Response of CBA/N x DBA2/F1 mice to Nocardia asteroides

Nocardia infections in solid organ transplantation: Guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of Nocardia infections after solid organ transplantation (SOT). Nocardia infections have increased in the last two decades, likely due to improved detection and identification methods and an expanding immunocompromised population. The risk of developing nocardiosis after transplantation varies with the type of organ transplanted and the immunosuppression regimen used. Nocardia infection most commonly involves the lung. Disseminated infection can occur, with spread to the bloodstream, skin, or central nervous system. Early recognition of the infection and initial appropriate treatment is important to achieve good outcomes. Species identification and antimicrobial susceptibility testing are strongly recommended, as inter- and intraspecies susceptibility patterns can vary. Sulfonamide is the first-line treatment of Nocardia infections, and combination therapy with at least two antimicrobial agents should be used initially for disseminated or severe nocardiosis. Trimethoprim-sulfamethoxazole (TMP-SMX) prophylaxis may be helpful in preventing Nocardia infection after SOT.

Nocardiosis of the central nervous system: experience from a general hospital and review of 84 cases from the literature

Central nervous system (CNS) nocardiosis is a rare disease entity caused by the filamentous bacteria Nocardia species. We present a case series of 5 patients from our hospital and a review of the cases of CNS nocardiosis reported in the literature from January 2000 to December 2011. Our results indicate that CNS nocardiosis can occur in both immunocompromised and immunocompetent individuals and can be the result of prior pulmonary infection or can exist on its own. The most common predisposing factors are corticosteroid use (54% of patients) and organ transplantation (25%). Presentation of the disease is widely variable, and available diagnostic tests are far from perfect, often leading to delayed detection and initiation of treatment. The optimal therapeutic approach is still undetermined and depends on speciation, but lower mortality and relapse rates have been reported with a combination of targeted antimicrobial treatment including trimethoprim/sulfomethoxazole (TMP-SMX) for more than 6 months and neurosurgical intervention.

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.

Mycetoma

Mycetoma is a granulomatous infection affecting mainly the feet and lower extremities. It can be caused either by aerobic, branched actinomycetes or by eumycetes. Most cases are found in tropical and subtropical regions. The infection is usually produced by the introduction of the etiologic agents through minor wounds caused by thorns and wood splinters. Clinically the disease begins as small, firm nodules that can enlarge to form extensive lesions with fistulae and abscesses with pus containing granules of the causative microorganisms. Antimicrobials and surgery are used in the management of mycetoma. The actinomycetomas generally respond well to antimicrobials. For eumycetomas, surgery may be required. New therapeutic options for drug-resistant cases are discussed.

Cytokine production and lymphocyte proliferation in patients with Nocardia brasiliensis actinomycetoma

IFN-gamma, TNF-alpha, IL-4, IL-10 and IL-12 concentrations in the supernatant of peripheral blood mononuclear cell (PBMC) cultures and the in vitro proliferation of PBMC were studied in 25 patients with actinomycetoma caused by Nocardia brasiliensis and in 10 healthy controls from endemic zones. Cell cultures were stimulated by a N. brasiliensis crude cytoplasmic antigen (NB) and five semi-purified protein fractions (NB2, NB4, NB6, NB8, and NB10) separated by isoelectric. Phytohemagglutinin (PHA) and purified protein derivative (PPD) of Mycobacterium tuberculosis were used as control antigens. Skin tests were performed by injecting 0.1 ml of candidin and PPD intradermally (ID). Patients showed a poor response to tuberculin, while their response to candidin was more than two fold greater than that observed in the controls. Cell proliferation showed no statistically significant differences in either group. IFN-gamma production was higher in the healthy controls than in the patients, whereas TNF-alpha secretion was slightly higher in the patients' cultures. IL-4 was detected in the patients' cultures but not in the controls. IL-10 and IL-12 were present at low concentrations in both groups. These results suggest that patients with actinomycetoma show normal antigen recognition, but with low IFN-gamma production, and higher concentrations of IL-4, IL-10 and TNF-alpha in the patients' PBMC cultures, indicating that they probably have a Th2 type of immune response.

Humoral immunity through immunoglobulin M protects mice from an experimental actinomycetoma infection by Nocardia brasiliensis

An experimental model of infection with Nocardia brasiliensis, used as an example of a facultative intracellular pathogen, was tested. N. brasiliensis was injected into the rear foot pads of BALB/c mice to establish an infection. Within 30 days, infected animals developed a chronic actinomycetoma infection. Batch cultures of N. brasiliensis were used to purify P61, P38, and P24 antigens; P61 is a catalase, and P38 is a protease with strong caseinolytic activity. Active and passive immunizations of BALB/c mice with these three purified soluble antigens were studied. Protection was demonstrated for actively immunized mice. However, immunity lasted only 30 days. Other groups of immunized mice were bled at different times, and their sera were passively transferred to naive recipients that were then infected with N. brasiliensis. Sera collected 5, 6, and 7 days after donor immunization conferred complete, long-lasting protection. The protective effect of passive immunity decreased when sera were collected 2 weeks after donor immunization. However, neither the early sera (1-, 2-, and 3-day sera) nor the later sera (30- or 45-day sera) prevented the infection. Hyperimmune sera with the highest levels of immunoglobulin G (IgG) to N. brasiliensis antigens did not protect at all. The antigens tested induced two IgM peaks. The first peak was present 3 days after immunization but was not antigen specific and did not transfer protection. The second peak was evident 7 days after immunization, was an IgM response, was antigen specific, and conferred protection. This results clearly demonstrate that IgM antibodies protect the host against a facultative intracellular bacterium.

Immunogenicity and biophysical properties of a Nocardia brasiliensis protease involved in pathogenesis of mycetoma

We isolated and purified to homogeneity a caseinolytic protease from a Nocardia brasiliensis cell extract. Preparative polyacrylamide gel electrophoresis and electroelution were employed for purification. This purified protease was injected in BALB/c mice and induced IgM and IgG anti-protease antibodies. Active immunization of mice with this protease prevented mycetoma development in experimentally infected animals. Passive immunization with hyperimmune sera containing a high anti-protease antibody titer conferred partial but transient protection when collected 30 days after donor's immunization. The protective effect of hyperimmune sera was lost when obtained from donors after 60 days from their immunization despite its higher anti-protease antibody concentration. Cytokines are good candidates to explain these findings.

Immune response to Nocardia brasiliensis antigens in an experimental model of actinomycetoma in BALB/c mice

Nine- to twelve-week-old BALB/c mice were injected in footpads with 10(7) CFU of a Nocardia brasiliensis cell suspension. Typical actinomycetoma lesions, characterized by severe local inflammation with abscess and fistula formation, were fully established by day 28 after infection. These changes presented for 90 days, and then tissue repair with scar formation slowly appeared, with complete healing after 150 days of infection. Some animals developed bone destruction in the affected area. Histopathology showed an intense inflammatory response, with polymorphonuclear cells and hyaloid material around the colonies of the bacteria, some of which were discharged from draining abscesses. Sera from experimental animals were analyzed by Western blotting, and immunodominant antigens P61 and P24 were found as major targets for antibody response. Anti-P24 immunoglobulin M (IgM) isotype antibodies were present as early as 7 days, IgG peaking 45 days after infection. Lymphocyte proliferation with spleen and popliteal lymph node cells demonstrated thymidine incorporation at 7 days after infection, the stimulation index decreasing by day 60. Levels of interleukin-1 (IL-1), IL-2, IL-4, IL-6, tumor necrosis factor alpha, and gamma interferon (IFN-gamma) were determined by enzyme-linked immunosorbent assay in the sera of infected animals. The circulating levels of IFN-gamma increased more than 10 times the basal levels; levels of IL-4, IL-6 and IL-10 also increased during the first 4 days of infection.

Effect of presensitization of Nocardia asteroides with specific antibody on the viability of the organism

Nocardia asteroides from various growth phases was treated in vitro with normal rabbit sera, immune rabbit sera containing nocardial polyclonal antibodies and a monoclonal antibody. At intervals, samples were grown in broth or on blood agar plates to determine their viability. Log and stationary phase cells were injected intra-peritoneally into female BALB/c mice and their survival rates in the liver and spleen were determined. Presensitization with antibodies reduced the viability of the log phase cells by 48% and that of the late stationary phase by 4%. The antibody-treated log phase organisms were less viable on the blood agar medium and in the spleen and liver than the control organisms. This indicates that pretreatment with antibody has a lethal effect on N. asteroides and affects its survival in vivo.

Nocardia species: host-parasite relationships

The nocardiae are bacteria belonging to the aerobic actinomycetes. They are an important part of the normal soil microflora worldwide. The type species, Nocardia asteroides, and N. brasiliensis, N. farcinica, N. otitidiscaviarum, N. nova, and N. transvalensis cause a variety of diseases in both normal and immunocompromised humans and animals. The mechanisms of pathogenesis are complex, not fully understood, and include the capacity to evade or neutralize the myriad microbicidal activities of the host. The relative virulence of N. asteroides correlates with the ability to inhibit phagosome-lysosome fusion in phagocytes; to neutralize phagosomal acidification; to detoxify the microbicidal products of oxidative metabolism; to modify phagocyte function; to grow within phagocytic cells; and to attach to, penetrate, and grow within host cells. Both activated macrophages and immunologically specific T lymphocytes constitute the major mechanisms for host resistance to nocardial infection, whereas B lymphocytes and humoral immunity do not appear to be as important in protecting the host. Thus, the nocardiae are facultative intracellular pathogens that can persist within the host, probably in a cryptic form (L-form), for life. Silent invasion of brain cells by some Nocardia strains can induce neurodegeneration in experimental animals; however, the role of nocardiae in neurodegenerative diseases in humans needs to be investigated.

Nocardia species: host-parasite relationships

The nocardiae are bacteria belonging to the aerobic actinomycetes. They are an important part of the normal soil microflora worldwide. The type species, Nocardia asteroides, and N. brasiliensis, N. farcinica, N. otitidiscaviarum, N. nova, and N. transvalensis cause a variety of diseases in both normal and immunocompromised humans and animals. The mechanisms of pathogenesis are complex, not fully understood, and include the capacity to evade or neutralize the myriad microbicidal activities of the host. The relative virulence of N. asteroides correlates with the ability to inhibit phagosome-lysosome fusion in phagocytes; to neutralize phagosomal acidification; to detoxify the microbicidal products of oxidative metabolism; to modify phagocyte function; to grow within phagocytic cells; and to attach to, penetrate, and grow within host cells. Both activated macrophages and immunologically specific T lymphocytes constitute the major mechanisms for host resistance to nocardial infection, whereas B lymphocytes and humoral immunity do not appear to be as important in protecting the host. Thus, the nocardiae are facultative intracellular pathogens that can persist within the host, probably in a cryptic form (L-form), for life. Silent invasion of brain cells by some Nocardia strains can induce neurodegeneration in experimental animals; however, the role of nocardiae in neurodegenerative diseases in humans needs to be investigated.

Nocardia as a pathogen of the brain: mechanisms of interactions in the murine brain--a review

Nocardia asteroides strain GUH-2 invades the brain without inducing an early inflammatory response in normal mice. This strain can grow within the neurons as well as adjacent areas causing neurological damage without abscess formation. At low inoculum doses, this organism is gradually cleared from the brain after the initial burst of growth. Therefore, at two weeks, the brains of these mice appear to become sterile, but the animals begin to develop a variety of neurological signs including an L-dopa responsive headshake. It was found that mice that recovered from sublethal infection with N. asteroides strain GUH-2 had progressive and permanent neuron damage in regions of the brain, the extent of which appeared to correlate with specific neurological signs. The mechanisms of this response are not known, but current data indicate that the level of nonspecific phagocyte activation (microglia?) within the brain represents an important first line of defense. Next, T-lymphocytes are important in the secondary response in the brain to nocardial invasion. Finally, B-lymphocytes and a humoral immune response may be involved in these complex interactions; however, it is not clear how these responses relate to the permanent and progressive brain damage induced by Nocardia. It is possible that these latter responses may exacerbate neurodegeneration.

Antibody response to Nocardia brasiliensis antigens in man

A crude extract from N. brasiliensis cells grown in brain heart infusion culture was analyzed. It showed a complex mixture of at least 37 bands when resolved with the discontinuous buffer system of Laemmli in a gradient SDS-PAGE. Western blot analysis of 16 sera from N. brasiliensis-infected individuals always showed the recognition of six bands of 61, 49, 45, 42, 26, and 24 kilodaltons (kDa). Some other bands also reacted but with less intensity. Sera from tuberculosis and leprosy patients reacted strongly with the 49, 45, and 42 kDa bands but weakly or not at all with the 61, 26, and 24 kDa. Sera from healthy control volunteers reacted with some bands but little or not at all with those three identified by the sera from mycetoma patients. These three immunodominant antigens (61, 26 and 24 kDa) may be of clinical value in the serodiagnosis of mycetoma by N. brasiliensis.

Acid phosphatase stimulation of the growth of Nocardia asteroides and its possible relationship to the modification of lysosomal enzymes in macrophages

Lysosomal acid phosphatase levels are reduced in murine macrophages by virulent strains of Nocardia asteroides. At the same time, other lysosomal enzymes either remain unchanged or increase in activity, indicating that acid phosphatase is not lost because of degranulation or membrane leakage. This study shows that acid phosphatase was utilized as a sole carbon source by Nocardia asteroides and that acid phosphatase combined with glutamate as a carbon source enhanced nocardial growth. As a consequence, the inverse relationship that was observed between acid phosphatase activity and the bactericidal capacity of macrophages infected with N. asteroides appears to be due to the ability of N. asteroides to preferentially metabolize this lysosomal enzyme during growth within phagocytes.

Effect of growth stage on mycolic acid structure in cell walls of Nocardia asteroides GUH-2

Mycolic acids were extracted from the cell walls of Nocardia asteroides GUH-2 during different phases of growth at 37 degrees C. These were subjected to structural analysis by combining thin-layer chromatography and gas-liquid chromatography with UV and infrared spectrophotometry and mass spectroscopy of both methyl esters and trimethyl silyl derivatives. By analyzing the fragmentation patterns of these derivatives by three different methods of mass spectroscopy combined with gas-liquid chromatographic separation, the different structural subclasses of mycolic acids were quantitated. Significant qualitative and quantitative modifications of specific mycolic acid subclasses occurred in the cell walls of N. asteroides GUH-2 that were growth stage dependent. The mycolic acids that were predominant in the log phase were polyunsaturated (greater than 2 double bonds per molecule), with long chain lengths and even carbon atom numbers (i.e., C54, C56). In contrast, those that were prominent in the stationary phase were more saturated (few or no double bonds) and of shorter overall carbon chain length (less than or equal to C52). Furthermore, stationary-phase cells had significantly increased amounts of mycolic acids with odd-numbered carbon chain lengths (i.e., C49, C51, C53).

Nocardia

N asteroides is an aerobic, gram-positive, partially acid-fast, branching rod. Cell-mediated immunity via both macrophage activation and direct cytotoxicity represents the main host defense. While clinical infection most commonly occurs in immunocompromised hosts, Nocardia can infect and exist as a saprophyte in normal hosts. Diligence on the part of the treating physician is necessary to confirm the diagnosis. A combination of trimethoprim and sulfamethoxazole is the mainstay of treatment. With an aggressive approach to diagnosis and therapy, the prognosis in patients with nocardiosis appears to be dependent on their underlying disease process.

Therapy of experimental cerebral nocardiosis with imipenem, amikacin, trimethoprim-sulfamethoxazole, and minocycline

A mouse model of cerebral nocardiosis was used to determine relative antibiotic efficacy by reducing bacterial colony counts per gram of brain tissue. The antimicrobial agents employed were demonstrated in vitro to be inhibitory to most strains of Nocardia asteroides at very low concentrations. The agents used in this study were imipenem-cilastatin, amikacin, trimethoprim-sulfamethoxazole, and minocycline. Antibiotics were administered every 4 h for 72 h before animal sacrifice. Bacterial colony counts were assayed at various time points before the completion of therapy. Imipenem-cilastatin and amikacin were the most effective agents tested. Trimethoprim-sulfamethoxazole was less effective than imipenem and amikacin but more effective than minocycline. Minocycline did not eradicate intracerebral organisms and was similar to saline (control) in its effects.

Protective immunity to systemic nocardiosis in mice immunized with cell extract antigens of Nocardia asteroides

Mice immunized with crude cell extract antigens of Nocardia asteroides as well as its purified fraction F1 elicited significant levels of both humoral and cellular immune responses. These animals when challenged with 50% lethal dose of N. asteroides, two weeks after the complete immunization exhibited significant protection as seen by decreased mortality and viable counts compared to nonimmunized. The immunized animals were capable of clearing the infection much faster as compared to control. Cell extract antigens which were mainly protein in nature are thought to have a prime role in prevention and restriction of nocardial infection.

Intracellular acid phosphatase content and ability of different macrophage populations to kill Nocardia asteroides

It has been reported that the activity of lysosomal acid phosphatase decreases inversely with numbers of ingested virulent Nocardia spp. in normal murine peritoneal and alveolar macrophages. These studies suggested that this relationship correlated with the effectiveness of these macrophage populations in killing Nocardia asteroides. Experiments were designed to determine if acid phosphatase activity is affected by infection with N. asteroides in four different macrophage populations isolated from normal and nocardia-immunized mice. Macrophages were also tested simultaneously for their ability to kill N. asteroides. Peritoneal, alveolar, and splenic macrophages and Kupffer cells were infected in vitro with strains of N. asteroides of differing virulence. Uptake and killing assays were performed. Acid phosphatase levels and numbers of intracellular nocardiae were quantitated in the same macrophages, using a computer-assisted cytophotometry system. Acid phosphatase activity decreased inversely with numbers of intracellular nocardiae in macrophages that could not kill or inhibit this pathogen. Acid phosphatase activity was not significantly changed in macrophages that inhibited growth of, but did not kill, N. asteroides, whereas activity was increased or enhanced in macrophages that killed most of the ingested nocardiae. The order of nocardicidal effectiveness (and resistance to enzyme activity reduction with infection) for normal macrophages was splenic greater than peritoneal greater than alveolar greater than Kupffer. In contrast, the order of these two parameters for macrophages isolated from immunized mice was Kupffer greater than peritoneal greater than alveolar greater than splenic. These results demonstrate that lysosomal acid phosphatase activity is an effective marker of the ability of macrophages to inhibit growth of and kill N. asteroides and that macrophages isolated from different anatomical sites differ functionally from each other with respect to nocardicidal and acid phosphatase activities.

Immunodeficient CBA/N mice respond effectively to Candida albicans

An immune defect in CBA/N mice diminishes their ability to respond adequately to certain well-defined antigens. Since the contribution of T and B cells to immunity in candidiasis has not been clearly defined, it was hoped that CBA/N mice might prove a useful model for the study of specific responses to Candida albicans. Therefore, immunodeficient CBA/N and immunocompetent CBA/J mice were immunized by two cutaneous inoculations of viable C. albicans B311 given 2 weeks apart and challenged iv 14 days after the second inoculation. Delayed-type hypersensitivity (DTH) was tested with a membrane-derived antigen (B-HEX) 7 days following the second inoculation, and lymphocyte stimulation with B-HEX, a cytoplasmic antigen (SCS), and mitogens was done at 12 days. Antibody to SCS was determined by ELISA 2 days after DTH testing and 28 days after iv challenge, at which time the animals were sacrificed for quantitative culture of kidneys and brains. Naive CBA/N mice were no more susceptible to challenge than CBA/J mice in that the mean log colony-forming units (CFU) were 3.79 and 5.48, respectively. Both strains responded to immunization by a similar reduction in CFU, a marked DTH response (e.g., reactions at 24 hr were 1.12 mm for CBA/N and 1.34 mm for CBA/J), and significant and similar quantities of antibody. The immune defect in CBA/N mice had no demonstrable effect on the development of immune responses to infection with C. albicans.

Nocardia in naturally acquired and experimental infections in animals

There are three commonly recognized species ofNocardiathat cause disease in a large variety of animals including humans. In the United States, pulmonary or systemic nocardiosis in humans caused byN. asteroidesis most frequently diagnosed. It should be noted thatN. brasiliensiscan cause nocardiosis also. In Central and South America mycetomas induced byN. brasiliensisappear to be more prevalent even thoughN. asteroidescan be seen in this type of infection. Sporadic cases of both mycetoma and nocardiosis caused byN. caviaehave been reported. These three species ofNocardiaappear to be present in the soils of most countries; butN. asteroidesis more frequently isolated in the temperate climates whereasN. brasiliensispredominates in the tropical and subtropical regions of the world. No specific geographic distribution has been noted withN. caviae. Infections involving these three species of bacteria are, therefore, worldwide in occurrence. Even though nocardial infections in both humans and animals were recognized as early as 1888, traditionally, they have been considered rare in frequency as compared to many other infectious diseases. This is a perception that probably is not accurate. During the past twenty years, greater diagnostic awareness combined with more intensive medical and veterinary surveillance have resulted in significantly increased recognition of disease caused by these aerobic actinomycetes.

Endogenous ocular nocardiosis: a clinical and experimental study

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Adoptive transfer of immunity to Nocardia asteroides in nude mice

Nude mice on a BALB/c background were adoptively transferred with unprimed spleen cells, Nocardia-primed spleen cells, or Nocardia-primed splenic T lymphocytes from syngeneic, heterozygous (nu/+) littermates. Two days later, these recipient mice and unmanipulated (control) nude mice were infected intravenously with a 50% lethal dose of Nocardia asteroides GUH-2 from an early stationary-phase culture. Antibody titers, spleen weights, percent mortality, and organ clearance of the microorganisms were measured at 3 h to 28 days after infection. Adoptively transferred nude mice had larger spleens and greater titers of anti-nocardial antibody 7 to 28 days after infection as compared with control nude mice. Adoptive transfer with either primed spleen cells or primed splenic T lymphocytes enhanced both the survival of recipient nude mice and their ability to eliminate N. asteroides from the liver and spleen. These data indicate that adoptive immunity to infection with N. asteroides can be transferred with either specifically primed spleen cells or splenic T lymphocytes. Thus, it appears that cell-mediated immunity and T lymphocytes are of uppermost importance in host resistance to nocardial infection.