Guido Funke

Coryneform bacteria are aerobically growing, asporogenous, non-partially-acid-fast, gram-positive rods of irregular morphology. Within the last few years, there has been a massive increase in the number of publications related to all aspects of their clinical microbiology. Clinical microbiologists are often confronted with making identifications within this heterogeneous group as well as with considerations of the clinical significance of such isolates. This review provides comprehensive information on the identification of coryneform bacteria and outlines recent changes in taxonomy. The following genera are covered: Corynebacterium, Turicella, Arthrobacter, Brevibacterium, Dermabacter. Propionibacterium, Rothia, Exiguobacterium, Oerskovia, Cellulomonas, Sanguibacter, Microbacterium, Aureobacterium, "Corynebacterium aquaticum," Arcanobacterium, and Actinomyces. Case reports claiming disease associations of coryneform bacteria are critically reviewed. Minimal microbiological requirements for publications on disease associations of coryneform bacteria are proposed.

The new VITEK 2 system (bioMérieux) was evaluated at two independent sites with the identification card for gram-negative bacilli (ID-GNB card). Of the 845 strains tested, which represented 70 different taxa belonging to either the family Enterobacteriaceae or the nonenteric bacilli, 716 (84.7%) were correctly identified at the species level. Thirty-two (3.8%) additional strains were identified to the species level after the performance of simple, rapid manual tests (oxidase, hemolysis, indole reaction, motility, and pigmentation). For 80 (9.5%) strains, these additional tests did not lead to an identification at the species level but the correct species identification was given among the organisms listed. Only 7 (0.8%) strains were misidentified, and 10 (1.2%) were not identified. Mistakes were randomly distributed over different taxa. Due to the new, more sensitive fluorescence-based technology of the VITEK 2 system, final results were available after 3 h. Since our evaluation was mainly a stress test, it is predicted that the VITEK 2 system in conjunction with the ID-GNB card would perform well under conditions of a routine clinical laboratory in identifying members of the family Enterobacteriaceae and selected species of nonenteric bacteria. This system is a promising, highly automated new tool for the rapid identification of gram-negative bacilli from human clinical specimens.

In the present study, 50 strains of yellow-pigmented gram-positive rods that had been isolated from human clinical specimens and collected over a 5-year period were further characterized by phenotypic and molecular genetic methods. All 50 strains belonged to the genus Microbacterium, and together they represented 18 different species. Microbacterium oxydans (n = 11), M. paraoxydans (n = 9), and M. foliorum (n = 7) represented more than half of the strains included in the present study. The isolation of strains belonging to M. hydrocarbonoxydans (n = 2), M. esteraromaticum (n = 1), M. oleivorans (n = 1), M. phyllosphaerae (n = 1), and M. thalassium (n = 1) from humans is reported for the first time. Microbacterium sp. strain VKM Ac-1389 (n = 1) and the previously uncultured Microbacterium sp. clone YJQ-29 (n = 1) probably represent new species. Comprehensive antimicrobial susceptibility data are given for the 50 Microbacterium isolates. This study is, so far, the largest on Microbacterium spp. encountered in human clinical specimens and outlines the heterogeneity of clinical Microbacterium strains.

Modern taxonomy has delineated Streptococcus gallolyticus subsp. gallolyticus, S. gallolyticus subsp. pasteurianus, Streptococcus infantarius subsp. coli, and S. infantarius subsp. infantarius within the heterogenous group of previously designated clinical Streptococcus bovis bacteria. In the present study, 58 consecutive blood culture isolates initially designated S. bovis were further characterized by applying phenotypic and molecular genetic methods, and possible disease associations were investigated by studying the patients' records. Published phenotypic characteristics of S. gallolyticus and S. infantarius were not unequivocal and did not allow an unambiguous phenotypic differentiation of the 58 clinical isolates. However, full-length 16S rRNA gene sequences clearly assigned the strains to S. gallolyticus subsp. gallolyticus (n = 29), S. gallolyticus subsp. pasteurianus (n = 12), and S. infantarius subsp. coli (n = 17). Only 28% of the patients with available records presented with endocarditis and 7% presented with colon carcinoma, whereas 37% of the patients had altered liver parenchyma and 28% had gall bladder disease as underlying diseases. Detailed antimicrobial susceptibility data on both S. gallolyticus subspecies and S. infantarius subsp. coli are given for the first time. As a result of the extensive characterization of the largest number of S. gallolyticus and S. infantarius human clinical isolates published so far, emended species descriptions are given. It is recommended that both clinical microbiologists and infectious disease specialists avoid the designation S. bovis for true S. gallolyticus and S. infantarius strains in the future in order to get a clearer picture of the possible disease associations of these species.