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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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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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-biofilm producers isolates (OD ≤ 0.7). E. coli ATCC 25922 and Pseudomonas aeruginosa strains were used as positive controls and E. coli DH5α as a negative control. Hypermucoviscosity (HMV) test The string test was

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