Chitosan (Cs) was extracted from shrimp shell and its derivative forms including N-alkyl (AlkCs) and nanoparticles (CsNPs) were prepared. First, the properties of nanoparticles were determined by dynamic light scattering (DLS) and the morphology of nanoparticles and N-alkylated by scanning electron microscopy (SEM). Then their antibacterial activity was evaluated by the test of minimum inhibitory (MIC) and lethal (MBC) concentration, diffusion on agar by disk, permeability of cell membrane by measurement of cytoplasmic beta-galactosidase release (ONPG). The type of apoptosis cell death was also examined by DAPI staining and changes in cell surface integrity by atomic force microscopy (AFM). The results showed that the nanoparticles are spherical with an average hydrodynamic diameter of 240 nm. N-alkyl had a rough surface structure compared to native chitosan. At the least of MIC (78 μg/ml) and MBC (100 μg/ml) points were observed for CsNPs (P < 0. 05). Nanoparticles and N-alkyl of chitosan showed the highest diameter of growth inhibition zone at 1250 concentration compared to other disks (p <0. 05). Outer membrane permeability of derivative forms of chitosan showed significant differences with native chitosan and cells of control. DAPI staining test showed higher cell death of chitosan-derived forms. DAPI staining test showed higher cell death of derivative of chitosan. The images obtained from AFM showed a change in the membrane integrity of the treated cells compared to spherical and clustered of control cells. Thus, the antibacterial properties of native chitosan improved by physical and chemical modification.

Background: Utilizing pomegranate peel as an antibacterial agent in topical formulations presents an opportunity for optimization through innovative drug delivery systems, notably encapsulating extracts and fractions within a nanoemulgel. Objective: This study aimed to formulate ethanol extract and ethyl acetate fraction of pomegranate peel into nanoemulgels and assess their antibacterial activity against skin disease-causing bacteria. Methods: The methodology encompassed extraction, formulation, testing, and antibacterial assays involving maceration and fractionation using ethanol and ethyl acetate solvents. The physical properties and antibacterial efficacy of the nanoemulgels were evaluated. Results: Nanoemulsions derived from pomegranate peel ethanol extracts and ethyl acetate exhibited promising attributes, demonstrating 98.27 % and 98.77 % transmittance levels and zeta potentials of 0.18 mV and 0.32 mV. The nanoemulgel with ethanol had a pH of 6.62 ± 0.02, 6.86 ± 0.01, 6.3 ± 0.01 in 0.5 %, 1 %, and 1.5 % concentrations. For nanoemulgels with ethyl acetate, the pH levels for concentrations 0.5 %, 1 %, and 1.5 % are 6.58 ± 0.00, 6.80 ± 0.01, and 6.94 ± 0.01, respectively. These nanoemulgels displayed consistent odour, colour, and homogeneity characteristics, highlighting their suitability for topical application. The adhesion, spreadability, and viscosity assessments showed concentration-dependent variations, influencing effectiveness and user comfort. Notably, these nanoemulgels displayed substantial potential as antimicrobial agents against S. aureus and S. epidermidis bacteria in inhibitory assays, signalling promise for addressing skin infections. Conclusion: Overall, the study underscores the potential of nanoemulgels derived from pomegranate peel extracts as a natural alternative for topical antimicrobial therapy against skin infections.

Background: Thyme (Zataria multiflora Boiss.) is one of the Iranian traditional spice and it has antimicrobial effect on the pathogenic bacteria which are agents for some current food borne intoxications.Objective: Evaluation of antimicrobial effect of mentioned plant essential oil on Staphylococcus aureus in Feta cheese.Methods: The essential oil of this plant was obtained by hydrodistillation and analyzed by GC/MS. Effects of different concentrations of this essential oil on Staphylococcus aureus were determined by evaluation of  the microorganism growth on the selective media in laboratory, and these were took place in Feta cheese.Results: Results indicated that 300 and 150 ppm of this essential oil have had the highest inhibitory effect on the growth of Staphylococcus aureus and when the mentioned concentrations of  the essential oil were used in combination with cheese starter culture, the counts of the pathogen were decreased significantly below its toxic dose in this kind of food product.Conclusion: The antimicrobial effect of Zataria multiflora Boiss. in 300 ppm was higher than its lesser concentrations and with concern to the control groups, the synergistic effect between the starter and the essential oil is necessary to achieve this inhibitory effect

Milk is considered a nutritious food because it contains several important nutrients including proteins and vitamins. Conversely, it can be a vehicle for several pathogenic bacteria such as Staphylococcus aureus. This study aimed to analyze the frequency of genes encoding the nine Staphylococcal enterotoxins (SEs) and enterotoxin gene profiles in S. aureus isolates derived from raw bovine milk. A total of 52S. aureus isolates were obtained from 246 milk samples of 246 dairy cows from eight different farms in Qom, Iran. On the basis of cultural and biochemical properties as well as by amplification of the 23S rRNA specific toS. aureus, all isolates could be identified as S. aureus. Of the 52 isolates studied, 80.7% were positive for one or more genes encoding the enterotoxins, and 12 different genotypes were identified. The gene encoding for enterotoxin A (Sea) was the most frequent (16 isolates, 30.7%), followed bySeb (14 isolates, 26.9%) and Sed (8 isolates, 15.37%). Among the genes encoding the other enterotoxins, Seg and Seh were the most frequently observed (8 isolates each, 15.38%), followed by Sej (6 isolates, 11.5%) and Sei (1 isolates, 3.84%). With the recent identification of new SEs, the frequency of enterotoxigenic strains has increased, suggesting that the pathogenic potential of Staphylococci may be higher than previously thought. These results of enterotoxin genes positivity of milkderived Staphylococci constitute a potential risk for consumers’ health.

Soil-dwelling nematodes from Steinernematidae family are obligate parasites of insects and usually referredto as entomopathogenic nematodes (EPNs). These nematodes are symbiotically associated with entomopathogenic bacteria Xenorhabdus spp. The bacterial symbionts are carried monoxenically in a special vesicle in the infectivejuveniles (IJs). In the present study we report the isolation of two species of non-symbiotic bacteria from infectedinsect cadavers by the EPN, Steinernema feltiae. Galleria mellonella L. larvae were exposed to surface sterilize dinfective juveniles of S. feltiae and transferred to sterile Petri dishes for a further 24 hours. Hemolymph was collected and streaked onto both MacConkey and NBTA agar. Bacteria were identified using biochemical and phylogenetic analysis.16S-rRNA gene sequence based maximum parsimony, maximum likelihood and neighbourjoining phylogenetic analyses were conducted. Two non-symbiotic species including Citrobacter freundii and Staphylococcus succinus were identified and reported to be associated with S. feltiae. Our results provide further evidence for the existence of non-symbiotic bacteria associated with EPNs infection.