Br J Ophthalmol: first published as 10.1136/bjo.73.11.859 on 1 November 1989. Downloaded from

British Journal of Ophthalmology, 1989, 73, 859

Editorial: Mollicutes: what are they?

An article in this issue (page 865) is concerned with composed for the most part of ribosomes and diffuse the possibility that mollicutes are involved in the or filamentous chromatin. pathogenesis of so-called orbital pseudotumours. What of their relevance to human pathology in But what are mollicutes? general and to ophthalmology in particular? About a Delving into the literature reveals that they are a dozen different Mollicutes, mostly Mycoplasmas and class of micro-organisms in the Prokaryote kingdom, related genera, have been identified in human tissues, that is, they are unicellular and, though they contain most occurring as part of the normal flora coating the chromatin material, they do not have a distinct several mucosal surfaces and, as such, of little or no nucleus. There are two types or divisions of Pro- clinical consequence. Nevertheless, occasionally they karyote: Photobacteria, which are sensitive to light, may be associated with opportunistic infections of and Scotobacteria, which are not. Of the Scoto- the mouth and urogenital tract. Mycoplasma pneu- bacteria there are three classes: Bacteria, Rickettsia, moniae, on the other hand, is an undoubted if weak and Mollicutes, the last being distinguished and pathogen in that is is a frequent cause of atypical defined by the absence of an outer cell wall. Hence pneumonia in young people. Another Mollicute of the source of their name, from the Latin mollis, soft tick origin is cataractogenic when injected into and cutis, skin. They are the smallest category of suckling mice, but reports of ocular and adnexal organism capable of growth in cell-free media. disease due to mycoplasmas and related organisms Their existence has been known for some time are sparse, being restricted to accounts of conjunc- although only in the last 10-15 years has their tivitis in the newborn and, with iridocyclitis, in taxonomic position been clarified. Previously, molli- Reiter's syndrome. copyright. cutes commonly went by the name of mycoplasmas, It is of some interest, therefore, that structures and it is still common practice for them to do so, but comparable to Mollicutes are now described in the more recently it has become proper to reserve the cytoplasm of leucocytes present in biopsies from term Mycoplasma for a defined genus within the patients with inflammatory orbital disease, given that Mollicute class. Many of the mycoplasmas and the aetiology of most so-called pseudotumours is at related genera are further distinguished by having a present quite obscure. The authors prefer the term low proportion of guanosine plus cytosine in the base mollicute-like organism, since the putative pathogen pairs of their cytoplasmic DNA and having a need of resists attempts at cultivation and is identifiable on http://bjo.bmj.com/ sterols, such as cholesterol, for growth. ultrastructural criteria alone. Whether the entities In appearance those of relevance to the animal described are indeed viable organisms involved in kingdom measure about 300 ,um, are bounded by a chronic orbital inflammation and, if so, whether they single unit membrane but have no wall, are variably are causal or merely coincidental remains to be seen. coccoid or filamentous in shape, and have a cytoplasm A GARNER on September 25, 2021 by guest. Protected