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Background & aim: Milk is a dairy product which is susceptible to contamination by pathogenic and spoilage microorganisms. One way to control the growth of pathogenic bacteria is to use preservatives and antimicrobial compounds. Due to the general concerns about the side effects of chemical preservatives, there is a tendency to consume products that use natural preservatives. Natural products provide unlimited opportunities for novel and suitable additives. The main objective of this study was to evaluate the antioxidant and antimicrobial activities of hydro-ethanolic extract of rosemary (Rosmarinus officinalis L.) against some gram positive (Staphylococcus aureus and Listeria innocua) and gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and the next stage was to investigate the impact of hydro-ethanolic extract of this plant at 0.25, 0.5 and 0.75% (w/w) concentrations on the shelf life of pasteurized milk. Methods: The present experimental study was conducted in 2022 at Nahavand Higher Education Complex. The total phenolic content of the extract was measured by Folin-ciocalteau method. Antioxidant activity of different concentration of extract were assessed by diphenyl picrylhydrazyl radical-scavenging activity and compared with synthetic antioxidant butylated hydroxyl anisole (BHA). Antibacterial effects of resemary on pathogenic bacteria was determined by well diffusion agar, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods. Experimental data were analyzed using ANOVA by the SPSS version 20 software and mean comparison were done using Duncan's multiple range test. Results: The phenolic content of hydro-ethanolic extract weas 96.47±0.35 mg galic acid/g extract. Hydro-ethanolic extract of rosemary had the greatest effect on Staphylococcus aureus. The MIC of rosemary ethanolic extract ranged from 12.5 to 50 mg/ml, depending on the type of bacteria (gram positive or gram negative). Also, the treatments of pasteurized milk with 0.5%, acceptable sensory properties had a significantly lower total microbial count and longer shelf life compared to the control sample. Conclusion: Therefore, considering that the hydro-ethanolic extract of rosemary had a significant effect on preventing the growth of pathogenic and spoilage microorganisms, as a result, this extract can be used as a natural antibiotic in milk.

Introduction Overuse of antibiotics and their entry into the environment is a global concern today. Much of the antibiotics taken by animals and humans are excreted unchanged and found in their feces which enter the environment through livestock waste and municipal wastewater disposal. Uncontrolled release and continuous introduction of antibiotics to the environment induced antibiotic resistance in microorganisms living in other habitats which pose a potential hazard to existing aquatic ecosystems and animals. Rivers act as the main sink for the effluents that distribute antibiotics and antibiotic resistant microorganisms in the environment. This study aimed to investigate the antibiotic resistant index (ARI) in Goharrood River. Seasonal variations and source of contamination, focusing on urban surface wastewater of Rasht, were investigated through sampling of river water and sediment in different points along the river during four seasons of a year.Materials and MethodsThe water and sediment of the river were sampled at three points along the river (focused on river course in Rasht city), in autumn, 2016 and in winter, spring and summer, 2017. The number of antibiotic resistant heterotrophic and coliform bacteria were counted via colony count method in the antibiotic supplemented 100 µg/mL Nutrient Agar and Eosine-Methylene Blue agar media respectively. Cephalexin, gentamicin, doxycycline, ciprofloxacin, and trimethoprim antibiotics were tested in this study. ARI was calculated by dividing number of bacteria colonies (heterotrophic and coliform bacteria) in plates supplemented with antibiotics to the number of colonies in control plate (without antibiotic). Escherichia coli as an indicator coliform bacterium was isolated from water and sediment samples (12 strains; 4 season and 3 sampling points) and their resistant pattern to these antibiotic was also tested by disk diffusion (Kirby-Bauer) method in Mueller-Hinton agar medium. The inhibition zone (ZOI) of E. coli growth was measured and its sensitivity/resistant was assessed based on CLSI standard protocol. The calculated ARI of heterotrophic and coliform bacteria of water and sediment of the River and the determined ZOI of E. coli isolated from water and sediment were analyzed by repeated measures of factorial arrangement in a completely randomized design format by SAS software package. Factors included sampling point at 3 levels (before entering river to the Rasht city; A, in the Rasht city; B, and after river exit from the Rasht city; C), and antibiotics at 5 levels (cephalexin, gentamicin, doxycycline, ciprofloxacin, and trimethoprim) as main plot and sampling time at 4 levels (autumn, winter, spring, and summer) as sub-plot.Results and Discussion The highest ARI value of water heterotrophic bacteria was obtained to cephalexin at the sampling point C. Mean ARI of water heterotrophic bacteria to all antibiotics (regardless of type of antibiotic) at three points of A, B and C was 3.77, 4.54 and 7.53%, respectively. The highest ARI levels of heterotrophic and coliform bacteria in water were obtained in the summer season. In fact, the change of seasons and clearly the summer season controlled the ARI in water bacteria rather than the type of antibiotics. So that in this season 30.78% of water heterotrophic bacteria were resistant to ciprofloxacin antibiotic and about half (50.78) of the river water coliforms were resistant to cephalexin. Although ARI for heterotrophic and coliform bacteria was lower in sediment rather than that in water, the highest ARI levels of heterotrophic and coliform bacteria in sediment were obtained against cephalexin in autumn and winter, respectively. In general, the mean ARI in water and sediment bacteria was as follows: cephalexin > gentamicin > ciprofloxacine > doxycycline > trimethoprim. The lowest ZOI value for E. coli was obtained against cephalexin. Therefore, in all three sampling points, isolated E. coli bacteria from water and sediment were resistant to cephalexin. In the study of the sampling time and sampling point interaction, it was also seen that the lowest ZOI of E. coli was in autumn and at sampling point C. Therefore, it seems that E. coli has become resistant to antibiotics when river crosses the city.Conclusion According to the results of this study, Goharrood river is contaminated with antibiotic-resistant, especially cephalexin resistant bacteria and it may distribute pollution downstream. If the river water is used in aquaculture and irrigation of downstream agriculture fields, the antibiotic resistant bacteria may be spread in the other ecosystems and finally may enter the human food chain.

The use of antibiotic drugs is associated with problems, such as unwanted side effects and drug resistance, and the lack of new and natural antimicrobial drugs that have fewer side effects than antibiotics. The aim of this study, investigating the effects of hydroalcoholic extract of sour lemon peel on a few of standard strains of G+ and G- bacteria. Concentrations of 25,50,100 and 200 mg/ml of extracts by percolation method were prepared to determine antibacterial effects and using a well publication method against ten different species of G+ and Gbacteria, then the Minimum Inhibitory Concentration of bacterial growth (MIC) and Minimum Bacterial Concentration (MBC) were evaluated by dilution in tube. Alcoholic extract of sour lemon peel in a dose-dependent manner significantly increased the diameter of zone to inhibit the growth of the bacteria, especially G+ bacteria, as compared to G- (p <0.05). In the concentration of 200 mg/ml, the maximum and minimum diameter of the inhibition zone was 20 mm for Streptococcus pyogenes and 12 mm for salmonella typhimurium, respectively. MIC and MBC methods had the strongest effect on Streptococcus pyogenes and had the least effect on Escherichia coli and Salmonella typhimurium. Extract of sour lemon peel has a significant antimicrobial effect, which can be used as an alternative to synthetic antibiotics with increasing microbial resistance. [ABSTRACT FROM AUTHOR]

Background and aim: Dental caries is a major health problem nowadays. polyphenolic compounds of tea can exert its anti-cariogenic effects by affecting the cariogenic Streptococcus Mutans bacteria. The aim of this study was to investigate the antimicrobial effect of ethanolic, methanolic and aqueous extracts of green tea in comparison with chlorhexidine on Iranian strain of this bacteria. Materials and Methods: 10 g of green tea powder was dissolved in 100 mg of ethanol, methanol and aqueous solvents separately. After one week, the obtained solutions were filtered and 100mg / ml solution was extracted. to evaluate the diameter of inhibition, zone The Swabs impregnated with suspension scrubbed on culture medium. the extracts were injected onto special paper discs and the impregnated disks were placed on the bacterial culture media, plates were kept in the incubator for 24 hours at 37 °C and then the diameter of inhibition zones was calculated. Using Muller Hinton Broth, herbal extracts were made at concentrations 1:2 (50 mg/ml) and 1:4 (25 mg/ml) and 1:8 (12.5 mg/ml) and 1:16 (6.25 mg/ml) and 1:32 (3.125 mg/ml). Then, 100 μl microbial suspensions made by standard McFarland 0.5 were transferred to all test tube. The test tubes were placed in an incubator at 37°C for 24 hours. After 1 day, contents of all test tubes were separately cultured on Muller Hinton Broth medium. The culture media were incubated at 37°C for 1 day. The results were evaluated in the form of growth or non-growth of bacterial colonies on culture media and MBC and MIC were determined. ANOVA and Post hoc test was used for statistical analyze with SPSS Software. Results: Experimental results after three iterations showed mean values of 16.16, 16.66, 12.5 and 17.5 mm for diameter of the inhibition zone of ethanolic, methanolic and aqueous extracts and chlorhexidine 0.2%, as control. Also, at the significant level of 0.05, there was no significant difference between the diameter of the inhibition zone of ethanol, methanol and chlorhexidine extracts. (p>0.05)The Aqueous Extract Showed Significant difference with other Extracts. MBC Reported 12.5mg/ml for Ethanolic and 50mg/ml for two other extracts. MIC Reported 6.25mg/ml for ethanolic and 25mg/ml for two other extracts. Conclusion: The results showed that the antimicrobial effects of ethanolic and methanolic extract of Iranian green tea are higher than aqueous extract and there is no significant difference between these two extracts with Chlorohexidine. [ABSTRACT FROM AUTHOR]

Background: This study aimed to examine the antibacterial effect of Polyamidoamine-G4 dendrimer on Escherichia coli, Enterobacter cloacae, Bacillus subtilis and Staphylococcus aureus. Materials and Methods: In this experimental study, the antibacterial effects of Polyamidoamine-G4 dendrimer were studied by disc diffusion and micro-dilution method. Different concentrations of Polyamidoamine-G4 inoculated onto blank disks and were placed in Mueller-Hinton agar media. Zone of inhibition was investigated by bacterial inoculation according to the McFarland standard 0.5. Minimum inhibitory concentration and minimum bactericidal concentration of Polyamidoamine-G4 dendrimer were determined by micro-dilution method in nutrient broth culture. Results: Zone of inhibition in concentration 500 &mug/ml of Polyamidoamine-G4 dendrimers for Escherichia coli, Enterobacter cloacae, Bacillus subtilis and Staphylococcus aureus were 14, 0, 35 and 29mm, respectively. Concerning the Zone of inhibition in gram negative bacteria with gram positive ones was p<0.05 and had significant difference. The minimum inhibitory concentration of Polyamidoamine-G4 dendrimer for Escherichia coli, Bacillus subtilis and Staphylococcus aureus were 1250, 2.5, and 1 &mug/ml, respectively. The minimum bactericidal concentration of Polyamidoamine-G4 dendrimer belonged to Escherichia coli, Bacillus subtilis and Staphylococcus aureus were 2500, 5 and 5 &mug/ml, respectively. Polyamidoamine-G4 dendrimer had not bacteriostatic and bactericidal effects on Enterobacter cloacae. Conclusion: According to the results, Polyamidoamine-G4 dendrimer can eliminate Escherichia coli, Staphylococcus aureus and Bacillus subtilis effectively. It is suggested in the rest of this study that the probable toxicity of nanostructured compounds examined in drinking water and, economic studies is done for synthesis and their applications in case of prevention of using. [ABSTRACT FROM AUTHOR]