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.

Although quinolone resistance results mostly from chromosomal mutations in Enterobacteriaceae,it may also be mediated by plasmid-encoded Qnr determinants.Qnr proteins protect DNA from quinolone action and compromise the effect of quinolones,such as nalidixic acid.Qnr proteins including QnrA,QnrB and QnrS,have been identified worldwide with a quite high prevalence among Asian isolates with a frequent association with clavulanic acid-inhibited expanded-spectrum b-lactamases and plasmid-mediated cephalosporinases.The QnrA genes are embedded in complex sul1-type integrons.A close relative and likely progenitor of the QnrA have been found in the water-borne species Shewanella algae.It may help to determine the location of in vivo transfer of the QnrA genes.Further analyses of the role of quinolones,if any,in enhancing this gene transfer may prevent the spreading of the drug resistance and possibly lead to the finding of a novel mechanism of antibiotic resistance.

BACKGROUND: Angiostatin(AS) can effectively inhibit proliferation and migration of vascular endothelial cells and also inhibit tumor angiogenesis.OBJECTIVE: To observe the inhibitory action of angiostatin, 131I and 131 I labeled angiostatin(131I-AS) on proliferation of human umbilical vein endothelial cell ECV304 and on mass and volume of Lewis lung carcinoma (LLC) in mice.DESIGN: A randomized controlled trial with human umbilical vein endothelial cell ECV304 and Lewis lung carcinoma tumors growing in C57BL/6 mice as subjects of research.SETTING: A radiological lab and a nuclear medicine department in a military university.MATERIALS: Totally 28 LLC carrying male C57BL/6 mice, weighing(20± 2) g, 5 - 7 weeks old.METHODS: 131I-AS solutions of four concentrations were made: solution A(131I 0. 74 GBq/L, AS 0. 5 mg/L); solution B(131I 0.74 GBq/L, AS 16 mg/L); solution C(131I 1.48 GBq/L, AS 0.5 mg/L); solution D(131I 1.48 GBq/L, AS 16 mg/L). The effect of 131I-AS, AS alone and 131I alone on proliferation of human umbilical vein endothelial cell ECV304 was observed with MTT method. The 28 tumor carrying mice were randomly assigned into 4 groups, in each of which was injected 0.3 mL of 131I AS(131I 11.1 MBq and AS 2.5 mg/kg), AS(2.5 mg/kg), 131I(11.1MBq) and saline respectively for twice with 7 days interval. Then the change in tumor mass and volume was observed.MAIN OUTCOME MEASURES: ① The inhibition rate on cell proliferation with MTT method; ② Change in tumor mass and volume.RESULTS: ① The inhibition rate of AS alone(0. 5 -64 mg/L) on ECV304 was (7.3 ± 3.5) % - (41.9 ± 4. 3 )% ( P = 0. 003 vs AS of 0). The inhibition rate of the 4 concentrations of 131I-AS on ECV304 was(23.9±2.8)% ,(58.2±3.9)%, (39. 1 ±4. 1)% and(78.4 ±5.4)%, which were much higher than AS alone or 131I alone( P =0. 000 3) . ② The mean volume of LLC in the four groups were (3 943 ± 236), (5 219 ± 351 ), ( 1 963 ± 126),(7 353 ±350) mm3 respectively. Compared with saline group, the tumor inhibiton rate in the other 3 groups were 46.4% , 29.0% , 73.3% respectively( P =0. 000 1 ).CONCLUSION: 131I-AS inhibits proliferation of endothelial cells in vitro and inhibits LLC growth in vivo and it outdoes AS or 131I alone.

Objective To investigate the relationship of resistance mechanisms of a Klebsiella pneumoniae strain and a Morganella morganii strain resistance to carbapenems isolated from a single specimen. Methods Sensibility of antimicrobial agents was detected by agar dilution method. Specific PCR and DNA sequence analysis were performed to detect resistance genes. Plasmid feature was detected by plasmid conjugation and electrophoresis analysis. Genetic environment around blaKPC was analyzed with sequencing. The changes of outer membrane permeability were analyzed with electrophoresis of outer membrane proteins. Results blaKPC-2 was detected in 2 original isolates strains and their transconjugants. Carbapenem-resistance was successfully transfered by conjugation experiments. blaKPC-2 was located on dissimilar plasmids, but genetic environment around blaKPC-2 was the same sequence. The Morganella morganii isolate showed a loss of 38 ×103 OMPs and an additional 36 ×103 OMPs appearance, while the Klebsiella pneumoniae isolate showed a loss of OMPK36. Conclusion blaKPC-2 was detected in 2 isolates. This gene encoded by two plasmids with different sizes was located on the same composite transposon. The lack of outer membrane proteins could also play an important role causing isolates to exhibite resistance to carbapenems.

Objective To investigate the resistant mechanism of carbapenem-resistant Escherichia coli and its relationship with endogenous infection. Methods Two carbapenem-resistant Escherichia coli strains were isolated from blood and stool of a same patient, respectively. The minimal inhibition concentrations (MIC) of the two isolates against imipenem and meropenem were determined by E-test. The susceptibility against other antimicrobial agents were done by disc diffusion method. Isoelectric focusing electrophoresis (IEF), polymerase chain reaction (PCR) amplification,cloning and sequencing, conjugation, Southern blotting were carried out to analyze the encoding gene of β-lactamases. Homology analysis of the two strains was done by pulsed field gel electrophoresis (PFGE). Results MIC against imipenem and meropenem of the two strains were both≥32 mg/L.Both strains produced KPC-2 (pI 6.7) and SHV-12 (pI 8.2) β-lactamases. blaKPC2gene was located on a 54 kb transferable plasmid. PFGE showed that the two Escherichia coli strains were derived from the same clone. Conclusions The resistance and enzyme digestion map of chromosome DNA of the two Escherichia coli strains are coincident. The Escherichia coli septicemia of this patient is probably an endogenous infection caused by the immigration of Escherichia coli from the gut.

Objective To investigate the molecular epidemiology and mechanism of carbapenem resistance of Escherichia coli collected from intensive care units(ICUs)of general surgery.Methods Agardilution were carried out to confirmed the drug-susceptibility,pulsed-field gel electrophoresis(PFGE)were performed to analyze the molecular epidcmiology of carbapenem-resistance isolates.Specific PCR,DNA sequencing,conjugation experiments,plasmids extraction,plasmid transformation assays and SDS-PAGE of outer membrane proteins(OMPs)were carried to confirm genotype of carbapenemase and its transmission mechanism.Results PFGE showed the isolates belonged to 10 clonotype,and all the clinical isolates were resistant to β-lactams including imipenem and meropenem,but uncertain to aminoglycosides,specific PCR and DNA sequencing revealed that all isolates encoded carbapenem-hydrolyzing enzyme gene,KPC-2.Plasmid DNA extraction and plasmid transformation assays from some isolates comfirmed that KPC-2 encoded on a 56 kb plasmid.SDS-PAGE analysis confirmed that there are alterations in OMPs of Escherichia coli.Conclusion Escherichia coli isolates with carbapenem resistance are collected from our hospital,production of KPC-2 carbapenemase mainly contributed to reduced susceptibility of carbapenem in Escherichia coli,the alterations in OMPs may as a cofactor in high-level drug-resistance in Escherichia coli.

Objective To investigate the application of vascularized free fibula flaps in reconstruction of mandibular defect,and to evaluate the survival rate and repair effect of the method.Methods 16 patients with mandibular tumor,having a desire to reconstruct mandible,and their systemic state could tolerate the long time operation, were selected to reconstruct mandibular defect by vascularized fibula flaps,of which 12 were male,4 female,aged 24-66 years old,average 45.2 years old.The resection of primary tumor and free fibula flaps were simultaneously conducted,then the fibular flaps were shaped according to the defect location and size of the mandible,and were fixed with reconstructive titanium plate for repair and reconstruction of mandible. The survival of flaps was determined by skin color, texture, and skin temperature of the flaps. The reconstruction effects were evaluated through the patients’surface like photos and X-ray picture of mandible before and after operation.Results All of flaps were survived and no serious complications were found. The complications of the supplied sites were skin tension and wound dehiscence, which were healed by dressing. The mandibular reconstruction effects were good through 2 or more persons’double blind evaluation.Conclusion Free fibula flaps have high survival rate and good results in mandibular reconstruction,and they can meet the needs of various types of mandibular defect repair.

Objective To investigate the relationship between H-type hypertension and unstable angina (UA).Methods Totally 147 elderly inpatients with hypertension and angina in our hospital were selected.Patients were divided into H-type hypertension group [n=72,serum homocysteine (Hcy) level ≥10 μmol/L] and primary hypertension group [n=75,serum homocysteine (Hcy) level ＜10 μmol/L].All patients underwent coronary angiography.Serum Hcy level was measured by enzyme method and compared between groups.Results There were statistical differences in the UA incidence,Gensini's score and high sensitive C-reactive protein (hsCRP) level between the H-type hypertension group and primary hypertension group [(44.4％ (32/72) vs.12.0％ (9/75),(44.2± 21.3) vs.(31.9±18.4),(4.3±2.1) μg/L vs.(2.0±1.9) μg/L,respectively,all P＜0.01].Serum Hcy level in H-type hypertension group was higher during UA attack than during UA remission [(22.2±7.1)μmol/L vs.(13.7±3.7)μmol/L,P＜ 0.01].Serum Hcy level during UA attack was increased in H-type hypertension group than in stable angina group [(22.2±7.1)μmol/L vs.(12.0± 4.2) μmol/L,P ＜ 0.01].Serum levels of Hcy,total cholesterol and low density lipoprotein cholesterol in primary hypertension group were higher in UA patients than in stable angina patients [(8.9±2.2)μmol/L vs.(6.6± 1.2)μmol/L,(6.9±0.7)mmol/L vs.(4.5±0.5)mmol/L,(4.6±0.8)mmol/L vs.(2.7 ± 0.6) mmol/L,respectively,P＜ 0.01 or P＜0.05].Logistic regression analysis showed that H-type hypertension was the independent risk factor for unstable angina in the elderly (OR =5.691,P ＜ 0.01).Conclusions H-type hypertension is closely correlated with unstable angina,which is the independent risk factor for unstable angina in the elderly.Serum Hcy level has significant correlation with coronary atherosclerotic plaque stability and the severity of coronary artery disease.

Objective:To investigate whether there is another resistance mechanism besides mecA gene in oxacillin-resistant(OR) isolates of Staphylococcus aureus(S.aureus). Methods:There were 130 oxacillin-resistant phenotype isolates of S. aureus. Of these isolates 125 were resistant to more than 3 of 5 non-?-lactams (gentamicin, ciprofloxacin, clindamycin, tetracycline, erythromycin) (OR-R) and 5 susceptible to more than 3 of the 5 non-?-lactams (OR-S) and 14 were oxacillin-susceptible (OS) phenotype isolates of S. aureus and resistant to more than 3 of 5 non-?-lactams (OS-R). All the strains were detected by the two disks diffusion tests with oxacillin (OXA) and oxacillin/clavulanic acid (OXA/CA), by the three-dimensional extract tests of penicillin (PEN) and OXA for penicillinase and oxacillinase, and by PCR tests for mecA. Results:The 130 OR and 14 OS isolates were all oxacillinase-negative with the two disks diffusion tests, all pencillinase-positive and oxacillinase-negative in the three-dimensional extract tests. The mecA gene was detected in 125 OR-R-type and 2 of the 5 OR-S-type isolates, but was not detected in the other 3 OR-S-type nor in any of the 14 OS-R-type isolates by PCR. Conclusion:In a few Staphylococcus aureus strains which are phenotype of oxacillin-resistant and are susceptible to mostly non-?-lactam agents there are both mecA-negative and oxacillinase-negative strains, 2.3% (3/130) of the OXA-resistant strains. The resistance mechanism may be associated with reduced binding capacity of the modified Preexisting PBPs with OXA.

Objective To use phage display for generating surrogate peptides of candida albicans mycelial-phase protein as mimic antigen to develop an enzyme-linked immunosorbent assay (ELISA) assay for detection of candida albicans antibodies.Methods A monoclonal antibody against candida albicans mycelial-phase protein P47, was used in this study for selecting immunoreactive peptides, mimotopes, from a 12 mer phage library.The peptides were characterized immunologically and used for coating antigen in ELISA to detect antibodies against candida albicans in the patients' serum.Results The sensitivity, specificity and replication of the ELISA assay was good enough for clinical use. The antibody was positive in all of 10 samples of patients with confirmed systemic candida albicans infection and the results were same to those obtained with the purified mycelial-phase protein P47; The positive rates in patients receiving immunosuppressive drug cyclosporin A are 33% and the healthy 2% respectively.Conclusion The surrogate peptides from a 12 mer phage library can be used in ELISA for detecting the antibodies of candida albicans P47.