Molecular Detection of Antimicrobial Resistance Gene Cassettes Associated with Class 2 Integron in Salmonella Serovars Isolated in Iran.

Aim: Salmonella is an important food-borne pathogen in humans and a broad range of animals. Antimicrobial resistance in Salmonella spp. is a serious health problem in human and veterinary medicine worldwide. The aim of this study was to detect integrons, the natural recombination systems that can be transferred in companion with mobile genetic elements and play a major role in spreading antibiotic resistance genes in clinical isolates. Place and Duration of Study: Salmonella clinical isolates were provided by a number of institutes and hospitals over the country through the years 2008-2009. Methodology: Antimicrobial susceptibility testing and serotyping were carried out for eighty four epidemiologically unrelated clinical isolates of Salmonella serovars collected from different provinces of Iran through the years 2008-2009. PCR assays were carried out to detect intI2 gene (integrase I attributed to class 2 integron) and internal variable regions (IVRs) of class 2 integron. These sequences were deposited in EMBL/GenBank database (www.ncbi.nlm.nih.gov). Results: Eleven isolates (13.1%) which were resistant to at least 4 groups of antimicrobial agents were considered as MDR (multidrug resistant) Salmonella serovars. PCR assays detected intI2 gene (integrase I attributed to class 2 integron) and internal variable regions (IVRs) of class 2 integron in Fourteen (16.7%) and eleven (78.6%) of Salmonella clinical isolates respectively. Analysis of the sequence data revealed 3 gene cassette arrays deposited in Genbank databases including the dhfrA1 (0.75 kb), dfrA14- lsp (1 kb), dhfrA1- sat2-aadA1 (3 kb) with three IVR distribution patterns. An artifact PCR product of 2 kb was reported in this study to be amplified together with IVRs of class 2 integrons which was associated with the fhuE- ptsG genes. Conclusions: Presence of MDR Salmonella serovars demonstrates that antimicrobial selection pressure is widespread in our clinical settings. Detection of class 2 integron carrying gene cassettes which confer resistance to different classes of antibiotics such as aminoglycosides, and trimethoprim confirms that integron-mediated antimicrobial gene cassettes are prevalent in Salmonella serovars isolated in Iran.

In vitro study of microleakage of different techniques of surface preparation used in pits and fissures.

Objective : The purpose of this in vitro study was to evaluate the effect of different techniques of surface preparation on the microleakage of a sealant applied with traditional acid etching and self-etched bonding agent. Study Design : A total of 60 extracted third molars were randomly assigned into six groups (n = 10/each). The occlusal surfaces were sealed with a sealant (Clinpro) after one of the following pretreatments: (1) phosphoric acid etching; (2) Prompt L-Pop; (3) laser + etching; (4) laser + Prompt L-Pop; (5) air abrasion + etching; (6) air abrasion + Prompt L-Pop. The specimens were immersed in a 0.5% basic fuchsin solution. Buccolingual cuts parallel to the long axis of the tooth were made. The surfaces were scored 0--2 for extent of microleakage using a microscope and the data were analyzed statistically. Results : The poorest results were obtained with laser + Prompt L-Pop which showed a greater number of specimens with microleakage (80%). Air abrasion surface preparation + phosphoric acid etching showed less microleakage than the other groups (40%). Kruskal--Wallis and t-tests revealed no significant difference in microleakage between six groups. Conclusion : The self-etching adhesive studied seems an attractive alternative to the acid-etch technique for sealant application in young children where simplifications in the clinical procedure are warranted. No significant difference was noted between the different types of enamel preparation before fissure sealant.

Investigation of Yersinia pestis in Xenopsylla astia.

In this study, at the Department of Parasitology in the Pasteur Institute of Iran, Xenopsylla were allowed to feed on mice infected with Yersinia pestis. After 24-48 hours, they were killed by ether and kept in alcohol (70%) for 20 minutes. They were then examined for pathological signs and bacilli in different tissues and organs, longitudinally and cross-sectionally. The samples were studied using conjugated antibody and fluorescence microscopy. The results of this study revealed that the bacilli are abundant in the proventriculus after 6 hours, but it was found in other organs, rarely.