ABSTRACT
Objective: To find a proper method to assess colistin resistance in multidrug resistant Gram negative bacteria (MDR-GNB) on a routine basis in resource limited settings. Methods: Clinical samples were processed. MDR-GNB were identified and were examined for colistin resistance by colistin broth elution method, colistin agar method, and colistin disk elution screening method. Broth microdilution method was used the gold standard. Results: A total of 10 235 clinical samples were processed, in which 857 (8.4%) MDR-GNB were identified. The very significant errors, categorical agreement, major errors, positive predictive values, negative predictive values, specificity and sensitivity of all the phenotypic methods were 5.5%, 0%, 94.4%, 100%, 99.6%, 100% and 94.4%, respectively for the detection of colistin resistance. The colistin elution screening method was cheap and easy to perform with similar results to broth microdilution method. Conclusions: All the evaluation methods for colistin resistance showed similar results. So the laboratories can choose any method for detection of colistin resistance. However, we recommend colistin disk elution screening method because, it is easy and cheap and can be performed in limited resources.
ABSTRACT
The non-Treponemal tests such as Rapid Plasma Reagin test (RPR) or the Venereal Disease Reference Laboratory test are the most commonly used test for screening of syphilis in the blood centers in India. Now, with the availability of Enzyme-linked immunosorbent assay (ELISA) and Immunochromatographic assays in the market, we decided to evaluate these assays in comparison with Treponema pallidum Haemagglutination Assay (TPHA) which was considered as a gold standard for this study. A total of 8 685 samples of voluntary blood donors were tested on Trepolisa 3.0 and then the initially reactive samples were retested in duplicate on the same assay as well as on Omega Pathozyme, RPR, RAPHA (Rapid Anti-Treponema pallidum Assay), and TPHA. Of the 158 initially reactive samples, 104 were repeatedly reactive on the same assay, 85 were reactive with RPR, 77 were reactive with RAPHA, 60 were reactive on Omega, and 53 were confirmed reactive on TPHA. 48 (56.4%) of the results on RPR were biological false positive, while 21.9% of results were false negative on RPR. We evaluated that Omega Pathozyme was quite in agreement with TPHA as compared with Trepolisa 3.0, RAPHA, and RPR. We concluded that Omega Pathozyme (ELISA) can be considered as a suitable test for screening of syphilis in a blood center.
