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OBJECTIVE To investigate the antibiotics resistance of multi-resistant Acinetobactor baumannii(ABA) and genotypes of beta-lactamases in ICU.METHODS The samples of 20 A.baumannii isolates were collected from Oct 2007 to Jul 2008 from patients in ICU.To determine the sensitivity to the 32 kinds of antibacterials,K-B method was used and the detection of ESBLs and AmpC beta-lactamases was performed by three dimensional test and 21 types of beta-lactamases genes were analyzed by polymerase chain reaction(PCR).RESULTS Among the 20 ABA isolates,all carried TEM beta-lactamases gens(100%),10 carried OXA-23 beta-lactamases gens(50%) and 15 strains carried ADC beta-lactamases gene(75%),50% strains produced TEM,OXA-23 and ADC beta-lactamases simultaneously.Through determining sequence of one PCR product from TEM,OX23 and ADC respectively,we found TEM-116,OXA-73 and ADC-25 type beta-lactamases genes.CONCLUSIONS The antibiotics resistance of ABA is very serious.TEM,OXA-23 and ADC exist in multi-resistant A.baumannii widely.It should be the main causes as high rate of drug-resistantce to beta-lactamantibiotics.
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OBJECTIVE To investigate the drug resistance and the status of producing ESBLs and AmpC beta-lactamases of Klebsiella pneumoniae isolates from 2006 to 2007 in local district.METHODS From 2006 to 2007,110 strains of K.pneumoniae insensitive to cefoxitin were collected.The sensitiveness to 16 antibiotics were tested by K-B method and microdilution method.Genes of TEM,SHV,GES,PER,CTX-M-1,CTX-M-2,CTX-M-3,DHA and MIR-1/ACT-1 were tested by PCR.The gene transfer was detected by conjugation test.RESULTS The resistance rate of 110 K.pneumoniae strains to meropenem,imipenem,piperacillin/tazobactam,cefoperazone/sulbactam,ceftazidime and cefepime was 0-49.9%.The resistance rate to other antibiotics was 80-100%.And ESBLs production was the main result.Genes of ESBLs were CTX-M and SHV.Genes of AmpC beta-lactamases were ACT and DHA.They all could transfer the drug-resistance from plasmid to receptor bacteria.CONCLUSIONS Co-existing of ESBLs and AmpC beta-lactamases is the main reason of multi-drug resistance that K.pneumoniae.Transferring of drug-resistance gene leads to the spreading of drug-resistance.The drug-resistance rate of K.pneumoniae decreased during the last two years.
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Objective To investigate the genotype distribution of extended-spectrum?-lactamases(ESBLs) and AmpC?-lacta- mases produced by Escherichia coli and Klebsiella pneumoniae in 10 teaching hospitals of China.Methods 90 clinical strains of E.coli and 61 strains of K.pneumoniae isolated in 2003 and confirmed to produce ESBLs were collected from 10 teaching hos- pitals in China.Analytical isoelectric focusing was used to measure the pI of the?-lactamases.Conjugation experiment was used to study the transfer of cefoxitin resistance.Plasmid-mediated AmpC enzyme genes were amplified and sequenced by multiplex polymerase chain reaction (MPCR).Results The prevalence of ESBL-producing E.coli and K.pneumoniae was about 50% in Wuhan,Nanjing and Jinan.The prevalence of ESBL-producing E.coli was lower than K.pneumoniae in Beijing.However,in other hospitals the prevalence of ESBL-producing E.coli was a little higher than K.pneumoniae.About 24.4% of ESBL-pro- ducing E.coli isolates and 19.4% of ESBL-producing K.pneumoniae isolates were resistant to cefoxitin.Cefoxitin-resistant i solate was identified in all hospitals except Shenyang.Major genotype of ESBL-producing isolates was CTX-M.The CTX-M-9 group was the most common group,followed by CTX-M-1.More K.pneumoniae isolates produced both ESBLs and AmpC en- zyme than E.coli.The genotype was CTX-M/DHA-1.The PCR results of 3 transconjugants producing both ESBLs and AmpC enzyme were the same as their donor isolates.Conclusions The genotype of ESBL-producing isolates is mainly CTX-M-9 group in these teaching hospitals.More K.pneumoniae isolates produced both ESBLs and AmpC enzyme than E.coli.Most of these isolates are due to geno type CTX-M/DHA-1,which can spread through plasmid.
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Objective To detect AmpC ?-lactamases from clinical isolates of escherichia coli and klebsoella pneumoniae in our hospital.Methods Using confirmatory test recommended by the NCCLS to detect ESBLs producing escherichia coli and klebsoella pneumoniae.Adopting three dimensional extract test and three dimensional depression test to detect AmpC ?-lactamases.Results Among 236 escherichia coli strains collected,104 were ESBLs producing strains.Among 135 klebsoella pneumoniae strains collected,29 were ESBLs producing strains.Among 106 cefoxitin-resistant strains,AmpC ?-lactamases producing strains were found in 3 strains.Conclusion ESBLs are the most important resistant mechanisms of the two bacteria isolates in our hospital.The strains cefoxitin-resistant may result from the loss of the membrane porin.
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OBJECTIVE To investigate the prevalence of DHA AmpC ?-lactamases mediated by plasmid in Klebsiella pneumoniae in China.METHODS Antimicrobial susceptibility test was conducted by the methods of double agar dilution and ESBLs confirmatory in K-B method according to the criteria of guidelines of CLSI.AmpC ?-lactamases were detected on the basis that AmpC ?-lactamases could be inhibited by 3-aminophenylboronic acid(APB).Gene chip technology and PCR were used to detect ESBLs and AmpC gene.RESULTS Among total 34 isolates of K.pneumoniae 32(94.1%) produced AmpC ?-lactamases and ESBLs.The most common(38.3%) were types DHA and TEM and SHV.MIC50 and MIC90 of all strains to all tested antimicrobial agents were lower than 34 strains tested 0.25?g/ml and 0.5?g/ml.Fourteen strains AmpC and ESBLs were conjugated successfully.CONCLUSIONS DHA AmpC ?-lactamases mediated by plasmid are the most common in K.pneumoniae in General Hospital of PLA of China.The most common(38.3%) are types DHA and TEM and SHV.Fourteen(41.2%) strains can be spreaded by plasmid.
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OBJECTIVE To explore occurrence, distribution,and resistance profile of ?-lactamases in clinical isolates of Enterobacter cloacae for rational use of antibiotics in clinic. METHODS Susceptibility test to 13 antibiotics was also performed through disk diffusion test.ESBLs were conformed according to NCCLS.DIDST test was adopted to detect AmpC ?-lactamases in E.cloacae isolates. RESULTS Among 78 isolates collected,13(14.9%) produced AmpC ?-lactamases,24(27.6%) produced ESBLs,10(11.5%) produced both ?-lactamases.These produced(?-lactamases) strains resisted to almost all ?-lactams,except for imipenem.The ?-lactamases producers possessed seriously multi-and cross-drug resistance. CONCLUSIONS ESBLs and AmpC ?-lactams are the main mechanism of E.cloacae resistance to antibiotic.
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87%. CONCLUSIONS The surveillance of overexpressing AmpC ?-lactamases in cefoxitin-resistant Gram-negative bacillus must be enhanced.The therapy of infections caused by related bacillus should make imipenem and meropenem a chief choice.DHA-1,CMY-2 and CMY-22 AmpC enzymes are found in Fuzhou.
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OBJECTIVE To study the AmpC ?-lactamases form clinical isolates of Escherichia coli and Klebsiella pneumoniae in our hospital.METHODS Using confirmatory test recommended by the NCCLS to detect ESBLs produced by 369 strains E.coli and K.pneumoniae,adopting three-dimensional test was performed and three-dimensional depression test and AmpC ?-lactamases inducing test to detect the phenotype of screening strains producing AmpC ?-lactamases.RESULTS Among 73 strains whose phenotypes doubted of production of AmpC ?-lactamases 34 were AmpC ?-lactamases producing strains,of which 24 strains were E.coli and 10 strains were K.pneumoniae.Five E.coli strains and 2 K.pneumoniae strains produced ESBLs and AmpC ?-lactamases.At AmpC ?-lactamases inducing test,2 K.pneumoniae strains produced AmpC ?-lactamases.CONCLUSIONS AmpC ?-lactamases are the another most important resistance mechanisms of E.coli and K.pneumoniae,much attention should be paid to their detections and surveillance,it will direct the clinics to use antibiotics reasonably,relieve the selective pressure of bacteria resistance and avoid the nosocomial infection.
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OBJECTIVE To analyze resistance and detect plasmid-mediated AmpC genes in Klebsiella pneumoniae.METHODS The susceptibility of the K.pneumoniae to 13 antibiotics was tested by K-B method.Modified three-dimensional extract test was adopted to detect AmpC lactamases in K.pneumoniae.The genotypes of AmpC lactamases were determined by polymerase chain reaction and sequencing.RESULTS Among the 105 isolates,the rate of extended spectrum ?-lactamases(ESBLs) was 41.90%,the rate of AmpC ?-lactamases was 0.95% strains,and the rate of ESBLs and AmpC ?-lactamases was 2.86%.DNA sequence analysis conformed that AmpC lactamases positive isolates were DHA AmpC gene.The resistance rate to penicillins,cephalosporins,?-lactam/?-lactam inhibitors,monobactams,and fluoroquinolones was very high.The susceptibility rate to imipenem was 100.00%.CONCLUSIONS The plasmid-mediated AmpC gene is present in clinically isolated K.pneumoniae.The resistance can be transferred to homologous or different genera of bacteria.
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OBJECTIVE To investigate the occurrence and the genotype character of AmpC ?-lactamases-producing Escherichia coli isolated from the Second Hospital affiliated to Harbin Medical University.METHODS K-B disk diffusion test and FOX(≤17mm) test were used as initial screen tests to detect the clinical isolates;AmpC ?-lactamases were confirmed by three-dimentional extract tests;multiple-PCR was used for detecting plasmid-mediated AmpC gene and their genotypes were determined by DNA sequencing;the regulator genes of high producing AmpC isolates of E.coli were cloned to pUCm vectors and sequenced,the difference among them was analyzed by blast method.RESULTS Among total 586 E.coli clinical isolates,10 isolates(1.70%) resisted to cefoxitin;three-dimensional extract tests were positive for all 10 isolates;4 isolates of E.coli were plasmid-mediated DHA-1 type AmpC ?-lactamases by using multiplex PCR and DNA sequencing;6 isolates of chromosomal high level AmpC ?-lactamases-producing E.coli were sequenced and contrasted to that of E.coli K12,showed that they were gene polymorphism.CONCLUSIONS E.coli clinical isolates producing high level AmpC ?-lactamases not only acquire plasmid-mediated DHA-1 AmpC ?-lactamases but also cause by chromosomal ampC promotor or attenuator gene mutations in our hostiptal.
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OBJECTIVE To investigate the productive rate of AmpC ?-lactamases and ESBLs produced by the Gram-negative bacilli from the nosocomial infection in our hospital. METHODS AmpC ?-lactamases and ESBLs were detected by the improved cefotaxime and ceftriaxone three-dimensional test. RESULTS The productive rate of AmpC ?-lactamases was 16.00%.Among them,the productive rate of AmpC ?-lactamases was only 8.84%.The Enterobacter cloacae,Serratia marcescens and Enterobacter aerogenes were easy to produce the enzymes(36.00%,31.25% and 28.00%).The productive rate of AmpC ?-lactamases and ESBLs at the same time was 7.16%. CONCLUSIONS The productive rate of the enzymes by the Gram-negative bacilli from the nosocomial infection is rather high.
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The ampC ?-lactamases gene in Escherichia coli(E.coli) is different from other Gram-negative bacteria.E.coli contains a chromosomal ampC gene which has a weak promoter as well as a transcriptional attenuator.The promoter of the ampC gene in E.coli is part of the preceding frd operon,the attenuator of the ampC gene is a transcription terminator for the frd operon.The ampC regulatory gene,ampR,is absent.Strains carrying the wild-type gene produce a low basal amount of AmpC.Studies on the molecular basis of AmpC overproduction in E.coli have shown that some hyperproducers contain mutation in the promoter region and/or attenautor and/or ampC-coding region of ampC,while others contain more than one copy of ampC.Acquisition of a stronger promoter or insertion of an insertion element containing promoter sequences or regulatory gene ampR has also been proposed as the molecular basis of hyperproduction of AmpC in some E.coli strains.Plasmid-mediated AmpC ?-lactamases have been discovered frequently in E.coli strains.This is another reason for hyperproduction of AmpC ?-lactamases.
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OBJECTIVE To develop a suitable and easy method for detecting AmpC ?-lactamases.METHODS The function with different cloxacillin concentrations in cloxacillin-potentiated disc diffusion test was compared and estimated with FOX three-dimensional extract test to show the best concentration of cloxacillin.RESULTS Cefoxitin three-dimesional test indicated that 48 strains were detected out to produce AmpC ?-lactamases among 130 clinical isolates of Gram-negative bacilli strains.when the discs contained 200 ?g cloxacillin the CAZ,CTX,CRO and ATM alone could separately detect 87.5%,87.5%,87.5% and 33.3% highly producing AmpC ?-lactamases strains.When the combination of CTX with CRO,almost 95.8% could be detected out.CONCLUSIONS With the combination of CTX and CRO,the cloxacillin-potentiated disc diffusion test can specifically detect AmpC ?-lactamases and easy to be used in clinical laboratories.
