Acridine orange stain in the histological identification of Helicobacter pylori.

The recent paper by Rotimi and colleagues 1 does not mention the acridine orange stain 2 when comparing staining methods for the identification of Helicobacter pylori. The acri-dine orange stain uses ultraviolet fluores-cence in the identification of bacteria. The typical curved morphology of H pylori can easily be diVerentiated from other bacteria. I have used this quick, cheap, and reliable stain in routine histopathology reporting for over 16 years and it has proved to be extremely useful in the identification of H pylori. Immunohistochemistry is now recognised as the " gold standard " because it is a highly sensitive and specific staining method. 1 After the publication of the above mentioned article, 20 consecutive gastric biopsies that were positive for H pylori using the acridine orange stain were also stained using the poly-clonal anti-H pylori antibody (Dako, Ely, Cambridgeshire, UK) at a dilution of 1/100. Twenty negative control cases were similarly studied. All 20 cases that were positive with the acridine orange stain were also positive by immunohistochemistry and all negative cases were also negative by immunohistochemistry. This small study clearly shows that ultraviolet fluorescence of H pylori using the acridine orange stain is highly sensitive and compares equally with the gold standard of immunohistochemistry. The acridine orange stain may not be specific, but the morphology of H pylori is clearly visible down to the single organism (fig 1). The only disadvantage of the acridine orange stain is that the microscopic needs a fluorescent attachment, which in my laboratory means turning the lever on a Leitz Diap-lan microscope to the required position, without the need for a dark room. 1 Rotimi O, Cairns A, Gray S, et al. Histological identification of Helicobacter pylori: comparison of staining methods. Acridine orange stain to identify Campylobacter pyloridis in formalin fixed paraYn embedded gastric biopsies. Lancet 1986;1:42. 4 Haqqani MT, Langdale-Brown B. Campylo-bacter pylori acridine orange stain and ultraviolet fluorescence. The authors reply In pointing out that we omitted to include acridine orange in our comparison of histo-logical stains for Helicobacter pylori, Dr Haqqani seems to have misunderstood the aim of our study. We sought to compare two recently described staining techniques for which there had been claims of superiority over routine methods with our own previously validated routine stain, the modified Giemsa, and with immunohistology using an anti-H pylori antibody—the acknowledged histological " gold standard ". There was no attempt to be comprehensive …