Nocardial brain abscess.

Nocardial infections, although rare, are challenging for clinicians to treat. The associated mortality rate remains high; such infections usually occur in immunocompromised patients who have predisposing factors such as malignancy, diabetes mellitus, malnutrition and uremia. However, there have been increasing reports of nocardial infections being observed in immunocompetent patients. Nocardial organisms are mostly isolated from plants and soil, and infection occurs most often as a result of inhalation or direct skin inoculation. Nocardial infections disseminate hematogenously from the primary location to distant end organs, including the brain, kidneys, joints and eyes. Sulfonamides are the drug of choice, based on empirical data. Given the high rate of relapse and the characteristic resistance pattern, treatment should be aggressive and continued for months, with antibiotic treatment being adjusted according to the drug sensitivity test. In our institution, there have been three documented patients with a nocardial brain abscess. All patients were treated with surgical evacuation followed by antibiotics. Here, we report on one patient and review the literature.

An unusual murine behavior following infection with log-phase Nocardia asteroides type 6 strain GUH-2 (Nocardia cyriacigeorgica GUH-2).

Nocardia asteroides (Nocardia cyriacigeorgica) strain GUH-2 infects the brains of mice following intravenous injection. Non-lethal infections resulted in a transitory increase of bacterial numbers in the brain followed by the development of permanent impaired movements at a time when bacteria appeared to be eliminated from the brain. These signs included headshake, rigidity, stooped posture, dyskinesia, retropulsion, and abnormal tail positioning in approximately 20% of infected animals. The attached video presents a typical mouse following infection with this organism, as compared to an age- and gender-matched uninfected control mouse.

Nocardia asteroides strain GUH-2 induces proteasome inhibition and apoptotic death of cultured cells.

Many bacterial pathogens have the ability to induce apoptosis in their hosts. It was previously shown that Nocardia asteroides strain GUH-2, a Gram-positive facultatively intracellular pathogen, is capable of inducing the apoptotic death of dopaminergic cells in the murine brain and in PC12 cells, a rat cell line. In this study, the apoptosis-inducing potential of N. asteroides GUH-2 was further explored using HeLa cells, a human epithelial cell line. HeLa cells were incubated for 5h with live nocardiae, heat-killed bacteria, or unconcentrated nocardial culture filtrate, and changes to the cells were monitored. Consistent with the previous studies, N. asteroides GUH-2 induced DNA fragmentation and apoptosis in HeLa cells. Caspase activation and disruption of the mitochondrial membrane potential were also investigated to determine their roles in the induction of cell death. In all these experiments, significant changes were only induced by live nocardiae. A recent publication demonstrated that systemic administration of proteasome inhibitors can induce a Parkinsonian syndrome in rats that includes intraneuronal inclusions and characteristic behavioral alterations. Similar effects have been observed in mice and monkeys infected with N. asteroides GUH-2. In addition, some reports have shown that proteasome inhibition causes apoptotic death of affected cells. We therefore investigated the ability of N. asteroides GUH-2 to inhibit proteasome activity. Proteasome activity was significantly reduced, suggesting that this mechanism may be involved in the induction of apoptosis by these bacteria.

Glycosylative inactivation of chalcomycin and tylosin by a clinically isolated Nocardia asteroides strain.

Studies on the susceptibility of pathogenic Nocardia to macrolide antibiotics, chalcomycin and tylosin, showed that most of the Nocardia species examined were highly resistant to both antibiotics, although N. nova was moderately susceptible. N. asteroides IFM 0339 converted these macrolides into inactive metabolites by glycosylation at 2'-OH or glycosylation and reduction of the 20-formyl group. The structures of the metabolites were determined from NMR and MS data to be 2'-[O-(beta-D-glucopyranosyl)]chalcomycin (2), 2'-[O-(beta-D-glucopyranosyl)]tylosin (5) and 20-dihydro-2'-[O-(beta-D-glucopyranosyl)]tylosin (4).

The cell wall porin of the gram-positive bacterium Nocardia asteroides forms cation-selective channels that exhibit asymmetric voltage dependence.

Detergent-solubilized cell wall extracts of the gram-positive, strictly aerobic bacterium Nocardia asteroides contain channel-forming activity as judged from reconstitution experiments using lipid bilayer membranes. The cell wall porin was identified as a protein with an apparent molecular mass of about 84 kDa based on SDS-PAGE. The porin was purified to homogeneity using preparative SDS-PAGE. The 84-kDa protein was no longer observed after heating in SDS buffer. The presumed dissociation products were not observed on SDS-polyacrylamide gels. The cell wall porin increased the specific conductance of artificial lipid bilayer membranes from phosphatidylcholine/phosphatidylserine mixtures by the formation of cation-selective channels, which had an average single-channel conductance of 3.0 nS in 1 M KCl. The single-channel conductance was only moderately dependent on the bulk aqueous KCl concentration, which indicated negative point charge effects on the channel properties. The analysis of the concentration dependence of the single-channel conductance using the effect of negative charges on channel conductance suggested that the diameter of the cell wall channel is about 1.4 nm. Asymmetric addition of the cell wall porin to lipid bilayer membranes resulted in an asymmetric voltage dependence. The cell wall channel switched into substates, when the cis side of the membrane, the side of the addition of the protein, had negative polarity. Positive potentials at the cis side had no influence on the conductance of the cell wall channel.

Differential binding of Nocardia asteroides in the murine lung and brain suggests multiple ligands on the nocardial surface.

The adherence of Nocardia asteroides in the murine brain and lungs was determined. Virulent strains had increased adherence in the brain and lungs, whereas less virulent strains bound in either the brain or lungs. Nocardiae that attached apically penetrated host cells. Multiple receptors on the nocardial surface may be involved in this differential attachment and penetration.

Acute primary cutaneous Nocardia asteroides infection in a patient with systemic lupus erythematosus. Case report.

We report a case of acute primary cutaneous infection of traumatic origin caused by Nocardia asteroides, appeared as cellulitis in a patient with systemic lupus erythematosus. Diagnosis was established by direct examination and cultures from aspirate specimens. The clinical forms of Nocardia infections that affect the skin, reported in Rio Grande do Sul and Uruguay, are discussed.

Adherence of Nocardia asteroides within the murine brain.

Nonlethal infection of BALB/c mice with Nocardia asteroides GUH-2 (GUH-2) produces a variety of neurological signs, including an L-dopa-responsive movement disorder in 10 to 15% of the infected population. To study nocardial interactions with the brain, we characterized the attachment of GUH-2 within specific regions through the use of microdissection. Following an intravenous injection of a single-cell suspension of log-phase GUH-2, viable cells were recovered from all regions of the brain, and the distribution of the nocardiae was independent of the size of the inoculum. In addition, two mutants of GUH-2 were found to possess significantly altered binding characteristics with regard to both the percentage of the inoculum bound per brain and the relative distribution of adherence to regions of the brain, when compared with the parental strain. These results indicated that GUH-2 bound throughout the murine brain and suggested that GUH-2 utilized specific receptors to facilitate this attachment.

The timing of exposure of mononuclear phagocytes to recombinant interferon gamma and recombinant tumor necrosis factor alpha alters interactions with Nocardia asteroides.

Nocardia asteroides modulates phagocyte function and grows within macrophages. Because interferon gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) have been shown to activate macrophages to kill a variety of microorganisms, the effects of IFN-gamma and TNF-alpha on the activation of murine macrophages and human monocytes to kill nocardiae were studied. It was found that macrophages or monocytes treated with either IFN-gamma, TNF-alpha, or lipopolysaccharide as a secondary signal did not demonstrate increased microbicidal activity against N. asteroides even though these phagocytes were effective at killing the fungus Coccidioides immitis and the protozoan Toxoplasma gondii. Preincubation of phagocytes for 24 h with these compounds resulted in an enhancement of nocardial growth. In contrast, coincubation of these factors with the nocardiae and mononuclear cells during phagocytosis resulted in inhibition of nocardial growth even though this bacterium was not killed. Therefore, the specific timing of the exposure of the phagocyte in vitro to IFN-gamma or TNF-alpha has a significant effect on its ability to alter nocardial growth.

A case of lung infection caused by an unusual strain of Nocardia farcinica.

A case of lung infection caused by an unusual strain of Nocardia farcinica is reported. This is the third case of the N. farcinica infection in this country. The strain failed to utilize rhamnose as sole carbon source, but could be identified by a numerical identification method. The mycolic acids contained 1-3 double bonds and the numbers of the carbon atoms of the mycolic acids were 50 to 60, average 56.

Natural occurrence of Nocardia in soil of Tucumán: physiological characteristics.

This is the first study initiated in Argentina to establish the presence of species of Nocardia from soil samples. These samples were gathered in different areas of Tucumán. Thirty three pathogenic strains of Nocardia were isolated by the paraffin bait method. Out of them, 28 were N. brasiliensis, 3 N. asteroides and 2 N. caviae. N. brasiliensis was widely distributed in the soil of the areas tested. It is proved that N. caviae, so rarely found in other regions of the world, occurs in Tucumán. A detailed study of the morphological and physiological characteristics for identification is discussed.

The role of cell-wall associated lipids in the pathogenesis of lesions in experimental murine nocardiosis vs lesions produced by Mycobacterium fortuitum.

The pulmonary pathogens, Nocardia asteroides and Mycobacterium fortuitum classically produce a markedly different tissue response ranging from the acute suppurative lesion of nocardiosis to the granulomatous disease produced by the Mycobacterium. Both organisms have similar cell-wall associated lipids which have been chemically characterized as types of saturated and unsaturated fatty acids. Earlier studies of virulence factors from M. tuberculosis and other Mycobacteria have shown that much of the host response is due to lipid constituency of the organism cell wall. In order to determine that contribution which the cell-wall associated lipids make in the pathogenesis of nocardiosis produced by N. asteroides and mycobacteriosis due to M. fortuitum, separate lipid fractions were obtained using the Anderson extraction technique as modified by Asselineau (Asselineau, J. 1966. The Bacterial Lipids. Hermann, Paris). These lipid fractions were injected into mice and the lesion development observed. Waxes A and D from the two organisms exhibited distinct differences in tissue response. Wax A from Nocardia produced a pronounced tissue response composed of multiple abscesses, macrophages, and reactive fibrous tissue. Wax A from Mycobacterium showed transient aggregations of polymorphonuclear leukocytes. Mycobacteria-derived wax D elicited a marked granulomatous response which persisted throughout the duration of the study, contrasting with a minimally acute inflammatory response to Nocardia-derived wax D. The phosphatide and soluble-fat fractions also showed aggressive lesions; however, these were similar for both organisms. These results indicate that the differences in tissue response elicited by lipids from N. asteroides and M. fortuitum may reside in wax fractions A and D.

Variations in properties of Nocardia asteroides resulting from growth in the cell wall-deficient state.

Several revertants possessing a cell wall were obtained from L-forms of Nocardia asteroides 10905. These L-form revertants differed from the parent in respect to colonial and cellular morphology, pigmentation, metabolic, capacities, cell wall structure, and mycolic acid composition. These data suggest a possible mechanism for the taxonomic heterogeneity and phenotypic diversity observed among N. asteroides strains.

Cell wall modification resulting from in vitro induction of L-phase variants of Nocardia asteroides.

The chemical composition of the cell walls of several L-form revertants derived from Nocardia asteroides 10905 was determined at different stages of growth. It was observed that each L-form revertant had a cell well that differed from that of the parental strain when grown under identical conditions. In some strains the peptidolipid and mycolic acid components were affected the most, whereas in other strains the fatty acid, sugar, and mycolic acid moieties were altered. Shifts in mycolic acid size were prominent, whereas the basic peptidoglycan structure appeared to be affected the least. Both the method used to induce the L-form of N. asteroides 10905 and the length of time these organisms were maintained in the wall-less state affected the degree of cell wall modification during the reversion process. Thus, removal of the cell wall appeared to potentiate and select for mutational alterations within the cell envelope of N. asteroides, and these changes resulted in altered cellular and colonial morphology.

[Nocardia asteroides (Eppinger) Blanchard in the soils of the Ukrainian SSR]. / Nocardia asteroides (Eppinger) Blanchard v pochvakh Ukrainskoi SSR.

The distribution of Nocardia asteroides (Eppinger) Blanchard, the main causative agent of nocardiosis in humans and animals, in the soils of the Ukrainian SSR was studied. This species was found to inhabit cultivated soils in various soil-climatic zones of the Ukrainian SSR. The isolated strains proved to be heterogeneous in their properties. N. asteroides fell into 2 groups: acetamidase-negative (A) and acetamidase-positive (B). Newly isolated N. asteroides belonging to the acetamidase-positive group were shown to be always pathogenic, whereas the organisms of the acetamidase-negative group could be pathogenic and non-pathogenic in white mice.