Showing 608 results for Yan
Volume 0, Issue 0 (Articles accepted at the time of publication 2024)
Abstract
In spite of the potential merit of technology-enhanced education in offering an innovative educational game in the arena of English teaching and learning, they have not garnered much momentum in terms of practical research, particularly in ELT speaking domain and their potential role in the Covid-19 pandemic and post-pandemic eras. This constitutes a substantial gap in the extant corpus of literature, which will be addressed in the current study by exploring the short- and long-term impacts of immersive virtual reality and space team ESL games on the speaking abilities of Iranian EFL learners. To this light, 54 basic EFL students from private language institutions in Urmia were selected through convenience sampling and an intact group design. Three classes were randomly exposed to two treatments, encompassing virtual reality, space team, and a control group receiving traditional instruction. The participants were pre-tested with the IELTS speaking test before receiving the treatment, and the same instrument was utilized for post-tests and delayed post-tests. In contrast to the traditional group, the results demonstrated that both immersive virtual reality and space team games enhanced students' short- and long-term oral performance. The findings of this study could be well-regarded as an important proposal for considering game-based instruction as an integral component of ELT classrooms and a technique for promoting language proficiency in non-native contexts.In spite of the potential merit of technology-enhanced education in offering an innovative educational game in the arena of English teaching and learning, they have not garnered much momentum in terms of practical research, particularly in ELT speaking domain and their potential role in the Covid-19 pandemic and post-pandemic eras. This constitutes a substantial gap in the extant corpus of literature, which will be addressed in the current study by exploring the short- and long-term impacts of immersive virtual reality and space team ESL games on the speaking abilities of Iranian EFL learners. To this light, 54 basic EFL students from private language institutions in Urmia were selected through convenience sampling and an intact group design. Three classes were randomly exposed to two treatments, encompassing virtual reality, space team, and a control group receiving traditional instruction. The participants were pre-tested with the IELTS speaking test before receiving the treatment, and the same instrument was utilized for post-tests and delayed post-tests. In contrast to the traditional group, the results demonstrated that both immersive virtual reality and space team games enhanced students' short- and long-term oral performance. The findings of this study could be well-regarded as an important proposal for considering game-based instruction as an integral component of ELT classrooms and a technique for promoting language proficiency in non-native contexts.
Volume 0, Issue 0 (Articles accepted at the time of publication 2024)
Abstract
Among increasing interest in emotional and relational dimensions of language teaching, this conceptual review highlights the essential effect of interpersonal justice in promoting learner well-being and engagement in English as a Foreign Language (EFL) settings. Based on Self-Determination Theory (SDT), asserting that learning is most effective when individuals' basic psychological needs for competence, autonomy, and relatedness are fulfilled, this review investigates the effect of interpersonal justice can address these needs and it also synthesizes extended empirical results to investigate the effect of respectful, empathetic, and dignified class interactions on cultivating engagement, and well-being in EFL students. Recontextualization of the previous research in this review illustrates that previously examined justice-related elements had contributed to enhancing learner engagement and well-being. Justice educational activities, including unbiased feedback, active listening, and dignity-preserving communication, reduce anxiety, foster trust, and maintain learner persistence, thereby promoting engagement and well-being. The review ends with practical implications for teachers and policymakers and outlines future research directions focused on extending comprehension of interpersonal justice as an affective and motivational structure in EFL settings.
Volume 0, Issue 0 (In press 2023)
Abstract
Urban growth boundaries are considered one of the key tools for controlling and managing the physical development of metropolitan areas. Uncontrolled and unplanned expansion in these regions has become a major challenge for urban and regional planners and managers, as this process leads to the destruction of agricultural lands and natural resources. The aim of this research is to simulate and assess future changes in growth boundaries in the Isfahan metropolitan area with the goal of preserving environmental resources and controlling physical expansion. In this regard, by adopting a positivist approach that follows an analytical and measurement-driven process, satellite imagery was utilized to assess changes in the physical expansion of the Isfahan metropolitan area. Artificial neural networks and machine learning algorithms were employed to predict the extent of future physical growth, and the projected growth boundaries were delineated. The research findings indicate that the Isfahan metropolitan area has experienced significant uncontrolled expansion, particularly in terms of physical development, over recent decades, and the reduction of agricultural and natural lands has become one of its major challenges. Based on the conducted simulations, the proposed growth boundaries can serve as an effective tool for managing and planning urban-regional development and preventing further degradation of natural resources and lands.
Suryono Suryono, Anton ApriYantono, Ester Restiana Endang Gelis,
Volume 0, Issue 0 (ARTICLES IN PRESS 2024)
Abstract
Yogurt is a widely consumed fermented product celebrated for nutritional benefits and distinctive aroma, influenced by factors such as the type of probiotic bacteria, incubation methods, and the used milk type. Common bacteria in yogurt production include Lactobacillus bulgaricus and Streptococcus thermophilus. Aroma is crucial for consumers’ acceptance and varies according to the compounds formed during fermentation. Therefore, this study aimed to investigate the effect of different probiotic bacteria on aroma of yogurt through a unique incubation process. Probiotic bacteria examined were Lactobacillus, Streptococcus, and Bifidobacterium. Additionally, yogurt production process included sterilizing skim milk, introducing bacterial cultures, and incubating at specific temperatures. Aroma components of yogurt were analyzed using Gas Chromatography and Mass Spectrometry. The result showed that yogurt comprised various aroma compounds classified into four categories, namely acids, alcohols, ketones, and aldehydes. The dominant acid components found were acetic, octanoic, decanoic, and dodecanoic acids. Among the components, alcohol affected aroma despite being present in minimal quantities. Ketones such as acetoin and diacetyl were identified along with aldehydes including octadecanal and dodecanal in yogurt. This study provided valuable insights into the effect of probiotic bacteria on aroma profile of yogurt, assisting manufacturers in refining production processes to prepare product appealing to consumers.
Nematollah DaYani, Mohammad Chamani, Parvin Shawrang, Asa Ebrahimi, Ali Asghar Sadeghi,
Volume 0, Issue 0 (ARTICLES IN PRESS 2024)
Abstract
This study aimed to determine the effects of energy levels and sources on growth performance, antibody titers, and the gene expression of pro-inflammatory cytokines in broilers exposed to heat stress. 450 one-day-old Ross chickens were assigned to six dietary treatments and five replicates in a completely randomized design. Chickens have received diets differentiated by main energy source (corn grain and soybean oil) and energy level (equal, 3 or 6% lower or higher than Ross 308 recommendation). Treatments were as follows: corn grain and equal as control (CON), corn grain, 3% lower (T1), corn grain, 6% lower (T2), corn grain and soybean oil, equal (T3), corn grain and soybean oil, 3% higher (T4), corn grain and soybean oil, 6% higher (T5). The room temperature was increased to 34 °C (6-h daily) from day 12 to 42 of age to induce heat stress. The highest corticosterone level was observed in the T1, T2, and T5 groups. The lowest antibody titers were observed in the T2 group and the highest expression levels of pro-inflammatory cytokines genes were in chickens receiving T5 diet. The highest feed conversion ratio (FCR) during the grower and finisher periods was observed in T2, and the lowest FCR was observed in T3 and T4 groups. It was recommended to feed Ross broiler chickens with a diet containing oil instead of a part of grain based on energy recommended by the strain recommendation.
Mohammad Bagher KiYanisefat, Marjaneh Sedaghati, Mohamad Javad Shakouri,
Volume 0, Issue 0 (ARTICLES IN PRESS 2024)
Abstract
This study was conducted aiming at evaluating the physicochemical, antioxidant, microbial and sensory properties of functional fermented camel milk (FCM) with varying β-glucan concentrations (0, 0.1, 0.2, and 0.3%), and a combination of the bacterial cultures Lactobacillus Plantarum and Lactobacillus Rhamnosus. The FCM matrix was assessed for pH/acidity, phase separation, viscosity, color, total phenolic content (TPC), antioxidant activity (AO), probiotic viability, and sensory characteristics by 12 participants. The results were analyzed using one-way ANOVA applied to data from a completely randomized design with three replicates, followed by LSD post hoc tests for comparison of treatment means. The pH, acidity, antioxidant activity (IC50), viscosity, and probiotic viability of fortified FCM ranged from 3.46-4.4, 0.141%-0.429%, 27.01-69.67 (mg.mL-1), 1025-2355 (mPa.s-1), and 6.17-8.95 (cfu.mL-1) respectively. The Results demonstrated that β-glucan fortification (0–0.3%) significantly (P˂0.05) increased acidity, TPC, AO, viscosity, and probiotic viability in FCM, while reducing pH and phase separation. Increasing β-glucan concentration in the samples was associated with a significant decrease in the brightness index (L), accompanied by significant increases in the yellowness (b) and redness (a*) indexes (P<0.05). According to the sensory panelists' assessments, increasing the β-glucan concentration to 0.2% was deemed favorable. These findings suggest that fortification of fermented camel milk with 0.2% β-glucan optimally enhances its functional, physicochemical, and sensory properties, supporting its potential as a health-promoting dairy product.
Behrooz Alizadeh Behbahani, Hossein JooYandeh, Morteza Taki, Fereshteh Falah,
Volume 0, Issue 0 (ARTICLES IN PRESS 2024)
Abstract
Probiotic juices have experienced a notable rise in popularity due to their potential health benefits, particularly for digestive health. This study examined the viability, physicochemical characteristics, and sensory qualities of kiwifruit juice containing Lacticaseibacillus paracasei B31-2. To analyze the data, Gaussian Process Regression (GPR) and Multi-Layer Perceptron (MLP) models were used to predict various factors, including pH, acidity, viable cell counts of L. paracasei B31-2, color differences (ΔE), and overall acceptance. Probiotic L. paracasei B31-2 was added to the kiwifruit juice at different concentrations (0%, 1% and 2%) and stored at 4 °C. The probiotic juices showed fewer changes in pH, acidity, and color compared to the control juice during storage at room temperature. The sample with a 2% probiotic concentration exhibited the highest viable cell count (7.98 log CFU/mL) and received the most sensory scores among the tested samples. A strong correlation between the predictions made by the GPR model and the actual observed data further validated its effectiveness in similar experimental contexts. This suggests that GPR could offer strategic benefits by lowering laboratory costs and improving analytical efficiency. The GPR model's precision in closely matching real-world data demonstrates its potential as a cost-effective and expedited tool for scientific inquiries. Overall, these findings indicate that kiwifruit juice serves as a promising substrate for carrier of L. paracasei B31-2
Volume 0, Issue 0 (Articles accepted for Publication 2024)
Abstract
Aim and Introduction
By integrating insights from psychology—especially cognitive psychology—into economic theory, behavioral economics provides a more realistic understanding of human behavior and economic decision-making (Thaler, 2017). A key subset of this field is behavioral finance, which posits that investment decisions are not always based on rational optimization. Instead, behavioral factors often lead to perceptual distortions, biased judgments, and irrational interpretations. These tendencies stem from various behavioral biases—collectively referred to as irrational behaviors—which commonly arise due to investors’ limited capacity to process information and the impact of emotional factors on their decision-making (Abildgren et al., 2018; Di Stefani, 2021; He & Xia, 2020; Glavatsky et al., 2021; Lan, 2014; Mayer & Siani, 2009; Tan, 2022; Yang et al., 2020).
One notable cognitive bias is herding behavior, which refers to individuals mimicking the actions of the majority. This phenomenon is particularly notorious in markets such as housing, coins, and currency, where it is widely regarded by experts as a primary driver of severe and irrational price fluctuations (Rook, 2006).
Methodology
This research employs spatial econometric techniques to analyze the effects of dependency culture on herding behavior in the housing market across 31 Iranian provinces from 1390 to 1400 (2011–2021) on a seasonal basis. Spatial econometrics extends traditional panel data models by incorporating geographical dimensions, which enables the analysis of spatial interdependence and regional heterogeneity. In the presence of spatial components, two primary issues must be addressed: spatial dependence, which refers to correlation among geographically proximate units, and spatial heterogeneity, which refers to structural differences across regions.
Before estimating the spatial panel models, tests for spatial autocorrelation were conducted to determine the necessity of incorporating spatial effects into the analysis. Specifically, Moran’s I, Geary’s C, and Getis-Ord J statistics were used to assess the presence of spatial autocorrelation among the error terms. A significant spatial dependence justifies the application of spatial econometric models. To define spatial relationships, two forms of spatial weighting structures were considered: coordinate-based distances derived from latitude and longitude, and neighborhood-based contiguity matrices that capture the relative location of each province in relation to others. Based on the detection of significant spatial autocorrelation, the Spatial Autoregressive (SAR) model was selected to capture the dynamic spatial interactions within the housing market across Iranian provinces.
Findings
The results of the spatial econometric analysis confirm that exchange rate fluctuations have a positive and statistically significant impact on the housing market across both the target provinces and their neighboring regions. This finding supports the hypothesis that dependency culture, shaped by sensitivity to macroeconomic signals such as exchange rate movements, plays a key role in fostering herd behavior within Iran’s housing sector during the study period. The presence of spatial spillovers indicates that changes in one province can influence housing activity in surrounding areas, reinforcing regional contagion effects.
In addition to the exchange rate, the variables of inflation rate, population density index, and the logarithm of stock exchange transaction volume were also found to have positive and significant effects on housing market dynamics. These factors appear to stimulate speculative behavior and intensify market activity. Conversely, the logarithm of the distance from Tehran province exhibited a negative and significant effect on housing market outcomes.
Discussion and Conclusion
In Iran, there are no legal limitations on the frequency of property transactions, which allows a residential unit or parcel of land to be repeatedly traded within a year. This lack of regulation encourages speculative and herding behavior. To mitigate this, the study recommends implementing transaction limits and a more effective taxation system, similar to those used in developed countries. For example, imposing higher taxes on multiple home ownership and on vacant housing units can discourage speculation.
Despite the high number of vacant units, a significant proportion of Iranian households remain without access to adequate housing and face declining welfare due to soaring rents. Targeted housing assistance—including free land allocation—could help meet the actual demand and reduce speculative demand, thereby limiting herd behavior.
Furthermore, price booms typically originate in metropolitan and affluent regions, suggesting that a more balanced spatial development strategy could help diffuse housing market pressures. Introducing region-specific construction and transaction regulations, especially in high-risk speculative areas, could further manage housing price volatility.
Finally, encouraging investment in parallel financial markets and increasing stability and public trust in those markets could redirect speculative behavior away from real estate. Creating viable alternative investment opportunities would absorb excess liquidity and help stabilize the housing sector.
Volume 1, Issue 1 (NO. 1- 2011)
Abstract
The process of globalization and the formation of new competitive environment have not only led to the necessity of export for the economy of nations, but also to the survival and growth of many companies. The type of a company's strategic orientation is considered as one of the most important factors for export success. Among them is proactive versus reactive orientation. Being proactive is defined as a managerial understanding, in which an organization can affect its destination through the systematic analysis of opportunities and threats. On the other hand, being reactive indicates low levels of demand analysis and market research of an organization. It is expected that exporting companies with proactive strategic orientation enjoy a more successful exporting experience. In contrast, reactive strategic orientation undermines the export success of a company. Accordingly, the conceptual model of this study was formulated and four hypotheses were established based on this conceptual model. Through the data collected by a questionnaire from a sample of 34 exporting companies located in Mashhad (Iran), and then using regression analysis, the results obtained showed that proactive strategic orientation has a positive effect on export success and expected both export success. On the other hand, the negative impacts of reactive strategic orientation on export success and expected export success were rejected.
Volume 1, Issue 1 (NO. 1- 2011)
Abstract
According to the resource based attitude, the capabilities of information systems improve firms’ performance and competitive advantages through three ways: 1) inside-outside capabilities, 2) outside-inside capabilities and 3) spanning capabilities. Because of the importance of systematic study on the relationship between these capabilities and firms’ performance this paper was aimed at investigating this relationship using fuzzy analytic hierarchy process (FAHP). We utilized the FAHP because of existing several indices, complexity of decisions and uncertainties that are intrinsically involved in the evaluation of these capabilities. The results imply that among the criteria, return on sales and cost of sold goods are two key criteria that facilitate firms’ success. Moreover, inside-outside capabilities regard a good stimulus for improving firms’ performance. Then, firms’ internal capabilities are more important in responding to market than outside-inside capabilities.
Volume 1, Issue 1 (4-2014)
Abstract
Background and Objectives:HBV and HTLV-I are life threatening infectious agents in patients who receive blood and blood products. Although serological methods have been proved to be useful, detection of these viruses has remained a challengingissue due to the many obstacles. By the advent of Nucleic Acid Testing methods, especially in multiplex format, more precise detection is possible.The objective of this study was to develop a reliable, rapid and cost- effective method tosimultaneously detect HBV and HTLV-I. Materials and Methods: We have developed a multiplex Real time-PCR assay for simultaneous detection of HBV and HTLV-I. Primer sets were designed for highly conserved regions of genome of each virus. Using these primers and standard plasmids, we determined the limit of detection, clinical and analytical specificity and sensitivity of the assay. Monoplex and multiplex Real-time PCRs were performed. Results: Analytical sensitivity was considered to be 1000 and 100 copies/ml for HBV and HTLV-I, respectively. High concentration of one virus had no adverse effect on detection of t low concentrations of the other one. By analyzing 30 samples, clinical sensitivity of the assay was determined to be 87% and 96% for HBV and HTLV-I, respectively. Using different viral and human genome samples, the specificity of the assay was verified to be 100%. Conclusions:We have developed a reliable, rapid and cost effective method tosimultaneously detect HBV and HTLV-I.Our results indicatedthe high capability of this simple and rapid method for detecting these viruses in clinical samples.
Volume 1, Issue 1 (4-2013)
Abstract
Comparative literature is a branch of literature that considers the literary relation and influences of the countries. Scholar of comparative literature sits between two or more branches and records the literary-cultural transfers. This article is an attempt to study the cultural and story similarities between two the literary works; an Iranian and a French. "Leili o Majnoun", Nezami’s literary work and "Cyrano de Bergerac", Rostand’s piece have commons aspects about the content and the personality of their heroes; platonic love is the most important element in these literary works. Among the other similarities, we can represent the reality of their stories and the common literary structure. In spite of the similarities, we should consider the differences of the heroes in their manner of love-affair. An innocent love is another common point between these masterpieces, which finished with the death of heroes, Majnoun and Cyrano. In this article, we try to expand these similarities and the differences with a comparative consideration in order to conquer a new horizon.
Volume 1, Issue 1 (Spring 2020)
Abstract
This study aimed to determine the effect of selected physical activities on life skills. For this purpose, 80 male students aged 12-15 were selected as available samples. Then, the Beck Physical Activity Questionnaire and Walker Walker Lifestyle Questionnaire were divided into two groups of control and experimental based on their scores. The experimental groups performed the selected exercise protocol for 12 sessions, each for 1.5 hours. After 12 sessions for both groups, a post-test was performed. In order to compare the subscales of accountability, interpersonal relationships, growth and prosperity of the two experimental and control groups, the pre-test and post-test stages of the mixed variance analysis test are used in a 2 × (group) 2 design. A one-way covariance analysis test was used to compare subscales of appropriate nutrition, stress management and exercise and physical activity. All statistical calculations were performed in SPSS software at a significant level of 5%. Given that the role of exercise and physical activity in childhood and adolescence is undeniable in developing social skills, responsibility, happiness, vitality, etc., it is suggested that three sessions per week of out-of-school physical activity be improved. And the development of life skills.
Volume 1, Issue 2 (6-2013)
Abstract
Recently the previous Caspian ecosystem is in a catastrophic condition which caused changes in the absolute and relative abundance of the commercially important Caspian kutum (Rutilus frisii kutum) in Iranian waters. The paper presents estimates of yield-per-recruit and spawning biomass-per-recruit under various harvest strategies of Fmax, F0.1, F30%. It proposes a method for estimating acceptable biological catch (ABC) that accounts for large differences in the quality and quantity of information and available data. The current average Y/R (with F=0.61/y, and tc=3.2 y) was 218.3 g per recruit, which indicates that the fishery is operating below the maximum Y/R at 236.9 g when tc = 3.5 y. The Y/R was the highest at Fmax and F0.1, when tc = 4 y (244.8 g and 214.2 g), respectively. The F30% value was 0.85/y at tc of 4 y with the SB/R of 338.3 g. The Fcurrent (0.61/y at current tc is 3.2 y) is higher than the corresponding reference points, F0.1 (0.47/y) and F30% (0.46/y). The ABC of kutum was estimated at 7,850 mt in 2009-2010.
Volume 1, Issue 2 (12-2015)
Abstract
A survey was conducted in fields of cucumber and watermelon in Bengaluru, India during April 2014 for dertermination of the common parasitoids (Hym.,Braconidae, Aphidiinae) attacking melon aphid, Aphis gossypii Glover (Hemi., Aphididae). Three species of Aphidiinae, including Aphidius platensis Brethes, 1913; Binodoxy sacalephae (Marshall, 1896) and Lipolexis oregmae(Gahan, 1931) were collected and identified, from which Aphidius platensis is newly recorded from India. The early evidence of Aphidius colemani in India can also be contributed to A. platensis. Diagnostic characters of three species with closely related species are briefly discussed.
Volume 1, Issue 3 (Summer 2021)
Abstract
Thoughts Kierkegaard, one of the leading pioneers of existentialist philosophy, has greatly influenced Sartre's existentialist ideas and his literary and theatrical works and prominent filmmakers in the history of world cinema and other artists in other fields. In this article, organized in three parts, we aim to examine the reflection of Thoughts Kierkegaard's on categories such as "truth, forgetfulness, domination of popular beliefs, existential and non-existent human beings, individualization and liberation from Intermediate, and freedom and Selection." Sepehr Hasti and ... " are among the factors that Sartre's literary works are completely influenced by and in artistic forms and forms and the form of images and dramatic phenomena in dramatic and literary works, Sartre's screenplays are skillfully, creatively, and attractively reflected. Has found. In the form of fascinating visual events, stories, and adventures, these phenomena have woven and implemented the abstract ideas of existentialism in such a way that its created characters, as if living in their natural life and in a completely real way, disappear. Sartre's plays The Flies, a historical work adapted from the Greek playwright Euripides, The Noble Prostitute, the subject of contemporary American society, and The Infected Gangs, whose adventures and events take place. Concerned with World War II and the French resistance movement, it has received the most influence from Kierkegaard's philosophical thought. In this article, we have shown the extent of Sartre's influence on Kierkegaard by examining these plays.
Volume 1, Issue 4 (12-2012)
Abstract
Fungi belonging to the Mycosphaerella s. l. are widely distributed all over the world. Most taxa cause leaf spot diseases, and have considerable impact on cultivation of many economically important crops. On Eucalyptus species, for example, Mycosphaerella leaf spots are one of the major diseases responsible for severe damage in most parts of the word especially outside of their native cultivation range. Mycosphaerella leaf blotches on Eucalyptus have little been studied in Iran. During a study on fungi associated with leaf spots on Eucalyptus spp. several specimens of mitosporic fungi which have been collected from Guilan province were examined and two species viz. Kirramyces epicoccoides and Pseudocercospora eucalyptorum were found to be new records for Iran mycobiota. Moreover, another species of Pseudocercospora is described on Eucalyptus. This species is clearly distinguished from related taxa by its conidium morphology, and appears to represent a new species; however, due to complicated taxonomy of the genus Pseudocercospora (especially on Eucalyptus spp.) further information is required to confirm its taxonomical position.
Volume 2, Issue 1 (3-1991)
Abstract
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Volume 2, Issue 1 (1-2017)
Abstract
To determine the occurrence of Work related Musculoskeletal Disorder (WMSD), its prevalence and risk factors among school teachers in India. 100 questionnaires was passed out and sent to teachers of different schools ranging from primary school to higher secondary schools across Kolkata and Aizawl. 72 percent of the teachers responded. A standardized Dutch Musculoskeletal Questionnaire (DMQ) was used. Neck pain was the most prevalent musculoskeletal complaint, reported by 53.52% of the respondents while chronic neck pain was not reported by the teachers. Shoulder and back pain were less prevalent than neck pain but the prevalence of chronic pain in these body sites were higher. Furthermore wrist/hand and knee pain were less prevalent than the other complaints. Working with hands above the shoulder was the highest reported risk factor (62.27%). School teachers are susceptible to WMSD with a significant prevalence for neck, shoulder, back, wrist/hand and knee pain. Prolonged working nature like bending the neck forward/backward or holding the neck in a Forward/backward posture, same movements with arms, hands or fingers many times, hands above the shoulder level, reaching with arms or hands and standing are important factors which affect the occurrence of musculoskeletal disorders.
Volume 2, Issue 1 (3-2016)
Abstract
Abstract
Background:
Streptococcus mutans in the oral cavities sable to produce mutacin (bacteriocin-like substances) with antibiotic properties. The aim of this study was to investigate the frequency and expression of genes encoding mutacins typeI, II, III and IV and also two of 8 genes in a cluster encoding the putative bacteriocins, the designated bsm 283, bsm 299, bsm 423, bsm 1889c, bsm 1892c, bsm 1896, bsm 1906c and bsm 1914, were also screened by PCR and specific primers for each type of mutacin biosynthesis gene and then mutacin activity against the indicator strains determined.
Methods
: In this study, dental clinic samples were collocated; Streptococcus mutans was detected using biochemical tests and molecular methods (PCR). Frequency of mutacin biosynthesis genes types I, II, III and IV, bsm299 and bsm1899 were measured by PCR, using specific primers for each type of mutacin biosynthesis gene. Furthermore, the antimicrobial spectra of Streptococcus mutans isolates against other indicators, including Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Salmonella typhi, Pseudomonas, Escherichia coli were evaluated using well diffusion, disk diffusion and the minimal inhibitory concentrations (MICs) methods.
Results
: Out of 56 samples collected from patients referred to Milad Hospital dental clinic on October 2011 and three private dental clinics on November 2011, 24 strains of Streptococcus mutans produced mutacins. 67.52% of the strains had a wide antimicrobial spectrum and 37.5% of 67.5% had a high frequency of genes with more inhibitory activity against, Staphylococcus epidermidis, Staphylococcus aureus and Enterococcus faecalis respectively that are more related to putative bacteriocins. The expression frequency of the bsm gene (putative bacteriocins) was higher than that of the characterized mutacins types (I–IV). The lowest dilution rate mutacin was found against Staphylococcus epidermidis (0.0625 unit/mL).
Conclusion
: These findings suggested that all putative bacteriocins may represent a large repertoire of inhibitory substances produced by Streptococcus mutans. Therefore, the high diversity of mutacin-producing phenotypes, associated with high frequency of expression of the biosynthesis genes screened and wide antimicrobial activity against Staphylococcus epidermidis could be used as safe antimicrobial agents in treatment of superficial infections such as, removing the pimple caused by Staphylococcus epidermidis.
