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Objective To investigate the method of preparing black phosphrous quantum dot (BPQD)-loaded erythrocyte membrane nanovesicles (BPQD-EMNVs), and to study its efficiency in photothermal therapy for breast cancer. Methods Fresh red blood cells (RBCs) of healthy mice were extracted to prepare erythrocyte membrane, and BPQD-EMNVs were prepared by sonication method. The morphology of BPQD-EMNVs was observed by a transmission electron microscopy. The particle size distribution was measured by a nano-particle size and Zeta potential meter. The encapsulation efficiency of BPQD was determined by inductively coupled plasma emission spectrometry. The uptake rate of BPQD-EMNVs was observed by a laser scanning confocal microscope. 4T1 tumor-bearing Balb/c mice were randomly divided into PBS, EMNVs, BPQD and BPQD-EMNVs groups, and the tumor sites were irradiated with 808 nm near-infrared light for 10 min after 4 hours of tail vein injection. The growth of the tumors was continually observed. Results The prepared BPQD-EMNVs have a regular spherical shape with an average particle diameter of 228 nm and an encapsulation efficiency of about 47％. Cellular uptake in vitro experiments showed that BPQD-EMNVs were rapidly taken up by 4T1 tumor cells. The results of animal in vivo experiments showed that BPQD-EMNVs had the highest enrichment after 4 h of injection at the tumor site, and BPQD-EMNVs could effectively kill tumor tissues after 10 min of 808 nm near-infrared light irradiation. Conclusions The BPQD-EMNVs are easy to prepare, and the prepared nanovesicles have good biocompatibility and photothermiotherapy effect, which is expected to be a promising method for breast cancer therapy.
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Objective To understand the resistance mechanism and clinical feature of linezolid-resistant S.capitis isolated from blood samples.Methods Antimicrobial susceptibility testing was carried out to determine the susceptibility of clinical strains.PCR and sequencing analysis were used to analyze cfr gene and 23S rRNA mutation,which were associated with linezolid resistance.Patterns of pulsed-field gel electrophoresis (PFGE) were analyzed in combination with clinical data to understand the clinical feature of S.capitis strains.Results Five linezolid-resistant S.capitis strains were isolated from blood samples of 3 patients.These strains were resistant not only to linezolid,but also to most of the commonly used antimicrobial agents except glycopeptides,rifampin,and trimethoprim-sulfamethoxazole.Mutation was identified in 23S rRNA genes of all the five strains and cfr gene was found in four of the five strains.PFGE typing showed the same type,which supported the homology of the 5 strains.Three patients had deep vein indwelling catheter and two of them were treated with linezolid.Conclusions Linezolid-resistant S.capitis isolates showed the phenotype of resistance to multiple antimicrobial agents.Linezolid resistance may be mediated by cfr gene and 23S rRNA mutations in S.capitis.Long-term use of deep vein indwelling catheter and linezolid treatment may increase the risk of linezolid-resistant S.capitis infection.
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Objective To investigate the profile of antimicrobial susceptibility of the Mycoplasma pneumoniae (Mpn)strains isolated from pediatric patients with respiratory tract infection.Methods Antimicrobial susceptibility testing was conducted with a total of 112 Mpn clinical strains by broth microdilution method.Sequence analysis of full 23S rRNA genes was performed for all Mpn strains.Results One hundred and twelve Mpn strains were isolated from January 2009 to March 2011. Of these clinical isolates,98 (87.5%)were resistant to erythromycin and azithromycin.All macrolide-resistant Mpn strains harbored an A2063G or A2064G transition mutation in domain V of 23S rRNA genes.Mpn isolates were still very susceptible to the tetracyclines and fluoroquinolones tested.Conclusions The Mpn strains from pediatric patients are highly resistant to macrolides.The mechanism of macrolide resistance may be associated withthe transition mutation on 23S rRNA gene.
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ObjectiveTo investigate the clinical pharmacokinetics (PK) and pharmacodynamics (PD) of gemifloxacin tablet in healthy Chinese volunteers and to provide evidences for optimal clinical dosing.MethodsTwenty volunteers were enrolled in the randomized (1∶1) double-blind study,and divided into administration group and control group.Each group received multiple oral doses of 320 mg of gemifloxacin tablet or placebo.The plasma and urine samples for gemifloxacin were analyzed by igh-performance liquid chromatogram(HPLC)-fluorometricmethod. Theminimuminhibition concentrations (MIC)of gemifloxacin against190clinical isolateswere determinedby broth microdilution method.The fAUC0～24 h/MIC and fCmax/MIC,with target value of 25 and 5,were used as the indices to evaluate PK and PD characteristics of gemifloxacin. The cumulative fraction of response (CFR) of gemifloxacin against each bacterium and the probability of target attainment (PTA) under various MIC level were evaluated using Monte Carlo simulation following multiple administration at steady state.ResultsThe Cmax of gemifloxacin after once-daily oral doses for 7 days were (1.55 ±0.32) μg/mL and (1.57±0.31) μg/mL for the first and last dose,while the AUC0～24 h were (7.91±1.52) and (8.91±1.15) h · μg · mL-1,respectively.The accumulation factor was 1.13±0.05.The time-profile of gemifloxacin could be described using two-compartment model and the half-life of distribution and elimination phase were (0.64 ± 0.17) and (7.10 ± 2.10) h,respectively. The cumulative urinary excretion rates within 24 h of gemifloxacin were 34.83 ％ and 38.95 ％ for the first and the last dose,respectively.PD study showed that the MIC90 of gemifloxacin were 0.25 mg/L and 0.125 mg/L against Streptococcus pneumoniae and Moraxelle catarrhalis,respectively,while the MIC90 was 2 mg/L against Hemophilus influenza. However,most of Klebsiella pneumoniae and methicillin-resistant Staphylococcus aureus (MRSA) were resistant to gemifloxacin ( MIC90 ＞ 32mg/L).The PTA values of fAUC0～24 h/MIC and fCmax/MIC of gemifloxacin 320 mg daily for 7 days were close to 100％ when MIC was ≤0.06 mg/L.ConclusionsGemifloxacin is rapidly absorbed after oral administration of single doses in healthy Chinese volunteers,and the plasma concentration could reach steady state at the third day,while a minimal accumulation is shown after consecutive 7 days dosing.The PK/PD analysis suggests that the favorable clinical and bacteriological efficacy could be obtained when using thisregimen in treatment of sensitive patients with community-acquired pneumonia and acute exacerbation of chronic obstructive pulmonary disease.
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Objective To screen fosfomycin-resistant genes in the clinical isolates of Enterococcus faecium Efm-HS0661 and verify their functions. MethodsAntimicrobial susceptibility and conjugation experiments were carried out to determine if the antimicrobial resistance in clinical strain was transferable.By Solexa high-throughput sequencing,the genes conferring fosfomycin resistance were screened. The function of resistance gene was identified by cloning.ResultsThe clinical isolates of Enterococcus faecium Efm-HS0661 were resistant to glycopeptide antibiotics and fosfomycin, and the fosfomycin resistance was found to be transferred by conjugation. Within the 2414 bp nucleotide sequence obtained by high-throughput sequencing, fosB, a plasmid-mediated fosfomycin resistance gene was found. The fosB gene was 420 bp in length, which shared 99. 8％ amino acid identity with other fosB from Staphylococcus spp. The minimal inhibitory concentration (MIC) of DH5α transformant containing fosB gene against fosfomycin was higher than that of DHSa transformant without fosB gene. ConclusionsThe high-throughput sequencing can be used to screen unknown resistance genes in clinical isolates. The plasmidmediated resistance gene fosB can confer fosfomycin resistance in Enterococcus faecium.
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Objective To develop a method for rapid detection of Mycoplasma pneumoniae and its macrolide resistance mutation. Methods The primers and cycling probe sets were designed to detect two single nucleotide mutation, A2063G and A2064G, in the 23s rRNA gene of Mycoplasma pneumoniae. By using recombinant plasmids containing 23s rRNA gene fragments, 102 Mycoplasma pneumoniae clinical isolates from 2005 to 2008, and 136 nasopharyngeal suction specimens from pediatric patients with low respiratory tract infections in Shanghai Children's Hospital from November to December in 2009 were investigated to determine the specificity and the sensitivity of the CycleavePCR method. PCR amplification and sequence analysis of 23S rRNA genes were performed for all Mycoplasma pneumoniae strains and Mycoplasma pneumoniae positive specimens to confirm the results of the CycleavePCR method. Results Of 102 clinical isolates, 83 was resistant to erythromycin and sequence results show that all macrolide-resistant Mycoplasma pneumoniae strains harbored an A2063G ( 82/83 ) or A2064G ( 1/83 ) transition mutation in 23S rRNA genes. Twelve was Mycoplasma pneumoniae detected positive by CycleavePCR in 136nasopharyngeal suction specimens. The CycleavePCR results were consistent with those of routine PCR and sequencing. There was no signal production from other bacterial species. Sensitivity and specificity were 100%. The detection limit of the CycleavePCR was 10 plasmid copies per reaction. Experiment can be done within 1.5 h. Conclusion A novel method is developed to detect erythromycin-resistant strains harboring A2063G and A2064G transition mutation in the 23s rRNA gene using CycleavePCR.
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Objective. To understand drug susceptibilities to common antibacterials, resistance mechanism to β-lactams and quinolones and the clonal spread of resistant stains of Haemophilus influenzae (H. influenzae) and Haernophilus parainfluenzae (H. parainfluenzae) isolated from some hospitals in Shanghai. Methods The in vitro antimicrobial susceptibilities to 13 antibacterials, such as ampicillin, of 156 Haemophilus strains collected from 5 hospitals of Shanghai in 2006 were tested by agar dilution method. The β-lactamase production was determined by chromogenic cephalosporin test. TEM and ROB type of β-lactamase genes and quinolone resistance determining regions (QRDR) of ciprofloxacin-resistant strains were detected by polymerase chain reaction (PCR) amplification. The homology of H. influenzae strains were analyzed by enterobacterial repetitive intergenic consensus (ERIC)-PCR. Results The susceptible rate of 109 strains H. influenzae to ampicillin was 74.3%, while those to ampicillin-sulbactam, cephatosporins and fluoroquinolones were all 100.0%. The β-lactamases-producing rates of 109 strains H. influenzae and 47 strains H. parainfluenzae were 25.7% and 19.1% (χ2=0.776,P=0.378), respectively. TEM gene was detected in all β-lactamases-producing strains. Of 109 H. influenzae isolates, only one was resistant to ciprofloxacin, and Ser84Leu mutation was detected in gyrA gene and Gly206Arg mutation in parC gene. The results of ERIC-PCR showed that 106 H. influenzae strains were clustered into 73 groups with similarity level of 85%. Conclusions Clinical isolates of H. influenzae from hospitals in Shanghai remain highly susceptible to common antimicrobial agents except ampicillin. TEM type of β-lactamase production is the main ampicillin-resistant mechanism of the tested stains. The clonal spread of H. influenzae, including ampicillin-resistant strains, is not prevalent.
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Objective To learn the current in vitro antimicrobial susceptibility of Mycoplasma pneu-moniae in Shanghai and to understand the mechanisms of resistance to macrolides. Methods M. pneumoniae was isolated from pediatric patients with low respiratory tract infections(RTI) using broth and PPLO agar medi-um. PCR amplification and sequence analysis of P1 adhesion gene were performed to identify all M. pneumoniae strains. Susceptibility testing was carried out for macrolides, tetracyclines and fluoroquinolones using broth mi-crodilution method with SP4 broth. PCR amplification and sequence analysis of 23S rRNA genes were performed for all M. pneumoniae strains. P1 gene PCR-RFLP typing was performed to subtype the M. pneumoniae strains. Results One hundred and two M. pneumoniae strains were isolated in Shanghai from Oct 2005 to Dec 2008. All M. pneumoniae isolates were susceptible to the tetracyclines and fluoroquinolones tested. Of 102 clinical isolates, 83(81.4%) was resistant to erytbromycin and all 83 erythromycin-resistant strains had MIC>128 mg/L. An increasing trend of resistance rates were showed: 16.7% (1/6) in 2005, 76.5% (13/17) in 2006, 100.0% (24/24) in 2007 and 81.8% (45/55) in 2008. All macrolide-resistant M. pneumoniae strains harbored an A2063G transition mutation in domain V of 23S rRNA genes. The P1 gene RFLP type 1 is predominant (85.3%, 87/102) in M. pneumoniae clinical isolates. Conclusion The macrolide resistance rate of M. pneu-moniae is very high in Shanghai. The mechanism of macrolide resistance is associated with transition mutation on the 23S rRNA gene.
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Objective To investigate the mechanism of the different levels of ciprofloxacin resistance in qnrA-containing transconjugants.Methods E. coli J53AzR as the recipient,4 qnrA-containing transconiugants were constructed by conjugation from 4 qnrA-carrying clinical isolates.MICs of the transconjugants were measured by E test.aac(6')-Ib-cr was detected by PCR,and qnrA mRNA expression level was determined by real-time RT-PCR.The promoter sequences of qnrA were amplified by PCR from qnrA-bearing plasmids and cloned into plasmid pKK232-8,then transformed into HB101.All promoter fragments were sequenced.Resuits The MICs of ciprofloxacin against 4 transconjugants demonstrated a 10-fold difference from 0.094 μg/ml to 1.000 μg/m1.Of 4 qnrA-bearing plasmids in E.coli J53,ciprofloxacin MICs of pHS4 and pHS5 were 0.094 μg/ml and 0.125 μg/ml,respectively;pHS3,which contained the aac(6')-Ib-cr gene as well,MIC was 0.25μg/ml;and pHS5,which had a high expression level of qnrA and the aac(6')-Ib-cr gene,MIC was 1.00μg/ml.The relative expression levels of qnrA mRNA in J53 pHS6 was 32.5,much higher than the other 3 transconjugants(from 1.0 to 2.5).The promoter in plasmid pHS6 was 12-fold stronger than that in the other 3 plasmids.Compared with pHS3,there was 7 bp(GTTAGCA)deletion between the transcription initiation site and the start of qnrA in pHS6.Conclusion Co-existence of qnrA and aac(6')-Ib-cr in a single plasmid and high level of qnrA expression can account for the different levels of ciprofloxacin resistance in transconjugants.
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Objective To study dIe ESBLs and plasmid-mediated AmpC enzymes in E.Coli and Klebsiella spp. with CLSI ESBL-screening test positive,confirmation test negative but cefepime susceptible.Methods Antimierobial susceptibility testing were performed by Kirby-Bauer(K-B)method.The genes encoding ESBLs and plasmid-mediated AmpC enzymes were detected by PCR Transfer of ESBLs or plagmid-mediated AmpC resistance was studied by conjugation experiments.The homology of donor (E.coli),recipient(E.coli J53)and their transconjugants were analyzed by ERIC-PCR DNA fingerprints of E.coli and Klebsiella pneumoniae were analyzed by PFGE as recommended bv PulseNet protocoL Results Of 18 isolates from Huashan Hospital,11 were E.coli.6 were Klebsiella pneumoniae and 1 was Klebsiella oxytoca.Antimicrobial susceptibility testing indicated all of 18 isolates were positive on the CLSI ESBL screening test but negative on the confirmation test.and all of isolates were susceptible to cefepime(a zoneof-inhibition diameter of≥18 mm wag considered to indicate susceptible).PCR results indicated that 9 of the 11 E.coli isolates predued CMY-2 AmpC enzyme.TEM,SHV,CTX-M,PER,VEB or SFO type β-lactamages were not identified.Of 6 Klebsiella pneumoniae isolates.5 were DHA-1 AmpC-producing strains.4 of the 5 DHA-1 AmpC-producing strains were coexistence of broad-speetrumβ-lactamaae or extended-spectrumβ-lactamase.including two producing SHV-11 and two producing CTX-M-14 and SHV-62 type ESBL respectively.One Klebsiella oxytoca wag also DHA-1 AmpC producing strain.Conjugation experiments indicated that both ESBLs and AmpC enzymes could be transfefred from donor to recipient.PFGE indicated that the DNA fingerprints of K.pneumoniae were difierent but seven CMY-2 AmpC-producing E.coli isolates from general surgieal ward were similar.Concluslons The main mechanism of antibiotic resistance in CLSI ESBLs-screening test-positive but eefepime.susceptible E.coli and KIebsiellaspp.is production of plagmid-mediated AmpC enzymes.Some strains produce both AmpC enzyme and ESBLs.Such strains should be reported as resistant to cefepime.The results suggest that laboratories should routinely conduct research on the ESBLs and plnsmid.mediated AmpC enzymes in Enterobacteriaceae in order to report antimicrobial susceptibility testing results more correcdy.
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Objective To investigate the resistance of clinical isolates from Shanghai Huashan Hospital in 2005.Methods Antimicrobial susceptibility test was carried out by Kirby-Bauer method.Results were analyzed according to CLSI 2005.Results Of the 3 896 clinical isolates,gram negative bacilli and gram positive cocci accounted for 68.1% and 31.9% respectively.About 93.2%(465/499)of S.aureus isolates were identified as methicillin-resistant Staphylococcus,94.9%(260/274)of coagulase negative Staphylococcus(CNS)isolates were methicillin-resistant.No vancomycin-resistant strain was found.The resistance rates of E.faecalis and E.faecium to high level gentamicin(120 ?g)were 67.4% and 82.8% respectively.Two strains of VRE were isolated.Both were VanA type.ESBLs-producing strains accounted for 47.6%(206/433)in E.coli and 69.6%(391/562)in Klebsiella spp(K.pneumoniae and K.oxytoca).Isolates of Enterobacteriaceae were still highly sensitive to imipenem and meropenem,resistance rates being 0-4% except Citrobacter isolates,9.1% of which were resistant.However,39.3% and 59.6% of P.aeruginosa strains were resistant to the above carbapenems,respectively.Conclusions The prevalence of MRSA and MRCNS is very high.ESBLs are prevalent in E.coli and Klebsiella spp.Two glycopeptide-resistant E.faecium isolates are identified firstly in Huashan Hospital.Our data will be useful for rational use of antimicrobial agents in the treatment of bacterial infections.