Effectiveness of Two Types of Photostimulable Phosphor Plate Plastic Barrier Envelopes for Prevention of Microbiological Contamination

Abstract Objective: To compare the effectiveness of two types of commercially available photostimulable phosphor plate (PSP) protective barrier envelopes to prevent microbiological contamination. Material and Methods: In this cross-sectional study, 80 barrier envelopes were tested in 40 volunteers. The PSP plates were placed individually in Asia Teb and Soredex protective barrier envelopes and were placed in the mouth for two minutes, similar to periapical films. The protective barrier envelopes were then removed under sterile conditions, and the sensors were placed on different culture media. The number of colonies on each plate was counted. Data were analyzed using SPSS via McNemar and Wilcoxon tests. Results: Bacterial growth was noted in 17.5% of PSPs with Soredex, and 32.5% of PSPs with Asia Teb barrier envelopes. Gram-positive bacilli were the most commonly isolated bacteria. The difference between the Asia Teb and Soredex barrier envelopes for the protection of microbiological contamination was not significant (p>0.05). Conclusion: The use of different types of protective barrier envelopes was not sufficient for prevention of microbiological contamination of PSP plates, and some adjunct modalities were required to decrease microbiological contamination of PSP plates.

Leishmania tropica: The comparison of two frequently-used methods of parasite load assay in vaccinated mice

Objective: To compare limiting dilution assay and real-time PCR methods in Leishmania tropica parasite load measurement in vaccinated mice.Methods: BALB/c mice were vaccinated by Leishmania tropica soluble Leishmania antigen or recombinant Leishmania tropica stress-inducible protein-1 with/without adjuvant. After three vaccinations, mice were challenged by Leishmania tropica promastigotes. Two months after challenge, the draining lymph nodes of mice footpad were removed and parasite load was assayed by limiting dilution assay and real-time PCR methods. Limiting dilution assay was done by diluting tissue samples to extinction in a biphasic medium. For real-time PCR, DNA of the lymph nodes was extracted, equal dilutions of each sample were prepared and hot-start real-time PCR was done using appropriate primers. The data of the two methods were compared by appropriate statistical methods. Results: Both methods were able to measure different levels of parasite load in vaccinated/unvaccinated mice. In addition, wherever parasite load of a group was estimated high (or low) by one method, the estimated parasite load by another method was the same, although statistically significant differences were found between some groups. Conclusions: Both methods lead to approximately similar results in terms of differentiating parasite load of the experimental groups. However, due to the lower errors and faster process, the real-time PCR method is preferred.