Central nervous system aspergillosis in patients with human immunodeficiency virus infection. Report of 6 cases and review

A Systematic Review to Assess the Relationship between Disseminated Cerebral Aspergillosis, Leukemias and Lymphomas, and Their Respective Therapeutics

Disseminated disease following invasive pulmonary aspergillosis (IPA) remains a significant contributor to mortality amongst patients with hematologic malignancies (HMs). At the highest risk of mortality are those with disseminated disease to the central nervous system, known as cerebral aspergillosis (CA). However, little is known about the risk factors contributing to disease amongst HM patients. A systematic review using PRISMA guidelines was undertaken to define HM patient subgroups, preventative measures, therapeutic interventions, and outcomes of patients with disseminated CA following IPA. The review resulted in the identification of 761 records, of which 596 articles were screened, with the final inclusion of 47 studies and 76 total patients. From included articles, the proportion of CA was assessed amongst HM patient subgroups. Further, pre-and post-infection characteristics, fungal species, and mortality were evaluated for the total population included and HM patient subgroups. Patients with acute myeloid leukemia and acute lymphoid lymphoma, patients receiving corticosteroids as a part of their HM therapeutic regimen, and anti-fungal prophylaxis constitute the top identified patient populations at risk for disseminated CA. Overall, information presented here indicates that measures for the prevention of IPA should be taken in higher-risk HM patient subgroups. Specifically, the type of anti-fungal therapy used should be carefully considered for those patients with IPA and increased risk for cerebral dissemination. Additional reports detailing patient characteristics are needed to define further the risk of developing disseminated CA from IPA in patients with HMs.

Diagnosis and management of Aspergillus diseases: executive summary of the 2017 ESCMID-ECMM-ERS guideline

The European Society for Clinical Microbiology and Infectious Diseases, the European Confederation of Medical Mycology and the European Respiratory Society Joint Clinical Guidelines focus on diagnosis and management of aspergillosis. Of the numerous recommendations, a few are summarized here. Chest computed tomography as well as bronchoscopy with bronchoalveolar lavage (BAL) in patients with suspicion of pulmonary invasive aspergillosis (IA) are strongly recommended. For diagnosis, direct microscopy, preferably using optical brighteners, histopathology and culture are strongly recommended. Serum and BAL galactomannan measures are recommended as markers for the diagnosis of IA. PCR should be considered in conjunction with other diagnostic tests. Pathogen identification to species complex level is strongly recommended for all clinically relevant Aspergillus isolates; antifungal susceptibility testing should be performed in patients with invasive disease in regions with resistance found in contemporary surveillance programmes. Isavuconazole and voriconazole are the preferred agents for first-line treatment of pulmonary IA, whereas liposomal amphotericin B is moderately supported. Combinations of antifungals as primary treatment options are not recommended. Therapeutic drug monitoring is strongly recommended for patients receiving posaconazole suspension or any form of voriconazole for IA treatment, and in refractory disease, where a personalized approach considering reversal of predisposing factors, switching drug class and surgical intervention is also strongly recommended. Primary prophylaxis with posaconazole is strongly recommended in patients with acute myelogenous leukaemia or myelodysplastic syndrome receiving induction chemotherapy. Secondary prophylaxis is strongly recommended in high-risk patients. We strongly recommend treatment duration based on clinical improvement, degree of immunosuppression and response on imaging.

Invasive Aspergillus Sinusitis in Human Immunodeficiency Virus Infection: Case Report and Review of the Literature

Invasive Aspergillus (IA) sinusitis is a life-threatening opportunistic infection in immunocompromised individuals, but it is uncommon in human immunodeficiency virus (HIV) infection. To gain a better understanding of the characteristics of IA sinusitis in this population, we present a unique case of chronic IA sinusitis in an HIV-infected patient taking antiretroviral therapy and review the literature summarizing published cases of invasive aspergillosis of the paranasal (n = 41) and mastoid (n = 17) sinuses in HIV-infected individuals. Among these cases, only 4 were reported after 1999, and 98% of patients had acquired immune deficiency syndrome. Orbital invasion occurred in 54% of paranasal sinus cases, whereas intracranial invasion was reported in 53% of mastoid sinus cases. The overall mortality was 79%. We also discuss various clinical and immunologic factors that may play a role in the development of IA and consider the changing epidemiology of aspergillosis in the era of effective antiretroviral therapy.

Infektionen

In diesem Kapitel werden zunächst die für die Neurointensivmedizin wesentlichen bakteriellen Infektionen (Meningitis, spinale und Hirnabszesse, Spondylodiszitis, septisch-embolische Herdenzephalitis) abgehandelt, die trotz gezielt eingesetzter Antibiotika und neurochirurgischer Therapieoptionen noch mit einer erheblichen Morbidität und Mortalität behaftet sind. Besonderheiten wie neurovaskuläre Komplikationen, die Tuberkulose des Nervensystems, Neuroborreliose, Neurosyphilis und opportunistische Infektionen bei Immunsuppressionszuständen finden hierbei besondere Berücksichtigung. Der zweite Teil dieses Kapitels behandelt akute und chronische Virusinfektionen des ZNS sowie in einem gesonderten Abschnitt die HIVInfektion und HIV-assoziierte Krankheitsbilder sowie Parasitosen und Pilzinfektionen, die in Industrieländern seit Einführung der HAART bei HIV zwar eher seltener, aber mit zunehmender Globalisierung auch in unseren Breiten immer noch anzutreffen sind.

Cerebral aspergillosis with multiple enhancing nodules in the right cerebral hemisphere in the immune-competent patient

Aspergillosis in the central nervous system (CNS) is a very rare disease in immune-competent patients. There was a case of a healthy man without a history of immune-compromised disease who had invasive aspergillosis with unusual radiologic findings. A 48-year-old healthy man with diabetes mellitus, presented with complaints of blurred vision that persisted for one month. Brain magnetic resonance imaging (MRI) showed multiple nodular enhancing lesions on the right cerebral hemisphere. The diffusion image appeared in a high-signal intensity in these areas. Cerebrospinal fluid examination did not show any infection signs. An open biopsy was done and intraoperative findings showed grayish inflammatory and necrotic tissue without a definitive mass lesion. The pathologic result was a brain abscess caused by fungal infection, morphologically aspergillus. Antifungal agents (Amphotericin B, Ambisome and Voriconazole) were used for treatment for 3 months. The visual symptoms improved. There was no recurrence or abscess pocket, but the remaining focal enhanced lesions were visible in the right temporal and occipital area at a one year follow-up MRI. This immune-competent patient showed multiple enhancing CNS aspergillosis in the cerebral hemisphere, which had a good outcome with antifungal agents.

Systemic mycoses in immunodepressed patients (AIDS)

Infectious and noninfectious skin diseases are observed in about 90% of HIV patients, and their incidence increases and is more severe as the immune system weakens. Cutaneous manifestations are considered good clinical predictors for the immunological condition of the patient with AIDS and the introduction of highly effective antiretroviral therapy totally changed the prognosis of the mycoses, among other diseases associated with AIDS, permitting longer survival and acceptable level of quality of life for these patients. This contribution describes the systemic mycoses that are more frequent in the seropositive population, that is, patients with HIV/AIDS, which are cryptococcosis, histoplasmosis, coccidioidomycosis, blastomycosis, paracoccidioidomycosis, sporotrichosis, penicilliosis, and aspergillosis. Their causative agents, mode of transmission, clinics, laboratorial diagnosis and therapy, in the aspects related to immunodepressed patients, are reviewed.

Ultraviolet irradiation: An effective inactivation method of Aspergillus spp. in water for the control of waterborne nosocomial aspergillosis

Invasive aspergillosis is the second most common cause of nosocomial fungal infections and occurring mainly by Aspergillus fumigatus, Aspergillus flavus, and Aspergillus niger. There is evidence that nosocomial aspergillosis may be waterborne. This study was conducted to evaluate the ultraviolet (UV) irradiation efficiency in terms of inactivating the most important Aspergillus species in water since these are potential sources for nosocomial aspergillosis. A continuous flow UV reactor which could be used as a point-of-use (POU) system was used to survey Aspergillus inactivation by UV irradiation. The inactivation efficiency of UV fluence (4.15-25 mJ/cm(2)) was measured by determination of fungal density in water before and after radiation. Because turbidity and iron concentration are two major water quality factors impacting UV disinfection effectiveness, the potential influence of these factors on UV inactivation of Aspergillus spp. was also measured. The 4 log inactivation for A. fumigatus, A. niger and A. flavus at a density of 1000 cfu/ml was achieved at UV fluences of 12.45 mJ/cm(2), 16.6 mJ/cm(2) and 20.75 mJ/cm(2), respectively. The inactivation efficiency for lower density (100 cfu/ml) was the same as for the higher density except for A. flavus. The removal efficiency of Aspergillus spp. was decreased by increasing the turbidity and iron concentration. UV disinfection could effectively inactivate Aspergillus spores from water and eliminate potential exposure of high-risk patients to fungal aerosols by installation of POU UV systems.

Central nervous system aspergillosis: a series of 14 cases from a general hospital and review of 123 cases from the literature

Central nervous system (CNS) aspergillosis is a highly fatal infection. We review the clinical presentation, diagnosis, and outcome of this infection and present a case series of 14 consecutive patients with CNS aspergillosis admitted to Massachusetts General Hospital (MGH) from 2000 to 2011. We also review 123 cases reported in the literature during that time. We included only proven CNS aspergillosis cases conforming to the European Organization for Research and Treatment of Cancer/Mycoses Study Group (EORTC/MSG) definitions of invasive fungal infections. In the MGH case series, neutropenia, hematologic malignancies, autoimmune diseases requiring steroid treatment, and solid organ transplantation were the predominant comorbid conditions. Notably, all MGH patients were immunosuppressed, and more than half (n = 8) had a history of previous brain injury, unrelated to their index hospitalization. For most MGH patients (11 of 14), the lung was the primary focus of aspergillosis, while 2 had paranasal sinus involvement, and 1 had primary Aspergillus discitis. Among reported cases, paranasal sinuses (27.6%) and the lung (26.8%) were the primary foci of infection, whereas 22% of those cases had no obvious primary organ involvement. Although a selection bias should be considered, especially among published cases, our findings suggest that patients who underwent neurosurgery had improved survival, with MGH and literature patients having 25% and 28.6% mortality, respectively, compared to 100% and 60.4%, respectively, among patients who received only medical treatment. Although this was not the case among MGH patients, CNS aspergillosis can affect patients without significant immune suppression, as indicated by the high number of reported immunocompetent cases. In conclusion, mortality among CNS aspergillosis patients remains high, and the infection may be more common among patients with previous brain pathology. When indicated, neurosurgical procedures may improve prognosis.

47 year-old man with HIV infection and hemiplegia

CNS aspergillosis is often missed in the setting of advanced HIV infection, especially in the absence of presumed risk factors such as neutropenia or prior steroid treatment. We describe the postmortem evaluation of the brain of a patient with AIDS that developed progressive neurologic deterioration. Sequence brain MRIs, CSF analysis, and multiple presumed treatments failed to reveal the possible causes or improve his ongoing condition. His brain autopsy showed numerous abscesses with septated hyphae consistent with CNS angioinvasive aspergillosis.

Mouse models for the study of fungal pneumonia: a collection of detailed experimental protocols for the study of Coccidioides, Cryptococcus, Fusarium, Histoplasma and combined infection due to Aspergillus-Rhizopus

Mouse models have facilitated the study of fungal pneumonia. In this report, we present the working protocols of groups that are working on the following pathogens: Aspergillus, Coccidioides, Cryptococcus, Fusarium, Histoplasma and Rhizopus. We describe the experimental procedures and the detailed methods that have been followed in the experienced laboratories to study pulmonary fungal infection; we also discuss the anticipated results and technical notes, and provide the practical advices that will help the users of these models.

Infektionen

Trotz Weiterentwicklung moderner Antibiotika in den letzten Jahren sind die Letalitätszahlen der bakteriellen (eitrigen) Meningitis weiterhin hoch; Überlebende haben häufig neurologische Residuen. Die ungünstigen klinischen Verläufe der bakteriellen Meningitis sind meist Folge intrakranieller Komplikationen, wie z. B. eines generalisierten Hirnödems, einer zerebrovaskulären arteriellen oder venösen Beteiligung oder eines Hydrozephalus.

Intracranial Aspergillus granuloma

Intracranial fungal granulomas are rare and of the histologically verified granulomas, Aspergillus spp. is the commonest causative fungal pathogen. Most of the reported large series of aspergillus granulomas are from countries with temperate climate like India, Pakistan, Sudan, and Saudi Arabia. In contrast to disseminated aspergillosis that occurs in immunosuppressed individuals, most of the intracranial aspergillus granulomas are reported in immunocompetent individuals. The temperature, humidity, high spore content in the atmosphere during ploughing, and occupation as agricultural worker are implicated in the pathogenesis. The sinocranial spread is the most common route of intracranial extension. Extracerebral firm fibrotic lesions and skull base lesions are common. Extensive fibrosis and large number of multinucleated giant cells are the characteristic histological features and these pathological features have therapeutic relevance.

A rare, fatal case of invasive spinal aspergillosis in an antiretroviral-naive, HIV-infected man with pre-existing lung colonization

Infection of the central nervous system (CNS) is a rare but devastating complication of invasive aspergillosis. We report a case of invasive aspergillosis with spinal involvement in a human immunodeficiency virus (HIV)-infected patient without neutropenia. A 42-year-old, antiretroviral-naïve, HIV-infected man presented with progressive weakness in the lower limbs and urinary and faecal incontinence for 2 weeks. The patient had been prescribed broad-spectrum antibiotics and prednisone. He had upper motor neuron signs and a sensory level at T1, with accompanying neck stiffness on flexion. Magnetic resonance imaging revealed diffuse abnormal signals of the vertebral bodies in the lower cervical and thoracic areas, with cord compression in the C2 and C3 region and signal distortions of the T2 and T3 vertebral bodies. Chest X-ray and computerized tomography demonstrated post-tuberculous apical cavities with suspected fungal colonization. Histopathology of an extradural spinal lesion at T1/T2 suggested invasive aspergillosis. The patient was started on fluconazole in response to the histopathological evidence of Aspergillus infection, but died within 3 weeks. Post-mortem analysis of the biopsy sample by PCR identified the infectious agent as Aspergillus fumigatus. Atypically, his CD4(+) T-cell count was 239 cells mm(-3) and he had no evidence of neutropenia. Invasive aspergillosis should be considered as part of the differential diagnosis among HIV-infected patients with non-specific, focal CNS symptoms, even among those without classical risk factors such as neutropenia, and aggressive antifungal therapy should be instituted as early as possible.

Multiple Aspergillus cerebellar abscesses in a middle-aged female: case report and literature review

Aspergillus abscesses in the cerebellum are extremely rare, and most cases are solitary. Here, we report the first case of multiple Aspergillus cerebellar abscesses in a 46-year-old female after one mastoidectomy, two craniectomies, and extended use of antibiotics. The possible pathogenesis of this unusual event is discussed. Good outcome was achieved by treatment with a combination of neurosurgical resection and voriconazole (VRC) administration, which we suggest is a potential management plan.

Antifungal drug discovery through the study of invertebrate model hosts

There is an urgent need for new antifungal agents that are both effective and non-toxic in the therapy of systemic mycoses. The model nematode Caenorhabditis elegans has been used both to elucidate evolutionarily conserved components of host-pathogen interactions and to screen large chemical libraries for novel antimicrobial compounds. Here we review the use of C. elegans models in drug discovery and discuss caffeic acid phenethyl ester, a novel antifungal agent identified using an in vivo screening system. C. elegans bioassays allow high-throughput screens of chemical libraries in vivo. This whole-animal system may enable the identification of compounds that modulate immune responses or affect fungal virulence factors that are only expressed during infection. In addition, compounds can be simultaneously screened for antifungal efficacy and toxicity, which may overcome one of the main obstacles in current antimicrobial discovery. A pilot screen for antifungal compounds using this novel C. elegans system identified 15 compounds that prolonged survival of nematodes infected with the medically important human pathogen Candida albicans. One of these compounds, caffeic acid phenethyl ester (CAPE), was an effective antifungal agent in a murine model of systemic candidiasis and had in vitro activity against several fungal species. Interestingly, CAPE is a potent immunomodulator in mammals with several distinct mechanisms of action. The identification of CAPE in a C. elegans screen supports the hypothesis that this model can identify compounds with both antifungal and host immunomodulatory activity.

Primary aspergilloma and subacute invasive aspergillosis in two AIDS patients

Although uncommon, invasive aspergillosis in the setting of AIDS is important because of its peculiar clinical presentation and high lethality. This report examines two AIDS patients with a history of severe cellular immunosuppression and previous neutropenia, who developed subacute invasive aspergillosis. One female patient developed primary lung aspergilloma, with dissemination to the mediastinum, vertebrae, and spine, which was fatal despite antifungal treatment. The second patient, who had multiple cavitary brain lesions, and eye and lung involvement, recovered following voriconazole and itraconazole, and drugs for increasing neutrophil and CD4+ lymphocyte levels. These cases demonstrate the importance of Aspergillus infections following neutropenia in AIDS patients, and emphasize the need for early and effective antifungal therapy.

CNS aspergillosis: recognition, diagnosis and management

Early diagnosis of CNS aspergillosis requires a high degree of clinical suspicion, because there are no typical clinical symptoms or CSF findings. Clinical features are usually dramatic and tend to progress rapidly. Changes in mental status, hemiparesis and seizures are most common, but other nonspecific neurological features may occur and should always be an indication for neuroradiological examination in high-risk patients, in order to allow early initiation of antifungal therapy. Low density lesions with little or no mass effect and minimal or no contrast enhancement on CT scans that are usually more numerous on MRI and show intermediate signal intensity within high-signal areas on T2-weighted images, may suggest CNS aspergillosis. Cerebral lesions in CNS aspergillosis are often located not only in the cerebral hemispheres but also in the basal ganglia, thalami, corpus callosum and perforator artery territories. There is frequently a lack of contrast enhancement or perifocal oedema, due to the immunosuppressed status of the patient. A definite diagnosis requires brain tissue for histopathological analysis. However, neurosurgery is often not feasible, so that any of the neuroradiological findings mentioned above should raise the suspicion of CNS aspergillosis in immunocompromised patients and lead to early initiation of antifungal therapy. In the past, amphotericin B-based therapy was the treatment of choice for CNS aspergillosis, but this treatment produced negligible effects. Recently, voriconazole has been reported to be more effective than amphotericin B in the treatment of invasive aspergillosis. Response rates of about 35% have been achieved with voriconazole in patients with CNS aspergillosis. Combination therapy with antifungal agents, such as voriconazole plus caspofungin or liposomal amphotericin B, is being investigated in vitro and in animal models, and optimistic results have been observed. A combined medical and neurosurgical treatment should be considered in all patients with this disease.

A renal aspergilloma--an unusual presentation of aspergillosis in an HIV patient

BACKGROUND

Aspergillosis is a fungal infection occasionally found in immunosuppressed patients. The recommended management of patients with renal aspergilloma remains unclear.

METHODS

An HIV patient presented with flank pain and an abdominal mass. Renal aspergilloma was diagnosed.

RESULTS

The patient with CD4 above 200 did well with nephrectomy followed by amphotericin therapy for 14 days.

CONCLUSIONS

The merits of surgery followed by antifungal chemotherapy or vice versa are limited. More studies are needed to ascertain the most effective method of treatment for Aspergillosis in HIV patients.

The invasive and saprophytic syndromes due to Aspergillus spp

Aspergillus spp. produce a wide range of invasive and sapropytic syndromes which may involve any tissue. Within a given tissue or organ the pathology and pathogenesis varies enormously, ranging from angioinvasive disease to noninvasive saprophytic disease. The individual invasive and saprophytic syndromes in which a causative role can be attributed to Aspergillus spp. are detailed specifically with reference to the underlying pathology and pathogenesis, the clinical setting and features, and the manner in which a diagnosis can be established.

Cerebral aspergillosis due to Aspergillus fumigatus in AIDS patient: first culture - proven case reported in Brazil

Cerebral aspergillosis is a rare cause of brain expansive lesion in AIDS patients. We report the first culture-proven case of brain abscess due to Aspergillus fumigatus in a Brazilian AIDS patient. The patient, a 26 year-old male with human immunodeficiency virus (HIV) infection and history of pulmonary tuberculosis and cerebral toxoplasmosis, had fever, cough, dyspnea, and two episodes of seizures. The brain computerized tomography (CT) showed a bi-parietal and parasagittal hypodense lesion with peripheral enhancement, and significant mass effect. There was started anti-Toxoplasma treatment. Three weeks later, the patient presented mental confusion, and a new brain CT evidenced increase in the lesion. He underwent brain biopsy, draining 10 mL of purulent material. The direct mycological examination revealed septated and hyaline hyphae. There was started amphotericin B deoxycholate. The culture of the material demonstrated presence of the Aspergillus fumigatus. The following two months, the patient was submitted to three surgeries, with insertion of drainage catheter and administration of amphotericin B intralesional. Three months after hospital admission, his neurological condition suffered discrete changes. However, he died due to intrahospital pneumonia. Brain abscess caused by Aspergillus fumigatus must be considered in the differential diagnosis of the brain expansive lesions in AIDS patients in Brazil.

The art of serendipity: killing of Caenorhabditis elegans by human pathogens as a model of bacterial and fungal pathogenesis

The nematode worm, Caenorhabditis elegans, has been used to develop a facile model system of host-pathogen interactions to identify basic evolutionarily conserved pathways associated with microbial pathogenesis. The model involves the killing of Caenorhabditis elegans by a variety of human pathogens. Several virulence-related genes in a variety of pathogens previously shown to be involved in mammalian infection have also been shown to play a role in Caenorhabditis elegans killing. Screening of large numbers of microbial mutants for attenuation in a mammalian model would require thousands of mice, rats or rabbits. In contrast, the Caenorhabditis elegans model allows rapid identification of mutants in microbial genes associated with pathogenesis and then these phenotypes can be confirmed in a relevant mammalian model.

Les aspergilloses cérébrales

INTRODUCTION

The brain is almost always a localization of invasive aspergillosis, after hematogenous spread from pulmonary aspergillosis. Brain aspergilosis is not rare and is one of the worst prognosis factors of invasive aspergillosis.

STATE OF ART

The incidence of this severe mycosis is currently on the rise due to the development of major immunosuppressive treatments. Brain aspergillosis is noteworthy for its vascular tropism, leading to infectious cerebral vasculitis, mainly involving thalamoperforating and lenticulostriate arteries, with a high frequency of thalamic or basal nuclei lesions. Extra-neurologic features that suggest this diagnosis are: i) risk factors for invasive aspergillosis (major or prolonged neutropenia, hematologic malignancies, prolonged corticosteroid treatment, bone marrow or solid organ transplant, AIDS); ii) persistent fever not responding to presumptive antibacterial treatment; iii) respiratory signs (brain aspergillosis is associated with pulmonary aspergillosis in 80 to 95 p. 100 of cases). Perspectives. Two recent major improvements in brain aspergillosis management must be outlined: i) for diagnostic purposes, the development of testing for Aspergillus antigenemia (a non-invasive procedure with good diagnostic value for invasive aspergillosis); ii) for therapeutic purposes, the demonstration that voriconazole is better than amphotericin B in terms of clinical response, tolerance and survival, for all types of invasive aspergillosis, the benefit being probably even greater in case of brain aspergillosis because of the good diffusion of voriconazole into the central nervous system.

CONCLUSIONS

Brain aspergillosis is a severe emerging opportunistic infection for which diagnostic and therapeutic tools have recently improved. Thus, this diagnostic must be suspected early, especially in the immunocompromised patient, in the event of respiratory symptoms and when the brain lesions are localized in the central nuclei and the thalamus.

Tuberculous brain abscess in a patient with AIDS: case report and literature review

Tuberculous brain abscesses in AIDS patients are considered rare with only eight cases reported in the literature. We describe the case of a 34-year-old woman with AIDS and previous toxoplasmic encephalitis who was admitted due to headache and seizures. A brain computed tomography scan disclosed a frontal hypodense lesion with a contrast ring enhancement. Brain abscess was suspected and she underwent a lesion puncture through a trepanation. The material extracted was purulent and the acid-fast smear was markedly positive. Timely medical and surgical approaches allowed a good outcome. Tuberculous abscesses should be considered in the differential diagnosis of focal brain lesions in AIDS patients. Surgical excision or stereotactic aspiration, and antituberculous treatment are the mainstay in the management of these uncommon lesions.

Killing of Caenorhabditis elegans by Cryptococcus neoformans as a model of yeast pathogenesis

We found that the well-studied nematode Caenorhabditis elegans can use various yeasts, including Cryptococcus laurentii and Cryptococcus kuetzingii, as a sole source of food, producing similar brood sizes compared with growth on its usual laboratory food source Escherichia coli OP50. C. elegans grown on these yeasts had a life span similar to (C. laurentii) or longer than (C. kuetzingii) those fed on E. coli. However, the human pathogenic yeast Cryptococcus neoformans killed C. elegans, and the C. neoformans polysaccharide capsule as well as several C. neoformans genes previously shown to be involved in mammalian virulence were also shown to play a role in C. elegans killing. These included genes associated with signal transduction pathways (GPA1, PKA1, PKR1, and RAS1), laccase production (LAC1), and the alpha mating type. C. neoformans adenine auxotrophs, which are less virulent in mammals, were also less virulent in C. elegans. These results support the model that mammalian pathogenesis of C. neoformans may be a consequence of adaptations that have evolved during the interaction of C. neoformans with environmental predators such as free-living nematodes and amoebae and suggest that C. elegans can be used as a simple model host in which C. neoformans pathogenesis can be readily studied.

The impact of culture isolation of Aspergillus species: a hospital-based survey of aspergillosis

The term "aspergillosis" comprises several categories of infection: invasive aspergillosis; chronic necrotizing aspergillosis; aspergilloma, or fungus ball; and allergic bronchopulmonary aspergillosis. In 24 medical centers, we examined the impact of a culture positive for Aspergillus species on the diagnosis, risk factors, management, and outcome associated with these diseases. Most Aspergillus culture isolates from nonsterile body sites do not represent disease. However, for high-risk patients, such as allogeneic bone marrow transplant recipients (60%), persons with hematologic cancer (50%), and those with signs of neutropenia (60%) or malnutrition (30%), a positive culture result is associated with invasive disease. When such risk factors as human immunodeficiency virus infection (20%), solid-organ transplantation (20%), corticosteroid use (20%), or an underlying pulmonary disease (10%) are associated with a positive culture result, clinical judgment and better diagnostic tests are necessary. The management of invasive aspergillosis remains suboptimal: only 38% of patients are alive 3 months after diagnosis. Chronic necrotizing aspergillosis, aspergilloma, and allergic bronchopulmonary aspergillosis have variable management strategies and better short-term outcomes.

Central nervous system infections in the compromised host: a diagnostic approach

The diagnostic approach to the compromised host with CNS infection depends on an analysis of the patient's clinical manifestations of CNS disease, the acuteness or subacuteness of the clinical presentation, and an analysis of the type of immune defect compromising the patient's host defenses. Most patients with CNS infections may be grouped into those with meningeal signs, or those with mass lesions. Other common manifestations of CNS infection include encephalopathy, seizures, or a stroke-like presentation. Most pathogens have a predictable clinical presentation that differs from that of the normal host. CNS Aspergillus infections present either as mass lesions (e.g., brain abscess), or as cerebral infarcts, but rarely as meningitis. Cryptococcus neoformans, in contrast, usually presents as a meningitis but not as a cerebral mass lesion even when cryptococcal elements are present. Aspergillus and Cryptococcus CNS infections are manifestations of impaired host defenses, and rarely occur in immunocompetent hosts. In contrast, the clinical presentation of Nocardia infections in the CNS is the same in normal and compromised hosts, although more frequent in compromised hosts. The acuteness of the clinical presentation coupled with the CNS symptomatology further adds to limit differential diagnostic possibilities. Excluding stroke-like presentations, CNS mass lesions tend to present subacutely or chronically. Meningitis and encephalitis tend to present more acutely, which is of some assistance in limiting differential diagnostic possibilities. The analysis of the type of immune defect predicts the range of possible pathogens likely to be responsible for the patient's CNS signs and symptoms. Patients with diseases and disorders that decrease B-lymphocyte function are particularly susceptible to meningitis caused by encapsulated bacterial pathogens. The presentation of bacterial meningitis is essentially the same in normal and compromised hosts with impaired B-lymphocyte immunity. Compromised hosts with impaired T-lymphocyte or macrophage function are prone to develop CNS infections caused by intracellular pathogens. The most common intracellular pathogens are the fungi, particularly Aspergillus, other bacteria (e.g., Nocardia), viruses (i.e., HSV, JC, CMV, HHV-6), and parasites (e.g., T. gondii). The clinical syndromic approach is most accurate when combining the rapidity of clinical presentation and the expression of CNS infection with the defect in host defenses. The presence of extra-CNS sites of involvement also may be helpful in the diagnosis. A patient with impaired cellular immunity with mass lesions in the lungs and brain that have appeared subacutely or chronically should suggest Nocardia or Aspergillus rather than cryptococcosis or toxoplasmosis. Patients with T-lymphocyte defects presenting with meningitis generally have meningitis caused by Listeria or Cryptococcus rather than toxoplasmosis or CMV infection. The disorders that impair host defenses, and the therapeutic modalities used to treat these disorders, may have CNS manifestations that mimic infections of the CNS clinically. Clinicians must be ever vigilant to rule out the mimics of CNS infections caused by noninfectious etiologies. Although the syndromic approach is useful in limiting diagnostic possibilities, a specific diagnosis still is essential in compromised hosts in order to describe effective therapy. Bacterial meningitis, cryptococcal meningitis, and tuberculosis easily are diagnosed accurately from stain, culture, or serology of the CSF. In contrast, patients with CNS mass lesions usually require a tissue biopsy to arrive at a specific etiologic diagnosis. In a compromised host with impaired cellular immunity in which the differential diagnosis of a CNS mass lesion is between TB, lymphoma, and toxoplasmosis, a trial of empiric therapy is warranted. Antitoxoplasmosis therapy may be initiated empirically and usually results in clinical improvement after 2 to 3 weeks of therapy. The nonresponse to antitoxoplasmosis therapy in such a patient would warrant an empiric trial of antituberculous therapy. Lack of response to anti-Toxoplasma and antituberculous therapy should suggest a noninfectious etiology (e.g., CNS lymphoma). Fortunately, most infections in compromised hosts are similar in their clinical presentation to those in the normal host, particularly in the case of meningitis. The compromised host is different than the normal host in the distribution of pathogens, which is determined by the nature of the host defense defect. In compromised hosts, differential diagnostic possibilities are more extensive and the likelihood of noninfectious explanations for CNS symptomatology is greater. (ABSTRACT TRUNCATED)