Tehran University Medical Journal

Background: Staphylococcus aureus and Staphylococcus epidermidis are major human pathogens of increasing importance due to the spread of antibiotic resistance. Novel potential targets for therapeutic antibodies are products of staphylococcal genes expressed during human infection. Previously, the secreted and surface-exposed proteins among seroreactive antigens have been discovered. Furthermore, approximately 60 immunogenic proteins were identified and have shown that bacterial surface display is uniquely suited to assess the value of the antigenic epitope.     

Methods: Using a bioinformatic analysis, a novel gene family was identified in Staphylococcus aureus and S. epidermidis. NCBI (National Center for Biotechnology Information) BLAST and TIGR search were used for identification of the loci on Staphylococcal genomes.

Results: The members of nine gene family from S. aureus based on a conserved C-terminal domain following an N-terminal domain which varies in sequence and length. Further Blast P searches for paralogues revealed the novel Sca gene family in S. epidermidis has also highly conserved 110 amino acid C-terminal domain. Thus the Sca family has a conserved domain across different genera.

Conclusion: Further studies to determine the role of the conserved Sca domain in ligand binding and demonstration of conserved epitope may establish the domain as a credible target for cross species vaccination.

Background: Clindamycin is a suitable antibiotic for treatment of skin and soft tissue infections. Moreover, it can suppress toxin production in many pathogenic bacteria such as S. aureus. There are two mechanisms of resistance in this antibiotic. Constitutive resistance can be detected by standard disk diffusion method but in the case of inducible resistance, D-test should be carried out. The main aim of this study is to determine prevalence of clindamycin inducible resistance among methicillin resistant and susceptible isolates of S. aureus isolated from different clinical samples.

Methods: A total of 87 clinical isolates from clinical samples were collected. Methicillin resistance was determined using standard disk diffusion method. Subsequently, D-test was carried out according to CLSI guideline. Presence of the sea gene (enterotoxin A) was detected by PCR using specific primers.

Results: Out of 87 isolates, 18(20.7%) were clindamycin inducible resistant while constitutive resistance was detected among 21(24.1%) isolates. The 95% Confidence intervals for the proportion of inducible clindamycin resistance among clinical isolates of S. aureus was 12.2% to 29.2%. The inducible phenotype in MRSA isolates was more common than that of MSSA isolates (33.3% vs 5.1%).Significant differences were found between prevalence of inducible clindamycin resistance and type of infection (p=0.045). Importantly, there was a significant correlation between sea gene and the constitutive/inducible resistance (p<0.0001).

Conclusions: Due to the high prevalence of clindamycin inducible resistance among clinical isolates of S. aureus, we recommend D-test to avoid treatment failure.

Background: Staphylococcus aureus is a major foodborne pathogen throughout the world. Enterotoxins and toxic shock syndrome toxin-1 are important virulence factors and as pyrogenic toxin superantigens have profound effects on the ir host. Thus circulation of TSST1 producing S.aureus among people and food chain is a worrying issue. The present paper was conducted to study Prevalence of tst, entC, entA and entA/C genes in staphylococcus aureus strains isolated from different foods.
Methods: Over 1040 food samples have been analyzed differentially according to Iran national standard (number= 1194) for S.aureus identification. After DNA extraction, PCR reactions were carried out by reference strain as positive control, adequate primers.

Results: At present study, prevalence of foodstuffs contaminated by S.aureus isolates was about 9.5% (100 strains). Of 25% of isolates producing entC, 28% (seven strains) had tst gene at the same time and of 8% of isolates producing entA, 12.5% (one strain) were positive for tst genes simultaneously. Altogether of 9% isolates producing combination of entC and entA, 44.4% (four strains) were also producer of tst gene.

Conclusion: Prevalence of TSST1 producing strains in combination with enterotoxin genes is considerable especially with entC and A plus C. On the other hand, circulation of these isolates in humans, animals, foods and environment has hazardous effect for general public health.

Normal 0 false false false EN-US X-NONE AR-SA MicrosoftInternetExplorer4 Background: Nocardiosis is a rare and potentially life-threatening infection caused by several species of the Nocardia genus. The objective of this study was to develop and evaluate a rapid and new method to clinically identify relevant Nocardia species. Rapid and accurate diagnosis of Nocardia species is essential for the treatment of severe infections and prevention of cerebral abscess.
Methods:  One hundred and eighty patients, 103 (57.22%) male and 77 (42.78%) female, with severe symptomatic pulmonary infection were studied in the course of a 12-month period in Dr. Shariati Teaching Hospital affiliated to Tehran University of Medical Sciences in 2010. The specimens were cultured and identified using microbiological and biochemical tests. Polymerase chain reaction (PCR) was used to directly identify the organism in the broncoalveolar lavage samples collected from the patients. NG1 and NG2 primers were used to amplify a Nocardia genus-specific 598-bp fragment of 16S rRNA.
Results:  Nineteen samples (10.56%) were positive with PCR and 5 samples (2.78%) with conventional methods. All samples with positive cultures were also positive by PCR.
Conclusion: The results of this study showed that PCR has a high sensitivity and accuracy for the detection of Nocardia compared with culture and biochemical tests. Considering the rapidity, precision, high sensitivity and specificity of molecular techniques, use of these techniques is suggested in conjunction with conventional methods for the detection of Nocardia phenotypes in clinical laboratories and research centers.

Background: Staphylococcus aureus is the most common pathogen responsible for skin and soft tissue infections worldwide. Methicillin-resistant S. aureus is a major cause of both nosocomial and community acquired infections. The emergence of antimicrobial-resistant S. aureus is of global concern. Fluoroquinolone antimicrobials including ciprofloxacin, levofloxacin, and moxifloxacin are used to treat skin and soft tissue infections due to S. aureus. Emergence of ciprofloxacin resistance has increased in community acquired methicillin-resistant S. aureus strains. The aim of this study was to evaluate the minimum inhibitory concentration of ciprofloxacin and hexahydroquino-line derivatives against methicillin- and ciprofloxacin-resistant S. aureus.
Methods: Identification of S. aureus was performed by routine microbiological tests in the Department of Pathobiology in Winter 2012. The susceptibility of S. aureus strains to both methicillin and ciprofloxacin was examined by the Kirby-Bauer disk-diffusion method. The minimum inhibitory concentration of ciprofloxacin, hexahydroquinoline derivatives and their combination were separately determined by broth microdilution method against methicillin- and ciprofloxacin-resistant S. aureus.
Results: The minimum inhibitory concentration of ciprofloxacin decreased in the presence of hexahydroquinolinein derivatives in comparison with ciprofloxacin alone.
Conclusion: This study showed that hexahydroquinoline derivatives enhance the antibacterial effect of ciprofloxacin against methicillin- and ciprofloxacin-resistant S. aureus. Therefore, these derivatives could be used as inhibitors of antibiotic resistance in combination therapies. This enhancement may be related to the inhibitory effect of hexahydroquinoline derivatives on the expression of antibiotic efflux pump in the bacteria. However, the structural features of a fluoroquinolone that determine whether it is affected by efflux transporters are not fully defined.

Background: Renal transplantation is the treatment of choice in patients with end-stage  renal disease. Urinary tract infection (UTI) is one of the most common complications after renal transplantation and it has serious consequences. The aim of this study was assessing UTIs in renal transplanted patients and evaluation of risk factors associated with post-transplant UTI.
Methods: In this prospective study, 173 patients (48 hospitalized patients and 125 outpatients) were enrolled in this study. These renal transplant recipients evaluated for bacterial urinary tract infection in urology research center at Sina Hospital. After collecting urine samples from symptomatic and asymptomatic patients, urinalysis and colony count were performed. Identification of bacteria was performed by routine microbiological tests in the Department of Pathobiology, School of Public Health, Tehran, Iran, in 2011.
Results: UTI was observed in 47 patients and the most prevalent microorganism was Escherichia coli (E.coli) 18(38.2%). Nearly 71% of UTI cases were diagnosed during the first three months post transplantation. Risk factors for post transplant UTI were female gender, age, length of hospitalization and diabetes mellitus. Female patients were more susceptible than males (OR=0.50 and P=0.047) to infection. There were no significant difference between diabetes mellitus and UTI. Most of the isolated bacteria were susceptible to imipenem and resistant to tetracycline and trimethoprim- sulfamethoxazole.
Conclusion: Our study confirmed that bacterial infections remain as the most common infectious complication in the early post-transplant period, and antibiogram rather than empirical treatment is needed to find the best effective antibiotics. Moreover, risk factors such as female gender, increased age and length of hospitalization are predisposing factors to increased urinary tract infection in renal transplantation.

Thymoglobulin is a purified polyclonal immunoglobulin that has been used widely over the last decades in the prevention and treatment of rejection following renal transplantation. This immunoglobulin works against human thymocytes. Since thymoglobulin does not contain the nephrotoxic properties therefore it can be used in induction therapy especially in patients with higher risk of graft rejection such as patients who receive graft from cadavers. Recent research showed also its beneficial role in cross-match-positive transplantation, a role that is mediated through conjunction with inhibitors of terminal complement activation. This immunoglobulin has also been used for treatment of rejection following renal transplantation. Thymoglobulin can have various effects on various Immune system cells including T cells, B cells and also plasma cells. Thymoglobulin also affects the Tcell surface antigens, natural killer-cell antigens, B cell antigens, plasma cell antigens, adhesion molecules and chemokine receptors. Diverse effects of thymoglobulin on the immune system includes: T cell depletion, induce apoptosis in B cell lineage and interference with dendritic cell functional properties. Thymoglobulin can cause acute complications, delayed complications as well as infectious complications. Acute reaction events includes: anaphylaxis, fever, chills, dyspnea, nausea, vomiting and diarrhea. Thymoglobulin also induces cytokine release syndrome manifested by high grade fevers and chills and treated by steroid therapy. Delayed reactions events usually present as serum sickness and infections. Infectious complications are more important and include cytomegalovirus (CMV) infection, sepsis, candidiasis, herpes simplex and urinary infections. Thymoglobulin can also induce cytokine release syndrome. It has been thought that thymoglobulin increases the risk of post-transplant lymphoproliferative disorder (PTLD), however, debate still exists whether such an association is present when lower dosing regimens are used. In this review, we aimed to present first a brief history of thymoglobulin development and its mechanism of action and then assess the most recent published data regarding the role of thymoglobulin in following issues: immunological tolerance, ischemia-reperfusion injury, delayed graft function, prevention and treatment of acute allograft rejection, live donor transplantation, graft and patient survival and posttrans-plant lymphoproliferative disorder. This review can help specialist in transplant domain to appropriately used thymoglobulin in transplant patients.

Conclusion: Many characteristics of eubacteria and archaebacteria are significantly associated with genomic properties. Comparison genomics of bacteria will help in identification of evolutionary origins as well as differences between different categories of bacterial.