Nocardia Isolation of Soil

© 2017 Advanced Biomedical Research | Published by Wolters Kluwer Medknow Sir, We read with interest article that published (Adv Biomed Res 2014; 3:151) by Faghri J et al. entitled *comparison of three phenotypic and deoxyribonucleic acid extraction methods for isolation and Identification of Nocardia spp.* however, authors and researchers should be noted that: 1. According to the literature, Nocardia isolation of soil sample used of paraffin baiting technique, paraffin agar, humic acid‐vitamin agar, sucrose‐gradient centrifugation, conventional media with antibacterial and antifungal agents and diagnostic sensitivity test agar.[1] In some literature, paraffin baiting technique is the best method for Nocardia isolation of soil and clinical samples[2,3] but in this study, authors were reported is inappropriate that they did not optimize presumably 2. Based on scientific evidence, growth in lysozyme broth is important for the genus Nocardia identification[4] but in this study, used of Gram‐stain and partially acid‐fast characteristics. Hence we should mention that Tsukamurella spp., Gordonia spp. and Rhodococcus spp. are partially acid‐fast and Gram‐positive[5‐7] 3. Authors used of slip‐buried method with streptomycin/chloramphenicol for Nocardia isolation while many species of Nocardia are sensitive to chloramphenicol,[8] so streptomycin is used for the treatment of Nocardia infections[9] 4. In this article that describes DNA extraction methods from Nocardia, it needs revision based on the following comments: i. Authors mentioned that cetyltrimethylammonium bromide method is not satisfactory for DNA extraction while in some literature this method is suitable for DNA extraction of Nocardia and Mycobacterium[10] ii. Authors did not describe the amount of DNA recovered by the described method of extraction. This can be described in terms of the average μg of DNA per amount of cells and should include the range of DNA yield iii. Authors indicated that extracted DNA was visualized on a 1% gel to assess quality and purity, but did not indicate the amount of DNA run on the gel. In addition, no additional method of assessment of DNA purity was used such as the standard ultraviolet spectrophotometry method, which generates A260/A280 ratios.