Host Defense Peptides (HDPs) are small cationic peptides found in several organisms. They play a vital role in innate immunity response and immunomodulatory stimulation. This investigation was designed to study the antimicrobial activities of β-defensin peptide-4 (sAvBD-4) and 10 (sAvBD-4) derived from chickens against pathogenic organisms including bacteria and fungi. Ten bacterial strains and three fungal species were used in investigation. The results showed that the sAvBD-10 displayed a higher bactericidal potency against all the tested bacterial strains than that of sAvBD-4. The exhibited bactericidal activity was significant against almost the different bacterial strains at different peptide concentrations except for that of P. aeruginosa and Str. bovis strains where a moderate effect was noted. Both peptides were effective in the inactivation of fungal species tested yielding a killing rate of up to 95%. The results revealed that the synthetic peptides were resistant to salt at a concentration of 50mM NaCl. However, they lost antimicrobial potency when applied in the presence of high salt concentrations. Based on blood hemolysis studies, a little hemolytic effect was showed in the case of both peptides even when applied at high concentrations. The data obtained from this study indicated that synthetic avian peptides exhibit strong antibacterial and antifungal activity. In conclusion, future work and research should be tailored to a better understanding of the mechanisms of action of those peptides and their potential use in the pharmaceutical industry to help reduce the incidence and impact of infectious agent and be marketed as a naturally occurring antibiotic.

In this study we identified the expression patterns of β-defensin-9 in chickens from Saudi Arabia, evaluated the antimicrobial activities of synthetic chicken β-defensin-9 (sAvBD-9) against pathogenic bacteria and fungi, and investigated the mode of action of sAvBD-9 on bacterial cells. The AvBD-9 gene of Saudi chickens encodes a polypeptide of 67 amino acids, which is highly similar to the polypeptide in duck, quail, and goose (97%, 86%, and 87%, respectively) and shares a low sequence similarity with the mammalian defensins. AvBD-9 is expressed in various organs and tissues of Saudi chickens and inhibits the growth of both Gram-negative and Gram-positive bacteria, as well as showing activity against unicellular and multicellular fungi (Aspergillus flavus, A. niger, and Candida albicans). sAvBD-9 completely inhibited the growth of both Gram-positive and Gram-negative bacterial strains as well as Candida albicans. The haemolytic effects of sAvBD-9 were limited. Morphological analysis by TEM revealed that sAvBD-9 induces shortening and swelling of Staphylococcus aureus and Shigella sonni cells, opens holes and deep craters in their envelopes, and leads to the release of their cytoplasmic content. Our data shed light on the potential applications of sAvBD-9 in the pharmaceutical industry.

This study was carried out to figure the potentiality of d-loop of mitochondrial DNA in discriminating among Saudi native chicken strains and other species of genus Gallus. The first 500 base pairs of d-loop region were amplified and successfully sequenced. The results indicated that native chicken strains and genus Gallus species have a tandem repeat sequence with (14) base units into a two copy. Also, there was clear evidence that the native chickens have a unique tandem repeat sequence with (42) base units as a two copy. Two haplotypes (T) and (C) were observed in native chicken strains. Our research displayed approximately (26) transition substitutions in nucleotide sequences specific for native chicken strains, whereas it was 120 mutant sites in case of other species of Gallus. We found that the genetic divergence between these types of chickens was very low (0.022). The phylogenetic tree revealed that each strain of native chicken belonged to each other with the same cluster. In addition, each strain has its own cluster in some individuals. The results showed that the native chicken strains are closely related to Gallus gallus and its subspecies G. g. spadiceus and G/. g. bankiva.

This study was conducted to find out the fraud in chicken-processed meat ingredients to protect consumers from commercial adulteration and authentication through a reliable way: direct amplification of conserved segment of cytochrome b gene of mitochondrial DNA, in addition, using species-specific primer assay for a certain cytochrome b. The results reported that chicken-processed meats were identified as a chicken meat based on amplification of conserved cytochrome b gene of mtDNA, while different fragments sizes were produced after the application of species-specific primer as follows: 227, 157, 274, 331, 389 and 439 bp for raw meat of chicken, goat, cattle, sheep, pig and horse, respectively. The results revealed that all chicken meat products are produced with 227 bp in size. While, an adulteration with pork stuffs was observed in some of the chicken meat products using a species-specific primer of cytochrome b gene, namely, chicken luncheon and chicken burger. This study represents a reliable technique that could be used to provide a promising solution for identifying the commercial adulteration and substitutions in processed meat in retail markets.

This was the second study to apply using of a cytochrome b gene as barcoding tool in distinguishing among chicken strains. We performed polymerase chain reaction (PCR) amplification using universal primer to amplify around 415 bp fragment of cytochrome b gene of mtDNA. The tree reported that both Saudi chicken strains (black and dark brown) are closely related and it might be separated from same origin rather than bronze ones. The phylogenetic tree also, exploited that native chicken strains were closely related to cluster of Ceylon jungle fowl, black Minorca egg chicken and Fayoumi egg chicken. The genetic divergence between these populations or types of chickens in Saudi Arabia was low (0.02) and it was very low (0.011), when compared to other species of Gallus. We confirmed that short fragment of cyt-b gene as a universal DNA barcode region. It was much more accurate and efficient tool to discriminate inter-species than intra-species. Applying cyt-b of mtDNA was successfully distinguished among native strains and other species of Gallus as in a previous study. However, applying this thought on different species of farm animal species is recommended.