CLINICAL-SIGNIFICANCE OF NEWLY RECOGNIZED CORYNEFORM BACTERIA

Coryneform bacteria have been increasingly recognized as human pathoge ns in recent years. Their emergence is related to the increased number of immunocompromised or intensively treated patients with prolonged s urvival rates, and also because their identification in the clinical l aboratory has significantly improved. Still, an important number of or ganisms have not yet been identified to species level. There have been profound changes in the taxonomy of these organisms, deriving mainly from chemotaxonomic and molecular methods. This has allowed new genera and species to be recognized and previously established taxa to be re -defined. The actual medical importance and frequency of isolation of the different coryneform bacteria is barely known because of the pauci ty of reports considering new taxonomic advances. It seems likely, how ever, that a few species represent the most common clinical isolates. Corynebacterium diphtheriae has been almost eliminated from western co untries but several recent outbreaks have been recognized in countries of the former Soviet Union, and systemic diseases caused by non-toxig enic strains are increasingly reported. Other important species within this genus include: C. urealyticum, C. jeikeium, the newly recognized C. amycolatum, C. striatum, C. minutissimum, and C. pseudo-diphtherit icum. C. xerosis (as presently defined) is rarely isolated from clinic al samples. A great variety of other Corynebacterium species have also been isolated from clinical samples, but for most of them clinical in formation is lacking. Other medically important genera of coryneform b acteria are Actinomyces, Brevibacterium, Rhodococcus, Rothia and Turic ella. Other genera (some of them newly defined) and Centers for Diseas e Control and Prevention (CDC) coryneform groups have been isolated fr om clinical samples, but usually only microbiological and taxonomic st udies have been reported. There are few data supporting therapeutic op tions for infections caused by coryneform bacteria other than glycopep tides, resistance to which has been described in only a few isolates. Standardized methods for evaluating the in-vitro activity of antimicro bial agents are not available, although several studies, reported duri ng this decade, show promising results from the more convenient method s for susceptibility testing of these organisms. Clinical studies are needed to define breakpoints for clinical categorization of in-vitro d ata. Clinical and microbiological collaboration is essential in order to define the actual medical importance of coryneform bacteria.