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Aim: Group A Streptococcus (GAS) is the causative agent of several invasive and non-invasive diseases. Several virulence factors contribute to the pathogenesis of GAS, such as M protein, hemolysins, and extracellular enzymes. Due to the improper use of antibiotics, the resistance of these microorganisms to antibiotics is increasing. Bacteriocins as an alternative to antibiotics are of great importance. In this study, the effect of antimicrobial Bacteriocin nisin was investigated on the expression of smeZ gene.
Materials & Methods: Samples were taken from the site of infection on the skin surface of the patients at the dermatology clinics of Tehran public hospitals. The specimen was immediately transferred to the primary culture medium or basal medium. Chromosomal DNA extraction was performed using the standard method for the extraction of Streptococcus pyogenes genomes. Multiplex PCR was performed to identify the presence of smeZ, speI, and speH genes in the isolates. The expression of smeZ gene was evaluated using the real-time PCR technique.
Findings: The frequencies of smeZ, speI, and speH genes in 12 S. pyogenes isolates were 25, 8.3, and 8.3%, respectively. The fold change rate for smeZ gene was -1.209, indicating that this gene was decreased 1.209 folds in the treated group compared to the untreated group.
Conclusion: Bacteriocin not only reduces the number of pathogens but may also affect the metabolism of the bacteria by producing toxins. The use of new antimicrobial agents in place of previous drugs for psoriasis patients could be considered as a way to treat the disease more effectively in the future.
 

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Background: The escalating prevalence of multidrug-resistant (MDR) commensal intestinal bacteria characterized by extended-spectrum β-lactamase (ESBL) production is an alarming global health threat. Drug users have been introduced as a major source of antibiotic-resistant bacteria, possibly due to drug abuse. The present study aimed to investigate the potential factors related to fecal carriage of MDR ESBL-producing intestinal Escherichia coli (E. coli) in drug users in the southwest of Iran.
Materials & Methods: In this cross-sectional study, stool samples of 109 drug users were collected and cultured. After the biochemical confirmation of E. coli isolates, the antimicrobial resistance pattern and ESBL production of the isolates were determined. Then logistic regression analysis was conducted to determine possible factors related to fecal carriage of MDR ESBL-producing intestinal E. coli.
Findings: Logistic regression analysis indicated that increasing age and duration of addiction were associated with increased risk of MDR ESBL-producing E. coli carriage in the intestinal flora of drug users (p< .05). Moreover, oral drug use compared to the smoking method led to a higher carriage rate of MDR ESBL-producing E. coli in the intestinal flora of drug users (p< .05). Also, self-employed drug users compared to those with fixed public occupation showed higher rates of MDR ESBL-producing E. coli carriage in their intestinal flora (p< .05).
Conclusion: Age, duration of addiction, method of drug use, and occupation were significantly associated with MDR ESBL-producing E. coli colonization.

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Chicken meat is one of the most popular and perishable foods. One of the effective ways to increase the retention time of fresh chicken meat is the use of appropriate packaging coatings containing natural antimicrobial compounds. The aim of this study was to investigate the antimicrobial effect of soy protein coating containing tarragon essential oil on chicken meat stored in a refrigerator.Tarragon essential oil was extracted by water distillation method and its antimicrobial properties were tested on Staphylococcus aureus PTCC 1113, Salmonella enterica PTCC 1709, Escherichia coli PTCC 1399, and then the effect of concentration 0, 2 and 3% (vol / vol) soluble essential oil in soybean protein coating on these bacteria were studied. Finally, the antimicrobial effect of soy protein content containing tarragon essential oil on chicken fillets kept in the refrigerator was investigated and characteristics of the changes in its chemical and organoleptic properties were evaluated.The highest inhibitory concentration of essential oil was from Staphylococcus aureus, and the lowest was E.coli and Salmonella enterica. The total microbial count for the sample treated with 3% essential oil during the 12 days storage in the refrigerator was significantly lower than the control sample (P <0.05). The greatest effect of antimicrobial films after 12 days of storage in the refrigerator was on inoculated samples of Staphylococcus aureus. Protein film of 3% essential oil prevented the increase of pH and peroxide value during the storage period in the refrigerator. According to the sensory evaluation results, the film containing 2% essential oil obtained the highest overall acceptance rating. Although this property is reduced by the mixing of essential oil with film coating. The essential oil coating also has positive effects on the chemical and organoleptic properties of chicken fillet.

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Meat products are highly perishable and require protection to maintain their quality. Bioedible films incorporated with essential oils have recently received attention due to their benefits as AntiMicrobial (AM) active packaging. The aim of this study was to evaluate the physico-mechanical properties and antimicrobial activity of Isolated Soy Protein (ISP) film containing Peppermint Essential Oil (PEO) on shelf life and sensory quality of raw hamburger. The ISP film incorporated with PEO at 1, 2, and 3% (v/v) were prepared by solvent casting method. The results showed that the incorporation of PEO caused a significant decrease and an increase (P< 0.05) in tensile strength and elongation-at-break, respectively. Increment of thickness, Water Vapor Permeability (WVP), and decline in moisture content was recorded as the amount of oil increased (P< 0.05). In addition, Lightness/darkness (L*), Whiteness Index (WI), and redness/greenness (a*), and yellowness/blueness (b*) increased, while the total color difference (ΔE) decreased by adding PEO. PEO-incorporated film (at 3% v/v) exhibited higher inhibitory activity against Staphylococcus aureus, Escherichia coli, and lower for Salmonella enterica using disc diffusion method. Microbial analysis and pH measurement of raw hamburger covered with ISP-PEO film showed no inhibitory effect against test bacteria when applied on raw hamburger, whereas the inhibited total bacterial growth exceeded the acceptable limit until the end of refrigerated storage. This film was able to prolong the shelf life of hamburger for up to 7 days. Therefore, this new antibacterial film has considerable potential to be used as meat packaging material.