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Objective To study the prevalence and sequence homology of virulence genes exoU and exoS in 53 strains of pan-drug-resistant Pseudomonas aeruginosa .Methods The virulence genes exoU and exoS were detected by PCR.Sequence homo-logy was analyzed by BOX-PCR.Results Of the 53 clinical isolates of pandrug-resistant Pseudomonas aeruginosa ,the exoS+/exoU- genotype was identified in 40 strains,exoU+/exoS - genotype in 10 strains,exoS +/exoU+ genotype in 1 strain, and exoS-/exoU- genotype in 2 strains.BOX-PCR results showed that 41 exoS+ isolates belonged to 24 genotypes,and 11 exoU+ strains could be grouped into 7 genotypes.Conclusions The prevalence of virulence genes is high in clinical isolates of pandrug-resistant Pseudomonas aeruginosa .BOX-PCR fingerprint analysis combined with sequence homology analysis is help-ful for effective monitoring and control of hospital pandrug-resistant pseudomonas aeruginosa infection.
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Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is one of the most important pathogen and can cause infection ranging from superficial skin infections to life-threatening disease. The prevalence of CA-MRSA is rising in children in these years. Therefore, the review will cover the research progress in the CA-MRSA prevalence, risk factors, clinical manifestation, treatment and preventions in children. The risk factors and disease patterns and antimicrobial resistant rates in different parts of China in the recent decade will be also discussed.
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Objective To investigate antimicrobial resistance among Streptococcus pneumoniae clinically isolated from 14 teaching hospitals located at different areas in China in 2005-2008 and to give logical guidance for clinical empirical therapy.Methods A total of 1 317 non-repetitive S.pneumoniae isolates in 14 teaching hospitals from 2005-2008 were collected and sent to the central lab for reidentification and susceptibility testing, including 271 isolates collected in 2005, 391 isolates collected in 2006, 363 isolates collected in 2007 and 292 isolates collected in 2008. Most of the isolates were from community-acquired respiratory tract infections, which were isolated from outpatient or emergency department patients with respiratory tract infections or those patients with respiratory tract infections within ≤48 hours hospitalization.The districts where the organisms were isolated include North China, Northeast China, South China, Central and Northwest China and East China.The patients included adults, teenagers and children.The minimum inhibitory concentrations (MICs) or inhibitory zone diameter of 17 antimicrobial agents were determined by Etest method, agar dilution method or disk diffusion method.WHONET5.5 software was used to analyze susceptibility rate, intermediate rate, resistance rate, MIC50 and MIC90.Results Linezolid (100%) and fluoroquinolones (95.2%-99.7%) showed excellent activities against S.pneumoniae.Among β-lactams, amoxicillin-clavulanic acid remained high activities (73.8%-92.1%),followed by penicillin, ceftriaxone and cefepime with year-over-year decrease in activities.The activities of three second-generation cephalosporins were low (36.3%-38.4% in 2008).The activities of erythromycin, azithromycin, clindamycin, trimethoprim/sulfamethoxazole and tetracycline against S.pneumoniae were poor and decreased year over year.The incidence of penicillin non-susceptible S.pneumoniae (PNSP) was increasing especially for PISP (from 4.4% in 2005 to 20.2% in 2008).The incidence of PNSP in North China was low (6.0%), while this value were high in central China and East China (30.1% and 38.7%, separately).The incidence of PNSP in adults (15.7%) was obviously lower than that in children(≤5 years:33.0%) and teenagers (6-17 years:38.2%).Conclusions linezolid and fluoroquinolones showed excellent in vitro activity against S.pneumoniae, followed by penicillin and cephalosporins with year-over-year decrease of activity. Clinicians should pay more attention when using those antimicrobial agents with poor activity against S.pneumoniae, which include macrolides, clindamycin, trimethoprim/sulfamethoxazole and tetracycline.
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Objective To evaluate the influences of susceptibility interpretation of Escherichia coli,Klebsiella pneumonia and Proteus mirabilis in China mainland according to the old and new ceftazidime,cefotaxime and ceftriaxone breakpoints in CLSI M100-S20 and CLSI M100-S19. Methods First, We analyzed the antibacterial susceptibility results of the three bacteria by agar dilution method in the SEANIR surveillance item, which were collected from 15 national hospitals between the year of 2005 and 2007 and excluded the AmpC enzyme positive isolates according to the PGR-DNA sequencing method and/or the antibacterial susceptibility phenotype. ESBL phenotype was confirmed by the CLSI phenotypic confirmatory test. Antibacterial susceptibility of the total 2733 Escherichia coli, Klebsiella pneumonia, Proteus mirabilis isolates was retrospectively analyzed by WHONET 5. 4 software according to the breakpoints of the CLSI M100-S19 (S19) and CLSI M100-S20 (S20). Second, 207 isolates of Peking Union Medical College Hospital with the results of both agar dilution method and disk diffusion method were performed by recurrent analysis. Then we observed the inter-method agreement through the scatter diagram according to the breakpoints of S19 and S20. Results First, as to the ESBL positive Escherichia coli, Klebsiella pneumonia and Proteus mirabili.s, the resistant rate of cefotaxime increased from 65.2% , 55.5%, 14. 6% under S19 (64 μg/ml) to 99. 7%, 96. 2% , 93. 8% under S20 (4 μg/ml). The susceptibility rates decreased from 6. 0%, 11.5%, 33.3% under S19 (8 μg/ml) to 0%, 0. 2%, 0% under S20 ( 1 μg/ml). Ceftriaxone had the same trend as cefotaxime. Though ceftazidime was more active than cefotaxime and ceftriaxone, as to the ESBL positive Escherichia coli and Klebsiella pneumonia, the resistant rates slightly increased from 30. 3%,43. 2% under S19 (32 μg/ml) to42.0%, 56. 0% under S20 (16 μg/ml). The susceptibility rates slightly decreased from 58. 1%, 44. 1% under S19 (8 μg/ml) to 44. 7%, 28.0% under S20 (4 μg/ml). Second,as to the ESBL negative Escherichia coli, Klebsiella pneumonia and Proteus mirabilis, all the susceptibility rates of ceftazidime, cefotaxime and ceftriaxone were between 99. 2%-100. 0%, the resistant rate were between 0%-0. 4%. Third, the S20 MIC breakpoints had a good correspondence with the ESBL phenotype.Fourth, according to the recurrent analysis of MIC testing and disk dilution method, r value was 0. 67,0. 79, 0. 77 for ceftazidime, cefotaxime and ceftriaxone, respectively, and all P value were under 0. 01. The intermethod rates of S19 and S20 were both acceptable. Conclusions If the cefotaxime and ceftriaxone S20 new breakpoints were used, the concordance of antibacterial susceptibility results and ESBL phenotype would increase greatly. The clinician could select proper antibiotics according to the antibacterial susceptibility results and clinical symptoms. It is no longer necessary to edit results for cephalosporins, aztreonam, or penicillins from susceptible to resistant. However, until laboratories implement the new interpretive criteria,ESBL testing should be performed as described in Supplemental Table 2A-S1. The relationship between the new breakpoints of ceftazidime and clinical outcomes need to be further evaluated.
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OBJECTIVE To explore the relationship between multidrug resistance of Acinetobacter baumannii(ABA) and its class Ⅰ integron.METHODS In this study,39 multidrug resistant strains and 41 non-multidrug resistant strains of ABA were collected.The improved Kirby-Bauer was employed to check the collected strains′ drug-resistant phenotype;PCR was administrated to detect the distribution of class Ⅰ integron.and their relationship was also analyzed.RESULTS Results showed that ABA′s drug-resistance rate to the most antibiotics was high.imipenem,cefoperazone-sulbactam,ABA was sensitive to ciprofloxacin,amikacin and Piperacillin-tazobactam,however,ABA′s drug resistance rates to other antibiotics were all over 40%.It revealed that ABA′s drug-resistance rate was high.The study indicated that the positive rate of Class Ⅰ integron in multidrug resistant ABA was as hight as 82.1%(32/39).The positive rate of non-multidrug resistant strains was 26.8%(11/41),and the differences were statistically significant(?2=24.6,P
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OBJECTIVE To investigate the genotypes of aminoglycoside-modifying enzymes(AMEs)genes of Acinetobacter baumannii.METHODS Clinical isolates of A.baumannii were collected from 2003 to 2006,and their resistance to gentamicin,amikacin and tobramycin were tested by K-B method.Twenty-three isolates were chosen because of their resistance to aminoglycoside antibiotics(at least resistant to one kind of the drugs).Nine types of the AMEs were detected by PCR.RESULTS Drug resistant rates of 23 isolates of A.baumannii to gentamicin,amikacin and tobramycin,were 86.96%,56.5% and 69.56%,respectively.The detection rates of the 9 AMEs,including ant(3')-Ⅰ,aac(3)-Ⅰ、aac(6')-Ⅰ,aph(3')-Ⅵ,aac(3)-Ⅱ,aac(6')-Ⅱ and ant(2″)-Ⅰ were 69.56%,60.87%,56.52%,47.82%,30.4%,26.09% and 21.73%,respectively.CONCLUSIONS The resistance to aminoglycoside antibiotics of A.baumannii is mainly caused by AMEs.
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Objective To construct a new molecular biological method for the analysis of microbial species in lower respiratory tract infections based on 16S rRNA gene by denaturing high-performance liquid chromatograph(DHPLC).Methods The universal primer set was analyzed basing on the highly conserved regions of 16S rRNA gene.DNA amplicons of lower respiratory tract were analyzed by DHPLC to generate peak profiles respectively.The incorporation of 40-bpGC clamp into the amplification primet was essential to effectively discriminate genetic differences identification.Results The primers could only amplify bacterial 16S rRNA.Bacterial of amplicons which incorporation of a 40-bpGC clamp were effectively discriminated genetic differences in DHPLC.The results of clinical isolares identification showed 100%according with the traditional method.Conclusion DHPLC has not only high accuracy,but also is a convenient,rapid and high-through technique for the discrimination bacteria.It has potential value in the detection of lower respiratory pathogenic bacteria.
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Objective To investigate the prevalence of 16S rRNA methylase genes in Klebsiella pneumoniae isolates from Guangzhou.Methods K-B test was used to determine the resistant rates of these stains.Five 16S rRNA methylase genes,armA,rmtA,rmtB,rmtC,and rmtD,were detected by PCR.Results All 55 K.pneumoniae isolates showed resistant to arbekacin,gentamicin,tobramycin,and neomycin.Susceptibility rates were 5.5%,20.0%,72.7%,and 100% to ceftazidime,ciprofloxacin,piperacillin/tazobactam,and imipenem respectively.ESBLs were positive in 52 of 55 (94.5%) isolates.Among 55 K.pneumoniae isolates,34 were positive for armA and 1 for rmtB.Conclusions In K.pneumoniae resistant to arbekacin,the positive rate of 16S rRNA methylase genes was high,predominantly with armA positive.These strains were highly resistant to some antibiotics.
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Objective To investigate the resistance and ?-lactamase of cefoxitin-resistant Klebsiella pneumoniae. Methods The minimal inhibitory concentrations were determined by standard agar dilution.Isoelectric focusing was used to measure the PI(s) of an isolate,s ?-lactamase,AmpC and ESBLs activity was confirmed by a three-dimensional extract method. Results The resistant rates of 40 strains were as follows: imipenem and meropenem 0.0%,cefepime 20.6%,cefotaxime(22.5%),ceftazidime 60.0%.The most isolates were demonstrated two or more ?-lactamase bands by IEF.Of 39 strains tested,ESBLs was detected in 31(70.5%) strains and AmpC-type?-lactamase in 16(41.0%) strains by three dimensional extract test. Conclusions These cefoxitin-resistant Klebsiella pneumoniae produced two or more ?-lactamases.It is imperative for clinical microbiology laboratories to detect and research ?-lactamases,especially AmpC enzyme.
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OBJECTIVE To investigate the antimicrobial resistance of hospital-and community-acquired pathogens collected from 10 teaching hospitals located at different areas in China in 2006.METHODS According to the study protocol,the strains of Streptococcus pneumoniae,meticillin-susceptible Staphylococcus aureus(MSSA),Escherichia coli and Klebsiella pneumoniae were collected and sent to the central lab for reidentification and susceptibility testing.The minimal inhibitory concentrations(MICs) of antimicrobial agents against Str.pneumoniae were determined by Etest method and MICs of antimicrobial agents against S.aureus,E.coli and K.pneumoniae strains were determined by agar dilution method.WHONET5.4 software was used to analyze the data.RESULTS Among 353 Str.pneumoniae strains,74.2% were penicillin-susceptible(PSSP),9.6% were penicillin-intermediate(PISP) and 16.2% were penicillin-resistant(PRSP).Strains from different hospitals showed different sensitivity to penicillin.Among ?-lactam antibiotics,cefuroxime showed the lowest susceptibility rate of 0%(for PRSP) to 76.7%(for PSSP).The susceptibility rate to ceftriaxone and amoxicillin-clavulanic acid was 98.1% and 98.9% in PSSP group,61.8% and 64.7% in PISP group,and 15.8% and 10.5% in PRSP group.The ESBLs rate was 56.2% among 267 Escherichia strains and 42.7% among 206 K.pneumoniae strains.For ESBLs-producing strains,the susceptibility rates to cefotaxime and ceftriaxone were low and the rate to ceftazidime was relatively high among ?-lactam antibiotics.73.4% MSSA strains produced ?-lactamase.?-Lactam antibiotics tested showed high susceptibility against MSSA strains.The susceptibility rate was 98.9-100%.The susceptibility rate to ciprofloxacin and levofloxacin was 80.8% and 88.1%,separately.CONCLUSIONS Fluoroquinolones show high susceptibility against Str.pneumoniae.Ceftriaxone and amoxicillin-clavulanic acid have relatively high susceptibility among ?-lactams.For MSSA and non-ESBLs-producing E.coli and K.pneumoniae strains,?-lactams show high susceptibility.For ESBLs-producing E.coli and K.pneumoniae strains,the susceptibility rates to cefotaxime and ceftriaxone are low and that to ceftazidime,cefepime and cefoperazone-sulbactam are relatively high.
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OBJECTIVE To analyze the sequence of IMP-4 metallo-?-lactamases(MBLs) encoding gene from clinical isolates of multiple-drug-resistant Klebsiella oxytoca strains and attempt to know the integrons composing the drug resistance gene box.METHODS The antibiotic sensitivity test of multi-resistant K.oxytoca strains was done according to Kirby-Bauer method of CLSI 2005,and the double disk synergy test and Etest were for detecting their MBLs.The Class 1 integrons were detected by PCR.The purified amplicons of Class l integrons were sequenced.The type and order of gene cassettes in integrons were analyzed by searching GenBank.RESULTS The K.oxytoca was resistant to carbapenems,the third-generation cephalosporins,cefoxitin,quinolones,cefoperazone/sulbactam,sulfamethoxazole/trimethoprim,amoxicillin/clavulanate,ticacillin/clavulanate,piperacillin,cefepime,rifampicin and piperacillin/tazobatam,only susceptible to amikacin and polymyxin B.The IMP-4 metallo-?-lactamases,aadA1,AmpC,CTX-M-14,qacE△1-sull and intI1 were positive.CONCLUSIONS Integrons are important molecular mechanism in the development of multidrug resistance.There are resistance gene boxes in them.
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Objective To study the antimicrobial resistance changes of common pathogenic bacterial isolates in Guangzhou. Methods Disc diffusion test was used to measure the antibiotic susceptibility of 5063 strains collected from 13 hospitals in Guangzhou from 1998 to 2000 (Fastidious bacteria were detected by E test). Results From 1998 to 2000, the percentage of methicillin resistant Staphylococcus aureus was 45.3%,53.0%, and 50.8%, respectively, and that of methicillin resistant coagulase negative Staphylococcus was 64.1%, 86.0%, and 79.0% accordingly. There was no resistance to vancomycin in the strains of Staphyloccocas and there were 40.7%, 31.8% and 36.4% in E.coli and 43.1%, 42.7%, and 31.5% in Klebsiella found to be extended spectrum lactamases producing in the 3 years. Resistant rates of Enterobacter spp against the third generation cephalosporins increased. Resistant rates of P.aeruginosa against cefoperazone/sulbactam, ceftazidime,amikacin were changed unmarkedly in recent years. Conclusions The antimicrobial resistance of common pathogenic bacteria is serious in Guangzhou area. The surveillance of antimicrobial susceptibility is of great significance.
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OBJECTIVE To understand characteristics of TEM-116 ?-lactamases through comparative study on resistance to antibiotics of clinical isolates of Klebsiella pneumoniae producing TEM-116 ?-lactamases.METHODS K.pneumoniae susceptibility to ?-lactamases was determined by disk diffusion tests,and their isoelectric points(PI) were detected using analytic isoelectric focusing(IEF),and resistance to antibiotics of clinical isolates of K.pneumoniae producing TEM-116 and TEM-1?-lactamases was studied.RESULTS Both of K.pneumoniae producing TEM-116 ?-lactamases and producing TEM-1 ?-lactamases were 100% resistant to AMP,and highly resistant to the first and second generation cephalosporin,but greatly susceptible to FEP and IPM.There was greatly difference between resistance to AMC,TZP,AMK,and GEN of clinical isolates of K.pneumoniae producing TEM-116 ?-lactamases and that of K.pneumoniae producing TEM-116 ?-lactamases,the TEM-116 isolates were higher resistant than TEM-1 isolates.Analytic IEF results showed that PI of TEM-116 ?-lactamases was 5.4,and most strains of K.pneumoniae TEM-116 ?-lactamases displayed two electrophoresis bands or more,only one strain of them just displayed one band,resistant to majority of antibiotics.CONCLUSIONS The results show that K.pneumoniae producing TEM-116 ?-lactamases are more resistant to antibiotics than K.pneumoniae producing TEM-1 ?-lactamases,and indicate TEM-116 ?-lactamases work as ESBLs.