M u r~i a ,~ SpainUrealytic strains of coryneform bacteria that are designated Corynebacterium group D2 and are isolated from human urine are a cause of urinary tract infections. Cell wall and lipid analyses confirmed that these organisms are members of the genus Corynebacterium but can be separated from other species in the genus on the basis of DNA base composition and DNA-DNA hybridization values. Biochemically, strains in this taxon can be distinguished from other Corynebacterium spp. by their failure to produce acid from carbohydrates, by their failure to reduce nitrates, and by their ability to hydrolyze urea. We regard these bacteria as a new species of the genus Corynebacterium and propose the name Corynebacterium urealyticum. The type strain is strain NCTC 12011 (= ATCC 43042).The identification system for medically important coryneform bacteria devised by the Centers for Disease Control, Atlanta, Ga., designates one group of urealytic, nonfermentative bacteria as Corynebacterium group D2 and suggests that these organisms may be nitrate-negative variants of Corynebacterium pseudodiphtheriticum (9). This group has tentatively been referred to as Corynebacterium urealyticum (23), but this name has not been validly published previously. Strains identified as C. urealyticum have been associated with cases of encrusted cystitis and other urinary tract infections in hospital patients (20), where they have been highly resistant to antibiotics (22). The natural habitat of these strains is human skin (24), but they readily colonize urinary tracts (22); strains have also been isolated from blood (14, 17) and wounds (28). C. urealyticum is relatively inactive in conventional tests apart from its ability to hydrolyze urea rapidly. Colonially and microscopically, this species resembles Corynebacterium jeikeium, with which it shares a common habitat and resistance to antibiotics (4). However, the latter species is consistently nonurealytic and acidifies glucose and maltose. Evidence from lipid analysis (7, 21), from pyrolysis-mass spectrometry (8), and from rRNA gene restriction fragment polymorphism studies (26) indicates that there are clear differences between the two species. Chemotaxonomic evidence that group D2 is related to the genus Corynebacterium has been provided by Herrera-Alcarez et al. ("), who determined that the cell wall type is chemotype IV, with mycolic acids having chain lengths of 26 to 36 carbon atoms, and that the isoprenoid quinone MK-9(H2) is present.In this study, we estimated the DNA base compositions of Corynebacterium strains and levels of DNA-DNA relatedness between strains of C. urealyticum and other Corynebacterium species; we concluded that this taxon merits status as a new species in the genus Corynebacterium.* Corresponding author. MATERIALS AND METHODSBacterial strains and culture. The strains used in this study are listed in Table 1. Strains identified as C. urealyticum were isolated in Madrid, Spain, from the urine (strains A516/89, A524190, A532/90, A548/90, and NCTC 12011T [T =...

Nocardia brasiliensis is a Gram-positive facultative intracellular bacterium frequently isolated from human actinomycetoma. However, the pathogenesis of this infection remains unknown. Here, we used a model of bacterial delipidation with benzine to investigate the role of N. brasiliensis cell wall-associated lipids in experimental actinomycetoma. Delipidation of N. brasiliensis with benzine resulted in complete abolition of actinomycetoma without affecting bacterial viability. Chemical analyses revealed that trehalose dimycolate and an unidentified hydrophobic compound were the principal compounds extracted from N. brasiliensis with benzine. By electron microscopy, the extracted lipids were found to be located in the outermost membrane layer of the N. brasiliensis cell wall. They also appeared to confer acid-fastness. In vitro, the extractable lipids from the N. brasiliensis cell wall induced the production of the proinflammatory cytokines interleukin-1␤ (IL-1␤), IL-6, and CCL-2 in macrophages. The N. brasiliensis cell wall extractable lipids inhibited important macrophage microbicidal effects, such as tumor necrosis factor alpha (TNF-␣) and nitric oxide (NO) production, phagocytosis, bacterial killing, and major histocompatibility complex class II (MHC-II) expression in response to gamma interferon (IFN-␥). In dendritic cells (DCs), N. brasiliensis cell wall-associated extractable lipids suppressed MHC-II, CD80, and CD40 expression while inducing tumor growth factor ␤ (TGF-␤) production. Immunization with delipidated N. brasiliensis induced partial protection preventing actinomycetoma. These findings suggest that N. brasiliensis cell wall-associated lipids are important for actinomycetoma development by inducing inflammation and modulating the responses of macrophages and DCs to N. brasiliensis.

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A trehalose-containing glycolipid was detected in several strains of Mycobacteriutn fortuitum and characterized as 2,3-di-O-acyltrehaIose (DAT) by constituents of the molecule were identified as a mixture of straight-chain (14-18 carbon atoms) and methyl-branched-chain (17-21 carbon atoms) fatty acyl groups. DAT was further fractionated by reverse phase TLC into four fractions that were designated DAT-I-DAT-IV. DAT-I contained 70-75 O/ O straightchain acyl substituents (hexadecanoyl and octadecanoyl predominating) and 25-30 O/ O 2-methyl branched substituents (mainly 2-methyl octadecadienoyl). DAT-II was composed of a mixture in which the acyl groups were almost exclusively 2-methyl branched, with 2-methyl octadecadienoyl and 2-methyl octadecen-2-oyl predominating. DAT-Ill, which was the major isolated fraction, consisted of compounds in which the ratio linear to branched acyl groups varied between 0.8 to 09,2-methyl octadecen-2-oy1, hexadecanoyl and octadecanoyl being the most abundant. Finally, DAT-IV comprised a mixture of DAT molecules containing mostly 2-methyl octadecadienoyl, 2-methyl octadecen-2-oy1, 2-methyl eicosadienoyl and 2-methyl eicosen-2-oyl groups.combined NMR spectroscopy, IR spectroscopy, GLC and GLC-MS. Lipid