مجله میکروب شناسی مواد غذایی
سال دوم شماره 2 (تابستان 1394)

To evaluate the antibacterial effect of Padina sp. and Sargassum sp. extracts¡ collected from coastal areas of Bushehr port¡ on Vibrio cholera and Escherichia coli¡ after washing in distilled water¡ the Padina sp. and Sargassum sp. were dried. Extraction was performed by immersion in 96% methanol to obtain methanol extract. Serial dilutions of the algal extracts were prepared by methanol and DMSO to find effect of solvent on algea potential as pure (100 percent)¡ 25 percent and finally 12.5 to 0.195 percent. Concentration of bacteria for inoculating in tubes were prepared base on McFarlane turbidity and was used to determine Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of algal extracts. The results showed that both Padina sp .and Sargassum sp. were effective on V. cholera and E. coli¡ although the results were not statistically significant (P>0.05). However the effect of Padina sp. on both bacteria and methanol extract was more. The relationship between the concentration of algal extracts with MIC and MBC based on linear regression method showed that there is a significant relationship between two parameters (P≤0.05). Keywords:

There is a growing interest to replace synthetic chemicals by natural compounds as essential oils in food industries. The purpose of this study was the effect of chitosan coating contained lemon essential oil on microbial quality of rainbow trout. In this experimental study, after prepared lemon essential oil, evaluated antibacterial activities against Shigella dysenteriae, Listeria monocytogenes, Streptococcus pyogenes and Salmonella typhi by micro dilution method. The effects of chitosan with concentrations of 0.25% and 0.5% (v/w) of lemon essential oil at 2±1 °C and 8±1 °C were examined on microbial quality of rainbow trout in zero, 3 and 6 days. Results showed that Minimum inhibitory concentration and Minimum bactericidal concentration for above bacteria was same and was to equal 1.41 mg/ml and 2.81 mg/ml, respectively. The use of chitosan and lemon essential oil caused decrease the total count of bacteria, enterobacteriaceae and psychrotrophic bacteria in two temperature above (P

Chitosan is a biodegradable and antibacterial polymer with simple preparation methods. The main problem of its film is its poor mechanical stability and amphiphilic structure. In this research Ag nanoparticles was synthesized in the matrix of chitosan (biopolymer) to reduce humidity absorbance and increase mechanical stability for application in food packaging. AgNO3 and Na2H2B4 and chitosan was used as precursors. The characteristic of nanoparticles and film was studied by X-Ray diffraction pattern. Surface morphology of the film was studied using scaning electrone microscopy. The result of the X-ray diffraction analysis showed that the maximum absorbance of the silver nanoparticles belongs to (111), (200), (311) and (222) direction and the domain phase of silver crystals are cubic. Scanning electron microscopy image revealed homogenous distribution of nanoparticles in polymer film. The microbial results showed an antibacterial effect for Ag nanoparticles in chitosan solution against gram negative bacteria. Furthermore, it didn’t show any effect against gram positive bacteria. Antibacterial activity of the composite was studied by the inhibition zone effect against Gram positive and gram negative using Muller-Hinton agar in different concentration of AgNO3. The result demonstrated that the maximum antibacterial activity was observed in the concentration of 0.15 mol/L. The effect of nanoparticles in the humidity absorbance of the film was investigated. WVP was decreased from 7.6% to 5.7% g/m.h.Pa.

Salad is one of the most popular components of the diets. E. coli Shiga toxin producing STEC is considered as one of the most important food pathogens. This study aimed to investigate the prevalence of salad contamination with this pathogen in Isfahan city and Chaharmahal va Bakhtiari Province STEC, determine the pattern of antibiotic-resistant and tracking virulence genes in bacteria were isolated. In this study, eighty samples of salad were randomly collected from Chaharmahal va Bakhtiari Province and Isfahan city from fast food restaurants and shopping malls. Following isolation of E. coli in the culture, PCR test to determine the virulence factors, Shiga toxin-producing bacteria was performed using specific primers. Then antibiotic resistance patterns were determined by standard methods and disk diffusion. The results showed that 80 salads, 11 samples (13/75 percent) are infected with E. coli. All strains of E. coli are resistant to at least one antibiotic. The highest and the lowest resistance were observed in tetracycline (58.82 percent) and nitrofurantoin (3.92%), respectively. The lowest prevalence and Stx1 had the highest frequency in the virulence genes. However STEC strains are not highly virulent in Iran, the findings of this study showed the possibility of contamination of the salads offered at fast food centers and restaurants. Therefore, preventive measures to avoid salad contamination with these bacteria are necessary.

The important of transmission of pathogens through ice is not less than transmission it through the water. The cause''s ice contamination is contaminated water¡ unhealthy ways of transit¡ distribution and inappropriate keeping conditions. In this cross-sectional study¡ a total sample of 36 from four factories¡ ice storage of Urmia City is selected randomly from 3 parts of feed water¡ production process and ice output in the summer. The samples are investigated from the view of total coli form and fecal coli form. The health condition of factories and the method of chlorination of water resources are assessed by check list. The results showed that¡ 50 percent of the samples of raw feed water to ice maker factories and the product process more than standard and 16.67% from them contaminated with fecal coli form. And in ice output 58.33% and 8.33%. The survey about health condition of factories showed that¡ 75% factories in order to buildings position and personal health¡ 56.2% with tools and 25% by chlorination in were appropriate situation¡ but the method preservation and storage of all factories were inappropriate from the view of health. The survey results showed that¡ lack of water chlorination to ice maker factories is the main factor of bacterial contamination of ice production. Therefore¡ authorities should pay more attention on microbiological health conditions of ice including microbiological investigation and supervision on production process distribution and transit.

In this study the antibacterial effects of ethanolic extract of eight medicinal plants (Artemisia aucheri, Satureja bachtiarica, Tanacetum parthenium, Cuminum cyminum, Salvia officinalis, Achillea kellalensis, Stachys lavandulifolia, Myrtus communis) and the essential oil of Satureja bachtiarica, Artemisia aucheri, Tanacetum parthenium, Cuminum cyminum, Achillea kellalensis, Myrtus communis on Vibrio parahaemolyticus were evaluated. Standard tube dilution method was used for evaluation of Minimum Bactericidal Concentration value (MBC) and Minimum Inhibitory Concentration value (MIC) of each plant. Then inhibitory zone of bacterial growth for each plant was also measured and compared to positive and negative control. The results showed that the extracts of Satureja bachtiarica had the highest antibacterial effects on V. parahaemolyticus with the inhibitory bacterial growth zone of 15 mm. The extract of Tanacetum parthenium and Cuminum cyminum were also effective with the inhibitory bacterial growth zone of 14 and 11.67 mm against V. parahaemolyticus. Other herbal extract showed no antibacterial effects. The results revealed the higher antibacterial effects of essential oils comparing to the extracts and the highest antibacterial effect were belonged to Satureja bachtiarica, Tanacetum parthenium and Cuminum cyminum. It can be concluded that regarding to high antibacterial effect of Satureja bachtiarica, Tanacetum parthenium and Cuminum cyminum, they can be used in elimination of V. parahaemolyticus.

The aim of this study was to evaluate the antibacterial activity of olive leaf extracts from four important Iranian native cultivars (Dezfol, Roghani, Zard and Shiraz) against E. coli. Acetonic, methanolic and ethanolic olive leaf extracts were prepared using a microwave. The extracts were concentrated and lyophilized. The growth inhibition effect of different concentrations of extracts was determined using the broth micro-dilution assay. The growth curves of E. coli during 24 h incubation at 37°C were drawn. The area under the bacterial growth curve and the percentage inhibition of the growth were calculated. Extracts with the concentrations of 5 and 10 mg/ml had no considerable inhibition effect on the bacterium. Acetonic extract of Dezfol and Zard cultivars with the concentration of 20 mg/ml inhibited the bacterial growth 93% and 94.9%, respectively and showed significantly stronger inhibition effect in comparison with acetonic extract of Shiraz and Roghani cultivars. Methanolic extract of Roghani cultivar with the bacterial growth inhibition of 93.4% showed significantly stronger effect in comparison with its acethonic and ethanolic extracts. Ethanolic extracts of four studied cultivars showed no antibacterial effect. Among the four important Iranian native olive leaf cultivars, Dezfol and Zard were found to possess the highest antimicrobial activity and aceton was the best solvent. On the basis of these results, it can be concluded that extracts of the Iranian native olive leaf cultivars could be used as a natural antimicrobial agent in food preservative, ointment and drugs.

Bacteriocins are proteins produced by bacteria especially Acid lactic bacteria having antimicrobial characteristics and used for food preservation. In recent years, especial considerations have been taken to detection of acid lactic bacteria and Bacteriocins in food industries to use them as food preservatives. In this study, 120 samples of different traditional dairy products were examined to investigate genes of Enterocin, Entrain A, Enterocin P and Enterocin AS-48. After separation and detection of bacteria in presence of special primers related to Enterocingenes, their frequencies were studied. Among 120 samples, 44 (36.36%) were contaminated to Enterococcusfireclays. The gene related to EnterocinA in 14 isolates (31/81%), the gene related to Enterocin P in 13 isolates (29/54%), the gene related to EnterocinAs-48 in 9 isolates (20/45%), the simultaneous presence of the gene related to EnterocinA and P in 2 isolates (4/54%), the gene related to Enterocins A and As-48 in 7 isolates (15/09%) and the gene related to Enterocins A, P and As-48 in 5 isolates (11/36%) were observed. According to the presence of a lot of Enterocingenes in Enterococcusfaecalis separated from dairy products, doing research on antimicrobial characteristics of Enterocins produced by this bacterium is of great necessity.