Ducks as a potential reservoir for Pasteurella multocida infection detected using a new rOmpH-based ELISA

Proteomics approaches: A review regarding an importance of proteome analyses in understanding the pathogens and diseases

Proteomics is playing an increasingly important role in identifying pathogens, emerging and re-emerging infectious agents, understanding pathogenesis, and diagnosis of diseases. Recently, more advanced and sophisticated proteomics technologies have transformed disease diagnostics and vaccines development. The detection of pathogens is made possible by more accurate and time-constrained technologies, resulting in an early diagnosis. More detailed and comprehensive information regarding the proteome of any noxious agent is made possible by combining mass spectrometry with various gel-based or short-gun proteomics approaches recently. MALDI-ToF has been proved quite useful in identifying and distinguishing bacterial pathogens. Other quantitative approaches are doing their best to investigate bacterial virulent factors, diagnostic markers and vaccine candidates. Proteomics is also helping in the identification of secreted proteins and their virulence-related functions. This review aims to highlight the role of cutting-edge proteomics approaches in better understanding the functional genomics of pathogens. This also underlines the limitations of proteomics in bacterial secretome research.

The immune response and protective efficacy of a potential DNA vaccine against virulent Pasteurella multocida

Background

Pasteurella multocida is the main cause of several infections of farm animals, and the immunity gained from commercial vaccines is for the short term only and needs to be routinely administered, so work on new vaccines against virulent P. multocida is crucial.

Results

In this study, the OmpH gene was amplified from ten P. multocida strains, and the PCR products were sequenced and analyzed. The results of RFLP analysis of OmpH gene digested by MspI enzyme showed that all of ten strains examined possessed one restriction site and two fragments, 350 and 650 bp. The OmpH sequence of strain No. 10 was cloned into bacterial expression vector pUCP24, and the recombinant pUCP24-OmpH was expressed in E. coli DH5α. Serum samples obtained from the ELISA test from a group of vaccinated rats indicate that the antibodies were present at high titer in immunized rats and can be tested as a vaccine candidate with a challenge.

Conclusions

In rats infected with the DNA vaccine and inactivated vaccine, a significant increase in serum antibody levels was observed. In addition, the DNA vaccine provided the vaccinated rats with partial protection; however, the protective efficacy was greater than that offered by the live attenuated vaccine. This successful recombinant vaccine is immunogenic and may potentially be used as a vaccine in the future.

Development of an in-house ELISA for detection of antibodies against Enterococcus cecorum in Pekin ducks

Enterococcus cecorum (EC) is known to cause skeletal lesions in broiler chickens and also systemic infections in Pekin ducks. Despite the importance of the pathogen, there is still a lack of serological diagnostic tools for the detection of EC infections. Here we describe the development of an in-house indirect enzyme-linked immunosorbent assay (ELISA) for the detection of EC-specific antibodies and its application by examination of 67 sera from experimentally infected Pekin ducks, 710 field samples from four Pekin duck breeder flocks previously vaccinated with inactivated vaccines, and 80 samples from commercial Pekin ducks coming from vaccinated parent flocks. All groups that had been experimentally inoculated via the air sac route were positive in the new ELISA, with significantly (P ≤ 0.05) increased mean sample/positive (S/P) ratios of 0.71-2.70 at days 7, 14 and 21 post-infection, while orally inoculated ducks and the EC-free control group remained negative with mean S/P ratios of 0.0-0.15. Antibodies were also detected in each of four vaccinated Pekin duck breeder flocks; 67.8% of the samples were antibody positive. The highest S/P ratios were found between 16 and 26 weeks (median S/P ratios from 0.15 to 1.03), but antibodies were still detected in some serum samples in weeks 61-67 post-hatch. No antibodies were detected in the commercial Pekin ducks. Antibody development in the ducks may be influenced by the composition of the inactivated vaccine. The new ELISA provides a useful tool for investigations of response to EC infections and vaccinations.

Pasteurellaceae members with similar morphological patterns associated with respiratory manifestations in ducks

Aim:

A total of 112 freshly dead ducks aged from 2 to 20 weeks old with a history of respiratory manifestations were investigated for the implication of Pasteurellaceae family members.

Materials and Methods:

Isolation and identification to the family level were conducted by conventional bacteriological methods, including microscopic examination and biochemical characterization. Identification to the species level was conducted by polymerase chain reaction (PCR) and analytical profile index (API) 20E kits.

Results:

Conventional bacteriological isolation and biochemical characterization revealed the infection of 16/112 examined birds with a prevalence rate of 14.3%. PCR confirmed the detection of Pasteurellaceae family conserved genes RpoB and Bootz in 16/16 (100%) isolates. PCR was also used for genus and species identification of the isolated Pasteurellaceae members; the results revealed that 5/16 (31.3%) of isolates were Gallibacterium anatis and 2/16 of isolates (12.5%) were Pasteurella multocida. Riemerella anatipestifer, Mannheimia haemolytica, and Avibacterium paragallinarum were not detected by PCR. Biotyping by API 20E successfully identified 5/16 (31.3%) isolates that could not be typed by PCR and confirmed their belonging to Pasteurella pneumotropica. Neither the available PCR primer sets nor API 20E succeeded for species identification of 4/16 (25%) isolates. Antibiotic susceptibility profiling of isolates revealed that 16/16 (100%) of isolates demonstrated multidrug resistance (MDR) phenotypes. Moreover, 16/16 (100%) of isolates demonstrated a phenotypic resistance pattern to neomycin.

Conclusion:

Combined genotypic, phenotypic, biotyping, and virulence characterizations are required for laboratory identification of pathogenic Pasteurellaceae. Moreover, P. multocida was not the prevailed member implicated in respiratory problems in ducks as P. pneumotropica, G. anatis, and unidentified strains were involved with higher prevalence. Chloramphenicol and ampicillin demonstrated the highest in vitro effects on the studied Pasteurellaceae. Furthermore, the prevalence of multidrug-resistant isolates signified the demand to implement targeted surveillance in the ducks’ production sector, and MDR survey in poultry sectors in Egypt to apply effective control measures.