2.65, P=0.012), step length [(36±8) cm and (52±5) cm, t=9.97, P<0.001], stride length [(70±16) cm and (103±8) cm, t=10.00, P<0.001], velocity [(0.60±0.18) m/s and (1.05±0.19) m/s, t=9.54, P<0.001], left knee range of motion [(42±17)° and (63±4) °, t=6.49, P<0.001], and right knee range of motion [(37±18) ° and (62±3)°, t=7.54, P<0.001], for which the differences were statistically significant. Conclusion:Gait analysis can quantitatively evaluate the condition of patients with KOA, making it possible to transform the diagnostic criteria of KOA from qualitative to quantitative.