Vol 6 No 3-4 (2017)

Original Articles

  • XML | PDF | downloads: 318 | views: 615 | pages: 1-13
    Background:   The genus Bordetella harbors 16 species; three of them are well-known for their high medical importance. The phylogenetic diversity of the genus is currently not very well investigated.Methods:    In this study, 16S rRNA gene sequence of 16 type strains of the Bordetella species were analyzed. Also, phylogenies conducted on the same gene of 247 isolates of Bordetella species, comprising a wide physiological as well as ecological diversity and encompassing ex-type representatives of the 16 Bordetella species, were analyzed.  Results:   It was found that the phylogenetic diversity of the genus may be very different from that is currently assumed. Interestingly, the 16S rRNA gene signals could not resolve some species with promising bootstrap and posterior probability values as our phylogenies, using maximum likelihood and Bayesian inference methods, showed.Conclusion:   Our results indicate a probable need for additional phylogenetic signals which can be provided by coding genes. Therefore, sequence data of ompA gene of Bordetella species, a critically significant genomic region in pathogenesis, was here analyzed, phylogenetically. This gene confirmed the tree topology and the phylogenetic species boundaries already revealed by the 16S rRNA gene, but showed a better discriminatory power which resolved Bordetella species with higher statistically significant values.
  • XML | PDF | downloads: 584 | views: 601 | pages: 14-22
    Background:   Aerobic actinomycetes can be detected in soil, worldwide. But, their diversity can differ depending on ecological and environmental factors including, temperature, humidity and vegetation, etc. The aim of this study was antimicrobial activities of aerobic actinomycetes Isolated from soil in Northern Iran.Methods:   Fifty soil samples throughout Northern Iran provinces, including Guilan, Mazandran and Golestan, have been collected and cultured in selective medium, Starch Casein Agar (SCA). In the first step, isolates were assayed by pointing inoculation in solid medium, agar spot, for antimicrobial activity. Then, for antibiotic production, International Streptomyces Projects 2 (ISP2) and Glucose Yeast Extract Malt extract (GYM) media by submerge technique were used. Well diffusion agar method was used for detection of antimicrobial activity and antibiotic sensitivity, and finally metabolites of most active specious detected by GC/MS and GC techniques.Results:   In this study eighty strains were isolated from soil samples. In primary screening, 12 strains (15%) recognized as active actinomycetes, among them strain SA3 showed the highest antimicrobial potential. In the secondary screening in the liquid ISP2 medium, 3 (25%) isolates (SA7, SA3, SA16) and in GYM medium 7 (58.33%) isolates (SA28, SA27, SA7, SA26, SA16, SA2, SA3) have shown the highest antimicrobial potentials; also it was found that there is a significant relation between humidity and pH of soil with the number of isolated colonies. According to results of primary and secondary screening, strains SA3 and SA7 were selected as active actinomycetes and biochemical test revealed that these two active strains isolates belong to the genus Streptomyces. Finally, produced metabolites by strain SA3 were analyzed by GC/MS and GC methods and Oleic acid was revealed as the highest peak.Conclusion:   The findings of the present research show that actinomycetes from Northern Iran soils have considerable antimicrobial activities against different microbial pathogens.
  • XML | PDF | downloads: 589 | views: 997 | pages: 23-30
    Background:    Probiotics are living microorganisms that have useful effects on health of digestive system when acquired in a defined dosage. E. coli O157:H7 is known as one of the most important agents of diarrhea in developing countries. Therefore, attention to the treatment of such gastrointestinal disease is essential. The aim of this study was to determine antagonistic activity of food born lactobacilli against E. coli O157:H7.Methods:     Lactobacilli were isolated from traditional dairy products (yogurt and buttermilk samples). Then, they were characterized using biochemical and molecular tests. Bifidobacterium bifidum PTCC 1644 was obtained from the microbial collection of Iranian Research Organization for Science and Technology in Lyophilized form. Similarly, E. coli O157:H7 PTCC12900 was obtained from faculty of veterinary medicine university of Tehran. The antagonistic activity of probiotics supernatants against E. coli O157:H7 was investigated using the disk diffusion agar, well diffusion agar and pour plate methods.Results:   The isolates were characterized as Lactobacillus plantarum and Lactobacillus fermentum. All isolates showed antagonistic activities against E. coli O157:H7 in all of the three methods, where the activity of L. plantarum and B. bidifum PTCC 1644 was greater than that of L. fermentum. Conclusion:   Metabolites produced by the probiotic bacteria are able to inhibit the growth of E. coli O157:H7. This can be an important solution for the prevention and treatment of E. coli O157:H7 infection and ultimately improve human health.
  • XML | PDF | downloads: 821 | views: 937 | pages: 31-43
    Background:    Nowadays, the use of probiotic bacteria for the prevention and treatment of urinary tract infections is growing. Lactobacillus, as probiotic bacterial genus, is well known for its benefits for the human health.Methods:      The effects of partially purified antimicrobial compounds (bacteriocins and biosurfactants) of Lactobacillus strains was assessed and their capacity to in vitro inhibit growth and urease production of various strains of Proteus spp, was studied. Inhibition of the urease production of Proteus spp. at sub-MIC levels was screened using spectrophotometry method.  Results:   Results revealed that semi-purified bacteriocins of L. acidophilus and L. plantarum showed a greater inhibitory activity on the bacterial urease, compared to biosurfactants of L. rhamnosus, L. casei and L. fermentum (P < 0.05).Conclusion:    It can be concluded that bacteriocins may affect Proteus pathogenesis by inhibition of the bacterial urease activity and therefore eliminate the stone formation by these bacteria.
  • XML | PDF | downloads: 374 | views: 684 | pages: 44-50
    Background:   Staphylococcus aureus is an important human pathogen causing varieties of mild to life threatening community and hospital on-set infections. This study was carried out to determine the antibiotic susceptibility profile of Staphylococcus aureus isolated from wounds of patients at a tertiary healthcare facility in Sokoto, Nigeria.Methods:  All wound swabs obtained from patients with wound infections during the study period were cultured on mannitol salt agar media. The isolates were identified using standard microbiological methods. Antibiotic susceptibility test was carried out on the identified isolates using the modified Kirby-Bauer disc diffusion method and methicillin resistant Staphylococcus aureus (MRSA) test was carried out using Oxacillin agar screen test as described by Clinical and Laboratory Standard Institute (CLSI, 2016).Results:     A total of twenty (20) Staphylococcus aureus were isolated from thirty-eight (38) wound specimens investigated. Out of which, five (25.0%) were found to be MRSA. The isolates were resistant to most of the antibiotics tested and susceptible only to Gentamicin (85%), Norfloxacin (80%) and Amoxiclav (50%).Conclusion:    The high incidence of Staphylococcus aureus isolates resistant to the commonly used antibiotics in the hospital calls for urgent need to put in place measures to curtail the spread of MRSA infections in the hospital.
  • XML | PDF | downloads: 430 | views: 728 | pages: 51-58
    Background:    Antibacterial and biofilm removal effects of agar hydrogel incorporating silver nanoparticles (SNP) at various concentrations were studied against Staphylococcus aureus and Salmonella typhimurium in vitro.Methods:      The minimum inhibitory concentrations (MIC) of SNP was determined by agar dilution method. Then, hydrogels were prepared by mixing of 0.5% w/v agar and SNP (1/2 MIC, MIC, and 2 MIC) and their inhibitory efficacies against planktonic and biofilm forms of bacteria were measured using agar spot and microtiter test, respectively.Results:    The MIC value was 125 µg/ mL for both bacteria. All SNP hydrogels represented antibacterial activity against Staphylococcus aureus and S. typhimurium on agar culture, which was significant compared to control group (silver sulfadiazine cream). The developed biofilm of S. aureus and S. typhimurium were strongly (85% reduction) and modernly affected (60% reduction) by SNP hydrogels during 15 min contact time, respectively. A dose-dependent biofilm reduction was not demonstrated when different SNP concentrations were tested. Moreover, the results from this study confirmed the moderate sanitizing ability of SNP loaded hydrogel against planktonic forms of both bacteria, which SNP (2MIC) hydrogel decreased only 2.3 log10 CFU/ mL in a primary population of S. typhimurium during 15 min exposure time.Conclusion:     We recommended SNP incorporated agar hydrogel as an effective biofilm removal sanitizer.