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4 - Coryneform bacteria
- Edited by W. C. Noble, University of London
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- Book:
- The Skin Microflora and Microbial Skin Disease
- Published online:
- 04 December 2009
- Print publication:
- 28 January 1993, pp 102-117
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- Chapter
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Summary
Coryneform bacteria include both aerobic and anaerobic, non-acid fast, nonbranching, pleomorphic, Gram-positive rods that do not form spores. Because of their similarity to the diphtheria bacillus, these organisms were formerly referred to as ‘diphtheroids’. They are commonly arrayed in palisades giving the appearance of Chinese lettering; cells vary from short, coccobacilli to long, bacillary forms and may be rod-shaped or club-shaped. Coryneform is thus a designation of a large, ill-defined group of bacteria. The diverse genera that have been included with the coryneforms include Actinomyces, Arachnia, Arcanobacterium, Arthobacter, Bacterionema, Bifidobacterium, Brevibacterium, Cellulomonas, Corynebacterium, Eyrsipelothrix, Eubacterium, Kurthia, Listeria, Mycobacterium, Nocardia, Oerskovia, Propionibacterium, Rhodococcus and Rothia.
Classification
In the past, coryneforms found on humans were assumed to belong to the genus ‘corynebacterium’. Attempts were made to construct taxonomic classifications through the use of various biochemical tests. During the past 20 years, important advances in methods for classifying bacteria have been developed, many of which have been applied to coryneforms. While this has led to clarification of their taxonomy, much further work is needed to establish agreed-upon species and their role in skin and systemic infections.
The early work of Somerville provided a classification scheme based on a battery of biochemical tests as well as other properties such as fluorescence under ultraviolet light, lipid requirement (lipophilia) and lipolysis. Other schemes, such as those of Evans and Marples, also used biochemical variables. In early studies of skin coryneforms, lipid dependency was a major feature of identification schemes.
5 - Coryneforms as pathogens
- Edited by W. C. Noble, University of London
-
- Book:
- The Skin Microflora and Microbial Skin Disease
- Published online:
- 04 December 2009
- Print publication:
- 28 January 1993, pp 118-134
-
- Chapter
- Export citation
-
Summary
In Chapter 4 the evolving taxonomy of the coryneform bacteria was discussed, as well as their role as members of the resident skin flora. The excellent review of Coyle and Lipsky discusses the coryneforms, particularly the multipleantibiotic resistant Corynebacterium jeikeium and group D2, that have been associated with systemic infections and difficult to treat urinary tract infections. Corynebacterium xerosis has been identified as a cause of endocarditis, septicaemia and osteomyelitis. Likewise, C. minutissimum has been described as a cause of septicaemia and endocarditis.
In cutaneous infections, C. diphtheriae is clearly involved both as a primary pathogen as well as in secondary superinfection of other cutaneous infections such as syphilis and streptococcal pyoderma. There are several cutaneous lesions from which coryneforms can be recovered and in which they are seen as playing important pathophysiological roles. These include trichomycosis axillaris, erythrasma, interdigital toe-web space infections, acne and pitted keratolysis.
Trichomycosis axillaris
Trichomycosis axillaris commonly comprises waxy, nodular coatings on the axillary hair shafts of individuals with poor hygiene. Similar lesions can arise, but less frequently, in the pubic and beard areas. Not infrequently, the waxy nodules may be red, black or yellow and will fluoresce a variety of colours under Wood's ultraviolet light.
Crissey and coworkers gave the name ‘C. tenuis’ to the coryneforms recovered from trichomycosis axillaris. They found a number of very different colonial morphologies with varying biochemical reactions among 31 isolates studied.