In vitro Effect of Silver Nanoparticles on Blastocystis hominis.

INTRODUCTION: This study aims to assess the efficacy of silver nanoparticles (Ag Nps) alone and combined with metronidazole (Ag Nps + MTZ) as potential alternative therapeutic agents for Blastocystis hominis. METHODS: The parasites were challenged with Ag Nps, Ag Nps + MTZ and MTZ. To assess the efficacy of drugs, counting of viable parasites was done after 1, 2, and 3 hours of adding the drugs. RESULTS: Blastocystis hominis count was reduced by 20.72%, 28.23%, and 18.92% after one hour of adding Ag Nps, Ag Nps + MTZ, and MTZ, respectively. Cysts count was further reduced by 51.49%, 61.61%, and 40.78% after 2 hours and by 71.69%, 79.67%, and 62.65% after 3 hours of adding the drugs in the same order, respectively. CONCLUSION: There was a statistically significant difference (P<0.05) in the in vitro growth inhibition of the parasite over the different time intervals when using the tested drugs against the control drug.

Acanthamoeba DNA can be directly amplified from corneal scrapings.

This study evaluated the performance of direct amplification of Acanthamoeba-DNA bypassing DNA extraction in the diagnosis of Acanthamoeba keratitis in clinically suspected cases in comparison to direct microscopic examination and in vitro culture. Corneal scrapings were collected from 110 patients who were clinically suspected to have Acanthamoeba keratitis, 63 contact lens wearers (CLW), and 47 non-contact lens wearers (NCLW). Taken samples were subjected to direct microscopic examination, cultivation onto the non-nutrient agar plate surface seeded with Escherichia coli, and PCR amplification. The diagnostic performance of these methods was statistically compared. The results showed that Acanthamoeba infection was detected in 21 (19.1%) of clinically suspected cases (110); 17 (81%) of them were CLW and the remaining 4 (19%) positive cases were NCLW. Regarding the used diagnostic methods, it was found that direct amplification of Acanthamoeba DNA bypassing nucleic acid extraction was superior to microscopy and culture in which 21 cases (19.1%) were positive for Acanthamoeba by PCR compared to 19 positive cases by culture (17.3%) and one case (0.9%) by direct smear. The difference in detection rates between culture and direct smear was highly statistically significant (P = 0.001). On the other hand, there was no significant difference in detection rates between culture and PCR (P = 0.86). On using culture as the gold standard, PCR showed three false-positive samples that were negative by culture and one false-negative sample that was positive by culture. At the same time, direct smear showed 18 false-negative samples. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of PCR were 94.7, 96.7, 85.7, 98.9, and 96.4, respectively, while those of direct smear were 5.3, 100, 100, 83.5, and 83.6, respectively. In conclusion, direct amplification of Acanthamoeba-DNA bypassing DNA extraction is a reliable, specific, sensitive method in the diagnosis of Acanthamoeba keratitis in clinically suspected cases. It should set up in ophthalmological centers as an easy diagnostic tool.