Down-regulation of Hsp90 could change cell cycle distribution and increase drug sensitivity of tumor cells

:AIM To construct Hsp90 antisense RNAeukaryotic expression vector, transfect it intoSGC7901 and SGC7901/VCR of MDR-type humangastric cancer cell lines, HCC7402 of humanhepatic cancer and Eel09 of human esophagealcancer cell lines, and to study the cell cycledistribution of the gene transected cells andtheir response to chemotherapeutic drugs.METHODS A I .03kb cDNA sequence of Hsp90Pwas obtained from the primary plasmid phHsp90by EcoR 1 and BamH I nuclease digestion andwas cloned to the EcoR 1 and BamH 1 site ofthe pcDNA by T4DNA ligase and an antisenseorientation of Hsp900 expression vector wasconstructed. The constructs were transfectedwith lipofectamine and positive clones wereselected with G418. The expression of RNA wasdetermined with dot blotting and RNaseprotection assay, and the expression of Hsp90protein determined with Western blot. Cell cycledistribution of the transfectants was analyzedwith flow cytometry, and the drug sensitivity ofthe transfectants to adriamycin (ADR ),vincrinstine (VCR ), mitomycin (MMC ) andcyclophosphamide (CTX ) with MTT andintracellular drug concentration of thetransfectants was determined with flowcytometry.RESULTS In EcoR 1 and BamH I restrictionanalysis, the size and the direction of the clonedsequence of Hsp900 remained what had beendesigned and the gene constructs were namedpcDNA-Hsp90. AH^SGC7901, AH^SGC7901/ VCR,AH-HCC7402 and AH-Eel09 cell clones allexpressed Hsp90 anti--sense RNA. Theexpression of Hsp90 was down--regulated in AHSGC7901, AH--SGC7901/ VCR, AH-HCC7402 andAH--Eel09 cell clones. Cell cycle distribution waschanged differently. In AH-SGC7901/ VCR andAH-Ec109 cells, G, phase cells were increased; Sphase and G, phase cells were decreased ascompared with their parental cell lines. In AHSGC7901 cell, G, phase cells were decreased, Qphase cells increased and S phase cells were notchanged, and in AH-HCC7402 cells G,, S and qphase cells remained unchanged as comparedwith their parental cell lines. The sensitivity ofAH--SGC7901, AH--SGC7901/ VCR, AH-HCC7402 andAH-Ec109 to chemotherapeutic drugs, thesensitivity ot AH--SGC7901/ VCR to ADR, VCR,MMC and CTX the sensitivity of AH-HCC7402 toADR and VCR, and the sensitivity of Eel09 toADR, VCR and CTX all increased as comparedwith their parental cell lines. The meanfluorescence intensity of ADR in AH--SGC7901,AH-SGC7901/ VCR, AH--HCC7402 and AH-Ec109was also significantly elevated (P< 0. 05).CONCLUSION Down-regulation of HsP90 couldchange cell cycle distribution and increase thedrug sensitivity of tumor cells.

Effect of Survivin-siRNA on Drug Sensitivity of Osteosarcoma Cell Line MG-63

Objective： Survivin is one of the apoptosis inhibitor genes and is rarely expressed in adult tissues. However, survivin expression has been detected in various human cancers and correlations have been recognized between the level of expression of this gene in tumors and prognosis. In this study, we investigated the effect of Survivin-siRNA on the drug sensitivity of osteosarcoma cell line MG-63. Methods： Two siRNAs （Survivin-siRNA1, Survivin-siRNA2） specifically targeting Survivin gene were chemically synthesized and transfected into MG-63 ceils. The Survivin mRNA level was detected by reverse transcription-polymerase chain reaction （RT-PCR）. The survivin protein expression and cell apoptosis rate were analyzed by flow cytometry （FCM）. The 50% inhibition concentration （IC50） of cisplatin （DDP） and adriamycin （ADM） on MG-63 cells was determined by MTT method. Results： Two short siRNA targeting survivin down-regulated the transcription of survivin gene dramatically and elevated apoptosis rate. They increased the drug sensitivity of MG-63 cells to ADM by five-fold and to DDP by nine-fold. Conclusion： Validated Survivin specific siRNA can effectively inhibit Survivin expression in survivin-overexpressing osteosarcoma MG-63 cell line and enhance the drug sensitivity of MG-63 cell line to ADM and DDP. Short survivin-siRNA mediated gene silencing may be a useful therapeutic strategy for osteosarcoma. These results suggest that survivin might be helpful for diagnosis of osteosarcoma and survivin siRNA combined with adriamycin or cisplatin may be a feasible strategy to enhance the effects of chemotherapy in patients with osteosarcoma.

Isolation and Identification of Pseudomonas solanacearum and Its Drug Sensitivity Test

Ten pathogenic strains were isolated fi-om gingers infected by blast, and were identified by substrate utilization test and biochemical test. The identifica- tion results showed that these ten strains accorded with the basic characteristics of Pseudomonas solanacearum. Drug sensitivity test of ten strains was carried out, and prevention agents were screened to provide an experimental basis for the control of ginger blast.

Drug Sensitivity Test and Regression Verification of Escherichia coli from Rex Rabbit

[ Objectives] The paper aimed to select drugs reasonably for treatment of rex rabbit colibacillosis, and to isolate the pathogenicity of Escherichia coll. [ Methods ] Pathogen isolation, drug sensitivity test and pathogen regression test were performed with rex rabbits killed by E. coli in clinic. [ Results] The isolate was E. coli 0-23, susceptible to amikacin and cefotaxime sodium; when the challenge dose was 1.0 mL/rabbit （about one billion E. coli）, the test animal would discharge mucous feces. [ Conclusions] The results provided model support for clinical medicine selection against rex rabbit colibacillosis.

Isolation, Identification and Drug Sensitivity Test of a Pathogenic Escherichia coli Strain from Minks with Diarrhea

[Objectives] The study aimed to identify the pathogen that causes diarrhea in minks. [Methods] Liver tissues were aseptically collected from dead minks with diarrhea. By bacterial isolation and culture,morphological observation,biochemical test and pathogenicity test,the isolated strain was identified as pathogenic E. coli. [Results]The pathogen causing diarrhea in minks was confirmed as a pathogenic E. coli strain. Drug sensitivity test indicated that the isolated pathogenic E. coli strain was highly sensitive to ceftazidime,cefotaxime,enrofloxacin,florfenicol and cephradine,moderately sensitive to ampicillin,ciprofloxacin,amikacin,doxycycline,lincomycin and gentamycin,and resistant to amoxycillin,neomycin,spectinomycin,polymyxin and penicillin. [Conclusions] This study provided reference for the prevention and control of abortion in female minks in Qinhuangdao region.

Effect of all-trans retinoic acid on drug sensitivity and expression of survivin in LoVo cells

Background All-trans retinoic acid （ATRA） can influence the tumor cell proliferation cycle, and some chemotherapeutic drugs are cycle specific. In this study, we hypothesize that ATRA can enhance chemotherapeutic drug sensitivity by affecting the cell cycle of tumor cells.Methods The cell cycle of LoVo cells was evaluated using flow cytometry （FCM）. Cell viability was analyzed using the MTT assay. The morphologic changes in the treated LoVo cells were measured with acridine orange （AO）/ethidium bromide （EB） staining. Expression of survivin in LoVo cells was analyzed by immunofluorescence assay.Results After LoVo cells were treated with ATRA, the G0/G1 ratio of the tumor cells increased and the cell ratio of S-and G2/M-phase decreased. Viability of the cells decreased significantly after combined treatment with ATRA and 5-fluorouracil （5-FU） or mitomycin c （MMC） and was evaluated by fluorescence microscopy. Expression level of survivin in the tumor cells decreased after ATRA combination treatment.Conclusions ATRA enhances drug sensitivity of the LoVo cell line to cell cycle-specific agents and inhibits the expression of survivin in LoVo cells. The combination of ATRA and 5-FU or MMC promoted cell apoptosis, and the mechanism involved in apoptosis may be related to inhibition of survivin gene expression.

Establishment and drug sensitivity evaluation of murine ascites hepatocarcinoma cell line with high lymphatic metastatic potential (Hca-P/L_(6))

In order to provide a sensitive cell line model for investigating the mechanisms underlying the lymphatic metastasis of tumors and the effect of medicine against cells,a new murine ascites hepatocarcinoma cell line with high lymphatic metastatic potential(Hca-P/L_(6))was established and the effect of curcumin on biological behavior of Hca-P/L_(6) was observed.Murine ascites hepatocarcinoma cell strain with low lymphatic metastatic potential(Hca-P)was subcutaneously inoculated into the medioventral line of a mouse 615 and thefirst generation of metastatic tumor cells of inguinal lymph node(Hca-P/L_(1))was obtained.Then,Hca-P/L_(1) was screened by the route of mouse foot pad subcutaneously!lymph node!scale-up culture in vitro!mouse foot pad subcuta-neously forfive times consecutively.The sensitivity of two murine ascites hepatocarcinoma cell lines(Hca-P and Hca-P/L_(6))and two anchorage-dependent human hepato-carcinoma cell lines(SMC7721 and HepG_(2))to curcumin were studied by use of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)assay after these cells had been pretreated by curcumin at the concentration of 15–240μmol/L for 48 h.After pretreatment by curcumin at the maximum non-cytotoxic dose of 15μmol/L in vitro,the effect of curcumin against cell proliferation of Hca-P and Hca-P/L6 was observed by inverted micro-scope,cell growth curve and cell population doubling time;the effects of curcumin on cell cycles of Hca-P/L6 and Hca-P were studied byflow cytometry(FCM).The results showed Hca-P/L_(6) spreading to the lymph nodes at multiple sites in mice was screened from Hca-P.The lymph node metastatic rate was 100%.Curcumin had significant growth inhibiting effect on both murine ascites and human hepatocarcinoma cell lines in a dose-dependent manner(P<0.05).At concentrations of 30–120μmol/L,curcu-min had more inhibition on murine ascites hepatocarci-noma cell lines than on human anchorage-dependent hepatocarcinoma cell lines.At concentrations of 60–240μmol/L,curcumin had more inhibition on Hca-P/L_(6) with the 50%inhibitory concentration(IC50)of 51.48μmol/L than on Hca-P with IC50 of 90.87μmol/L.After pretreatment by curcumin at the maximum non-cytotoxic dose of 15 mol/L for 7 days,the proliferations of Hca-P/L_(6) and Hca-P were inhibited(P<0.05)in a time-dependent manner(P<0.01)and the population doubling time of Hca-P/L6 and Hca-P was prolonged(P<0.01),and curcumin had more inhibition on Hca-P/L6 than on Hca-P(P<0.05).After pretreatment by 15μmol/L curcumin for 48 h,the morphous of Hca-P/L_(6) was influenced more seriously than that of Hca-P and the cell cycle was redistributed with Hca-P/L6 being blocked in the S phase and Hca-P in the S and G_(2)/M phases.Hca-P/L_(6) was validated to be more sensitive to curcumin than Hca-P.Hca-P/L_(6) is a novel sensitive cell line model for investigating the mechanisms underlying tumor lymphatic metastasis and the effect of the medicine against cells.

In vitro cultures of circulating tumor cells:a potential tool to unravel drug sensitivity

Since taking part as leading actors in driving the metastatic process,circulating tumor cells(CTCs)have displayed a wide range of potential applications in the cancer-related research field.Besides their well-proved prognostic value,the role of CTCs in both predictive and diagnostics terms might be extremely informative about cancer properties and therefore highly helpful in the clinical decision-making process.Unfortunately,CTCs are scarcely released in the blood circulation and their counts vary a lot among different types of cancer,therefore CTC detection and consequent characterization are still highly challenging.In this context,in vitro CTC cultures could potentially offer a great opportunity to expand the number of tumor cells isolated at different stages of the disease and thus simplify the analysis of their biological and molecular features,allowing a deeper comprehension of the nature of neoplastic diseases.The aim of this review is to highlight the main attempts to establish in vitro CTC cultures from patients harboring different tumor types in order to highlight how powerful this practice could be,especially in optimizing the therapeutic strategies available in clinical practice and potentially preventing or contrasting the development of treatment resistance.

Clinical Distribution and Drug Resistance of Acinetobacter baumannii in a Hospital from 2019 to 2021

Objective:To analyze the clinical distribution and drug resistance of Acinetobacter baumannii(AB)and provide reference for the treatment of AB infection.Methods:AB isolated from clinical specimens of Huaihua First People’s Hospital from 2019 to 2021 were collected and identified by VITEK 2 Compact,an automated microbial identification and susceptibility testing system,in which drug sensitivity test was also performed.Excel was used for statistical analysis.Results:Among the 1,311 AB strains,81.16%(1,064 strains)were from sputum samples,and the departments with the highest detections rates of AB were neurosurgery(24.33%),intensive care(15.48%)and infectious disease(11.44%).The drug sensitivity test showed that the resistance rate of 1,311 AB strains to compound sulfamethoxazole and amikacin was 28.38%and 20.54%,respectively,and the resistance rate to 10 other kinds of common antibiotics was more than 40%.Conclusion:The 1,311 AB strains isolated were widely distributed in clinical settings and had strong resistance to commonly used antibiotics.Therefore,it is necessary to strengthen the monitoring of pathogens and drug resistance,formulate reasonable and effective infection control measures,and ensure that antibiotics are used in a reasonable manner.

Predicting colorectal cancer prognosis based on long noncoding RNAs of disulfidptosis genes

BACKGROUND A recently hypothesized cause of cell death called disulfidptosis has been linked to the expansion,emigration,and vascular rebuilding of cancer cells.Cancer can be treated by targeting the pathways that trigger cell death.AIM To discover the long non-coding RNA of the disulfidaptosis-related lncRNAs(DRLs),prognosis clinical survival,and treat patients with colorectal cancer with medications.METHODS Initially,we queried the Cancer Genome Atlas database to collect transcriptome,clinical,and genetic mutation data for colorectal cancer(CRC).Training and testing sets for CRC patient transcriptome data were generated randomly.Key long non-coding RNAs(lncRNAs)related to DRLs were then identified and evaluated using a least absolute shrinkage and selection operator procedure,as well as univariate and multivariate Cox regression models.A prognostic model was then created after risk scoring.Also,Immune infiltration analysis,immune checkpoint analysis,and medication susceptibility analysis were used to investigate the causes of the different prognoses between high and low risk groups.Finally,we validated the differential expression and biomarker potential of riskpredictive lncRNAs through induction using both NCM460 and HT-29 cell lines,as well as a disulfidptosis model.RESULTS In this work,eight significant lncRNAs linked to disulfidptosis were found.Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses of differentially expressed genes between high-and low-risk groups from the prognostic model showed a close relationship with the immune response as well as significant enrichment in neutrophil extracellular trap formation and the IL-17 signaling pathway.Furthermore,significant immune cell variations between the high-risk and low-risk groups were seen,as well as a higher incidence of immunological escape risk in the high-risk group.Finally,Epirubicin,bortezomib,teniposide,and BMS-754807 were shown to have the lowest sensitivity among the four immunotherapy drugs.CONCLUSION Our findings emphasizes the role of disulfidptosis in regulating tumor development,therapeutic response,and patient survival in CRC patients.For the clinical treatment of CRC,these important LncRNAs could serve as viable therapeutic targets.

Leveraging diverse cell-death patterns to predict the clinical outcome of immune checkpoint therapy in lung adenocarcinoma:Based on muti-omics analysis and vitro assay

Advanced LUAD shows limited response to treatment including immune therapy.With the development of sequencing omics,it is urgent to combine high-throughput multi-omics data to identify new immune checkpoint therapeutic response markers.Using GSE72094(n=386)and GSE31210(n=226)gene expression profile data in the GEO database,we identified genes associated with lung adenocarcinoma(LUAD)death using tools such as“edgeR”and“maftools”and visualized the characteristics of these genes using the“circlize”R package.We constructed a prognostic model based on death-related genes and optimized the model using LASSO-Cox regression methods.By calculating the cell death index(CDI)of each individual,we divided LUAD patients into high and low CDI groups and examined the relationship between CDI and overall survival time by principal component analysis(PCA)and Kaplan-Meier analysis.We also used the“ConsensusClusterPlus”tool for unsupervised clustering of LUAD subtypes based on model genes.In addition,we collected data on the expression of immunomodulatory genes and model genes for each cohort and performed tumor microenvironment analyses.We also used the TIDE algorithm to predict immunotherapy responses in the CDI cohort.Finally,we studied the effect of PRKCD on the proliferation and migration of LUAD cells through cell culture experiments.The study utilized the TCGA-LUAD cohort(n=493)and identified 2,901 genes that are differentially expressed in patients with LUAD.Through KEGG and GO enrichment analysis,these genes were found to be involved in a wide range of biological pathways.The study also used univariate Cox regression models and LASSO regression analyses to identify 17 candidate genes that were best associated with mortality prognostic risk scores.By comparing the overall survival(OS)outcomes of patients with different CDI values,it was found that increased CDI levels were significantly associated with lower OS rates.In addition,the study used unsupervised cluster analysis to divide 115 LUAD patients into two distinct clusters with significant differences in OS timing.Finally,a prognostic indicator called CDI was established and its feasibility as an independent prognostic indicator was evaluated by Cox proportional risk regression analysis.The immunotherapy efficacy was more sensitive in the group with high expression of programmed cell death models.Relationship between programmed cell death(PCD)signature models and drug reactivity.After evaluating the median inhibitory concentration(IC50)of various drugs in LUAD samples,statistically significant differences in IC50 values were found in cohorts with high and low CDI status.Specifically,Gefitinib and Lapatinib had higher IC50 values in the high-CDI cohort,while Olaparib,Oxaliplatin,SB216763,and Axitinib had lower values.These results suggest that individuals with high CDI levels are sensitive to tyrosine kinase inhibitors and may be resistant to conventional chemotherapy.Therefore,this study constructed a gene model that can evaluate patient immunotherapy by using programmed cell death-related genes based on muti-omics.The CDI index composed of these programmed cell death-related genes reveals the heterogeneity of lung adenocarcinoma tumors and serves as a prognostic indicator for patients.

Identification of cell surface markers for acute myeloid leukemia prognosis based on multi-model analysis

Given the extremely high inter-patient heterogeneity of acute myeloid leukemia(AML),the identification of biomarkers for prognostic assessment and therapeutic guidance is critical.Cell surface markers(CSMs)have been shown to play an important role in AML leukemogenesis and progression.In the current study,we evaluated the prognostic potential of all human CSMs in 130 AML patients from The Cancer Genome Atlas(TCGA)based on differential gene expression analysis and univariable Cox proportional hazards regression analysis.By using multi-model analysis,including Adaptive LASSO regression,LASSO regression,and Elastic Net,we constructed a 9-CSMs prognostic model for risk stratification of the AML patients.The predictive value of the 9-CSMs risk score was further validated at the transcriptome and proteome levels.Multivariable Cox regression analysis showed that the risk score was an independent prognostic factor for the AML patients.The AML patients with high 9-CSMs risk scores had a shorter overall and event-free survival time than those with low scores.Notably,single-cell RNA-sequencing analysis indicated that patients with high 9-CSMs risk scores exhibited chemotherapy resistance.Furthermore,PI3K inhibitors were identified as potential treatments for these high-risk patients.In conclusion,we constructed a 9-CSMs prognostic model that served as an independent prognostic factor for the survival of AML patients and held the potential for guiding drug therapy.

CRISPR accelerates the cancer drug discovery

Emerging cohorts and basic studies have associated certain genetic modifications in cancer patients,such as gene mutation,amplification,or deletion,with the overall survival prognosis,underscoring patients’genetic background may directly regulate drug sensitivity/resistance during chemotherapies.Understanding the molecular mechanism underpinning drug sensitivity/resistance and further uncovering the effective drugs have been the major ambition in the cancer drug discovery.The emergence and popularity of CRISPR/Cas9 technology have reformed the entire life science research,providing a precise and simplified genome editing tool with unlimited editing possibilities.Furthermore,it presents a powerful tool in cancer drug discovery,which hopefully facilitates us with a rapid and reliable manner in developing novel therapies and understanding the molecular mechanisms of drug sensitivity/resistance.Herein,we summarized the application of CRISPR/Cas9 in drug screening,with the focus on CRISPR/Cas9 mediated gene knockout,gene knock-in,as well as transcriptional modification.Additionally,this review provides the concerns,cautions,and ethnic considerations that need to be taken when applying CRISPR in the drug discovery.

Monitoring and Analysis on Multi Drug Resistance of Escherichia coli from Captive Population Amur Tiger

In order to investigate the multi drug resistance to Escherichia coli from captive population Amur tiger,E. coli strains were isolated from the fecal samples of tiger in Heilongjiang Amur Tiger Park in Harbin. The sensitivity of E. coli isolates to 14 antibiotics was determined by scrip diffusion method. The results indicated that all the isolates varied in drug resistance to different antibiotics; the isolates gave high resistance to ampicillin,with a drug fast rate of 100%; over80% of the isolates were resistant to tetracycline and Paediatric Compound Sulfamethoxazole Tablets(SMZ- TMP),and over 70% of the isolates were sensitive to aztreonam,amoxicillin /potassium clavulanate. Most of the isolates had high sensitive to aztreonam and amoxicillin / clavulanate acid.

Isolation,Identification and Drug Tolerance Analysis of Pathogenic Staphylococcus aureus from Broilers

White feather broilers in some broiler farm in Chengde area developed arthritis and died acutely. In order to identify the pathogen inducing the disease and death of the white feather broilers, samples such as livers and joint pus were collected from dead broilers under sterile condition, and one pathogenic strain was isolated. The isolate was identified to be Staphylococcus aureus through isolated culture, morphologic observation, inspection of biochemical property and animal test. The drug sensitivity test showed that the isolate was sensitive to ceftazidime, enrofloxacin, ceftriaxone, lincomycin and amikacin, but resistant to other drugs to different degrees.

Apolipoprotein C1 promotes tumor progression in gastric cancer

Background:Gastric cancer(GC)is a malignancy with the worst prognosis that seriously threatens human health,especially in East Asia.Apolipoprotein C1(apoc1)belongs to the apolipoprotein family.In addition,apoc1 has been associated with various tumors.However,its role in GC remains unclear.Methods:Firstly,we quantified its expression in GC and adjacent tumor tissues,using The Cancer Genome Atlas(TCGA).Next,we assessed cell invasion and migration abilities.Finally,we revealed the role of apoc1 in the tumor microenvironment(TME),immune cell infiltration and drug sensitivity.Results:Firstly,in TCGA database,it has been shown that elevated expression of apoc1 was identified in various cancers,including GC,then we found that high expression of apoc1 was significantly correlated with poor prognosis in GC.Histologically,apoc1 expression is proportional to grade,cancer stage,and T stage.The experimental results showed that apoc1 promoted cell invasion and migration.Then GO,KEGG,and GSEA pathway analyses indicated that apoc1 may be involved in the WNT pathway and immune regulation.Furthermore,we found out the tumor-infiltrating immune cells related to apoc1 in the tumor microenvironment(TME)using TIMER.Finally,we investigated the correlation between apoc1 expression and drug sensitivity,PD-1 and CTLA-4 therapy.Conclusions:These results suggest that apoc1 participates in the evolution of GC,and may represent a potential target for detection and immunotherapy in GC.

Prognostic model and treatment plan analysis of hepatocellular carcinoma based on genes related to glutamine metabolism

Objective:To identify the prognosis of hepatocellular carcinoma(HCC)and the effect of anti-cancer drug therapy by screening glutamine metabolism-related signature genes because glutamine metabolism plays an important role in tumor development.Methods:We obtained gene expression samples of normal liver tissue and hepatocellular carcinoma from the TCGA database and GEO database,screened for differentially expressed glutamine metabolismrelated genes(GMRGs),constructed a prognostic model by lasso regression and step cox analysis,and assessed the differences in drug sensitivity between high-and low-risk groups.Results:We screened 23 differentially expressed GMRGs by differential analysis,and correlation loop plots and PPI protein interaction networks indicated that these differential genes were strongly correlated.The four most characterized genes(CAD,PPAT,PYCR3,and SLC7A11)were obtained by lasso regression and step cox,and a risk model was constructed and confirmed to have reliable predictive power in the TCGA dataset and GEO dataset.Finally,immunotherapy is better in the high-risk group than in the low-risk group,and chemotherapy and targeted drug therapy are better in the low-risk group than in the high-risk group.Conclusion:In conclusion,we have developed a reliable prognostic risk model characterized by glutamine metabolism-related genes,which may provide a viable basis for the prognosis and Treatment options of HCC patients.

Isolation and Identification of a Pathogenic E.coli Strain Causing Diarrhea in Foxes

[Objectives] The study aimed to identify the pathogenic E. coli strain that caused diarrhea in foxes and to analyze its drug sensitivity.[Methods] A pathogenic E. coli strain was isolated from dead foxes with diarrhea. By conventional bacterial isolation and culture, morphological observation, pathogenicity test and K-B disc method, the isolated strain was identified as pathogenic E. coli .[Results] The isolated pathogen was highly sensitive to ceftriaxone, cefotaxime, ciprofloxacin and lincomycin, moderately sensitive to enrofloxacin, neomycin, gentamycin, spectinomycin, florfenicol, amikacin and polymyxin, and resistant to ampicillin, amoxicillin and doxycycline.[Conclusions] This study provided reference for the prevention and control of diarrheal diseases in foxes in Qinhuangdao region.

Isolation and Characterization of E. Coli O157 : H7 from Infected Newborn Calves in Northeast China

Escherichia coli O157 : H7 is a foodborne pathogen that poses a major threat to public health. Epidemiologic investigations have identified dairy cows, especially calves, are the principal reservoir of E. coli O157 : H7. In this study, based on the results, E. coli O157 : H7 was the main cause of E. coli disease outbreak in late October, 2015, and more than 90% of newborn calves died of serious diarrhea. Through further experiments, the drug sensitivity and resistance of the strain, the expression of the virulence gene and virulence pathogenicity were studied. E. coli O157 : H7 isolates were resistant to 12 antibiotics including penicillin, tetracycline and ampicillin, and were sensitive to eight antibiotics including cefoperazone, ceftazidime and amikacin. Resistance genes included tetB, strB, aadB, aphA, floR, TEM and virulence genes included stx1, eaeA and hlyA. Using specific pathogen free mice, the result showed that the isolate was pathogenic with a median lethal dose of 7.9×107 CFU · mL-1. This study described the pathogenesis and clinical manifestations of E. coli O157 : H7 infection. These results guided the use of antibiotics in prevent and control of bacterial infections in the future.

Isolation and Identification of Aeromonas allosaccharophila from Procambarus clarkii

In order to provide a scientific basis for the control of Aeromonas allosaccharophila from Procambarus clarkii , a dominant strain was isolated from moribund P. clarkii in some farm in Hubei Province, and designated X1. It was preliminarily identified to be A. allosaccharophila through physiological-biochemical test. Further sequence analysis showed that 16S rDNA of this bacterium shared 90% identity with 16S rDNA of A. allosaccharophila , suggesting that it is A. allosaccharophila . Drug sensitivity test showed that isolate X1 was sensitive to doxycycline, cefotaxime, norfloxacin and gentamicin. In animal regression test, the bacterium the same as that from naturally-diseased P. clarkii could be isolated, with the same disease symptoms as well.