Iranian Journal of Medical Microbiology
Year:2008 | Volume:2 | Issue:1|Papers Count:10

Background and Objectives: Mycobacterium tuberculosis complex is consisted of homogenous organisms. They are slowly growing mycobacteria and their isolation and identification are difficult and time consuming. Differentiation of Mycobacterium bovis, causative mammalian tuberculosis, from other members of Mycobacterium tuberculosis complex is very important in epidemiology and control of disease in humans and animals. The aim of this study was to evaluate a molecular method to differentiate Mycobacteriom bovis from Mycobacterium tuberculosis.Material and Methods: DNA human isolates of Mycobacterium tuberculosis (n=6) and Mycobacterium bovis isolates (50) were extracted and used as template in PCR. A 548bp fragment of oxyR pseudogene was amplified and digested with AluI endo nuclease. The nucleotide 285 could be adenine (M. bovis) or guanine (M. tuberculosis). Such variation produces different restriction site for AluI.Results: There were three incisive fragments in all Mycobacterium bovis and Mycobacterium bovis BCG strains and one incisive fragment in other members of Mycobacterium tuberculosis complex.Conclusion: PCR-RFLP method on 548bp fragment of oxyR gene is a rapid and accurate method to differentiate Mycobacterium bovis and Mycobacterium bovis BCG from other members of Mycobacterium tuberculosis complex.

Background & Objectives: Natural staphylococcal infections and vaccines based whole bacteria lead to poor antibody responses, but recent research reveals that specific antibodies based on recombinant staphylococcal antigens are much more protective. Sacol is a novel antigen that its structural and immunological traits poorly characterized. This research aimed to clone of sacol, a novel gene from Staphylococcus aureus.Material and Methods: The specific primers with suitable restriction sites were designed and sacol amplified by PCR. The sacol and plasmid were produced as sticky ends by restriction enzymes NdeI and XhoI. To amplify the recombinant plasmid the pET21sacol transferred into competent cell E.coliTOP10. The recombinant plasmid harvested from the host and analyzed by restriction enzymes and sequencing. Finally, sacol gene analyzed by bioinformatics tools.Results: The sacol gene has 723bp which amplified, cloned and sequenced successfully. Sacol is highly conserved in Staphylococcus aureus strains. Moreover, software analysis shows that sacol encodes a protein with 32KDa molecular weight (267 amino acids) which has similarity with C51 peptidase in N-terminal with one alpha helix and 14 beta sheets.Conclusion: the sacol gene is conserved in majority of Staphylococcus aureus strains and may exist and express in most of staphylococcal infections. The role and regulation of the gene is thus of great interest.

Background and objectives: Although Enterococci are part of the normal flora of the gastrointestinal tract in humans; they cause infections under certain circumstances. Vancomycin Resistant Enterococci (VRE) cause serious problems resulting in limited therapeutic options in hospitalized patients. In this study we examined the VRE isolated from clinical specimens to determine the prevalence of vanA and vanB phenotypes.Material and Methods: Thirty-two vancomycin resistance Enterococci isolates cultured from clinical samples were investigated. Resistance of isolates to vancomycin, teicoplanin, tetracycline, gentamicin, erythromycin and ciprofloxacin were determined by disk diffusion method. MIC of vancomycin for all strains was determined using by micro-dilution method. Existence of vanA and vanB genes was checked by PCR.Results: Using microbroth dilution assay, 25 and 5 isolates appeared as vanA and vanB phenotypes respectively. All isolates were resistance to ciprofloxacin. Resistance to erythromycin, tetracycline and gentamicin were detected in 96.87%, 81.25% and 78.12% of isolates respectively. vanA and vanB genes were found in 25 and 6 isolates respectively. Co-existence of vanA and vanB were found in 13 isolates using PCR.Conclusion: Our results showed that 12 and 6 of the strains are phenotypically and genotypically vanA and vanB respectively. Although 13 of 25 isolates (52%) showed vanA phenotype, they have both vanA and vanB genes. With the possibility of genotypically alteration in enterococci, it seems that these isolates acquired vanB gene through conjugation.

Background and Objectives: Bacterial cells of Staphylococcus epidermidis are naturally occurring on skin and human mucosal membranes. They also cause nosocomial infections. Capability of biofilm formation plays an important role in the bacterial virulence. Quinolones have been used to treat urinary tract infections caused by S. epidermidis for several years. Thus, resistance to this type of antibiotics has emerged among the strains of this organism. Since the bacterial cells residing within biofilm structures are more resistant than those in planctonic stage, we conduct this study to examine the effect of quinolnes was the main goal of one’s study of higher resistance of native biofilm producing strains is the goal of this project.Material and Methods: In this research ten native isolates of S. epidermidis were obtained from pathients with urinary tract infection. Also standard strain of S. epidermidis PTCC 1435 was used as a control. Identification of strains was confirmed using morphological and biochemical tests. Challenge tests against the isolated was performed using three quinolone antibiotics including Ciprofluxacin, Ofluxacin, Nalidixic acid, with two different procedures : kirby bauer disk diffusion test, and broth dilution test.Results: Average of MICs of above mentioned antibiotics against ten isolated was obtained as follow: Ciprofluxacin (7/375 mg/ml), Ofluxacin (11/53 mg/ml), Nalidixic acid (259/ 2 mg/ml). Experimental biofilm model of these bacteria showed much higher resistance to quinolone antibiotic, from 15 times in case of Nalidixic acid to 18 times greater resistance in case of Ciprofluxacin. Average of MICs amang ten isolates against thethree antibiotics also showed increased resistance as follow: Ciprofluxacin (128/4 mg/ml), Ofluxacin (177/8 mg/ml), Nalidixic acid (3942 /4 mg/ml).Conclusion: S. epidermidis showed increased resistance to different quinolone antibiotics in biofilm structure, comparing to those of planktonic form. Results obtained from this research are in agreement with those of other similar projects; and emphesize on applying of a de quaite doses of antibiotics against urinary infection caused by biofilmic Staphylococcus epidermidis.

Background and objectives: The gastric pathogen Helicobacter pylori is introduced as an etiologic agent of gastritis and peptic ulcer and is associated with development of gastric adenocarcinoma. One of the most studied virulence marker of H. pylori is cytotoxin-associated gene A (cagA) with significant geographical heterogeneity around the world. This study was undertaken to assess the status of cagA gene of H .pylori strains infecting Iranian patients suffering from various gastrointestinal diseases and to evaluate the detection of this gene as a screening marker of high-risk patients.Material and Methods: In this study, 180 patients (Mean age: 44 years) with upper gastrointestinal manifestations referred for endoscopy to Amir-Alam Hospital or Cancer Institute in Tehran were included. Among one hundred twenty H. pylori infected patients 81, 17 and 22 had non–ulcer dyspepsia (NUD), peptic ulcer disease (PUD), and gastric carcinoma (GC) respectively. Tissue samples were homogenized and incubation was performed up to 5 days. Identification was based on morphology under Gram staining and biochemical tests. The status of conserved region of cagA gene was determined by gene specific PCR. For statistical analysis, c2 test was used.Results: Among the 180 of studied patients, 120 H. pylori strains were isolated. One hundred and one (84.2%) of the tested strains were positive for cagA and the remaining strains (15.8%) were negative. All of gastric cancer cases were infected with cagA-positive strains. The cagA-positive strains were significantly associated with GC as compared with NUD (p<0.05) but this association did not gain statistical significance for other clinical outcomes.Conclusion: Although the possession of cagA is associated with GC when compared to NUD, due to the uniform distribution of cagA in all other disease categories detection of cagA alone can not be considered as a discriminative marker for a specific clinical outcome. Hence, the study of other virulence determinants and functional characteristics of cagA gene might be necessary for screening high risk patients.

Background and objectives: Bacteriophages are microorganisms that have been using bacterial hosts for propagation and life cycle. Some of them are called lytic bacteriophages, that lyse bacterial hosts after growth. These kinds of bacteriophages are used for treatment of bacterial infections and phage typing. lytic bacteriophages have several advantages as a treatment against infections in contrast with antibiotics. Therapeutic effects of lytic phage isolated from natural habitates were studied against burn infection of Escherichia coli.Material and Methods: lytic bacteriophages were isolated from environmental resources using luria broth and overlay method. Then phages propagated using Escherichia coli as host, supernatant filtered, and after precipitation of polysaccharides used for treatment of Escherichia coli infections. For treatment experiments induced burn infections in laboratory mouse were used.Results: lytic bacteriophages were isolated frequently from human and sheep stools, and sewage. Phage titer isolated from sheep's stool was higher than other samples. X2 analyses results indicate that there was significant difference in death incidence of studied groups.Conclusion: Based on statistical analysis using lytic bacteriophage for treatment of burn infection of Escherichia coli inhibited 80 % of mouse from death. Results emphesis the potential of bacteriophages as potent antibacterial treatments.

Background and Objectives: Oral Streptococci especially Streptococcus mutans are the major cause of dental caries & periodontal diseases. Going along with the increasing antibiotic resistance of bacteria, new methods for decreasing of oral cavity pathogens must be investigated. The aim of this study was to determine the effect of lactobacillus fermentum ATCC9338 as a probiotic strain on the adhesion of oral streptococci to the surfaces.Material and Methods: S. mutans ATCC35668 with oral streptococci isolated from dental plaque & caries (40 isolates) were studied. The ability of biofilm formation was investigated using the colorimetric method.An isolates showing the strongest activity in forming biofilm were selected. Then the effect of probiotic strain on the adhesion of the selected isolate to the polystyrene microtiter plate was determined simultaneously and 30 minutes before streptococci entrance to the system.Results: this study showed that in the presence of probiotic strain, the streptococcal adhesion were reduced, and this reduction was significantly stronger if the probiotic strain was inoculated to the system before the oral bacteria. Adhesion reduction is likely due to bacterial interactions and colonization of adhesion sites with probiotic strain before the presence of streptococci.Conclusion: Adhesion reduction can be an effective way on decreasing cariogenic potential of oral streptococci.

Background and objectives: Sub-minimum inhibitory concentration (S-MIC) can induce changes in morphology, virulence factors and biochemical properties of bacterial pathogens. The goal of this study is to determine the Sub-MIC effect of ciprofloxacin and ampicillin on the haemotytic activity of E. coli.Material and Methods: Two clinical isolates of E. coli with high heamolytic activity was selected. Changes in haemolytic activity of the isolates were assessed after exposing them to MIC and Sub-MIC of ciprofloxacin and ampicillin.Results: Ciprofloxacin decreased haemolytic activity at 1/2, 1/4 and 1/8 Sub-Mic, whereas ampicillin showed no effect on haemolytic activity.Conclusion: We conclude that Sub-MIC concentrations of ciprofloxacin decreased the haemolytic activity of E. coli, wherease ampicillin had no such effect.