مجله میکروب شناسی مواد غذایی
سال دهم شماره 2 (تابستان 1402)

Salmonella is one of the important  food borne diseases, worldwide. Egg and meat are among the most important incriminated foods to cause salmonella infection in Iran. This study was designed to investigate possible inhibitory effects of ethanolic extract of basil on Salmonella in mayonnaise sauce. Salmonella is killed with baking food but there is problem with foods like sauce which contain raw egg and is not used any procedure for baking them while producing. The purpose of this project was to investigate the possibility to use ethanol extract of basil to control Salmonella Typhimurium in sauce. In the study, first of all the anti-bacterial property of ethanol extract of basil was tested. So, by appearing result test for final investigation densities of extract was purposed 0.25, 0.5 and 0.75%. Then anti-bacterial property of ethanol extract of basil on growth of salmonella in mayonnaise sauce for a period of 30 days in condition of 25oc and 4oc was investigated.The results of statistical studies showed that the three concentrations studied significantly (p <0.05) compared to the control sample reduced the growth of Salmonella Typhimurium during storage and with increasing the concentration of the extract increased the antibacterial activity of the extract so that the extract Basil with a concentration of 7500 ppm was significantly lower than other treatments in most cases (p<0.05). Sensory evaluation test was performed by 5-point hedonic method and the results of sensory analysis of appearance and color in different treatments were not significantly different from each other. Regarding the flavour, texture and total acceptability of the sauce, the lowest sensory score was related to the treatment with a concentration of 0.75%. Based on the obtained results, the amount of bacteria in both temperatures decreased in all treatments and this decrease was little in the control treatment and its antibacterial activity increased with increasing the concentration of the extract.

Pseudomonas aeruginosa as a waterborne pathogen is a growing concern to public health sectors. Many sources of environmental water could potentially be acting as a reservoir for potentially pathogenic strains of P. aeruginosa. Due to the fact that P. aeruginosa is an opportunistic pathogen and causes serious problems, it seems necessary to know the pathogenesis, antibiotic resistance, genetic diversity and methods of removing it from drinking water. The pathogenesis of P. aeruginosa has been extensively studied and proven to be a multifactorial process, mediated by quorum sensing. P. aeruginosa possess two quorum sensing systems, las and rhl that facilitate cell to cell communication through production of signalling molecules termed autoinducers to target specific receptors for activation. P. aeruginosa is intrinsically resistant to various antibiotics due to a low permeability in the outer membrane, which acts as a selective barrier. However, this bacterium is a highly diverse pathogen that is capable of adaptation to the surrounding environment. When subjected to antibiotic selective pressure, the induced response facilitates bacterial survival and develops antibiotic resistance. literature suggests that the large genome size and genome complexity are responsible for the ability of this bacterium to adapt and thrive in a diverse range of environments. The presence and persistence of these bacteria in environmental waters may pose a great risk to the public health and requires further work to fully characterize and quantify the input of MDR P. aeruginosa strains from the hospitals compared with those originating from the general community or other wastewater related sources.

The health concerns of the Food and Drug Organization and the imposition of strict health regulations have prevented the establishment of many home-based food businesses, including local dairy products, in Iran. This approach has caused the lack of development of this sector of rural and nomadic industries and even the loss of local knowledge of the production of some of these products, which is very worrying. The purpose of this research was to assess the conformity of some traditional dairy products with the national standard and health regulations of home businesses in order to help the development of entrepreneurship in this field. In this study, conformity assessment was done by the independent assessment method (third person). Initially, the legal requirements, i.e., the national standards related to dairy products and production health regulations, were selected and compiled. The sampling of products and measurement of physicochemical and microbial characteristics were carried out based on relevant national standards. Then, the degree of conformity of these products with the legal requirements (national standards) was determined by matching the findings with the standard limits. Based on the obtained results, the health conditions of Lighvan cheese, Jug cheese, skin cheese, Salmas cheese, Arushe, Kashk, Qaraqrout, Chiko, Tof, Dogh and ghee products were in good agreement with the national standard criteria. Therfore, these products can be consumed without worrying about microbial and heavy metals contamination. The development of these products in the form of home businesses can play an important role in creating employment and improving the economy of rural areas.

Dates are one of the most important agricultural products and have a high nutritional value. Quality control of dates is important to maintain the health of this food and also to compete in global markets. Annually, large quantities of dates lose their quality due to microbial contamination. This study is performed to analyze the microbiological quality of the date that is offered in the production units and the market in the southwest of Khuzestan province.70 date samples collected during 20 months were examined and analyzed according to relevant national and international standards. Total counts, mold and yeast, Enterobacteriaceae and Escherichia coli identification were performed on all date samples and the results were statistically analyzed. It was found that 38 samples (54.28%) of the total samples were infected with various microbes. 54.27% of the total samples were mold, 18.57% yeast, 10% total counts, 7.14% of Enterobacteriaceae and 4.28% of E.coli cases were higher than the standard allowable date.The results showed the growth of microbes, especially mold and yeast in a significant number of date samples, which is considered as a serious risk factor to challenge the quality and safety of dates. Therefore, different methods of washing, processing and packaging of dates in different regions that have this product should be studied and the best methods should be selected according to geographical and local conditions and type of date cultivar to maintain microbial quality and subsequent quality of the final date product.

The present study was conducted with the aim of evaluating the antibiotic resistance pattern of Bacillus cereus in ice cream, cake, cheese, and infant formula. For this purpose, 600 samples were prepared from food sales centers in Tehran and transferred to the quality control laboratory of the Faculty of Veterinary Medicine of Tehran University of Medical Sciences and cultured on the special culture medium of Bacillus cereus, MYP, which contained polymyxin B supplement and egg yolk. Then, from the pink colonies, gram staining and catalase test were performed and the sensitivity of the isolated bacteria to ampicillin, penicillin, vancomycin, cefazolin, methicillin, cefixime, sulfamethoxazole, trimethoprim, chloramphenicol, cefepime and tetracycline was evaluated based on the disc diffusion method. According to the results, no contamination with B. cereus was observed in any of the cake, cheese and ice cream samples. However, out of 150 infant formula samples, 30 samples were infected with B. cereus (18 samples < 10 CFU/g, 7 samples had 10-102 CFU/g, and 5 samples>102 CFU/g). B. cereus isolated from infant formula has the highest sensitivity to vancomycin (67.76%), tetracycline (70%), and chloramphenicol (33.63%) antibiotics and had the highest level of resistance to penicillin (100%), cefixime antibiotics (100%) and ampicillin (67.96%). The general results indicated a significant prevalence of B. cereus in the tested milk, which due to the growing trend of using milk powder and more importance to the quality and health evaluation of milk powders for consumption, contamination investigation and preventive approaches should be given more attention.

Isolation and identification of bacteria with useful properties from local products can play an important role in introducing unique types of probiotics. The aim of this study was to isolate, identify and evaluation of the ability of Bifidobacterium bacteria isolated from Tarkhineh traditional food in lowering cholesterol and triglyceride levels of the culture medium. Native strains of Bifidobacterium were isolated from a local food called Tarkhineh using general and specific culture media and identified based on phenotypic characteristics, standard biochemical tests and 16S rRNA sequencing. Then, samples with probiotic properties such as resistance to acid and bile were examined in terms of sensitivity to common antibiotics. Cholesterol and triglyceride lowering activity of their culture medium was also measured by o-phthaldehyde method. During this study, 210 bacteria were isolated from Tarkhineh food, including 13 strains of like Bifidobacterium bacteria. Among them, 10 strains were resistant to acid and bile condition. Antibiotic susceptibility analysis showed that most strains were sensitive to common antibiotics and S4 and S1 strains reduced cholesterol in culture medium by 75 ± 0.58 and 71±0.13%, respectively (p<0.01). Among the strains, strains S4, S10 and S1 applied 65%, 63% and 62% reduction of the medium triglyceride, respectively. The data of this study showed that the probiotics isolated from the local food of Tarkhineh had the potential to absorb and reduce cholesterol and triglycerides of the culture medium to a significant extent. It seems that the potential of these strains to improve the lipid pattern can be further investigated.

Salmonella is one of the most important bacteria which cause illnesses, may exist in raw foods. The presence of this bacterium in food also causes a decrease in the quality of productions and a decrease in the economic growth. Milk and its products are among the food that may contaminate with Salmonella both primarily and secondarily by employees, water, etc., and transmitted to human. In this study, 100 samples of raw milk and 50 samples of traditional cheese from different parts of Chaharmahal and Bakhtiari province were obtained to isolate and identify Salmonella bacteria using microbiological, and polymerase chain reaction tests. Also, the antibiotic resistance of Salmonella isolates was evaluated by the diffusion disk method. The results of microbiological tests showed that 7 samples were contaminated with salmonella. Suspicious isolates included 5 samples belonging to raw milk and 2 samples belonging to traditional cheeses. The results of PCR test revealed that 3 samples of suspected isolates of raw milk (%3) and 1 sample of suspected isolates of traditional cheese (%2) were S. typhimurium. The results of the antibiogram test on Salmonella isolates showed the highest sensitivity to Gentamicin and Ciprofloxacin, and the highest resistance to Ampicillin, Tetracycline and Trimethoprim sulfamethoxazole antibiotics. According to the results of the present study, raw milk and traditional cheeses are contaminated with Salmonella typhimurium, which are resistant to some antibiotics. Although the contamination of raw milk is removed during the heat treatment steps such as pasteurization, boiling or sterilization, traditional cheeses contaminated with this bacterium are considered a potential risk for the health of consumers. Therefore, the examination of traditional dairy products, especially cheese, in terms of preventing the occurrence of diseases in humans seems to be more necessary.

The present study was conducted with the aim of evaluating the antibiotic resistance pattern of Bacillus cereus in ice cream, cake, cheese, and infant formula. For this purpose, 600 samples were prepared from food sales centers in Tehran and transferred to the quality control laboratory of the Faculty of Veterinary Medicine of Tehran University of Medical Sciences and cultured on the special culture medium of Bacillus cereus, MYP, which contained polymyxin B supplement and egg yolk. Then, from the pink colonies, gram staining and catalase test were performed and the sensitivity of the isolated bacteria to ampicillin, penicillin, vancomycin, cefazolin, methicillin, cefixime, sulfamethoxazole, trimethoprim, chloramphenicol, cefepime and tetracycline was evaluated based on the disc diffusion method. According to the results, no contamination with B. cereus was observed in any of the cake, cheese and ice cream samples. However, out of 150 infant formula samples, 30 samples were infected with B. cereus (18 samples < 10 CFU/g, 7 samples had 10-102 CFU/g, and 5 samples>102 CFU/g). B. cereus isolated from infant formula has the highest sensitivity to vancomycin (67.76%), tetracycline (70%), and chloramphenicol (33.63%) antibiotics and had the highest level of resistance to penicillin (100%), cefixime antibiotics (100%) and ampicillin (67.96%). The general results indicated a significant prevalence of B. cereus in the tested milk, which due to the growing trend of using milk powder and more importance to the quality and health evaluation of milk powders for consumption, contamination investigation and preventive approaches should be given more attention.