Resistance-gene cassettes associated with Salmonella enterica genotypes

Background: The epidemiology of salmonellosis is complex because of the diversity and different serotypes of Salmonella enterica (S. enterica) that occur in different reservoirs and geographic incidences. Objectives: To determine the genotype distribution and resistancegene content of 2 classes of integron among S. enterica isolates. Methods: Thirty-six S. enterica species were isolated and tested for their serological distribution and the resistance-gene contents of 2 classes of integron, as well as for their genetic diversity, using the pulsed-field gel electrophoresis (PFGE) genotyping method. Results: Serogroups E (36.1) and D (30.5) were dominant among the isolates. All of the isolates in serogroup D belonged to the serovar enteritidis. The aadA1 gene was found within all resistance-gene cassettes. We observed 4 common and 26 single pulsotypes among the isolates, which indicated a high degree of genetic diversity among the isolates. Using the PulseNet International standard protocol, it was found that these isolates were different from those reported previously in Iran. Conclusions: The presence of a few common and new pulsotypes among the isolates suggests the emergence and spread of new clones of S. enterica in Iran

Comparison of Gomori’s Methenamine Silver Method with PCR Technique on Oral Swab, Bronchoalveolar Lavage and lung Ho-mogenate Specimens in Detection of Pneumocystis

Background: Pneumocystis carinii is one of opportunistic organisms especially in immuno-compromised patients. For years, diagnosis of Pneumocystis pneumonia (PCP) has relied on microscopic visualization of organism in specimens obtained from the lung either by bronchoalveolar lavage (BAL) or by induction of sputum, but failed to provide efficient diagnosis. The aim of this study was to compare of PCR result and Gomori's methenamine silver (GMS) of invasive and noninvasive specimens in infected rat. Methods: Thirteen stimulated rat with methylprednisolone acetate used as test group and 4 non-stimulated rats were used as control group. Oral swabs (OS), BAL and lung homogenate (LH) specimens were collected from weeks 0, 2, 4, 5, 6 and 7. All samples were tested with (GMS) staining method and PCR technique.  Results:  The results showed the sensitivity of PCR method higher than GMS (69.2% versus 0%) in oral swab samples (P> 0.001). The analysis of the results also proved that PCR test using noninvasive oral swab had comparable results with the GMS staining method on invasive lung biopsy specimens (69.2% versus 61% and 84.6 for BAL and Lung Biopsy). Conclusion: Higher sensitivity of PCR using noninvasive sample can made it a useful method in rapid diagnosis of PCP

Evaluation of selective and nonselective media for isolation of Helicobacter pylori from gastric biopsy specimens

The aim of the present study was to compare six media, three selective and three nonselective media, to determine the best combination of media for the primary isolation of Helicobacter pylori. Over a period of 8 months, mucosal antral biopsy specimens were obtained from 97 dyspeptic patients undergoing endoscopy. Biopsy samples were plated in parallel on all six media. Egg yolk emulsion agar (EYE), Skirrow's medium and modified Thayer-Martin medium were used as selective media; modified chocolate agar (MCHOC), Triptycase Soy Agar (TSA) and brain heart infusion agar were used as nonselective media. Overall, by using these six media, H. pylori were recovered from biopsy specimens from 48 of 97 patients, yielding an isolation rate of 49. Comparison of all possible combinations of the six media showed that the highest rate of isolation of H. pylori was 100 (48 of 48) with EYE-MCHOC, followed by 97 (47 of 48) when EYE-SK was used. Conversely, it was found that none of the media used alone yielded a 100 rate of recovery (the maximum recovery rate was 92, which was achieved with EYE). These results indicate that the association of EYE and MCHOC yielded the maximum recovery of H. pylori from gastric biopsy specimens. Therefore, the use of selective and nonselective media in parallel offers optimal recovery rates with only a slight increase in costs. © 2007 Asian Network for Scientific Information

Real-Time Assay as A Tool for Detecting lytA Gene in Streptococcus pneumoniae Isolates Citation

Abstract Objective: In-time diagnosis of Streptococcus pneumoniae (S. pneumonia) can play a significant role in decreasing morbidity and mortality rate. Applying molecular methods has gained popularity due to the existing limits of routine diagnostic methods. Examining the expression of different genes of this bacterium through different molecular methods suggests that lytA gene has a higher sensitivity and specificity in diagnosis of Streptococcus pneumoniae. The aim of this study was to evalutate lytA gene expression in diagnosis of invasive S. pneumonia in culture positive specimens by real-time polymerase chain reaction (PCR). Materials and Methods: IIn this a descriptive study, All received specimens were isolated to identify S. pneumoniae. DNA was then extracted and after optimizing the test and determining the detection limit, samples were tested by real-time PCR using lytA gene primers. Results: Twenty seven isolates were diagnosed as S. pneumoniae. In all, the extracted DNA was positive in real-time method. The electrophoresis of the products also confirmed the presence of single product b along with the 53 base pair fragment. The detection limit of the test was less 6 colony forming unit (CFU). Conclusion: Real-Time PCR seems to provide reliable and rapid results. We suggest that this test should be conducted on the preliminary isolated specimens, since applying various biochemical tests need one extra working day

Quality Assurance Program for Molecular Medicine Laboratories

Background: Molecular diagnostic methods have played and continuing to have a critical role in clinical laboratories in recent years. Therefore, standardization is an evolutionary process that needs to be upgrade with increasing scientific knowledge, improvement of the instruments and techniques. The aim of this study was to design a quality assurance program in order to have similar conditions for all medical laboratories engaging with molecular tests.Methods: We had to design a plan for all four elements; required space conditions, equipments, training, and basic guidelines. Necessary guidelines was prepared and confirmed by the launched specific committee at the Health Reference Laboratory.Results: Several workshops were also held for medical laboratories directors and staffs, quality control manager of molecular companies, directors and nominees from universities. Accreditation of equipments and molecular material was followed parallel with rest of program. Now we are going to accredit medical laboratories and to evaluate the success of the program.Conclusion: Accreditation of medical laboratory will be succeeding if its basic elements are provided in advance. Professional practice guidelines, holding training and performing accreditation the molecular materials and equipments ensured us that laboratories are aware of best practices, proper interpretation, limitations of techniques, and technical issues. Now, active external auditing can improve the applied laboratory conditions toward the defined standard level