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Objective To investigate antimicrobial resistance among gram-negative bacilli in China in 2010.Methods A total of 1 259 consecutive and non-repetitive gram-negative bacilli were isolated from 13 teaching hospitals from September to December in 2010 in China.All of these isolates were sent to the central laboratory for re-identification and susceptibility testing.The MIC of meropenem and other antibacterial agents were determined by agar dilution method.Interpretive results was determined by CLSI M100-S21.Results The activity of 14 antibacterial agents against 845 Enterobacteriaceae isolates was as follows in order:meropenem ( 98.1％,829 ),amikacin ( 94.0％,794 ),imipeuem ( 90.0％,761 ),piperacillin/tazobactam ( 87.5％,739 ),cefepime ( 83.0％,701 ),ertapenem ( 82.4％,696 ),cefoperazone/sulbactam ( 80.3％,678 ),colistin (75.4％,637),ceftazidime (70.0％,591 ),ciprofloxacin (59.1％,499 ),cefoxitin ( 54.8％,463 ),ceftriaxone ( 53.5％,452 ),cefotaxime ( 52.3％,442 ) and minocycline(51.5％,435).The prevalence of ESBL was 61.3％ (106/173) in Escherichia coli,which was much higher than 41.2％ (70/170) in Klebsiella pneumoniae.The susceptibility rate of Klebsiella pneumoniae against meropenem,imipenem,amikacin and colistin were more than 90％,but were highly resistant to ceftriaxone and cefotaxime.Over 80％ of Enterobacter cloacae,Enterobacter aerogenes,Citrobacter freundii,were susceptible to meropenem,amikacin,cefepine,cefoperazone/sulbactam,imipenem,piperacillin/ tazobactam,and ertapenem.The most active antibiotics against Pseudomonas aeruginosa were Colistin (98.4％,182),Amikacin ( 85.9％,159 ),Piperacillin/Tazobactam ( 80％,148 ),Ceftazidime ( 79.5％,147),Meropenem (74.1％,137),Ciprofloxacin (74.1％,137),Cefepime (73.5％,136),Imipenem (71.9％,132) and Cefoperazone/Sulbactam (70.8％,131 ).Less than 37％ of Acinetobacter baumannii isolates were resistant to carbapenems.The susceptible rate to Minocycline was 47.8％.Colistin kept good activity against Acinetobacter baumannii (susceptible rate,97.8％,n =176),The prevalence of Pan-drug resistant P.aeruginosa and A.baumannii was 18.9％ (n =35),and 61.8％ (n =108),respectively.Conclusions Carbapenems remained very high activity against Enterobacteriaceae.Increasing resistance to the antimicrobials agents test among A.baumanni and P.aeruginosa,especially carbapenems among A.baumanni brought great concern.
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Objective To evaluate the performance of modified Hodge test on the detection of carbapenemases among Enterobacteriaceae with decreased susceptibility to carbapenems. Methods Fortynine Enterobacteriaceae isolates with decreased susceptibility to carbapenems ( MIC of imipenem, meropenem or ertapenem was ≥ 2 μg/ml ) were collected from 16 teaching hospitals from 2004 to 2008. MICs of imipenem, meropenem and etapenem were determined by agar dilution method. Carbapenemases were detected by modified Hodge test. Carbepenemase-causing positive results and AmpCs-causing positive results were differentiated by phenyl boronic acid and oxacillin. Beta-lactamases encoding genes including blaNDM-1were detected by PCR and sequencing. Results Thirty-six of 49 isolates were non-susceptible to imipenem (MIC >4 μg/ml), 31 were non-susceptible to meropenem (MIC > 4 μg/ml) and 47 were non-susceptible to ertapenem (MIC > 2 μg/ml). Twenty-three isolates showed positive modified Hodge test result, including 9 weak-positive results and 14 strong-positive results. Through PCR detection and sequencing, 2 out of 9 isolates showing weak-positive results carried blaKPC-2 and other 7 did not carry any carbapenemase genes but AmpCs/ESBLs genes. Among the 14 isolates showing strong-positive results, 4 carried blaKPC-2, 8 carried blaIMP-4 and 2 caried blaIMP-8. All 26 isolates with negative modified Hodge test result didn't carry any carbapenemase genes. No isolate carried blaNDM-1. Carbapenemases genes PCR detection was regarded as a gold standard, and the sensitivity, specificity, positive predictive value and negative predictive value of modified hodge test was 100%, 79%, 70% and 100% on the detection of carbapenemases among Enterobacteriaceae with decreased susceptibility to carbapenems. Conclusions Modified Hodge test revealed great sensitivity but showed a few false positive results. True and false positive results can be effectively differentiated by phynel boronic acid and oxacillin.
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Objective To investigate antimicrobial resistance among nosocomial gram-negative bacilli in 2006.Methods About 987 consecutive and non-repetitive gram-negative bacilli were isolated from 10 teaching hospitals from Sep.to Dec.in 2006 in China.All of these isolates were sent to the central laboratory for reidentification and susceptibility testing.The minimal inhibitory concentration(MICs)of meropenem and other antibacterial agents were determined by agar dilution method.Results The activity of antibacterial agents against Enterobacteriaceae was as fol lows in descending order of susceptible rate: meropenem(susceptible rate 99.8%),imipenem(99.5%),piperacillin/tazobactam(91.3%),amikacin (89.3%),cefepime(83.8%),cefoperazone/sulbactam(79.7%),ceftazidime(74.7%),cefotaxime (57.7%),ceftriaxone(56.6%),ciprofloxacin(53.6%).The prevalence of extended-spectrum β-Iactamases(ESBL)was 59.0% in Escherichia coli,33.0%in Klebsiella pneumoniae and 8.0%in Proteus mirabilis.The most active agents against E.coli and K.pneumoniae were meropenem,imipenem(99.2%. 100%),piperacillin/tazobactam(90.8%-97.0%),and amikacin(83.8%-92.4%).Cefepime Was more active against K.pneumoniae than E.coli(85.4% vs.65.2%).Against E.cloacae,E.aerogenes and Citrobacter freundii,the most active agents were as follows in desecnding order:meropenem,imipenem (99.2%-100%),amikacin(85.2%-92.6%),cefepime(81.5%-85.9%),piperacillin/tazobactam (73.4%-87.2%),cefoperazone/sutbactam(65.6%-77.7%),and ciprofloxacin(53.1%-72.3%).The most active agents against Pseudomonas aeruginosa were amikacin(83.5%),followed by meropenem (79.1%),piperacillin/tazobactam(74.1%),and imipenem(70.9%).The most susceptible agents against Acinetobacter baumannii were imipenem(79.1%),meropenem(73.4%) and cefoperazone/ sulbaetam(54.7%).Mutiresistant A.baumannii increased up to 53.0%.The most active agents against Burkholderia cepacia were meropenem(73.3%),eeflazidime(73.3%),and piperacillin/tazobactam (62.2%).Conclusions Carbapenems remained very high activity against Enterobacteriaceae.Increasing resistance to 10 antimicrobials agents tested from A.baumanni and P.aeruginosa brought great concern.
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80% activity rate against E.coli included piperacillin/tazobactam(93.4%)、ceftazidime(86%),and amikacin(83.3%);The susceptible rate to piperacillin/tazobactam in K.pneumoniae was 84.6%. The susceptible rate to ceftazidime decreased from 82.3% to 69.9%, which was lower than to cefepime (77.2%). Over 50% of Enterobacter cloacae were resistant to ceftazidime, cefotaxime and ceftriaxone. Susceptible rates to piperacillin/tazobactam in E. cloacae,E. aerogenes,Citrobacter freundii and Serratia marcescens (67.7%-96.4%) were higher than those to cefepime (68.8%-77.5%), cefoperazone/sulbactam (59.7%-87.5%). Susceptibility to amikacin among these 4 species (70%-83.7%) was higher than to ciprofloxacin (48.1%-79.5%). All of Morganella morganii and Proteus vulgaris isolates were susceptible to meropenem and imipenem; Over 90% of the isolates were susceptible to cefepime, cefoperazone/sulbactam and piperacillin/tazobactam.The most active agent against Pseudomonas aeruginosa was meropenem (84%), followed by amikacin, piperacillin/tazobactam, ceftazidime and imipenem (72.5%-76.6%). Mutiple-drug-resistant Acinetobacter baumannii increased from 33% in 2003 to 48% in 2004. Resistance to carbapenems increased to 18% in this species in 2004. The most active agents against Burkholderia cepacia were meropenme (64.9%), cefoperazon/sulbactam (63.2%), ceftazidime (59.6%), piperacillin/tazobactam (56.1%) and cefepime (52.6%).Conclusions Carbapenems remained very high activity against Enterobacteriaceae. Increasing resistance to 10 antimicrobials agents tested among A. baumanni brought great concern. Meropenem was 4-to 16-fold more active against common gram-negative bacilli than imipenem.