OBJECTIVE To investigate the variation of in vitro activity,the ?-lactamases,type diversity and the homology of multiple resistances in Acinetobacter isolated.METHODS The multiple resistant Acinetobacter were selected to detect susceptibility test by K-B antimicrobial agents.The resistant rates were analyzed by WHONET 5.4,the isolates ?-lactamases phenotype was detected by three-dimensional test,genomic types were measured by PFGE.The ?-lactamases genotype was determined by PCR assay with specific-primer,and DNA sequencing was also used to analyze resistance-related gene.RESULTS Twenty-eight of 45 strains were OXA producing strains(68.3%),10 strains were IMP producing strains(24.4%),13 strains were TEM producing strains(31.7%),18 strains were CTX-M producing strains(43.9%),6 strains were PER producing strains(14.6%),and 7 strains were AmpC producing strains(17.1%).None produced SHV ?-lactamases.Twenty-four strains were produced 2 or more than 2 kinds of ?-lactamases.CONCLUSIONS The multiple resistance of Acinetobacter can produce kinds of ?-lactamases,but producing ?-lactamases are not the only one mechanism.

Objective To investigate the structure of Tn1546 like elements,the molecular features and genetic background of VanB phenotype-vanA genotype VREs and to explain the difference between phenotype and genotype. Methods Twenty-one VREs were collected in Beijing Hospital from March 2008 to January 2009. Etest was used to determin MICs of ten antibiotics. PCR product sequencing, PFGE and MLST were performed to study the molecular features and genetic background of the 21 VREs. Results All VREs were vanA genotype, but 3 of them( 14. 3% ) exhibited the VanB phenotype. Based on PFGE analysis, 21 VREs belonged to 9 different patterns. Six STs were identified by MLST analysis. The analysis of the structure of Tn1546 like elements showed the deletion of vanY, vanZ and the insertion of ISEfa4 in orf2-vanR intergenic region may be related to the formation of VanB phenotype-wanA genotype. Conclutions VanB phenotype-vanA genotype VREs were rarely found in China. The results of vanA cluster rearrangements could partly explain the causes of difference between phenotype and genotype.

Objective To analyze the antibiotic resistance of clinical isolated bacteria in elderly inpatients in Beijing Hospital from 2006 to 2008.Methods A total of 5710 strains isolated from elderly inpatients received antibiotic sensitivity test (AST) by using K-B method, and the data were analyzed with WHONET 5.4 software.Results During the 3 years, in constituent ratio of bacteria, P.aeruginosa, E.coli and Stenotrophomonas maltophilia were at the top of gram-negative bacteria.And S.aureus, coagulase-negative Staphylococcus (CONS), S.pneumoniae and Enterococcus spp.were at the top of gram-positive bacteria.The results of AST in vitro showed that 19 of 121 strains of S.pneumoniae were penicillin-insensitive S.pneumoniae (PNSP).In 690 strains of S.aureus, the methicillin-resistant S.aureus (MRSA) ratio was 80.2%, and vancomycin-insensitive strains were not found.And 114 strains of Enterococeus faecalis and 95 strains of Enterococcus faecalis were isolated, while the antibiotic resistance of the latter was stronger than the former, and 19 strains were vancomycin-resistant strains.The detection ratios of E.colt producing ESBLs were 41.7%, 55.0% and 56.8%, and the detection ratios of Klebiella pneumonia producing ESBLs were 16.0%, 22.4% and 27.3 %.The antibiotic resistance of ESBL-producing bacteria was much stronger than non-ESBLs producing bacteria.Multi-antibiotic resistant strains of Pseudomonas aeruginosa and Acinetobacter spp.were found.Conclusions It is necessary to detect the drug-resistant strains periodically for understanding the changes in bacterial resistance and providing a theoretical basis for the medication by the clinical experience.

OBJECTIVE To determine the mutant prevention concentration(MPC) of 3 cephalosporins against clinical isolates of Staphylococcus aureus and Streptococcus pneumoniae.METHODS Agar dilution was used to determine the minimum inhibitory concentration(MICs) and MPCs of cefaclor,cefprozil and cefuroxime against S.aureus and the MICs to Str.pneumoniae.The MPCs against Str.pneumoniae were determined by mixing-bacterium.RESULTS The MPCs and the ratio of MPC90/MIC90 of cefaclor,cefprozil and cefuroxime against S.aureus were 32,16;16,16;2,8;and the MPCs and the ratio of MPC90/MIC90 against Str.pneumoniae were 8,16;4,32;2,8,respectively.CONCLUSIONS The ability of cefuroxime for restricting the selection of resistant mutant of Str.aureus and S.pneumoniae is stronger than cefaclor and cefprozil.

Objective To study the discrepancy influence of the sulbactam content on susceptibility testing results of cefoperazone/sulbactam combination disks.Methods Agar dilution method was used to determine MICs of cefoperazone,cefoperazone/sulbactam(2:1 and 1:1),and disk diffusion was used to detect the zone diameters of cefoperazone,cefoperazone/sulbactam(75/30 and 75/75μg/disk)disks against 534 clinical gram-negative isolates.The discrepancy within the results of MICs,zore diameters,the method of agar dilution and disk diffusion was analyzed.Results By standard agar dilution method,MIC_(50) of cefoperazone,cefoperazone/sulbactam(2:1 and 1:1)were 32,16,16μg/ml,and MIC_(90) of those were ≥256.128,64 μg/ml respectively.No statistic discrepancy was found for MICs between the ratios of 2:1 and 1:1 combination by Wilcoxon ranks test(Z=-0.248,P=0.804).Susceptibility rate,resistance rate,and intermediate rate with 75/30μg disk were 55.3%,24.5%and 20.2%respectively,which were similar to those determined by agar dilution method.Susceptibility rate,resistance rate,and intermediate rate(I%)with 75/75μg disk were 72.5%,12.4% and 15.1% respectively,compared with the susceptibility rate from 75/30μg disk was 17.2% higher.Statistic discrepancy were tested by paired t-test (t=21.613,P＜0.01)with two groups of whole strains' zone diameters from 75/30μg and 75/75μg disks,and resulting in the difference of susceptibility or resistance rates for ESBL-producing strains,Acinetobacter bauamnnii and Enterobacteriaceae without ESBL tested isolates.On the contrary,for Pseudomonas aeruginosa,Stenotrophomonas maltophilia and ESBL negative isolates,the zone diameters discrepancy was not statistically significant between the results from 75/30μg and 75/75μg disks.Conclusions There is no statistic discrepancy between the susceptibility results from cefoperazone/sulbactam(2:1 or 1:1 ratios)in dilution method and in diffusion method with 75/30μg disk.When the 75/75μg disk is used to be tested for ESBL-producing strains,Acinetobacter bauamnnii and other Enterobacteriaceae,the results should be shown with sulbactam content.

Objective To investigate the susceptibility and resistance of clinical isolates from hospitals in several regions of China .Methods Fifteen general hospitals and two children′s hospitals were involved in this program . Antimicrobial susceptibility testing was carried out according to a unified protocol using Kirby‐Bauer method or automated systems .Results were analyzed according to CLSI 2014 breakpoints .Results A total of 78 955 clinical isolates were collected from January to December 2014 ,of which gram negative organisms and gram positive cocci accounted for 72 .6% and 27 .4% ,respectively . Methicillin‐resistant strains in S .aureus(MRSA)and coagulase negative Staphylococcus(MRCNS)accounted for an average of 44 .6% and 83 .0 % ,respectively .The resistance rates of methicillin‐resistant strains to β‐lactams and other antimicrobial agents were much higher than those of methicillin‐susceptible strains .However ,92 .0% of MRSA strains were still susceptible to trimethoprim‐sulfamethoxazole ,while 85 .6% of MRCNS strains were susceptible to rifampin .No staphylococcal strains were found resistant to vancomycin ,teicoplanin or linezolid .In Enterococcus spp .,the resistance rates of E .f aecalis strains to most tested drugs (except chloramphenicol) were much lower than those of E . f aecium .Some strains of both species were resistant to vancomycin .Vancomycin resistant strains of E . f aecalis and E . f aecium were mainly V anA ,V anB or V anM type based on their phenotype or genotype .Regarding non‐meningitis S .pneumoniae strains ,the prevalence of penicillin‐susceptible S .pneumoniae strains isolated from both adults and children were higher than those isolated in 2013 ,but the prevalence of penicillin‐intermediate S . pneumoniae or penicillin‐resistant S . pneumoniae strains decreased . The prevalence of ESBLs producingstrainswas55.8% in E.coliand29.9% in Klebsiellaspp.(K.pneumoniaeand K.oxytoca)and24.0% in Proteus mirabilis isolates on average . ESBLs‐producing Enterobacteriaceae strains were more resistant than non‐ESBLs‐producing strains in terms of antibiotic resistance rates . The strains of Enterobacteriaceae were still highly susceptible to carbapenems .Overall less than 10 % of these strains were resistant to carbapenems . About 62 .4% and 66 .7% of Acinetobacter spp .(A .baumannii accounts for 93 .0 % ) strains were resistant to imipenem and meropenem ,respectively . Compared with the data of year 2013 ,extensively‐drug resistant strains in K . pneumoniae and A .baumannii increased . Conclusions The antibiotic resistance of clinical bacterial isolates is growing .The disseminated multi‐drug or pan‐drug resistant strains in a special region poses a serious threat to clinical practice and implies the importance of strengthening infection control .

Objective To investigate the antimicrobial resistance of clinical strains of K lebsiella spp .isolated from 15 hospitals in China CHINET during 2012 .Methods Kirby-Bauer method and automatic microbiology analysis system were employed to study the antimicrobial resistance . WHONET 5 .6 software was applied for data analysis according to Clinical and Laboratory Standards Institute (CLSI) 2012 breakpoints .Results A total of 9 621 clinical K lebsiella isolates were analyzed ,including 8 772 strains of K . pneumoniae and 804 strains of K . oxytoca . About 54 .9% (5 285/9 621) of the K lebsiella strains were isolated from sputum ,and 16 .3% (1 564/9 621) were isolated from pediatric patients .Antimicrobial susceptibility testing showed that about 8 .9% ,10 .8% and 12 .9% of the strains were resistant to imipenem ,meropenem and ertapenem ,respectively .About 14 .1% and 17 .0% of the strains were resistant to piperacillin-tazobactam and cefoperazone-sulbactam , respectively . Carbapenem-resistant K lebsiella strains were identified from all the 15 hospitals ,including 945 strains of K .pneumoniae and 45 strains of K .oxytoca ,which were resistant to either imipenem ,meropenem or ertapenem .Conclusions The Klebsiella isolates collected from 15 hospitals in China during 2012 are relatively sensitive to carbapenems ,cefoperazone-sulbactam and piperacillin-tazobactam .The prevalence of carbapenem-resistant strains is still increasing in China ,about 10 .3% in 2012 ,and relatively higher in Eastern China .More efforts should be made to control the superbug .

Objective To investigate the antimicrobial resistance in the A cinetobacter baumannii strains in different parts of China during 2012 .Methods A total of 8 739 clinical isolates of Acinetobacter were collected from 13 general hospitals and two children’s hospitals ,of which most were A . baumannii (89 .6% , 7 827/8 739 ) . Antimicrobial susceptibility testing was carried out by means of Kirby-Bauer method according to the unified protocol . The susceptibility testing data were analyzed by WHONET 5 .6 software according to CLSI 2013 breakpoints .Results Majority (85 .4% ) of the Acinetobacter strains were isolated from inpatients .The remaining 14 .6% were from outpatients and emergency room patients .Of the 7 827 strains of A .baumannii , 10 .9% ,35 .2% ,35 .7% and 43 .4% were resistant to tigecycline ,minocycline ,cefoperazone-sulbactam and amikacin , respectively .The percentage of A .baumannii resistant to imipenem and meropenem was 63 .5% and 68 .2% ,respectively . The antimicrobial resistant pattern varied in different hospitals . The resistance of A . baumannii varied between different clinical departments .A number of pandrug resistant (PDR) (20 .0% ,1 567/7 827) and multidrug-resistant (MDR) (45 .0% , 3 521/7 827 ) A . baumannii were identified . Conclusions A . baumannii is the most popular pathogenic bacteria among Acinetobacter .The antibiotic resistance of A .baumannii is still increasing .Cefoperazone-sulbactam and minocycline has good in vitro antibacterial activity against A .baumannii .The antibiotic resistance of A .baumannii varies greatly with hospital and department .

Objective To investigate the distribution and antibiotic resistance of clinical Enterobacter isolates .Methods A total of 3 031 clinical strains of Enterobacter were collected from 15 hospitals from January 1 through December 31 , 2012 . Antimicrobial susceptibility testing was performed with Kirby-Bauer or minimum inhibitory concentration method .The results were analyzed according to CLSI 2012 breakpoints .Results Enterobacter cloacae and Enterobacter aerogenes accounted for 73 .0% (2 212/3 031) and 23 .9% (725/3 031) of all the Enterobacter strains .The isolates of other Enterobacter species accounted for 3 .1% (94/3 031 ) . The main source of the isolates was respiratory tract specimen , accounting for 53 .2% (1 612/3 031) .Most (> 89% ) of the Enterobacter strains were resistant to cefazolin and cefoxitin . Generally ,54 .4% ,47 .5% and 34 .3% of the strains were resistant to cefuroxime ,cefotaxime and cefazidime ,respectively . About 6 .6% to 26 .3% of the strains were resistant to amikacin ,gentamicin ,piperacillin-tazobactam ,cefepime ,cefoperazone-sulbactam ,ciprofloxacin and trimethoprim-sulfamethoxazole .Imipenem ,meropenem and ertapenem showed the highest activity , to which only 3 .5% ,3 .7% and 10 .3% of the strains were resistant ,respectively .About 8 .9% (269/3 031) of the strains were resistant to at least imipenem ,meropenem or ertapenem .Four Enterobacter strains were extensive-drug resistant (XDR) .Conclusions The prevalence of antibiotic resistance in Enterobacter isolates decreased slightly in 2012 compared to the data in 2011 ,but the situation is still very serious .We should continue to take effective measures to control the resistant strains .

Objective To investigate the distribution and susceptibility of carbapenem-resistant Enterobacteriaceae (CRE) isolates in 2012 from CHINET surveillance .Methods Antimicrobial susceptibility testing was carried out according to a unified protocol using Kirby-Bauer method or automated Systems .Results were analyzed according to the breakpoints of CLSI 2012 M100-S22 .Results A total of 1 499 CRE isolates were collected from January to December 2012 ,of which K lebsiella spp .,Enterobacter spp .and E .coli accounted for 63 .5% ,15 .1% and 13 .7% ,respectively .Of the 1 499 isolates , 48 .2% and 29 .3% were from respiratory tract and ICU , respectively . The results of antimicrobial susceptibility testing showed that the resistance rate of CRE isolates to most antimicrobial agents was 70 .0%-100% except amikacin (46 .9% ) and trimethoprim-sulfamethoxazole (49 .8% ) .CRE isolates from adults were more resistant to ciprofloxacin ,aminoglycosides and trimethoprim-sulfamethoxazole than those from children .Conclusions The antibiotic resistance of CRE isolates is very high . The spread of CRE strains in a specific region such as ICU and neurosurgery ward poses a serious threat to clinical practice and implies the importance of strengthening infection control .