Iranian Journal of Microbiology
Volume:4 Issue: 3, Sep 2012

Diarrheagenic Escherichia coli have developed different strategies for establishment of infection in their host. Understanding these pathogenic mechanisms has led to the development of specific diagnostic tools for identification and categorization of E. coli strains into different pathotypes. This review aims to provide an overview of the various categories of diarrheagenic Escherichia coli and the data obtained in Iran pertaining to these pathotypes.

Pseudomonas aeruginosa possesses a variety of virulence factors that may contribute to its pathogenicity. The aim of this study was to evaluate oprI, oprL and toxA genes for PCR identification of clinical P. aeruginosa.In order to find out any relation between special virulence factors and special manifestation of P. aeruginosa infections, we detected virulence factors among these isolates by PCR. Ribotyping was used to evaluate the clonal relationship between strains with the same genetic patterns of the genes studied. In this study, 268 isolates of P. aeruginosa were recovered from burn, wound and pulmonary tract infections. The prevalence of oprI, oprL, toxA, lasB, exoS and nan1 genes was determined by PCR. One hundred and four isolates were selected randomly to investigate clonal diversity of the isolates with ribotyping using SmaI.Results and All P. aeruginosa isolates in this study carried oprI, oprL and lasB genes. Difference between exoS prevalence in isolates from pulmonary tract and burn isolates was statistically significant. Prevalence of nan1 and toxA gene was significantly higher in pulmonary tract and burn isolates, respectively. Ribotyping showed that most of the isolates (87%) belonged to clone A and B.Detection of oprI, oprL and toxA genes by PCR is recommended for molecular identification of P. aeruginosa. Determination of different virulence genes of P. aeruginosa isolates suggests that they are associated with different levels of intrinsic virulence and pathogenicity. Ribotyping showed that strains with the same genetic patterns of the genes do not necessarily have similar ribotype patterns.

This study was carried out with the objective of determining the genomic variability of P. aeruginosa strains isolated from patients suffering from cystic fibrosis or from environmental cultures collected from different locations in the unit they admitted. A total of 57 clinical and environmental P. aeruginosa isolates were genotyped by enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR), and antimicrobial susceptibility testing was performed using the Clinical and Laboratory Standards Institute method. One predominant ERIC profile (type A) was identified in 46 strains (81% of all typed isolates) which was responsible for thirty-nine of 44 clinical isolates (89%) and 7 of 13 environmental isolates (54%). All clinical isolates were susceptible to piperacillin-tazobactam, ceftazidime and cefepime followed by ticarcillin, aztreonam, amikacin and tobramycin (96.5%). In our country CF patients are not segregated from other patients, and transmission of bacteria between these patients and other patients might occur in the wards via personal contact or contaminated environment. Future evaluation for policy of patient segregation is necessary and the elimination of contaminated sources and control of environmental spread and recurrent contamination risk is needed.

Group B Streptococci (GBS) is a major cause of neonatal and maternal infections. The aim of this study was to determine the serotype distribution and antibiotic resistance profile of GBS strains isolated from pregnant women in Ardabil. Antibiotic resistance of 56 GBS isolates was investigated using E-test strips and disk-diffusion method. Serotyping was performed using capsular antiserum. The results of MIC tests showed all isolates were susceptible to ampicillin, vancomycin and penicillin. One isolate (1.7%) showed reduced susceptibility pattern to penicillin (MIC; 0.25 μg/ml). There were 3 (5.3%) isolates semi-sensitive (0.25-1 μg/ml) to erythromycin (2; 0.5 μg/ml and 1; 0.38 μg/ml) and 2 (3.5%) isolates to clindamycin (1; 0.5 μg/ml, 1;0.38 μg/ml). Additionally, 2 (3.5%) isolates were resistant to clindamycin (1; 16 μg/ml, 1; 2 μg/ml). According to the disk diffusion test, 47 (83.9%), 8 (14.2%) and 7 (12.5%) isolates were resistant to Co-trimoxazole, ciprofloxacin and ceftriaxone respectively. Serotypes V (19.6%), II (12.5%) and IV (12.5%) were the most frequent followed by serotypes III (10.7%) and VI (10.7%), Ib (8.9%), Ia (7/1%), VII (5/3%) and VIII (5/3%); 7.1% of strains were nontypeable. In this study, most isolates were sensitive to common antibiotics, but increased resistance to other antibiotics indicates the importance of monitoring of antibiotic resistance in group B streptococci over time.

Varicella is a benign childhood infection with considerable complication in none immune adults. The aim of this study was to survey Varicella Zoster Virus (VZV) seroepidemiology in children, adolescents and medical students in Children Medical Center, Tehran, Iran. In this cross sectional study, serum sample of children, adolescents 10 to 18 years old and medical students 18 to 25 years old were tested for VZV IgG with a commercial ELISA kit. A total of 412 individuals who were 10 to 25 years of age participated in this study. Overall 269 individuals (65.3%) were seropositive for VZV IgG. Seroprevalence of VZV antibody increased with age of participants, from 59% in 10-11years children to 80% in 20-21 years old young adult students, except in 22-23 and 24-25 years old, whom the frequency of positive results decreased interestingly to 41.7 and 52.8%, respectively. Prevalence of positive VZV antibody between two genders was not statistically different. On-going monitoring of the seroepidemilogy of VZV is necessary to assess trends of infection in the community. A considerable proportion of young medical students in this study were still susceptible to VZV and consequent complications.

Phospholipases are a group of enzymes that breakdown phospholipid molecules producing second products. These second products play a diverse role in the cell such as signal transduction and digestion in humans.In this study, the effect of phospholipids on the expression of pld genes of A. fumigatus was investigated. The pld genes of this fungus were also investigated using bioinformatics studies. Real-time PCR was performed to study the expression of pld genes. These genes were investigated using bioinformatics studies. There was more significant expression for all three pld genes when A. fumigatus was grown in the presence of phospholipids in the medium. The sequence of pld genes of A. fumigatus was also interrogated using bioinformatics analysis and their relationship with the other microorganisms was investigated. The fungal pld genes were more closely related to pldgenes from animals and least related to bacterial pld genes. afpld1, afpld2 and afpld3 are expressed and are up-regulated by phosphatidylcholine. Although indirect evidence of extracellular PLD activity in A. fumigatus was demonstrated, conclusive proof by partially sequencing the isolated protein will be needed and its significance in pathogenicity will have to be assessed by constructing a knockout strain and testing its virulence in a mouse model.

Nosocomial rhino sinusitis causes major problems in all Intensive Care Units (ICUs). To describe incidence, epidemiologic, clinical manifestations, and microbiologic findings in ICUs admitted cases with nosocomial sinusitis. A prospective, cross sectional study done in Pediatric & Adult ICUs in Rasoul Akram Hospital;Tehran Iran (2007-2008). Para-nasal sinus computed tomography (CT) was performed in all adults with fever of unknown origin (FUO) within 48h of admission and repeated thereafter (4-7 days). Infectious sinusitis was diagnosed by icrobiologicalanalysis of sinus fluid aspirates. Acute bacterial nosocomial sinusitis proved in 82% (51/ 63) of all cases. Head trauma was the most common cause (n = 22, 45%) of cases. The results of culture were positive for 45 cases (82%). Of 45 culture positives, 19 yielded Gram negative organisms (41%) and 9 (22%) gave Gram positives (S. aureous, Streptococus spp). The remainders (n = 17, 37%) consisted of mixed aerobic/anaerobic bacteria.Seven cases, were positive in gram staining of sinus drainage and these were positive in culture for S. pneumonia (n = 5),Hemophilus influenza (n = 2). The type of organisms were not related to Glasgow Coma Scale in cases (P = 0.3). Nosocomial organisms isolated were quite different from community acquired rhino sinusitis cases. Investigation of CT scan and drainage of Para-nasal sinuses would be helpful in undiagnosed FUO cases, especially in traumatic patients.Optimal treatment usually consists of removal of the tubes, mobilizing the patient, and administration the broad-spectrum antibiotics.

Bloodstream infections with Salmonella typhi, is uncommon in human immunodeficiency virus (HIV)-infected persons. The symptoms in such patients are often non-specific and have a rather insidious onset and progression. We report a patient with sepsis and lower limb gangrene due to Salmonella typhi infection in an HIV-infected patient.

Azotobacter vinelandii, a gamma-proteobacterium, is an obligate aerobic free-living gramnegative soil bacterium capable of fixing nitrogen. Oxygen transfer rate into the cell is reduced by the increase of alginate concentrations during the course of A. vinelandii cultivation. This phenomenon provides a low intracellular oxygen concentration needed for nitrogenase activity. The aim of this study was to design a simple strategy to explain the alginate production, cell growth and nitrogenase activity correlation in A. vinelandii under aerobic conditions. Thirty-five different soil samples were taken from the rhizosphere of agricultural crops of Iran.Enrichment and isolation strategies were employed for microbial isolation. Physiological and biochemical characteristics were determined. Molecular identification was performed using selective nifH-g1 primers. Alginate production and nitrogenase activity assay by each isolate of Azotobacter were carried out. Bacterial growth, alginate production and Nitrogenase activitywere conducted by time-coursed quantitative measurements. Total of 26 isolates were selected after enrichment, isolation, and screening. The isolate was identified by molecular tests as A. vinelandii. The highest alginate productions of 1.02 g/l and 0.91g/l were noted after 4 days in 8 isolates, cell biomass of which were estimated 4.88-5.26 g/l. Six of 8 isolates were able to fix atmospheric N2 on nitrogen-free medium.Rates obtained in isolates were in the range of 12.1 to 326.4 nmol C2H4 h−1 vial−1. Nitrogen fixation and alginate production yielded significant and positive Pearson’s correlation coefficient of R2 = 0.760, p ~ 0.02. Finally association between bacterial growth, alginate production and nitrogenase activity almost noticeable yielded significant and positive Pearson’s correlation coefficient R2 = 0.723, p ~ 0.04.

The Magnetotactic bacterium Magnetospirillum gryphiswaldense (MSR-1) mineralizes the magnetite (Fe3 O4) crystals and organizes a highly ordered intracellular structure, called the magnetosome. Iron transport system supports the biogenesis of magnetite. Although iron is an essential trace element for many metabolic pathways of the body, increase or decrease in iron will cause many diseases. Mice were infected by MSR-1 to study survival of bacteria in mice when injected by different routes. The aim of this study was to investigate whether bacterial magnetite formation could take up Fe2+ ions from the blood an animal model. In this study, MSR-1 at a dose lower than LD50 in 200 μl volume of PBS buffer was injected as intravascular (i.v), peritoneal (i.p) and subcutaneous (s.c) in mice. Number of viable bacterial was determined in organs such as liver, spleen and lymph node by measuring colony-forming unit (CFU). Moreover, serum iron level was evaluated by using commercial kits.Results and According to CFU measurements, after 96 hours, mice can clear MSR-1 from their body with different routes of injection. We have also shown that MSR-1 bacteria can affect the blood iron level in mice. The serum iron level decreased from control level in the first 24 h after i.v injection (P < 0.05). Our research on optimizing the biological magnetic system is still continuing.