Check the age of the Iodine. Iodine solutions lose their activity over time (?notice the brown discolouration on the parafilm sealing a coplin jar) even though the solution still looks as brown as when it was made.
Magee, C. M., Rodeheaver, G., Edgerton, M. T., & Edlich, R. F. (1975). A more reliable gram staining technic for diagnosis of surgical infections. The American Journal of Surgery, 130(3), 341-346. "Opening the bottle in a warm room potentiated the loss of iodine so rapidly that no iodine could be detected in the solutions after fifteen days. The potentiation of loss of iodine by temperature elevation becomes a severe problem in the warm seasons of the year, particularly in tropical areas." And "When iodine concentration of the solution was less than 20 per cent of the original value, some of the stained slides revealed only gram-negative organisms." Regards Tony Henwood JP, MSc, BAppSc, GradDipSysAnalys, CT(ASC), FFSc(RCPA) Principal Scientist, the Children's Hospital at Westmead Adjunct Fellow, School of Medicine, University of Western Sydney Tel: 612 9845 3306 Fax: 612 9845 3318 Pathology Department the children's hospital at westmead Cnr Hawkesbury Road and Hainsworth Street, Westmead Locked Bag 4001, Westmead NSW 2145, AUSTRALIA -----Original Message----- From: Ken M via Histonet [mailto:histonet@lists.utsouthwestern.edu] Sent: Wednesday, 1 July 2020 7:21 AM To: histonet@lists.utsouthwestern.edu Subject: [Histonet] Gram Staining Hi. We are trying to stain a supposed Gram Positive paraffin Tonsil tissue block using Gentian Violet, Iodine (Lugol), Gram's decolorizer, Carbol Fuchsin Counter and Tartrazine and are having trouble distinguishing the positive from the negative. Anyone have any suggestions? _______________________________________________ Histonet mailing list Histonet@lists.utsouthwestern.edu http://lists.utsouthwestern.edu/mailman/listinfo/histonet This message is intended for the addressee named and may contain confidential information. If you are not the intended recipient, please delete it and notify the sender. Views expressed in this message are those of the individual sender, and are not necessarily the views of NSW Health or any of its entities. _______________________________________________ Histonet mailing list Histonet@lists.utsouthwestern.edu http://lists.utsouthwestern.edu/mailman/listinfo/histonet
