Comparative evaluation of different selective media for isolation of Helicobacter pylori from gastric biopsies

Four selective [Dent's, Egg Yolk, Glupezynski's, Skirrow's] media and the non selective blood agar were evaluated for the isolation of Helicobacter pylori from 42 antral biopsy specimens of 42 patients, with various upper gastrointestinal tract conditions. From the same enrollees other 42 biopsy specimens were tested for urease activity at room temperature. The organism was isolated from 31 biopsy specimens [73.8%], however none of the media revealed all the 31 isolates. The Dent's medium showed the highest sensitivity [77.4%], followed by the Egg yolk medium [61.3%] the two media together had sensitivity of 100% for Helicobacter pylori isolation. The urease test was 100% sensitive but 90.91% specific. The utilization of Dent's and Egg yolk media is recommended during culture of biopsy specimens, for the maximum isolation of the organism. The urease test must only be taken as a predictive preliminary test

Methicillin resistant staphylococcus aureus detection and antibiotic sensitivity test

To detect methicillin resistant staphylococcus aureus [MRSA] at low level of colonization, a selective medium consisted of columbia agar added to it 5% NaCI and 4 mg/L methicillin was used out of 101 isolates of MRSA, the selective medium detected 98% while the conventional medium detected only 48. 5%. The selective medium could inhibit different Gram positive and Gram negative species. Over growth of these species masks the presence of low number of colonies of MRSA on conventional non-selevtive medium. In addition the selective medium could differentiate between methicillin resistant and methicillin sensitive Staphylococcus aureus in the same culture. Identification of Staphylococcus aureus was done by slide coagulase, tube coagulase and thermonuclease tests. All isolates were sensitive to vancomycin. Less than 15% of isolates were resistant to each of amikacin, norfloxacin, pefloxacin and ciprofloxacin which suggests the possible therapeutic role of these agents in treatment of MRSA infection. on the other hand, chloramphenicol, doxycycline and cefoperazone showed high percentage of resistant strains [about 50% of isolates]

Comparison between sulfuric acid catalyst and some other oxirane cleavage catalysts

The effect of sulfuric acid as a catalyst on the rate of oxirane ring opening in epoxidized soybean oil in presence of glacial acetic acid has been studied and compared with p-toluene sulforic acid. Duolite C 26 and Lewatit S 100 cation resin catalysts. It has been proved that sulfuric acid has the strongest catalytic effect on the cleavage reaction. The matrix structure of the resin catalyst was claimed to be one of the most important rate-controlling variables. The use of Duolite; a macroporous resin, at a level of 10% of the weight of the aqueous phase resulted in an increase of the reaction rate constant by 70% compared to 35% using 10% Lewatit, a gel type resin. This results suggests that the cleavage reaction catalyzed by resin catalysts is determined by the degree of cross linking and porosity rather than the number of active sites