مجله میکروب شناسی مواد غذایی
سال هشتم شماره 3 (پاییز 1400)

Poultry meat is considered one of the sources of Escherichia coli O157. The present study was performed to evaluate the prevalence and antibiotic resistance of E. coli O157 isolates of poultry meat samples presented in Isfahan. In total, 500 meat samples were collected from diverse poultry samples supplied in Isfahan and evaluated for E. coli O157 using microbial culture. Suspicious isolates were confirmed by PCR test. The antibiotic resistance pattern of isolates was investigated using the antibiotic disk diffusion test. Forty-four out of a total of 500 samples (8.80%) were contaminated with E. coli O157. The highest level of contamination was related to duck meat (16%), and the lowest was related to quail meat (3%). There was a statistically significant difference of P <0.05 between the sample type and the prevalence of E. coli O157. Escherichia coli O157 isolates had the highest antimicrobial resistance to tetracycline (97.72%), ampicillin (95.45%), penicillin (95.45%), and gentamicin (72.72%) antibiotics. The highest variation in antibiotic resistance was found in E. coli O157 strains isolated from duck meat. Due to the high prevalence of antibiotic-resistant E. coli O157 strains in poultry samples, especially duck meat, consumption of these foods in raw or uncooked form, in addition to the transfer of antibiotic-resistant strains to human communities, can lead to lethal food poisoning.

The bio-production method has been respected due to the lack of energy consumption and environmental compatibility. In this study, the green synthesis of copper oxide nanoparticles from the extract of Iranian violent flower and its anti-bacterial properties compared to two common antibiotics was investigated. First, aqueous extract of Iranian violent flower prepared and admixed with CuO solution at a concentration of 1 mM. After changing the color of extract, the reaction product was examined by spectrophotometric and X-ray diffraction. Finally, antibacterial properties of synthesized nanoparticles were investigated using disk diffusion method. Also, the MIC (minimum inhibitory concentration of growth and MBC (minimum bactericidal concentration) were determined by two methods of micro dilution and dilution in the tube. The synthesized copper oxide nanoparticles showed the most absorbance at 266 nm and had a spherical shape with an average size of 50-80 nm. The results of the antibacterial studies showed that the synthesized copper oxide nanoparticles had more antibacterial activity against staphylococcus aureus than Escherichia coli. The extract of Iranian violent flower has the ability of reducing CuO ion to copper oxide nanoparticles. Also, synthesized copper oxide nanoparticles have good antibacterial activities.

People's concerns about the use of synthetic additives have doubled the importance of the need for research in the field of production of natural pigments, especially microbial pigments. Therefore, in this study, the spore suspension of Monascus purpureus was treated using ultraviolet light at random times (20, 30, 45, 60 seconds) and intervals (20, 30, 35 cm). Then, six suspicious colonies were selected to study the morphological characteristics, and their pigment production and biomass growth were studied as liquid culture. The results showed that ultraviolet light caused morphological changes in M. purpureus. Pigment production in treated samples increased significantly compared to wild strain (p <0.05). UV6 treatment in red, orange and yellow pigment production showed a 5, 7, and 2.8 times increase compared to wild strain significantly, respectively (p<0.05). Pigment production during the first and second generations in UV3, UV4, UV6, UV7, and UV8 treatments did not show a statistically significant difference with each other: in other words, the treatments were stable significantly (p<0.05). According to the results, ultraviolet light was an effective physical treatment to increase the production of red, orange, and yellow pigments from the fungus M. purpureus and generally causes lasting changes in the strain.

In developing countries, the presence and diversity of Staphylococcus species in foodstuffs have not been comprehensively studied. So, the present study aimed to investigate the dissemination of Staphylococcus spp. and their antimicrobial susceptibility pattern isolated from foodstuffs in Isfahan in 2015-2016. A total of 194 foodstuff samples were collected from different parts of Isfahan city and processed for the presence of Staphylococcus spp. The conventional tests were used for the primary detection of bacteria and the sequence analysis of 16S rRNA was used for the species identification. The antimicrobial susceptibility pattern of isolates was determined by the disk diffusion method. From a total of 194 food samples, 92 Gram-positive cocci (47.5%) were isolated. Of them, 84 isolates were Staphylococcus spp., 7 Macrococcus spp and one Micrococcus spp. The most prevalent species were S. aureus 25% (21/84), S. vitulinus 15.5% (13/84) and S. succinus sub casei 11.9% (10/84). The most antibiotic resistance rates were against penicillin (59/5%) and tetracycline (20.2%) while the lowest antibiotic resistance rates were observed for levofloxacin, rifampicin, gentamicin, and ciprofloxacin. Characterization of Staphylococcus species is important for epidemiological investigations. Proper identification and management practices including analysis of 16S rRNA for the species identification should be considered to increase food safety and prevent extra treatment costs.

The aim of this study was to evaluate the intra-species diversity of 10 strains of Lactobacillus plantarum isolated from different foods including fermented olives, jar cheese, camel milk and sourdough using RAPD-PCR method also to compare their probiotic potential. The results showed that different banding patterns were created by three types of primers for different strains and according to the similarity matrix drawn by NTSYS software based on Jacard coefficient, a total of 10 strains were divided into two main branches and seven subgroups. The two strains of KAO 17 and KAO 64 isolated from fermented olives were most similar. In addition, the probiotic properties of L. plantarum isolates were evaluated different at strain levels. The results of immunoassay showed that all different strains of L. plantarum were gamma-hemolytic and resistant to vancomycin and their resistance to other common antibiotics was different. Strains isolated from jar cheese containing KMC 37 and KMC 45 had the highest acid resistance. On the other hand, resistance to 0.3% of bile salt showed that there was no significant difference in this regard between the strains isolated from fermented olives and the KMM 5 strain had the highest resistance. In addition, the antimicrobial activity of the strains against gram-positive pathogenic bacteria L. monocytogenes and gram-negative E. coli was different and the highest antibacterial activity belonged to the KMC 45 strain. Therefore, according to the intended purpose, each of the L. plantarum strains can be suggested as a probiotic culture in the food or pharmaceutical Industries.

In this study, the effect of rice flour on the survival of Lactobacillus paracasei and the qualitative properties of fruit yogurt was investigated during storage, using the response surface method (RSM). For this, rice flour in three ranges of (0, 1.5, and 3%) was added to the milk. Then the milk and was pasteurized at 85ºC for 15 minutes. After cooling, yogurt starter culture and probiotic bacterium were inoculated at 43 ºC and added into sterile containers containing 15% peach puree. The samples were incubated at 42 ºC until reaching pH 4.6 ±0.1. Then the samples were cooled down to 4 ºC and refrigerated at the same temperature until experiment day. Survival of lactobacillus paracasei, pH, amount of moisture, acidity, syneresis, and apparent viscosity and sensory properties were investigated in three periods of (1, 11, and 21 days). The statistical analysis of the results showed that with the increase of rice flour, lactobacillus paracasei count increased and decreased during storage (p<0.05). The addition of rice flour decreased pH, moisture content, syneresis, and increased acidity and apparent viscosity (p<0.05). During storage pH and moisture content decreased and syneresis increased (p<0.05). In the sensorial evaluation of samples, the addition of rice flour increased the consistency score (p<0.05). Flavor score decreased during storage (p<0.05). In conclusion, using 3% of rice flour and a storage period of 7 days was determined as the optimum condition.

Spices may be contaminated during various stages of harvesting, drying, or transporting. Different methods are used to reduce the microbial level of spices, which has problems such as flavor changes. The purpose of this study was to introduce optimized conditions for UVradiation on the reduction of microbial load of some high-consumption spices. Six types of spices, including turmeric, ginger, red pepper, black pepper, cinnamon, and sumac, were sampled from the Tehran market. Tests were carried out based on reference standards. Infected spices were then exposed to ultraviolet cabinets at 254 nm in thicknesses of 1, 5, 10 mm and 15, 10, and 5 minutes. A microbial test was performed on irradiated samples. According to the results, It was revealed that the time factor on the total count of aerobic mesophilic bacteria of turmeric, red pepper, black pepper, cinnamon, and also on the coliform count of turmeric and red pepper, as well as on the mould count of turmeric, red pepper, and black pepper had a quite significant effect (P<0.01). It was observed that the thickness effect was quite significant on the total count of aerobic mesophilic bacteria, total coliform, and count of mould. It significantly impacted the total count (p<0.01). The results of this study show that irradiation with UV radiation in the optimized condition can reduce the microbial content of spices to an acceptable level.

The aim of this study was to evaluate methanolic extract (ME) and essential oil (EO) of cumin (C) on the chemical, microbial and sensory properties of traditional lactic cheese. In this experimental study, CEO and CME were prepared. The compounds in the CEO were analyzed by gas chromatography/mass spectrometer and the phenolic content of the CME and CEO by the Folin Ciocalteu method. The cheese treatments containing CEO (125 and 250 ppm), CME (1 and 2%) and control group were prepared. Then, during 60 days of storage of samples, microbial tests including coliform counts, Escherichia coli, Staphylococcus coagulase positive, mold and yeast as well as also, chemical tests including fat, moisture, pH, acidity and salt were performed. Most compounds in CEO were cumin aldehyde (30.40 %), phenylglycol (18.99 %) and γ-terpinene (15.52 %). The phenolic content and antioxidant activity in CME was significantly higher than CEO. Adding CEO and CME to the cheese absorbed less water and salt than the control group, but the fat content increased. During storage, the acidity decreased significantly. The pH has increased slightly during storage and was in accordance with the results obtained by the acidity. The results showed no microbial contamination including coliforms, mold and yeast, E. coli and S. aureus in all groups. Sensorial results demonstrated that there was significant difference between the control group and the CEO groups with the CME groups. The results of this study showed that CEO and CME had high antimicrobial and antioxidant activity in traditional lactic cheese.