[Prevalence of osteoarticular infections by Enterobacteria producing extended-spectrum -lactamases]. / Prevalencia de infecciones osteoarticulares por enterobacterias productoras de -lactamasas de espectro extendido.

INTRODUCTION: Infections of enterobacteria producing extended-spectrum -lactamases place a heavy burden on health systems. Little is known in osteoarticular infections, so this work studied the prevalence of these infections in a third-level hospital. MATERIAL AND METHODS: Prevalence study in patients of a Traumatology Service during 2016, with infection criteria provided by the CDC in Atlanta, Georgia. The VITEK® 2 AST-N272 (bioMérieux) system was used for bacterial identification at the species level and for antimicrobial susceptibility tests. RESULTS: 7.85% (n = 86) were reported with osteoarticular infections; 22.09% (n = 19) were by enterobacteria BLEEs. An average of 77.1 days of hospitalization (SD 37.7) (46-200 days); isolation of the microorganism occurred 15 days after entry. Sixteen (84.2%) patients had osteomyelitis, three (15.8%) had a prosthetic knee or hip infection. The average number of treatment days was 60 days (21-129 days). Eighteen patients (94.7%) were discharged with resolution of their infectious picture; one patient died with infection over aggregated pneumonia due to carbapenem-resistant K. pneumoniae. DISCUSSION: The prevalence of osteoarticular infections by enterobacteria BLEEs could not be accurately calculated, but we consider it to be within what is expected, infection control measures require higher standards and there is a lack of development programs to use antimicrobials rationally to control the emergence of these pathologies.

INTRODUCCIÓN: Las infecciones por enterobacterias productoras de -lactamasas de espectro extendido (BLEEs) ocasionan una gran carga a los sistemas de salud. Poco se conoce de las infecciones osteoarticulares, por lo que este trabajo estudió la prevalencia de estas infecciones en un hospital de tercer nivel. MATERIAL Y MÉTODOS: Estudio de prevalencia en pacientes de un servicio de traumatología durante 2016, con criterios de infección proporcionados por el CDC de Atlanta, Georgia. Se utilizó el sistema VITEK® 2 AST-N272 (bioMérieux) para la identificación bacteriana a nivel de especie y para las pruebas de susceptibilidad antimicrobiana. RESULTADOS: Se reportaron 7.85% (n = 86) con infecciones osteoarticulares; 22.09% (n = 19) fueron por enterobacterias BLEEs. Con un promedio de 77.1 días de hospitalización (DE 37.7) (46-200 días); el aislamiento del microorganismo se produjo 15 días posteriores al ingreso; 16 (84.2%) pacientes presentaron osteomielitis, tres (15.8%) tuvieron infección protésica de rodilla o cadera. El promedio de días de tratamiento fue de 60 días (21-129 días); 18 pacientes (94.7%) fueron dados de alta con resolución de su cuadro infeccioso; un paciente falleció con infección sobreagregada por neumonía debida a K. pneumoniae resistente a carbapenémicos. DISCUSIÓN: La prevalencia de infecciones osteoarticulares por enterobacterias BLEEs no se pudo calcular con precisión, pero consideramos que se encuentra dentro de lo esperado, las medidas de control de infecciones requieren tener estándares más elevados y falta desarrollar programas de uso racional de antimicrobianos para controlar la aparición de estas patologías.

Antimicrobial resistance in Enterobacteriaceae in Brazil: focus on -lactams and polymyxins

ABSTRACT During the last 30 years there has been a dissemination of plasmid-mediated -lactamases in Enterobacteriaceae in Brazil. Extended spectrum -lactamases (ESBL) are widely disseminated in the hospital setting and are detected in a lower frequency in the community setting. Cefotaximases are the most frequently detected ESBL type and Klebsiella pneumoniae is the predominant species among ESBL producers. Klebsiella pneumoniae carbapenemase-producing Enterobacteriaceae became widely disseminated in Brazil during the last decade and KPC production is currently the most frequent resistance mechanism (96.2%) in carbapenem resistant K. pneumoniae. To date KPC-2 is the only variant reported in Brazil. Polymyxin B resistance in KPC-2-producing K. pneumoniae has come to an alarming rate of 27.1% in 2015 in São Paulo, the largest city in Brazil. New Delhi metallo--lactamase was detected in Brazil in 2013, has been reported in different Brazilian states but are not widely disseminated. Antimicrobial resistance in Enterobacteriaceae in Brazil is a very serious problem that needs urgent actions which includes both more strict adherence to infection control measures and more judicious use of antimicrobials.

Detection on Phenotype of Extended-spectrum ?-Lactamases and Genotype of ?-Lactamases in Klebsiella pneumoniae / 中华医院感染学杂志

OBJECTIVE To investigate the produce of extended-spectrum ?-lactamases(ESBLs) and the presence of genotype of the ?-lactamases-encoding genes in Klebsiella pneumoniae isolated from the 98th Hospital of PLA,Huzhou,Zhejiang Province,China.METHODS Twenty-five strains of K.pneumoniae were isolated from the inpatients between Sep 2005 and Apr 2006.ESBLs were tested by phenotypic confirmatory tests recommended by CLSI.Twenty-one kinds of ?-lactamases genes of blaTEM,blaSHV,blaLEN,blaOKP,blaCTX-M-1 group,blaCTX-M-2 group,blaCTX-M-9 group,blaOXA-1 group,blaOXA-2 group,blaOXA-10 group,blCARB,blaPER,blaVEB,blaGES,blaLAP,blaDHA,blaACT/MIR,blaCMY/MOX,blaFOX,blaCMY/LAT,and blaACC were analyzed by PCR and verified by DNA sequencing.RESULTS In 25 strains of K.pneumoniae,the positive,negative,and "uncertainty" rates of ESBLs were 56.0%,20.0%,and 24.0%,respectively.The positive rate of genes of blaTEM,blaSHV,blaCTX-M-1 group,blaOXA-10 group,blaLAP,and blaDHA were 80.0%,4.0%,4.0%,80.0%,4.0% and 32.0%,respectively.The 15 kinds of rest genes were all tested negative.The total positive rate of 21 kinds of ?-lactamases gene was 92.0%.Among them,the blaLAP-2 gene sequence of the HZ12593 strain has been registered in GenBank(GenBank Accession Number: EU529981).CONCLUSIONS There are higher rate of ESBLs-producing strains in K.pneumoniae isolated from the inpatients,and at least 6 kinds of ?-lactamases gene existed.Both genes of blaTEM and blaOXA-10 group are the most common genotypes.Carring blaDHA Gene may influence the result of phenotypic confirmatory test for ESBLs in K.pneumoniae.

Monitoring of Drug-resistance in Klebsiella pneumoniae in a Oil Field Hospital / 中华医院感染学杂志

OBJECTIVE To investigate drug-resistance status of Klebsiella pneumoniae(KPN) among oil field staff-workers and provide the evidence for clinical application of antibiotics.METHODS Referring to the National Clinical Laboratory Operation Rules,KPN strains were isolated and identified.The drug-sensitivity testing was performed by K-B methods.The extended-spectrum-?-lactamases(ESBLs) producers were detected by double-disc synergy test and disc confirming test.RESULTS The 276 strains of KPN were mainly isolated from respiratory tract and urinary tract.The isolating rate of ESBLs-producing KPN was 37.0%.The results of susceptibility testing showed the drug-resistance to common antibiotics in ESBLs producers was generally higher than that in ESBLs nonproducer.There was no KPN resistant to imipenem and meropenem.CONCLUSIONS Drug-resistance status of KPN in a oil field hospital is very serious.We should strengthen monitoring and controlling of it.

VITEK32 Expert System for Detection and Analysis of Resistance Phenotypes in Commonly Encountered Bacteria:A Clinical Evaluation / 中华医院感染学杂志

OBJECTIVE To evaluate VITEK32 expert system(7.02) for detection and analysis of clinically important resistance phenotypes.METHODS A total of 508 known resistant phenotype clinial strains and 9 standards strains were tested by VITEK32 expert system(7.02) and antibiotic susceptibilities were determined by CLSI recommendation.RESULTS The correct phenotype was identified by the expert system in one or more choices for 312 from the 508(61.4%) isolates and standards.The resistant phenotypes for meticillin-susceptible,and resistant Staphylococcus spp,extended-spectrum ?-lactamases(ESBLs) producingEscherichia coli,Klebsiella spp,AmpC producing Enterobacter,cloacae,Serratia marcescens,and vancomycin-resistant Enterococcus faecalis were accurately identified by VITEK32 expert system,this expert system was not including ESBLs producing Proteus mirabilis.CONCLUSIONS VITEK32 expert system can be accurately identified most clinically important bacteria based on phenotype.The data of ESBLs Producing P.mirabilis should be included in the further work on expert system.

Distribution and Drug Resistance of Enterobacter cloacae from Clinic / 中华医院感染学杂志

OBJECTIVE To analyze the drug-resistance of Enterobacter cloacae isolated from clinic in the past two years.METHODS The drug-resistance by K-B method,and to perform 3-D test to detect AmpC ?-lactamase and ESBLs were detected.RESULTS One hundred and six strains of E.cloacae was detected.Burn department were the wards which had the highest detection rate.Sputum,wound,bile and drainage fluid had the highest positive rate.Sensitivity test results showed that the resistance rate to penicilins,Ⅰ,Ⅱ-generation cephalosporins and cefoxitin of E.cloacae was the highest,and the resistance rate to the third,and fourth-generation cephalosporins was 24.5-50.9%.The detection rate of ESBLs and AmpC was 27.4% and 40.6%,respectively.Twenty three strains produced both of them.CONCLUSIONS The detection rate and drug resistance of E.cloacae are increasing severely.Laboratory should pay more attention to their detections and surveillance so as to control hospital infection of E.cloacae.

Optimization of ?-Lactam Treatment Regimens for Extended-spectrum ?-Lactamases-producing Strains Infections Based on Pharmacokinetics/pharmacodynamics / 中华医院感染学杂志

MIC.RESULTS The bacteriostatic/bactericidal CFR of 0.5g q8h imipenem/cilastatin and 0.5g q8h meropenem were the highest(100%);that of 3.375g q4h sodium piperacillin/tazobactam sodium against ESBLs-producing E.coli was above 90%;the CFRs of ceftriaxone(1g q24h,2g q24h),ceftazidime(1g q8h,2g q8h),cefepime(1g q8h,1g q12h,2g q8h) and cefoperazone sodium/sulbactam(0.5g q8h,1g q8h,2g q8h) against ESBLs-producing strains were clearly less than those of non-ESBLs-producing ones,and the CFRs could not be effectively improved with the dose and frequency increased.CONCLUSIONS The PK/PD simulation is useful to optimize the regimen of anti-infective treatment,and guide its dosing accurately.

Relationships Between Antimicrobial Use and Producing Extended-spectrum ?-Lactamases / 中华医院感染学杂志

OBJECTIVE To evaluate the relationships between antimicrobial usage and the isolated rate of ESBLs-KPN and ESBLs-ECO.METHODS We monitored the data on the yearly patient-days and the yearly consumption(defined daily dose(DDD) per 1000 patient days) frequent antibiotics and the isolated rate of ESBLs-KPN and ESBLs-ECO causing nosocomial infections from Jan 2004 to Dec 2007 was analyzed.RESULTS The yearly patient-days of our department significantly increased from 64 203 days in 2004 to 74 442 days in 2007(P

Drug-resistance of Klebsiella pneumoniae in Mountain Hospitals / 中华医院感染学杂志

OBJECTIVE To investigate the drug-resistance status of Klebsiella pneumoniae(KPN) in mountain hospitals and provide the reference for rational application of antibiotics.METHODS Referring to Rules of Operation in Clincal Laboratory of Nationwide,146 KPN isolates were cultured and identified and the drug-sensitivity test was performed in our hospital.RESULTS 100% of KPN isolates were sensitive to imipenem and meropenem.The resistant rates to amikacin,piperacillin/tazobactam,cefoperazone/sulbactam and cefoxitin were all below 22.0%.And that to the other 11 antibiotics were higher and all above 30%.The detection rate of the extended-spectrum-?-lactamases(ESBLs) producing KPN was 28.8%.CONCLUSIONS The drug-resistance of KPN in mountain hospitals is obviously lower than that in general hospitals of developed cities.We should strengthen reasonable management of antibiotics to prevent and control the occurrence and dissemination of drug resistant strains.

Distribution and Drug Resistance of Klebsiella pneumoniae from Clinic / 中华医院感染学杂志

OBJECTIVE To analyze the distribution and drug-resistance of Klebsiella pneumoniae isolated from clinic in the past two years to help doctors to use antibiotic reasonably.METHODS To detect the drug-resistance of 470 strains of K.pneumoniae to 15 kinds of antimicrobial agents were detected by K-B method,and the AmpC ?-lactamase and ESBLs were detected through the way of 3-D test.RESULTS ICU and burn department were found where had the highest isolation rate,and sputum and wound that had the highest detection rate.Sensitivity test results showed that the resistance rate of K.pneumoniae to penicillins,first and second-generation cepholosporins,fluoroquinolones and sulfamethoxazole compound was high(51.1-88.3%),and resistance rate to the third and fourth-generation cephalosporins was high,too(32.6-40.4%).All strains were sensitive to imipenem,but two of them were resistant to meropenem.ESBLs were found in 152 strains,the detection rate was 32.3%,AmpC was found in 29 strains,the detection rate was 6.2%.Both of them were found out in 21 strains.CONCLUSIONS The lower respiratory tract infection is the most common one.The ICU and wound ward are the high-risk places ward of infection.Detection rate and drug resistance are increasingly severe,clinic and laboratory should make concerted efforts to reduce nosocomial infection and strengthen information feedback.

Extended-spectrum Beta-lactamases and AmpC Enzymes of Pseudomonas aeruginosa:Their Detection and Resistance Analysis / 中华医院感染学杂志

OBJECTIVE To investigate the prevalence of strains producing extended-spectrum ?-lactamases (ESBLs) and AmpC ?-lactamases in Pseudomonas aeruginosa,and to supply the laboratory evidence for antibiotic rational application in clinic. METHODS Totally 105 clinical isolates of P. aeruginosa were identified with VITEK-32. Drug sensitivities were determined by Kirby-Bauer methods. ESBLs were detected by double-disc synergy test,and cefoxitin three dimensional test was applied to filter AmpC positive strains. RESULTS Among 105 strains of P. aeruginosa,28 strains (26.7%) were AmpC enzymes positive,20 strains (19.0%) were ESBLs positive,and 5 strains(4.8%)were AmpC+ESBLs positive. The detective rate of producing AmpC ?-lactamases strains was higher than that of producing ESBLs strains. There was significant difference between them. CONCLUSIONS ESBLs and AmpC ?-lactamases are two main enzyme types conferring resistance to ?-lactam antibiotics in clinical isolates of P. aeruginosa. Imipenem can be the first choice for treating infections caused by P. aeruginosa producing ESBLs or AmpC ?-lactamases.

Genotype Distribution in Extended-spectrum ?-lactamases-producing Escherichia coli / 中华医院感染学杂志

OBJECTIVE To investigate the genotype distribution in extended-spectrum ?-lactamases-producing Escherichia coli in our hospital.METHODS Clinical strains of E.coli confirmed to produce ESBLs were collected from our hospital.ESBLs genotype was analyzed by plasmid conjugation,PCR and nucleotide sequencing analysis.RESULTS The susceptiblility rate of ESBLs-producing strains were 100% to imipenem,75.4% to piperacillin/tazobactam.A total of 4 genotypes were identified in the 28 ESBLs-producing strains.CTX-M type was identified in 92.9% of the strains,including CTX-M-14,CTX-M-24 and CTX-M-3.SHV Type was identified in 7.1% of the strains,including SHV-12.CONCLUSIONS ESBLs producers are common in E.coli isolated from our hospital.Most of them are multidrug resistant and CTX-M is the main genotype of ESBLs.Other genotypes of ESBLs are not found.

Antibiotics Resistance of Escherichia coli / 中华医院感染学杂志

OBJECTIVE To investigate the drug-resistance status of Escherichia coli(ECO)from various kinds of specimens to provide the scientific evidence for reasonable use of antibiotics.METHODS ECO strains were isolated and identified according to the National Clinical Laboratory Operation Rules.Drug resistance profile was analyzed by K-B method recommended by CLSI.RESULTS Among 275 ECO strains,50.2%(the most highest isolating rate)were isolated from urine.Detection rate of extended spectrum ?-lactamases(ESBLs)producing ECO was 32.4%(89/275).Except for 100% susceptibility to carbopenems,the drug-resistance to 14 antibiotics in ESBLs producers was higher than in the nonproducers.CONCLUSIONS Laboratory department should think highly of the monitoring of ECO to prevent and control the occurrence and prevalence of the nosocomial infection with ECO.

Nosocomial Escherichia coli Isolates:Their Extended Spectrum ?-Lactamases,AmpC Enzyme and Resistance Analysis 2005-2007 / 中华医院感染学杂志

OBJECTIVE To analyze the situation of extended spectrum ?-lactamases(ESBLs)and AmpC enzyme produced by nosocomial Escherichia coli isolates in 2005-2007.METHODS ESBLs were detected by double disk synergy test and disk diffusion confirmatory test.AmpC enzyme was detected by the three dimensional assay.Chi square test was used to test the significance.The application of different kinds of antimicrobials before the results of etiology be presented and the resistence rate of the ESBLs both producing and no producing were compared respectively.RESULTS The detectable rate of ESBLs in E.coli isolates of nosocomial and community infection was 55.1% and 21.3% and the detectable rate of AmpC enzyme nosocomial E.coli isolates was 17.4%.All strains were 100% susceptible to meropenem and imipenem but resistant to 15 other antimicrobials in different degree.The sensitivity to Piperacillin/tazobactam,cefoperazone/sulbactam and amikacin were relatively high.CONCLUSIONS The carrying rate of ESBLs from nosocomial E.coli isolates is high and AmpC enzyme and other resistance genes,which lead to multiple drug resistance.Standardized management of antimicrobials application should be strengthened and the consciousness of rational antimicrobials utilization should be raised.

Drug-resistance and Genotyping of Klebsiella pneumoniae Producing ESBLs and AmpC Beta-lactamases 2006 to 2007 / 中华医院感染学杂志

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.

Detection and Surveillance on Drug Resistance of ESBLs-producing Escherichia coli and Klebsiella pneumoniae in Nosocomial Infection / 中华医院感染学杂志

OBJECTIVE To investigate the drug resistance of ESBLs-producing Escherichia coli and Klebsiella pneumoniae in local nosocomial infection,for guiding the clinical drug resistance. METHODS ATB analysis system was used for identification of bacteria,extra-susceptibility tests were detected by K-B method. RESULTS The isolation rate of ESBLs-producing E. coli and the K. pneumoniae was 29.9% and 30.8%,respectively. The drug susceptibility was indicated the resistance rate of ESBLs producing strains to antibacterial agents except imipenem was higher than that of non-ESBLs producing strains. CONCLUSIONS Detecting drug resistance of ESBLs producing strains is of important significance for guiding the clinical rational use of antibacterials and controling the epidemics.

Distribution of Extended-spectrum ?-Lactamases Produced by Escherichia coli and Drug-resistance Analysis / 中华医院感染学杂志

OBJECTIVE To investigate the distribution and drug resistance of strains producing extended spectrum beta-lactamases (ESBLs) isolated from clinic samples and offer scientific basis for reasonable usage of antibioticsMETHODS ESBLs-producing strains isolated from Escherichia coli were identified by phenotypic comfirmatory test,drug resistance was analyzed by K-B method. RESULTS The positive rate of isolated ESBLs-producing E. coli strains was respectively 18.0%,20.3% and 28.4% in three years; that of ESBLs-producing strains isolated from urinary system was respectively 25.6%,29.0% and 39.0% in three years. The susceptibility to AMK and CFS was 70.4% and 85.2%,respectively in 2006. CONCLUSIONS The positive rate of ESBLs-producing strains and their resistance have been increasing in the near three years. so our clinic should pay attention to reasonable usage of antibiotic. AMK and CFS show significant antimicrobial activity for ESBLs-producing E. coli.

Extended-spectrum -lactamases producing Klebsiella pneumoniae isolated in two hospitals in Goiânia/Brazil: detection, prevalence, antimicrobial susceptibility and molecular typing

This study was developed to evaluate the prevalence of extended-spectrum -lactamases (ESBL) producing Klebsiella pneumoniae in two hospitals (A and B) in Goiânia, GO, Brazil. The antimicrobial susceptibility of the isolates was determined using the MicroScan WalkAway (Dade Behring, USA). Tests to evaluate the genetic correlation between the isolates were also performed. For the ESBL phenotypic test, the Double-disk diffusion (DD) method was used. The strainsisolated in Hospital B were submitted to DNA analysis by pulsed-field gel electrophoresis (PFGE). The study showed high prevalence of ESBL-producing K. pneumoniae (25% in hospital A and 66.7% in hospital B), with high rates of antimicrobial resistance. The most active compound was imipenem (100% susceptibility in vitro). The PFGE test showed similiarity in five strains and variability in six strains.The high prevalence of ESBL-producing Klebsiella may be due to individual selection and to dissemination of a common strain.

Este estudo foi desenvolvido para avaliar a prevalência de Klebsiella pneumoniae produtoras de ESBLem dois hospitais (A e B) de Goiânia, GO, Brasil. Os isolados foram analisados quanto à resistência a antibióticos através do MicroScan WalkAway (Dade Behring, USA). A correlação genética entre isolados produtores de ESBL também foi avaliada. O teste fenotípico para ESBL foi realizado através de teste de Disco de Difusão Dupla (DD) e a análise do DNA de K. pneumoniae produtoras de ESBL, isoladas no Hospital B, realizada por Pulsed Field Gel Electrophoresis (PFGE). O estudo demonstrou alta prevalência de K. pneumoniae produtora de ESBL (25,0% no hospital A e 66,7% no hospital B) com altas taxas de resistência aos antimicrobianos. O composto mais ativo foi o imipenem (100% de sensibilidade in vitro). O PFGE mostrou similaridade em cinco isolados e variabilidade em seis isolados. A alta prevalência Klebsiella produtora de ESBL pode ser devida à seleção individual e à disseminação de uma cepa comum.

Pathogens and their drug resistance in senile patients with lower respiratory tract infection / 重庆医科大学学报

Objective:To investigate the distribution of common pathogens of senile lower respiratory tract infection and drug resistance.to improve clinical therapeutic efficacy.Methods: The susceptibility to antimicrobial agents was tested with diffusion method on mueller-Hinton medium.The double-dish test for ESBLs Confirmed all putative ESBLs-producing strains.Results:A total of 263 strains were obtained from lower respiratory tract in senile patients.108 of 263 strains were Gram-negative bacilli(38.7%).There were 30 strains of Klebsiellae pneumonia,26 strains of Escherichia coli,21 strains of E.cloacae and 17 strains of Acinetobacter;64 strains of gram-positive bacteria(24.3%) and 91 strains of fungi(34.6%).Nineteen strains(33.9%) produced ESBLs in Escherichia coli and Klebsiella pneumoniae.Most gram-negative bacilli kept high susceptibility to the imipenem.Conclusions:Grau-negative bacilli were predominant in aged patients with lower respiratory tract infection.Attention should be paid to multi-drug resistance of pathogenic bacteria and fungus infection.

Genotype distribution of extended-spectrum and AmpC ?-lactamases produced by Escherichia coli and Klebsiella pneumoniae in 10 teaching hospitals of China / 中国感染与化疗杂志

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.