Objective:To explore the force distribution on the maxillary dentition when the first and second molars distalized simultaneously with different step sizes using clear aligners in vitro in order to provide a theoretical basis for the rational design of molar distalization. Methods:Clear aligners were designed to simultaneously distalize the maxillary first and second molars bilaterally, with rectangular attachments placed on the buccal surfaces of the first and second premolars, as well as the second molars. Based on different step sizes, the aligners were divided into three groups: Group A (0.15 mm per step), Group B (0.20 mm per step), and Group C (0.25 mm per step). Ten aligners were fabricated for each group using 0.76 mm thick polyethylene terephthalate glycol (PET-G) sheets. A three-dimensional force measurement system was used to measure the forces exerted on each tooth by the aligners, the first and second molars served as the target teeth and the remaining teeth as anchorage teeth. The three-dimensional force data were compared among the three groups.Results:In the mesiodistal direction, the forces on the central and lateral incisors were relatively small among all three groups, with no statistically significant differences ( P>0.05). However, significant differences were observed in the forces on the canines, first premolars, second premolars, first molars, and second molars ( P<0.05). The distal forces on the second molars in Groups B and C were (6.13±1.45) N and (6.83±1.58) N, respectively, significantly higher than that in Group A [(3.51±1.01) N] ( P<0.05). The distal force on the first molars in Group C [(6.62±0.89) N] was significantly higher than that in Groups A and B ( P<0.05). The mesial reactive forces on the first and second premolars in Groups B and C were significantly higher than those in Group A ( P<0.05). The mesial reactive force on the canines in Group C [(-2.98±1.33) N] was significantly higher than that in Group A [(-1.69±0.68) N] ( P<0.05), while there were no significant differences between Groups B and C in the forces on the canines, first premolars, and second premolars ( P>0.05). In the buccolingual direction, there were no statistically significant differences in the forces on the central and lateral incisors among three groups ( P>0.05), but significant differences were observed in the forces on the canines, second premolars, and second molars ( P<0.05). The buccolingual forces on the canines, second premolars, and second molars in Group B were (-0.56±0.54), (-2.07±0.95), (1.13±0.55) N, respectively, significantly higher than those in Group A ( P<0.05), but there were no significant differences compared to Group C ( P>0.05). Compared to the mesiodistal and buccolingual forces, the vertical forces on the target and anchorage teeth were relatively small in all three groups. Conclusions:When using 0.76 mm thick PET-G sheets to fabricate clear aligners for simultaneous molar distalization, a step size of 0.20 mm per step is recommended. To prevent buccal tipping of the molars during distalization, it is advisable to design lingual displacement for the molars and buccal displacement for the adjacent anchorage teeth to counteract the unfavorable forces, with attachments placed on the primary anchorage teeth.

Objective To investigate the distribution and antimicrobial resistance profiles of the common pathogens isolated from urine from 2015 to 2021 in the CHINET Antimicrobial Resistance Surveillance Program.Methods The bacterial strains were isolated from urine and identified routinely in 51 hospitals across China in the CHINET Antimicrobial Resistance Surveillance Program from 2015 to 2021.Antimicrobial susceptibility was determined by Kirby-Bauer method,automatic microbiological analysis system and E-test according to the unified protocol.Results A total of 261 893 nonduplicate strains were isolated from urine specimen from 2015 to 2021,of which gram-positive bacteria accounted for 23.8％(62 219/261 893),and gram-negative bacteria 76.2％(199 674/261 893).The most common species were E.coli(46.7％),E.faecium(10.4％),K.pneumoniae(9.8％),E.faecalis(8.7％),P.mirabilis(3.5％),P.aeruginosa(3.4％),SS.agalactiae(2.6％),and E.cloacae(2.1％).The strains were more frequently isolated from inpatients versus outpatients and emergency patients,from females versus males,and from adults versus children.The prevalence of ESBLs-producing strains in E.coli,K.pneumoniae and P.mirabilis was 53.2％,52.8％and 37.0％,respectively.The prevalence of carbapenem-resistant strains in E.coli,K.pneumoniae,P.aeruginosa and A.baumannii was 1.7％,18.5％,16.4％,and 40.3％,respectively.Lower than 10％of the E.faecalis isolates were resistant to ampicillin,nitrofurantoin,linezolid,vancomycin,teicoplanin and fosfomycin.More than 90％of the E.faecium isolates were ressitant to ampicillin,levofloxacin and erythromycin.The percentage of strains resistant to vancomycin,linezolid or teicoplanin was＜2％.The E.coli,K.pneumoniae,P.aeruginosa and A.baumannii strains isolated from ICU inpatients showed significantly higher resistance rates than the corresponding strains isolated from outpatients and non-ICU inpatients.Conclusions E.coli,Enterococcus and K.pneumoniae are the most common pathogens in urinary tract infection.The bacterial species and antimicrobial resistance of urinary isolates vary with different populations.More attention should be paid to antimicrobial resistance surveillance and reduce the irrational use of antimicrobial agents.

Objective To understand the distribution and changing resistance profiles of clinical isolates of Enterococcus in hospitals across China from 2015 to 2021.Methods Antimicrobial susceptibility testing was conducted for the clinical isolates of Enterococcus according to the unified protocol of CHINET program by automated systems,Kirby-Bauer method,or E-test strip.The results were interpreted according to the Clinical & Laboratory Standards Institute(CLSI)breakpoints in 2021.WHONET 5.6 software was used for statistical analysis.Results A total of 124 565 strains of Enterococcus were isolated during the 7-year period,mainly including Enterococcus faecalis(50.7％)and Enterococcus faecalis(41.5％).The strains were mainly isolated from urinary tract specimens(46.9％±2.6％),and primarily from the patients in the department of internal medicine,surgery and ICU.E.faecium and E.faecalis strains showed low level resistance rate to vancomycin,teicoplanin and linezolid(≤3.6％).The prevalence of vancomycin-resistant E.faecalis and E.faecium was 0.1％and 1.3％,respectively.The prevalence of linezolid-resistant E.faecalis increased from 0.7％in 2015 to 3.4％in 2021,while the prevalence of linezolid-resistant E.faecium was 0.3％.Conclusions The clinical isolates of Enterococcus were still highly susceptible to vancomycin,teicoplanin,and linezolid,evidenced by a low resistance rate.However,the prevalence of linezolid-resistant E.faecalis was increasing during the 7-year period.It is necessary to strengthen antimicrobial resistance surveillance to effectively identify the emergence of antibiotic-resistant bacteria and curb the spread of resistant pathogens.

Objective To examine the changing antimicrobial resistance profile of Enterobacter spp.isolates in 53 hospitals across China from 2015 t0 2021.Methods The clinical isolates of Enterobacter spp.were collected from 53 hospitals across China during 2015-2021 and tested for antimicrobial susceptibility using Kirby-Bauer method or automated testing systems according to the CHINET unified protocol.The results were interpreted according to the breakpoints issued by the Clinical & Laboratory Standards Institute(CLSI)in 2021(M100 31st edition)and analyzed with WHONET 5.6 software.Results A total of 37 966 Enterobacter strains were isolated from 2015 to 2021.The proportion of Enterobacter isolates among all clinical isolates showed a fluctuating trend over the 7-year period,overall 2.5％in all clinical isolates amd 5.7％in Enterobacterale strains.The most frequently isolated Enterobacter species was Enterobacter cloacae,accounting for 93.7％(35 571/37 966).The strains were mainly isolated from respiratory specimens(44.4±4.6)％,followed by secretions/pus(16.4±2.3)％and urine(16.0±0.9)％.The strains from respiratory samples decreased slightly,while those from sterile body fluids increased over the 7-year period.The Enterobacter strains were mainly isolated from inpatients(92.9％),and only(7.1±0.8)％of the strains were isolated from outpatients and emergency patients.The patients in surgical wards contributed the highest number of isolates(24.4±2.9)％compared to the inpatients in any other departement.Overall,≤ 7.9％of the E.cloacae strains were resistant to amikacin,tigecycline,polymyxin B,imipenem or meropenem,while ≤5.6％of the Enterobacter asburiae strains were resistant to these antimicrobial agents.E.asburiae showed higher resistance rate to polymyxin B than E.cloacae(19.7％vs 3.9％).Overall,≤8.1％of the Enterobacter gergoviae strains were resistant to tigecycline,amikacin,meropenem,or imipenem,while 10.5％of these strains were resistant to polycolistin B.The overall prevalence of carbapenem-resistant Enterobacter was 10.0％over the 7-year period,but showing an upward trend.The resistance profiles of Enterobacter isolates varied with the department from which they were isolated and whether the patient is an adult or a child.The prevalence of carbapenem-resistant E.cloacae was the highest in the E.cloacae isolates from ICU patients.Conclusions The results of the CHINET Antimicrobial Resistance Surveillance Program indicate that the proportion of Enterobacter strains in all clinical isolates fluctuates slightly over the 7-year period from 2015 to 2021.The Enterobacter strains showed increasing resistance to multiple antimicrobial drugs,especially carbapenems over the 7-year period.

Objective To understand the changing distribution and antimicrobial resistance profiles of Proteus,Morganella and Providencia in hospitals across China from January 1,2015 to December 31,2021 in the CHINET Antimicrobial Resistance Surveillance Program.Methods Antimicrobial susceptibility testing was carried out following the unified CHINET protocol.The results were interpreted in accordance with the breakpoints in the 2021 Clinical & Laboratory Standards Institute(CLSI)M100(31 st Edition).Results A total of 32 433 Enterobacterales strains were isolated during the 7-year period,including 24 160 strains of Proteus,6 704 strains of Morganella,and 1 569 strains of Providencia.The overall number of these Enterobacterales isolates increased significantly over the 7-year period.The top 3 specimen source of these strains were urine,lower respiratory tract specimens,and wound secretions.Proteus,Morganella,and Providencia isolates showed lower resistance rates to amikacin,meropenem,cefoxitin,cefepime,cefoperazone-sulbactam,and piperacillin-tazobactam.For most of the antibiotics tested,less than 10％of the Proteus and Morganella strains were resistant,while less than 20％of the Providencia strains were resistant.The prevalence of carbapenem-resistant Enterobacterales(CRE)was 1.4％in Proteus isolates,1.9％in Morganella isolates,and 15.6％in Providencia isolates.Conclusions The overall number of clinical isolates of Proteus,Morganella and Providencia increased significantly in the 7-year period from 2015 to 2021.The prevalence of CRE strains also increased.More attention should be paid to antimicrobial resistance surveillance and rational antibiotic use so as to prevent the emergence and increase of antimicrobial resistance.

Objective To understand the changing distribution and antimicrobial resistance profiles of Klebsiella strains in 52 hospitals across China in the CHINET Antimicrobial Resistance Surveillance Program from 2015 to 2021.Methods Antimicrobial susceptibility testing was carried out according to the unified CHINET protocol.The susceptibility results were interpreted according to the breakpoints in the Clinical & Laboratory Standards Institute(CLSI)M100 document.Results A total of 241,549 nonduplicate Klebsiella strains were isolated from 2015 to 2021,including Klebsiella pneumoniae(88.0％),Klebsiella aerogenes(5.8％),Klebsiella oxytoca(5.7％),and other Klebsiella species(0.6％).Klebsiella strains were mainly isolated from respiratory tract(48.49±5.32)％.Internal medicine(22.79±3.28)％,surgery(17.98±3.10)％,and ICU(14.03±1.39)％were the top 3 departments where Klebsiella strains were most frequently isolated.K.pneumoniae isolates showed higher resistance rate to most antimicrobial agents compared to other Klebsiella species.Klebsiella isolates maintained low resistance rates to tigecycline and polymyxin B.ESBLs-producing K.pneumoniae and K.oxytoca strains showed higher resistance rates to all the antimicrobial agents tested compared to the corresponding ESBLs-nonproducing strains.The K.pneumoniae and carbapenem-resistant K.pneumoniae(CRKP)strains isolated from ICU patients demonstrated higher resistance rates to majority of the antimicrobial agents tested than the strains isolated from non-ICU patients.The CRKP strains isolated from adult patients had higher resistance rates to most of the antimicrobial agents tested than the corresponding CRKP strains isolated from paediatric patients.Conclusions The prevalence of carbapenem-resistant strains in Klebsiella isolates increased greatly from 2015 to 2021.However,the Klebsiella isolates remained highly susceptible to tigecycline and polymyxin B.Antimicrobial resistance surveillance should still be strengthened for Klebsiella strains.

Objective To investigate the changing distribution and antibiotic resistance profiles of clinical isolates of Staphylococcus in hospitals across China from 2015 to 2021.Methods Antimicrobial susceptibility testing was conducted for the clinical isolates of Staphylococcus according to the unified protocol of CHINET(China Antimicrobial Surveillance Network)using disk diffusion method and commercial automated systems.The CHINET antimicrobial resistance surveillance data from 2015 to 2021 were interpreted according to the 2021 CLSI breakpoints and analyzed using WHONET 5.6.Results During the period from 2015 to 2021,a total of 204,771 nonduplicate strains of Staphylococcus were isolated,including 136,731(66.8％)strains of Staphylococcus aureus and 68,040(33.2％)strains of coagulase-negative Staphylococcus(CNS).The proportions of S.aureus isolates and CNS isolates did not show significant change.S.aureus strains were mainly isolated from respiratory specimens(38.9±5.1)％,wound,pus and secretions(33.6±4.2)％,and blood(11.9±1.5)％.The CNS strains were predominantly isolated from blood(73.6±4.2)％,cerebrospinal fluid(12.1±2.5)％,and pleural effusion and ascites(8.4±2.1)％.S.aureus strains were mainly isolated from the patients in ICU(17.0±7.3)％,outpatient and emergency(11.6±1.7)％,and department of surgery(11.2±0.9)％,whereas CNS strains were primarily isolated from the patients in ICU(32.2±9.7)％,outpatient and emergency(12.8±4.7)％,and department of internal medicine(11.2±1.9)％.The prevalence of methicillin-resistant strains was 32.9％in S.aureus(MRSA)and 74.1％in CNS(MRCNS).Over the 7-year period,the prevalence of MRSA decreased from 42.1％to 29.2％,and the prevalence of MRCNS decreased from 82.1％to 68.2％.MRSA showed higher resistance rates to all the antimicrobial agents tested except trimethoprim-sulfamethoxazole than methicillin-susceptible S.aureus(MSSA).Over the 7-year period,MRSA strains showed decreasing resistance rates to gentamicin,rifampicin,and levofloxacin,MRCNS showed decreasing resistance rates to gentamicin,erythromycin,rifampicin,and trimethoprim-sulfamethoxazole,but increasing resistance rate to levofloxacin.No vancomycin-resistant strains were detected.The prevalence of linezolid-resistant MRCNS increased from 0.2％to 2.3％over the 7-year period.Conclusions Staphylococcus remains the major pathogen among gram-positive bacteria.MRSA and MRCNS were still the principal antibiotic-resistant gram-positive bacteria.No S.aureus isolates were found resistant to vancomycin or linezolid,but linezolid-resistant strains have been detected in MRCNS isolates,which is an issue of concern.

Objective:To analyze the trend of medication use in patients with ulcerative colitis (UC) in recent ten years in at Xijing Hospital, Air Force Military Medical University.Methods:From 2010 to 2019, the clinical data of 1 425 patients diagnosed with UC in the Department of Gastroenterology at Xijing Hospital, Air Force Medical University, were retrospectively collected. According to the period of medication, the UC patients were divided into year 2010 to 2014 group and year 2015 to 2019 group. The general information and the medication trend of year 2010 to 2014 group and year 2015 to 2019 group were analyzed. And then according to gender and age (<40 years old and ≥40 years old), patients were divided into subgroups and analyzed. Independent sample t test and chi-square test were used for statistical analysis. Results:The number of UC patients of year 2010 to 2014 group and year 2015 to 2019 group was 369 and 1 056, respectively. The percentages of patients in remission of the two groups were 9.5% (35/369) and 12.0% (127/1 056), respectively; the percentages of mild patients were 40.4% (149/369) and 41.6% (439/1 056), respectively; the percentages of moderate patients were 37.4% (138/369) and 28.9% (305/1 056), respectively; the percentages of severe patients were 12.7% (47/369) and 17.5% (185/1 056), respectively. There was no significant difference in the proportion of UC patients with different degrees between year 2010 to 2014 group and year 2015 to 2019 group ( P>0.05). There were no significant differences in the age and proportion of female between the year 2010 to 2014 group and year 2015 to 2019 group ((46.2±15.3) years old vs. (44.6±30.6) years old; 45.8%, 169/369 vs. 44.8%, 473/1 056; both P>0.05). The utilization rates of 5-aminosalicylic acid (5-ASA), glucocorticoid, immunosuppressants, and biological agents of the year 2015 to 2019 group were all higher than those of the year 2010 to 2014 group (96.8%, 1 022/1 056 vs. 90.0%, 332/369; 29.9%, 316/1 056 vs. 14.6%, 54/369; 8.4%, 89/1 056 vs. 2.4%, 9/369; 4.8%, 51/1 056 vs. 0.5%, 2/369, respectively), and the differences were all statistically significant ( χ2=26.766, 33.256, 15.315 and 14.038, all P<0.01). Within each of the year 2010 to 2014 group and the year 2015 to 2019 group, there were no significant differences between the female and male in the age, utilization rates of 5-ASA, glucocorticoid, immunosuppressants and biological agents ((47.2±13.6) years old vs. (45.3±16.5) years old, (43.1±12.9) years old vs. (45.8±39.5) years old, 88.8%, 150/169 vs. 91.0%, 182/200; 96.8%, 458/473 vs. 96.7%, 564/583; 13.6%, 23/169 vs. 15.5%, 31/200; 28.3%, 134/473 vs. 31.2%, 182/583; 2.4%, 4/169 vs. 2.5%, 5/200; 7.0%, 33/473 vs. 9.6%, 56/583; 0 vs. 1.0%, 2/200; 5.3%, 25/473 vs. 4.5%, 26/583; all P>0.05). In the patients aged≥40 years old of the year 2010 to 2014 group, the proportion of females was higher than that of the patients aged <40 years old (50.2%, 121/241 vs. 37.5%, 48/128), and the utilization rate of 5-ASA in patients aged ≥40 years old was lower than that of patients aged <40 years old (85.9%, 207/241 vs. 97.7%, 125/128), and the differences were statistically significant ( χ2=5.438 and 12.824, P=0.020 and P<0.01). In the year 2010 to 2014 group, there were no statistically significant differences in the utilization rates of glucocorticoid, immunosuppressants and biological agents between patients aged ≥40 years old and patients aged <40 years old (13.7%, 33/241 vs. 16.4%, 21/128; 2.1%, 5/241 vs. 3.1%, 4/128; 0 vs. 1.6%, 2/128; all P>0.05). In the year 2015 to 2019 group, the utilization rate of biological agents in patients aged≥40 years old was lower than that in patients aged<40 years old (3.7%, 23/630 vs. 46.5%, 198/426), and the difference was statistically significant ( χ2=4.721, P=0.030). In the year 2015 to 2019 group, there were no statistically significant differences in female proportion, utilization rates of 5-ASA, glucocorticoid, immunosuppressants and biological agents between patients aged≥40 years old and patients aged <40 years old (43.7%, 275/630 vs. 46.5%, 198/426; 96.0%, 605/630 vs. 97.9%, 417/426; 29.7%, 187/630 vs. 30.3%, 129/426; 8.6%, 54/630 vs. 8.2%, 35/426; all P>0.05). Conclusions:Compared with year 2010 to 2014, the number of UC patients remarkably increased in the year 2015 to 2019 in the Department of Gastroenterology, Xijing Hospiatal, Air Force Medical University. The utilization rates of 5-ASA, glucocorticoid, immunosuppressants and biological agents all increased in UC patients. The medication trends of UC patients with different gender were almost the same. The medication trends of UC patients with different age were different.

Objective To investigate a self-designed catheter pump by using computational fluid dynamics (CFD) method, so as to predict its hydraulic performance and risk of thrombosis formation. Methods The thrombosis prediction models proposed by Grigioni and Danny Bluestein were used. The shear stress and exposure time during platelet motion were calculated by CFD method, and parameters of platelet activation state (PAS) were obtained for prediction of thrombogenic performance. Results At the flow rate of 4 L/min and rotating speed of 10 000 r/min, the differential pressure of the pump reached 14.763 kPa and the hydraulic performance was proved to fit the requirement of left ventricular assist device. The PAS values of Grigioni model and Danny Bluestein model were 6.35×10-6 and 7.68×10-4,respectively, both at a very low level, indicating a low possibility of thrombus formation. Conclusions This study investigated the feasibility of thrombosis prediction based on simulation method and the predicted hydraulic performance and thrombosis will provide references for further design optimization.