DIPHTHEROIDS OF NORMAL HUMAN SKIN *

THE study of diphtheroids inhabiting normal human skin lias bot^i retarded because of the need for, and the anccess of, methods distinguishing the non pathogenic diphtheroids from a ehnieally significant pathogen. In reeent years tlie ecological control of the normal flora on the colonization of skin and mucous membrane by pathogens has become recognized (Sprunt and Recbnan, 1968) and attention is now being paid t-o the less pathogenic bacteria. Indeed the distinction between pathogen and non patbogen is no longer useful because of the advances in medical and surgical technifjuos of life support. For instance the coagulase negative cocei were characterized (Baird Parker, 1965) allowing the recognition of a new potential pathogen (Mitehell. 1967). Similarly among the Gram-negatives the recognition of Mima-Herrellea Moraxella organisms as part of tho normal flora is of epidemiological importance (Taplin, 1963). The diphtheroids have had little critieal study. The anaerobie strains have received more attention than the aerobic forms, partially because Evans et al. (I9nO) found these diphfheroids to be the eommonest forms on the scapular area and becanse of the snggested association of anaerobic diphtheroids with acne (Strauss and Kligman, 1960). Zierdt (1968) believes that all these anaerobic to mieroacrophilic strains should be ineluded in tlie species C. acnes. We M'ould agree that these organisms are elosely related but regional differences may be detectable (Puhvel. 19f>8). Study of the fatty acids produced by C. acnes strains (Wayne Moss el al. 1007) continues to suggest that Propionibacterium is the more probable genus for these strains. The ecological and probably the pathological significance of the anaerobie dipbtheroids, C. acnes and ita relatives, canjiot be overestimated. The study of aerobic diphtheroids is unrewarding when the techniques applicable to the enterobaeteriaceae are nsed. A useful classifieation must at present be divorced from the ehaos of the Bergey system for this group (Breed et al., 1951). New eharacters have to be delineated and associated with the ecological niche occupied by the strain as well as the use of classical physiologieal tests. The Miami group has been instrumental in redirecting the approach to this collection of species. The detection of the porphyrin ])roduetion by fluoreacence on a special medium, which is eharaeteristie of the diphtheroid responsible for erythrasma, was a major advanee (Sarkany et al., 1961). Still greater was the recognitio'n (Taplin, 1967) of the significanee of the findings that some diphtheroids required oleic aeid for good growth (Pollock et al., 1949). In this age of detergents many synthetie fatty acid esters with hydrophiiic moieties have been produeed. These eompounds are water soluble fatty acid complexes permitthig available fatty acid to be dehvered to the organism in a watery medium without the teelniieal difficulties implicit in emulsions. Of these eompounds, the best known are the '' Tween " series of which " Tween 80 " is a polyethoxysorbitan oleate. Tliis is mi.scible with water and at above 0-5% concentration causes a great enhancement of growth of some dipbthcroid strains and also a great increase in their biochemieal capability. In a study of dairy diphtheroids (Jayne-Williams and Skerman, 1966), the signifieance of oxidase, phospliatase and urease production was emphasized and the necessity for incorporation of " Tween 80 " in the media designed for deteetion of these enzymes waa mentioned.