S almonellosis remains a major public health issue worldwide with a huge global burden of morbidity and mortality especially in developing countries (Sodagari et al., 2020). It is estimated to cause 93.8 million human infections and 300,000 deaths annually (WHO, 2020) besides causing a major challenge in the global poultry industry. It is well known that human salmonellosis is associated with the consumption of different kinds of food, in particular poultry and poultry products (Favier et al., 2013). Other routes of infection between individuals are represented by the fecal-oral route and contact with infected pets through contamination of food and drink by the hands, thus disease outbreaks can occur (Munck et al., 2020).

In Leishmania species, protein disulfide isomerase (PDI) is an essential enzyme that catalyzes thiol-disulfide interchange. The present work describes the isolation, cloning, sequencing and expression of the pdI-2 gene. Initially, the gene was amplified from L. tropica genomic DNA by PCR using specific primers before cloning into the expression vector pET-15b. The construct pET/pdI-2 was transformed into BL21(DE3) cells and induced for the protein expression. SDS-PAGE and western blot analysis showed that the expressed protein is about 51 kDa. Cloned gene sequence analysis revealed that the deduced amino acid sequence showed significant homology with those of several parasites PDIs. Finally, recombinant protein was purified with a metal-chelating affinity column. The putative protein was confirmed as a thiol - disulfide oxidoreductase by detecting its activity in an oxidoreductase assay. Assay result of assay suggested that the PDI-2 protein is required for both oxidation and reduction of disulfide bonds in vitro. Antibodies reactive with this 51 kDa protein were detected by Western blot analysis in sera from human infected with L. tropica. This work describes for the first time the enzymatic activity of recombinant L. tropica PDI-2 protein and suggests a role for this protein as an antigen for the detection of leishmaniasis infection.

Back ground: This study aimed to investigate Staphylococcus aureus (S. aureus) in some dairy products, Genotypically and phenotypically antibiotic resistance pattern as well as to evaluate the effectiveness of lactoferrin (LF) as a bio preservative for yoghurt. Methods: A total of 150 samples from yoghurt, ice cream and Damietta cheese (50 for each) in Assiut city, Egypt. Antimicrobial susceptibility against antibiotics commonly used in human and animals was tested using the disc diffusion method, S. aureus isolates, PCR was applied on multidrug resistant (MDR) S. aureus isolates for detection of blaz, mecA and VanA genesResults: The highest prevalence S. aureus was detected in yoghurt (38%) followed by Damietta cheese (30%) and ice cream (14%). Antimicrobial susceptibility against antibiotics S. aureus isolates showed high resistance to tetracycline, penicillin, oxacillin, ampicillin, streptomycin, amoxicillin/clavulanate and neomycin, in different percentages. blaz, mecA and VanA genes were detected at 60% for blaz gene, 40% for mecA gene and 20% for vanA gene. Lactoferrin has a satisfactory antibacterial activity MIC at 20mg/ml and MLC at 40mg/ml. The results revealed that 40mg/ml LF in yoghurt could inhibit MDR S. aureus at 2nd day while, 20mg/ml at the fourth day.Conclusion: The study concluded that LF can be used as a bio preservative in yoghurt due to its highest antimicrobial activity and acceptable sensorial properties.

C heese is considered a rich source of essential nutrients such as protein, vitamins, minerals, short chain fatty acids and some trans fatty acids; it plays an important role in human nutrition in many parts of the world (Khorshidian et al., 2018), but is also prone to contamination by different harmful bacteria; thus the world intended to use preservatives as a critical step in cheese making (Mena and Pamela, 2020).Several studies have been conducted on many plant-derived essential oils (EO) used to prevent pathogenic bacteria from causing significant human diseases (Basuny et al., 2022), these essential oils are environmentally friendly and bio friendly with antioxidants properties and antibacterial properties extend the shelf life and safety of food (Ekpo et al., 2019).One of the most important oils is Moringa oleifera, which is a good source of antioxidants and has many uses, including a natural food supplement and preservative due research Article Abstract | Cheese's shelf life may be shortened by pathogenic and spoilage bacteria, which are prone to contaminating food. This suggests that bio-preservatives may be used during the cheese-making process. So, this research was done to determine how well moringa oil (MO) and its nano emulsion (Nano-MO) work on some food poisoning bacteria inoculated into white cheese in vitro and in vivo. Prepared (Nano-MO) had the Z-average diameter of 76.04±51.13 nm and polydispersity index (PDI) of 0.319. The spherical shape of the generated nano-emulsion was revealed by Transmission Electron Microscope (TEM) and the flow of active functional groups was clarified by Fourier-transform infrared spectroscopy (FTIR). Antibacterial activity of MO and Nano-MO was assessed against reference bacterial strains by using agar well diffusion method. The minimum inhibitory concentration (MIC) of MO and Nano-MO was 3% and 2%, on Listerea monocytogenes, Staphylococcus aureus, Salmonella typhi and E. coli bacteria, respectively. While, in inoculation of MO and Nano-MO in cheese complete reduction of examined bacteria was recorded at 3 rd week of storage except for L. monocytogenes Nano-MO killed it at 2 nd week. Overall acceptability (OAA) investigations showed better results of Nano-MO than MO. Nano-MO showed a great antibacterial property against different pathogenic bacteria without any effect on the palatability of cheese which make it an excellent choice as a bio preservative.

The zinc protease gene was isolated and amplified by PCR using extracted B.melitensis genomic DNA as a template. A primer pair was designed from this gene containing restriction sites of NdeI and BamHI at 5'and 3' end, respectively. Those Primers were used to amplify an insert of 927 pb. This amplicon was digested and inserted into the NdeI-BamHI cut expression vector pET-15b. This recombinant plasmid was transformed into Escherichia coli BL21 (DE3) for protein expression. Following induction by several amounts of IPTG, the expression of this protease induced bacterial cell death, two hours after expression induction.