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Abstract  

Microcalorimetry was applied to study the toxic action of two cobalt compounds such as bis(salicylideniminato-3-propyl)methylaminocobalt(II) (denoted as Co(II)) and Co(III) sepulchrate trichloride (denoted as Co(sep)3+) on (E. coli) DH5α. The power-time curves of the E. coli DH5α growth were determined, and the thermokinetics parameters such as the growth rate constant k, the maximum power output P m and the time (t m) corresponding to the P m were obtained. The half-inhibitory concentrations (IC50) of Co(II) and Co(sep)3+ to E. coli DH5α were 15 and 42.1 mg mL−1, respectively. The experimental results revealed that the toxicity of the Co(II) compound was larger than that of Co(sep)3+. On the other hand, the scanning electron microscopy (SEM) demonstrated that the two cobalt compounds had the same toxic mechanism on E. coli DH5α, which was attributed to the damage of cell wall of the bacteria caused by both Co(II) and Co(sep)3+. Furthermore, accumulation of intracellular cobalt of E. coli DH5α, due to the interaction of Co(II) or Co(sep)3+ and E. coli DH5α, has been found by using inductively coupled plasma (ICP) analytical technique.

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Abstract  

The effects of Amoxicillin Sodium and Cefuroxime Sodium on the growth of E. coli DH5α were investigated by microcalorimetry. The metabolic power-time curves of E. coli DH5α growth were determined by using a TAM air isothermal microcalorimeter at 37�C. By evaluation of the obtained parameters, such as growth rate constants (k), inhibitory ratio (I), the maximum heat power (P m) and the time of the maximum heat power (t m), one found that the inhibitory activity of Amoxicillin Sodium vs. E. coli DH5α is enhanced with the increasing of the Amoxicillin Sodium concentration, and the Cefuroxime Sodium has a stimulatory effect on the E. coli DH5α growth when the concentration is about 1 μg mL−1. The IC50 for the Amoxicillin Sodium and the Cefuroxime Sodium are 1.6 and 2.0 μg mL−1, respectively, it implicates that the E. coli DH5α is more sensitive to Amoxicillin Sodium than Cefuroxime Sodium.

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Abstract  

A microcalorimetric technique based on the bacterial heat output was applied to evaluate the influence of antibiotics PIP (Piperacillin Sodium) and composite preparation of PIP and SBT (Sulbactam Sodium) on the growth of E. coli DH5α. The power–time curves of the growth metabolism of E. coli DH5α were studied using a TAM Air Isothermal Microcalorimeter at 37C. By analyzing the power–time curves, the parameters such as growth rate constants (k), inhibitory ratio (I), the maximum heat power (P m) and the time of the maximum heat power (t m) were obtained. The results show that different concentrations of antibiotics affect the growth metabolism of E. coli DH5α. The PIP in the concentration range of 0–0.05 g mL–1 has a stimulatory effect on the E. coli DH5α growth, while the PIP of higher concentrations (0.05 –0.25 g mL–1) can inhibit its growth. It seems that the composite preparation composed of PIP and SBT cannot improve the inhibitory effect on E. coli DH5α as compared with the PIP.

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Pasteurella multocida B:2 is responsible for haemorrhagic septicaemia in cattle and buffaloes, causing severe economic losses in the developing countries. In the present study, the ahpA gene of P. multocida B:2 (P52) was cloned, sequenced and compared with the previously reported ahpA gene sequence in P. multocida A:1, which is responsible for its haemolytic phenotype. E. coli DH5α cells were further transformed with recombinant plasmid carrying the ahpA gene from P. multocida B:2 (P52) but SDS-PAGE analysis failed to show the expression of haemolysin protein. Slight haemolysis was albeit observed in horse blood agar plates streaked with recombinant E. coli carrying the ahpA gene. Our study indicates that there is 99.6% similarity and 0.4% divergence between ahpA gene of P. multocida B:2 (P52) and P. multocida A:1, while membrane topology analysis has predicted that ahpA is an inner membrane protein with two strong hydrophobic regions at the N and C terminals. The presence of significant homology in ahpA sequence in A:1 and B:2 perhaps suggests a common mechanism of pathogenesis in different species of animals.

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Plasmid content was investigated in hundred copiotrophic Gram-negative river water isolates that exhibited resistance to four or more antibiotics. A total of seventy-seven isolates were found to carry plasmids of varying sizes. These isolates were primarily grouped as Pseudomonads and members of Enterobacteriaceae on the basis of physiological and biochemical tests. Fifty-six isolates that were rifampicin-sensitive and belonged to Enterobacteriaceae family were chosen as donors for the conjugal transfer assay. Eighteen of the isolates successfully transferred conjugable plasmids to the E. coli DH5 α recipient. Countable multiple antibiotic resistant transconjugants arose readily and conjugal transfer frequency was in the range of 3.75 × 10 −6 to 1.0 × 10 −1 . The most common carriage of resistances conferred by transmissible R plasmids was against ampicillin, cefotaxim and cephalexin. The residence of class 1 integrons on conjugative R plasmids was confirmed in only six transconjugants. Gene cassettes borne on the integrons were identified to be dihydrofolate reductases (dhfrs) . The major concern of this study was about the copiotrophs containing self-transmissible R plasmids which may be potential reservoirs of antibiotic-resistance genes and instrumental in dissemination of the same in the environment.

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The immunogenicity of a DNA vaccine expressing the surface protein NcSRS2 of Neospora caninum was studied in BALB/c mice. The NcSRS2-encoding DNA was obtained by PCR amplification of the NcSRS2 ORF gene from the p43 plasmid encoding the N. caninum surface protein NcSRS2, ligated to the mammalian expression vector pcDNA3.1/Zeo(+) and propagated in E. coli DH5α to produce the N. caninum NcSRS2 DNA vaccine. BALB/c mice were immunised by two intramuscular injections of the DNA vaccine with or without complete Freund’s adjuvant (CFA). Serum antibody titres and nitric oxide (NO) concentrations, and splenocyte proliferation and cytokine expression were measured after immunisation. The DNA vaccine induced T-cell-mediated immunity as shown by significantly increased NO concentrations, cytokine gene (IL-2 and IFN-γ) expression, and NcSRS2 protein-stimulated lymphocyte proliferation in mice immunised with the DNA vaccine. The vaccine also induced weak humoral immunity. The immunogenicity of the DNA vaccine was slightly enhanced by CFA. The immune response was specific to NcSRS2. No immune response was observed in mice immunised with the pcDNA3.1/Zeo(+) vector alone.

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Abstract  

Microcalorimetry was applied to study the effect of cephalosporins (cefazolin sodium and cefonicid sodium) on the E. coli growth. The microbial activity was recorded as power-time curves through an ampoule method with a TAM Air Isothermal Microcalorimeter at 37°C. The parameters such as the growth rate constant (k), inhibitory ratio (I), the maximum power output (Pm) and the time corresponding to the maximum power output (tm) were calculated. The change tendencies of k, with the increasing of concentration (C) of the two cephalosporins, are similar which show that cefazolin sodium and cefonicid sodium have the same inhibitory mechanism. The experimental results reveal that cefonicid sodium has a stronger antibacterial activity towards E. coli than that of cefazolin sodium and this was coincide with the clinical manifestations.

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column (QIAGEN, Courtaboeuf, France), cloned into the pET100/D-TOPO vector, and transformed into E. coli DH5α (Invitrogen Life Technologies, Saint Aubin, France). The transformant cells harboring plasmid vectors were selected on Mueller–Hinton (MH) agar

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. coli V517 [ 15 ] and E. coli 39R861 [ 16 ] as molecular mass standards. A Na-azide-resistant derivative of E. coli J53 (J53 RAZ ) was used as recipient in conjugation. Competent cells of E. coli J53 RAZ or of E. coli DH5α were used in

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introduced into E. coli DH5α; later, the clones were verified using Sanger sequencing (BGI, Denmark, Europe). Next, erp, hspR, mmaA4 , and ompA genes were cloned in Bam HI site, and lppX gene was cloned in Eco RI site of pET-28a(+) (Novagen, Germany

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