Vermamoeba vermiformis as etiological agent of a painful ulcer close to the eye.

In the present article, we report on the identification of Vermamoeba (Hartmannella) vermiformis as the etiological agent of a tissue infection close to the eye of a female patient. Laboratory examination revealed no involvement of any pathogenic bacteria or fungi in the tissue infection. V. vermiformis was identified by cultivation and morphology of trophozoites and cysts as well as phylogenetic analysis of nuclear 18S rDNA. The lesion improved in the course of 4 weeks by application of zinc paste.

Cytopathogenicity of acanthamoeba, vahlkampfia and hartmannella: quantative & qualitative in vitro studies on keratocytes.

OBJECTIVES: To compare the cytopathogenicity of Vahlkampfia and Hartmannella clinical isolates with a type culture of Acanthamoeba castellanii. METHODS: The cytopathic effect produced during 24 h co-incubation with cultured keratocytes was assessed at set time intervals. Formal quantative studies involved image analysis of the area of cells remaining after 6 h. The mechanism of cytopathogenicity was elucidated using time-lapse video, light and scanning electron microscopy. The ability to produce cell damage in the absence of physical contact was studied using the transwell apparatus. The role of apotosis was also investigated. RESULTS: All three isolates produced near destruction of the keratocyte monolayer within 24 h, although initial cell destruction was more rapid with Acanthamoeba. For all three genera, the mechanism of cell damage involved physical attack and trogocytosis: cytopathic products were also implicated as cell damage was produced in the absence of physical contact, but apoptosis was not demonstrated. CONCLUSIONS: While the results do not prove that Vahlkampfia and Hartmannella are pathogens, they provide important evidence supporting the thesis that they cause keratitis by demonstrating that their ability to produce a cytopathic effect on keratocytes in vitro is similar in magnitude and mechanism to that of the known pathogen Acanthamoeba castellanii. The mechanisms by which small free-living amoebae produce cell damage is poorly understood. The ability of genera of amoebae other than Acanthamoeba to produce corneal infection remains controversial. In this study, the cytopathogenicity of Vahlkampfia and Hartmannella isolated from a case human keratitis are compared both quantitatively and qualitatively with that to the known pathogen Acanthamoeba castellanii. The results suggest that representatives of each of the 3 genera produce a similar degree of cytopathic effect on keratocytes after 24h of co-incubation and that a combination of physical and chemical factors are responsible.

Coinoculation with Hartmannella vermiformis enhances replicative Legionella pneumophila lung infection in a murine model of Legionnaires' disease.

The effect of inhaled amoebae on the pathogenesis of Legionnaires' disease was investigated in vivo. A/J mice, which are susceptible to replicative Legionella pneumophila infections, were inoculated intratracheally with L. pneumophila (10(6) bacteria per mouse) or were coinoculated with L. pneumophila (10(6) bacteria per mouse) and Hartmannella vermiformis (10(6) amoebae per mouse). The effect of coinoculation with H. vermiformis on bacterial clearance, histopathology, cellular recruitment into the lung, and intrapulmonary levels of cytokines including gamma interferon and tumor necrosis factor alpha was subsequently assessed. Coinoculation with H. vermiformis significantly enhanced intrapulmonary growth of L. pneumophila in A/J mice. Histopathologic and flow cytometric analysis of lung tissue demonstrated that while A/J mice inoculated with L. pneumophila alone develop multifocal pneumonitis which resolves with minimal mortality, mice coinoculated with H. vermiformis develop diffuse pneumonitis which is associated with diminished intrapulmonary recruitment of lymphocytes and mononuclear phagocytic cells and significant mortality. Furthermore, coinoculation of mice with H. vermiformis resulted in a fourfold enhancement in intrapulmonary levels of gamma interferon and tumor necrosis factor alpha compared with mice infected with L. pneumophila alone. The effect of H. vermiformis on intrapulmonary growth of L. pneumophila in a resistant host (i.e., BALB/c mice) was subsequently evaluated. While BALB/c mice do not develop replicative L. pneumophila infections following inoculation with L. pneumophila alone, there was an eightfold increase in intrapulmonary L. pneumophila in BALB/c mice coinoculated with H. vermiformis. These studies, demonstrating that intrapulmonary amoebae potentiate replicative L. pneumophila lung infection in both a susceptible and a resistant host, have significant implications with regard to the potential role of protozoa in the pathogenesis of pulmonary diseases due to inhaled pathogens and in the design of strategies to prevent and/or control legionellosis.

Acanthamoeba, an opportunistic microorganism: a review.

Granulomatous amebic encephalitis due to Acanthamoeba spp. usually occurs in chronically ill and debilitated individuals. Some of these patients may have received immunosuppressive therapy. Another infection due to Acanthamoeba spp. has been corneal ulcerations which usually occur after minimal trauma to the corneal epithelium (1). In contrast, primary amebic meningoencephalitis due to Naegleria fowleri usually occurs in healthy, young individuals with a history of swimming in heated swimming pools, in manmade lakes or with recent contact with contaminated water and practising water-related sports. Subclinical infections due to free-living amebas are probably common in healthy individuals with the protozoa living as "normal flora" in the nose and throat. It is possible that in humans, antibodies and cell-mediated immunity protect the host in such ordinary circumstances against invasive infection. In debilitated and chronically ill individuals, depressed cellmediated immunity may allow these protozoa to proliferate, allowing a fulminant "opportunistic" infection to develop. In the case of acanthamoebic keratitis, it is important to keep in mind that the temperature and moist environment of the eye serve as a good medium for the growth and proliferation of the amebas and is not necessarily associated with immunosuppression but rather with trauma. This review confirms that opportunistic free-living amebic infections occur with increased frequency in patients treated with steroids, radiotherapy, chemotherapeutic drugs or with broad-spectrum antibiotics and suggest that the mechanism of such infection may be depressed cell-mediated immunity or some other alteration of the immune system, like acquired immunodeficiency syndrome (AIDS).

Primary amoebic meningoencephalitis.

As a serendipitous by-product of polio virus research, a highly fatal amoebic meningoencephalitis was recognized in animals. The causative microorganisms, contaminants of the viral cultures, were identified as small soil amoebae. These organisms, previously considered non-pathogenic, are prevalent throughout the world. Based on animal studies, the original investigators suggested the possibility of a similar disease in humans. Seven years later, human cases of amoebic meningoencephalitis were reported from widely separated areas of the world. Since 1965, a total of 79 cases have been reported. The literature of primary amoebic meningoencephalitis is presented. The history of the discovery and elucidation of this disease is reviewed. The 79 cases reported in the world literature are divided into two groups, those diagnosed retrospectively after reviewing previous deaths from meningoencephalitis, and those diagnosed at the time of the illness. The classification, morphology, pathogenicity, virulence and distribution of pathogenic soil amoebae are reviewed. The presenting clinical findings, diagnostic procedures, pathology, and management of this recently recognized, highly fatal, human disease is presented along with a report of a new case. Otolaryngologists should become familiar with this serious disorder with a transnasal portal of entry.