JOURNAL OF MICROBIAL WORLD
Year:2017 | Volume:9 | Issue:4 (29)|Papers Count:9

Background & Objectives: Staphylococcus epidermidisis one of the main causes of urinary tract infections and second cause of respiratory infections in human. The aim of this study was genotyping S. epidermidis strains isolated from nosocomial infections and detection of genetic clones using Multilocus Sequence Typing (MLST) method.Materials & Methods: In this cross-sectional study, 16 S. epidermidis isolates were selected and PCR products from amplification of seven housekeeping genes were sequenced. The nucleotide sequences of each gene in each isolate were analyzed in the MLST database and, besides identifying different clones, gene - specific alleles in each sequence types (ST) were determined.Results: A total of 3 clones including ST22, ST88 and ST153 were identified from 16 isolates, which was classified into two gene clusters of A and B. ST22 clone with a frequency of 50%, ST88 with 31.25% and ST153 with 18.75% were identified. The most dominant S. epidermidis clone isolated in 16 isolates is ST22.Conclusion: Dendrogram analysis of the isolates showed the homology of all isolates to alleles previously reported. Furthermore, our results suggest the genetic diversity of the isolates.

Background & Objectives: Staphylococcus aureus is one of the major causes of nosocomial infections throughout the world. Efflux pumps such as norA play a major role in the development of resistance to different antibiotics in this bacteria. The aim of this study was evaluation of the antibiotic resistance and detection of efflux pump (norA) in methicillin resistant (MRSA) and ciprofloxacin resistant S. aureus isolates using genotypic and phenotypic methods.Materials & Methods: During this sectional study, 250 clinical samples were collected from different hospitals in Tehran, Iran. S. aureus isolates were identified and the antimicrobial susceptibility patterns were determined. Ciprofloxacin minimum inhibitory concentration (MIC) was determined in both MRSA and ciprofloxacin resistant isolates. Furthermore, the presence of norA efflux pump gene in MRSA and ciprofloxacin resistant isolates was assessed phenotypically using ciprofloxacin and ethidium bromide MIC, with CCCP as efflux pump inhibitor, and genetically using PCR method.Results: Totally, 50 S. aureus isolates were recovered. The results of antibiotic susceptibility tests showed that 34 isolates (68%) were resistant to methicillin, of which 12 isolates (24%) were resistant to ciprofloxacin, as well. Moreover, all the MRSA- ciprofloxacin resistant strains harbored the norA gene and active efflux pump.Conclusion: The results showed the correlation between ciprofloxacin resistance and norA efflux pump gene in MRSA isolates. Development of efflux pump inhibitors can be useful in the control of MRSA ciprofloxacin resistant strains.

Background & Objectives: Acinetobacter baumannii a is a gram-negative coccobacillus which is increasingly reported as the major cause of nosocomial infections. The aim of this study was to determine the frequency of class I integron, and the prevalence of two important aminoglycoside modifying enzymese genes (aadA2 and aadB) in A. baumannii isolates.Materials & Methods: This cross-sectional study was performed on 33 A. baumannii isolated from patients who referred to Baghiatallah Azam and Shahid Modarres Hospitals in Tehran. Antimicrobial susceptibility of isolates was evaluated using disk diffusion method in accordance with CLSI guideline. The presence of intI1, sul1, aadA2 and aadB genes in clinical isolates was investigated by PCR technique.Results: The frequency of intI1, sul1, aadA2, and aadB genes in A. baumannii was observed as 51.5%, 51.5%, 24.2% and 36.4%, respectively. All isolates were multi-drug resistant, and the highest level of antibiotic resistance was shown to ampicillin, cefixime, cephalothin, nalidixic acid, clindamycin, chloramphenicol, sulfamethoxazole-trimethoprim, and streptomycin (100%). Furthermore, the minimum antibiotic resistance was shown to gentamicin (66.7%), and tetracycline (69.7%).Conclusion: A significant correlation was observed between class 1 integrons, and resistance to one antibiotic. However, this association was not remarkable in several other isolates with antibiotics resistance. This may imply that in addition to integrons, other determinants such as transposons and plasmids may also contribute to resistance.

Background & Objectives: Mercury is one of the polluting sources of the environment, plants as well as human. Microorganisms are resistant to mercury through different mechanisms. The main mechanism involves reduction of the toxic mercury to the elemental form which is mediated through a variety of bacterial genes. The aim of this study is to investigate the presence of mercury resistance gene in Raoultella planticula bacteria using polymerase chain reaction (PCR) and sequencing methods.Materials & Methods: Genomic and plasmid DNA was extracted from wastewater R. planticula isolates. PCR was set up with primers designed based on the presence of mer A gene in Klebsiella oxytoca. The PCR products were sequenced and analyzed using NCBI database.Results: Using PCR on plasmid and genomic bacterial DNA, a 1700 bps bond was obtained. Blasting the sequence, it was found that the amplified gene has 99% sequence homology to merA gene in Enterobacter cloacae, E. coli, Serratia marcescens, Klebsiella oxytoca and Acinetobacter.Conclusion: For the first time in this study, we found that Raoultella planticula isolated from Iran natural sources are resistant to mercury due to the presence of merA gene. Therefore, R. planticula can be considered an appropriate candidate to reduce or remove mercury from industrial wastewaters.

Background & Objectives: Phytate is the primary storage form of phosphorus in plant seeds. It has an anti-nutritive effect in both human and animals. Phytase is a subgroup of phosphatases which catalyzes the hydrolysis of phytate. Microbial phytases have potential biotechnological application in various fields, such as agriculture, human and animal foods. This study was aimed to investigate the optimal conditions for the production of phytase by Bacillus subtilis isolated from the soil.Materials & Methods: Samples were collected from Arak area, where the soil was contaminated with animal faces. Samples were incubated in PSM medium at 30oC for 48 hours. The screening of phytase - producing bacteria on PSM media was performed based on the formation of the clear halo. The most suitable bacterial strain was identified according to its biochemical and morphological characteristics. The level of enzyme production and phosphate- solubilising activity of this strain was assessed in different pH range, and on various media types including PSM, PVK, NBRIP, as well as NBRIY.Results: In this study, maximum enzyme production by the bacterial isolates has been observed following 36-48h incubation in PSM medium.12S phytase- producing bacterial strain was identified as Bacillus subtilis. Our results showed that the optimum pH for phytase production in PSM medium is pH of 7. Furthermore, investigating different media, phytate- containing PVK was recognised as the most appropriate medium for enzyme production.Conclusion: B. Subtiliseisolate can provide an opportunity to introduce new phytase to food as well as environmental industries. Moreover, PVK can be used as an effective medium to produce phytase enzyme and to screen phytase- producing bacterial starins.

Background & Objectives: Usually identification and characterization of ecosystems isolates of lactic acid bacteria (LAB) which have been rarely studied lead to obtaining LAB with unique characteristics. The aims of this study were molecular characterization and evaluation of the antibacterial properties of dominant LAB isolated from whole barley sourdough.Materials & Methods: In this experimental study, first the sourdough was prepared from the whole barley flour, and subsequently its dominant LAB was isolated. LAB isolate was identified by sequencing of PCR products. Antibacterial properties of the isolate and its cell free culture filtrate (CCF) which was obtained from logarithmic and stationary phases as crud and naturalized form were also investigated for some food-borne indicator bacteria using well diffusion and microdilution methods, respectively.Results: Sequencing results of PCR products lead to identification of Pediococcus pentosaceus as the dominant LAB in whole barley sourdough. This LAB isolate had more antagonistic effect (p<0.05) on Listeria monocytogenes than other indicator bacteria. Furthermore, crud CCF obtained from logarithmic phase of the isolate had the highest bacteriocin activity and antibacterial ability in comparison to other CCFs.Conclusion: Whole barley sourdough P. pentosaceus isolate and its CCF have proper antibacterial properties against food-borne indicator bacteria used in this study. Therefore, P. pentosaceus has high potential to be used as microbial starter or adjunct culture in processing fermented foods instead of chemical preservatives or antibiotics in order to increase shelf life and safety of these products.

H. Pyloriis an important cause of human peptic ulcers and stomach cancers. Once the bacterium is placed in the water, it changes into a viable, but non-cultivable coccoid form, which is considered as an important factor to spread out the infection. The aim of this study was to evaluate the survival rate of coccoid forms of H. pylori in water samples, using PCR and culture methods. This experimental study was performed on 10 strains of H. pylori isolated from clinical specimens. Isolates were added to water at the temperatures of 4oC, 22oC, and 37oC and incubated at intervals of 1 and 2 months. Each time, the samples were cultured on Brucella blood Agar medium. Following DNA extraction, the presence of glmM gene was confirmed using PCR method. Furthermore, the sensitivity and specificity of PCR method were evaluated. While culturing in first month at 4oC showed no H. pylori coccoid growth on medium, some positive results (growth rate of 10% and 20%, respectively) were detected at 22oC and 37oC during the same month. No positive result was obtained during the second month. Performing PCR, with more sensitivity as compared to culturing method, identified H. pylori coccoid growth of 10%, 30%, and 40%, for the first month, and 0%, 20%, and 30% for the second month at 4°C, 22°C, and 37°C, respectively. The results of this study showed that the non-cultivable cocoid forms of H. pylori in water can be detected by non-culturing methods such as PCR which is sensitive, specific, and accurate.

Background & Objectives: The antimicrobial activity of plant oils and extracts has been recognized for many years. There are many difficulties and deficiencies to control plant photogenic bacteria. Historically, natural plant products have been considered as great sources with therapeutic properties. This study was aimed to evaluate the chemical compositions and antibacterial activity of extract and essential oil of Artemisia aucheri collected from Iran.Materials & Methods: In this sectional study, the compositions of essential oil and ethanolic extract of Artemisia aucheri were determined by GC/MS and HPLC assays. Antibacterial activity of the essential oil and extract was evaluated using micro broth dilution and disc diffusion methods.Results: The main component of the oil was, 1.8 Cineol (22.65%), and the main polyphenolic compounds of the extract was chloregenic acid (264.9 mg/l). Evaluating MIC and MBC values of the essential oil, the maximum inhibition zone diameter (in the range of 6.4-8 mm, and 6.4-9 mm) was measured against Bacillus subtilis, Brenneria nigrifluens, Streptomyces scabies, Rhizobium radiobacter, Rhizobium vitis, Xanthomonas axonopodis pv. citri, and Xanthomonas arboricola pv. juglandis. Furthermore, evaluating MIC and MBC values of the extract the maximum inhibition zone diameter (in the range of 6.4-8 and 6.4-9 mm) was observe against Rhizobium Radiobacter, Brenneria nigrifluens, Rhizobium vitis, Streptomyces scabies, Bacillus subtilis, Xanthomonas axonopodis pv. citri, Xanthomonas arboricora pv. Juglandis, and Ralstonia solanacearum.Conclusion: In general, both essential oil and ethanolic extract showed desirable antimicrobial activity against plant photogenic bacteria. Therefore, Artemisia aucheri can be considered as a biopesticide.