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Microbiology's new names: a glossary.

This second in a three-part series, updating the 1980 taxonomy guide prepared by Dr. Paul Ellner for MLO, deals with changes in anaerobic bacteria nomenclature.

The majority of the newer anaerobic species were first described by researchers in oral microbiology. These organisms have been included because of their demonstrated pathogenic potential in oral infections. It seems likely that they will soon be seen in reports that discuss the etiologic agents associated with infections of the head and neck, as well as pleuropulmonaiy and other infections.

Anaerobic bacteria are the predominant nomial flora of the human body. They typically become involved in infectious processes when events such as trauma, surgery, or immunosuppression compromise natural barriers. Most of these infections are polymicrobial, and it is difficult to determine the specific pathogenic role of a particular organism.

Some anaerobes, especially the gram-negative rods, can produce a variety of tissue-destroying enzymes, such as hyaluronidase, collagenase, or hemolysins. There is also evidence that synergistic interactions occur in the complex mixture of organisms. Since most clinical labs are not equipped to identify many of the newly described anaerobic species , little is known about their role in disease.

Taxonomic studies of anaerobic bacteria are based on biochemical and chemical properties of the cell envelope, metabolic enzymes, and nucleic acids. Studies of 16S ribosomal RNA (rRNA) base sequence and rRNA-DNA homology may provide the most reliable evidence of phylogenetic relatedness of different taxa.

The Bacteroides studies conducted by Dr. Haroun Shah and colleagues at the London Hospital Medical College illustrate the impact of research efforts. The British investigators recently proposed that the genus Bacteroides be limited to those organisms now classified as B. fragilis group (B. fragilis, B. vulgatus, B. distasonis, B. caccae, B. merdae, B. thetaiotaomicron, B. uniformis, B. ovatus, and B. stercoris), plus B eggerthii. These organisms have similar DNA base compositions, ranging between 40 and 48 per cent G + C, and possess menaquinones, sphingolipids, and predominantly straight chain saturated, anteisomethyl and isomethyl branched long chain fatty acids.

As a result of such studies, several species in the genus Bacteroides have already been given new generic names-for example, Mitsuokella, Porphyromonas, and Anaerorhabdus.

My goal here has been to present a comprehensive listing of all anaerobes described since 1980 that have demonstrated human pathogenic potential. The list, however, does not include new taxa isolated only from human feces or animal and environmental sources.

Campylobacter concisus, which was in last month's update of aerobic bacteria names, is also in the update of anaerobic bacteria that follows because it is an obligate anaerobe. Unless otherwise noted, the organisms listed here are obligate anaerobes. A blank under the heading "previous designation" indicates a new species.
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Title Annotation:part 2
Author:Ward, Kevin W.
Publication:Medical Laboratory Observer
Date:Jun 1, 1989
Previous Article:A career ladder for MT growth.
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