Mycobacterial, Fungal, Actinomycotic, and Nocardial Infections of the Pleura

Granulomatous pleuritis caused by histoplasmosis in a healthy child

Pneumonia with pleuritis is a rare presentation of histoplasmosis infection. We present a 12-year old previously healthy boy in whom histoplasmosis presented with pleuritis, confirmed by detection of antigen in empyema fluid.

Nocardia cyriacigeorgica pleural empyema in an immunocompromised patient

A case of fatal Nocardia cyriacigeorgica pleural empyema in a patient with chronic obstructive pulmonary disease and long-term corticosteroid therapy is described. The organism was isolated from the pleural fluid in pure culture and was identified by conventional and molecular methods. Despite the early administration of the appropriate antibiotic treatment, the patient died 4 days after hospital admission.

Pathology of the Pleura

The pleura and lung are intimately associated and share many pathologic conditions. Nevertheless, they represent two separate organs of different embryonic derivation and with different yet often symbiotic functions. In this article, the authors explore the pathologic manifestations of the many conditions that primarily or secondarily affect the pleura.

Management of undiagnosed persistent pleural effusions

Difficult to diagnose pleural effusions are not uncommonly encountered in clinical practice. We define these effusions as those that remain undiagnosed after initial thoracentesis and repeat thoracentesis with pleural biopsy. Tuberculosis and malignancy are often found to be the underlying causes when a diagnosis is ultimately made, but other causes, including pulmonary embolism and intra-abdominal conditions, need to be considered as potential causes of the difficult to diagnose effusions. In selected cases, presumptive treatment of tuberculosis is indicated whereas in others, a decision must be made either to obtain a definitive diagnosis by invasive surgical procedures or to follow the patient with careful observation and watchful waiting.

Differential gene expression in response to adjunctive recombinant human interleukin-2 immunotherapy in multidrug-resistant tuberculosis patients

Administration of low-dose recombinant human interleukin 2 (rhuIL-2) in combination with multidrug chemotherapy to patients with multidrug-resistant tuberculosis (MDR TB) induces measurable changes in in vitro immune response parameters which are associated with changes in the clinical and bacteriologic status of the patients. To determine the molecular basis of these changes, we have used semiquantitative reverse transcriptase-initiated PCR (RT-PCR) and differential display technology. During rhuIL-2 treatment of MDR TB patients, decreased levels of gamma interferon (IFN-gamma) mRNA in peripheral blood mononuclear cells (PBMC) relative to baseline levels were observed. However, at the site of a delayed-type hypersensitivity (DTH) response to purified protein derivative of tuberculin (PPD), the expression of cellular IFN-gamma and IL-2 mRNAs was increased during rhuIL-2 therapy. Levels of other cytokine mRNAs were not significantly affected by rhuIL-2 administration. Using differential-display RT-PCR, we identified several genes expressed at the DTH skin test site which were up- or down-regulated during rhuIL-2 treatment. Cytochrome oxidase type I mRNA was increased in response to rhuIL-2 therapy relative to baseline levels, as was heterogeneous nuclear ribonuclear protein G mRNA. CD63, clathrin heavy chain, and beta-adaptin mRNAs, all of which encode proteins associated with the endocytic vacuolar pathway of cells, were also differentially regulated by rhuIL-2 administration. The differential effects of IL-2 were confirmed in vitro by using PBMC obtained from PPD-positive individuals stimulated with Mycobacterium tuberculosis and IL-2. The differential expression of genes may provide a surrogate marker for leukocyte activation at a mycobacterial antigen-specific response site and for the development of an enhanced antimicrobial response which may result in improved outcomes in MDR TB patients.

Bronchopleural fistula and lymphocytic empyema due to Histoplasma capsulatum

A patient presented with chest pain, fever, and chills and developed a large pleural effusion while receiving antibiotic therapy. On a CT scan of the chest, multiple loculi of fluid were noted, and at surgery, a complex empyema with an associated bronchopleural fistula related to a granulomatous process in the lower lobe of the right lung was demonstrated. Cultures revealed Histoplasma capsulatum in the pleural fluid as well as in the pulmonary parenchymal process.

Massive pleural effusion in diffuse granulomatous disease

Although recurrent, massive pleural effusions frequently are associated with malignancy, they rarely occur in granulomatous diseases of the lung. We report the case of a 50-year-old man with a recurrent, massive pleural effusion and a diffuse granulomatous disease that involved the lung, the lymphatics, and bone marrow. The cause of the effusion and granulomatous disease is not entirely clear; however, the effusion did resolve with antifungal therapy and a brief course of corticosteroids.

Pleural effusion as the major manifestation of actinomycosis

Pleural effusion represents an unusual but significant manifestation of actinomycosis, as illustrated in this case presentation. The diagnosis was made after bronchoscopy and examination of bronchoalveolar fluid and culture. No parenchymal abnormality was noted on the chest film.

The medically important aerobic actinomycetes: epidemiology and microbiology

The aerobic actinomycetes are soil-inhabiting microorganisms that occur worldwide. In 1888, Nocard first recognized the pathogenic potential of this group of microorganisms. Since then, several aerobic actinomycetes have been a major source of interest for the commercial drug industry and have proved to be extremely useful microorganisms for producing novel antimicrobial agents. They have also been well known as potential veterinary pathogens affecting many different animal species. The medically important aerobic actinomycetes may cause significant morbidity and mortality, in particular in highly susceptible severely immunocompromised patients, including transplant recipients and patients infected with human immunodeficiency virus. However, the diagnosis of these infections may be difficult, and effective antimicrobial therapy may be complicated by antimicrobial resistance. The taxonomy of these microorganisms has been problematic. In recent revisions of their classification, new pathogenic species have been recognized. The development of additional and more reliable diagnostic tests and of a standardized method for antimicrobial susceptibility testing and the application of molecular techniques for the diagnosis and subtyping of these microorganisms are needed to better diagnose and treat infected patients and to identify effective control measures for these unusual pathogens. We review the epidemiology and microbiology of the major medically important aerobic actinomycetes.

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.

Leukocytic responses to the intrapleural deposition of particles, particle-cell associations, and the clearance of particles from the pleural space compartment

Polystyrene microspheres (2.02 micron diameter) were instilled in the pleural space compartment (PSC) of the Fischer 344 rat. Rats that were administered carrier vehicle only, and untreated rats served as controls. On d 1, 6, 14, and 28 following the instillations, the pleural free cells were harvested by pleural lavage and the major cell phenotypes retrieved were quantitated to determine how the pleural free cell population was altered by the particles. Concurrent with these studies, quantitative analyses were performed to determine the numbers of particles lavaged from the pleural space at the above sacrifice times, and these particle retention data were used to estimate particle translocation rates from the PSC. Deposition of the particles in the PSC brought about an early recruitment of polymorphonuclear leukocytes (PMN) and an enlargement in the size of the pleural mononuclear phagocyte (PMP) population. PMN numbers substantially decreased by d 6, but continued to remain elevated over the course of the study. The early increase in PMP appeared to subside by d 6, but again increased thereafter. Other notable changes were decreases in the size of the pleural eosinophil population at later times after particle deposition, and an approximate 200-fold increase in lymphocytes by d 28. The particles were cleared from the PSC with a biphasic pattern. The most rapid phase, which accounted for the clearance of greater than or equal to 80% of the particles, had a t1/2 = 0.3 d and the slower component had a t1/2 = 6 d. Most of the particles were translocated from the PSC to the retrosternal, caudal mediastinal tissue. The slower phase of particle clearance appeared to be macrophage-mediated, suggesting the t1/2 for macrophages in the PSC is also approximately 6 d.