Free-living, amphizoic and opportunistic amebas

Amebas belonging to the genera Naegleria, Acanthamoeba and Balamuthia are free-living, amphizoic and opportunistic protozoa that are ubiquitous in nature. These amebas are found in soil, water and air samples from all over the world. Human infection due to these amebas involving brain, skin, lung and eyes has increased significantly during the last 10 years. The epidemiology, immunology, protozoology, pathology, and clinical features of the infections produced by these protozoa differ strikingly. Infection by the pathogenic Naegleria fowleri is acquired by exposure to polluted water in ponds, swimming pools and man-made lakes. Raised temperatures during the hot summer months or warm water from power plants facilitate the growth of N. fowleri. N. fowleri is a thermophilic ameba that grows well in tropical and subtropical climates. The CNS infection, called Primary Amebic Meningoencephalitis (PAM), produced by N. fowleri is characterized by an acute fulminant meningoencephalitis leading to death 3-7 days after exposure. Victims are healthy, young individuals with a history of recent water-related sport activities. The portal of entry is the olfactory neuroepithelium. The pathologic changes are an acute hemorrhagic necrotizing meningoencephalitis with modest purulent exudate, mainly at the base of the brain, brain-stem and cerebellum. Trophozoites can be seen within the CNS lesions located mainly around blood vessels. Thus far 179 cases have been reported; 81 in the USA alone. Balamuthia mandrillaris and several species of Acanthamoeba are pathogenic "opportunistic" free-living amebas which cause Granulomatous Amebic Encephalitis (GAE) in humans and animals. GAE is an infection, usually seen in debilitated, malnourished individuals, in patients undergoing immunosuppressive therapy for organ transplants and in Acquired Immunodeficiency Syndrome (AIDS). The granulomatous component is negligible, particularly in immunocompromised individuals. Pathologically these amebas produce a patchy, chronic or subacute granulomatous encephalitis with the presence of trophozoites and cysts. The portal of entry is probably through the respiratory tract or an ulceration of the skin reaching the CNS by hematogenous spread. As of October 1, 1996, 166 cases (103 due to Acanthamoeba and 63 due to Balamuthia) of GAE have been reported from around the world. Of these 103 cases due to Acanthamoeba (72 have been reported in the USA alone, > 50 in AIDS). It is well known that several species of Acanthamoeba can also produce, chronic sight threatening ulceration of the cornea called Acanthamoeba keratitis (AK), mostly in contact lens wearers or in individuals with minor corneal abrasions. Hundreds of cases of AK have been documented world wide.

Al Eskan disease: Persian Gulf syndrome

This article examines the potential relationship between Al Eskan disease and the Persian Gulf syndrome. Al Eskan disease, reported in Military Medicine in 1992, is a novel and previously unreported condition triggered by the exceptionally fine sand dust of the Central and Eastern Saudi Arabian peninsula. We repeat our study of the pathogenesis of Al Eskan disease to include the ultrastructural and microanalytical study of the sand, aerobiological studies of the Kingdom of Saudi Arabia, and the etiology, symptoms, and prevalence of the disease. We conclude that immunodepression resulting from the continued presence of sand particles less than 1 micron in diameter in the lungs and bodies of Persian Gulf veterans explains not only the symptoms of the hyperegic lung condition of phase I and the symptoms of phase II of Al Eskan disease, but also provides an important clue to a common factor in most cases of Persian Gulf illnesses. We include a discussion of most of the commonly suspected agents in the Persian Gulf syndrome. In this case, we conclude that each of these factors, such as oil well fires, old-world diseases, or depleted uranium, are probably adjuvant or contributing causes. The only common exposure that would lead to recognition of the Persian Gulf syndrome as a single medical condition, rather than a catch-all phrase for unrelated conditions, appears to be exposure to the ubiquitous, fine sand of the area, and a resulting immunosuppression that is aggravated by opportunistic infections and other nonmicrobial ailments.

Flavobacterium indologenes keratitis

Flavobacterium indologenes has recently been implicated in nosocomial or opportunistic infection. It has been isolated from lids, conjunctiva, and lacrimal system, and is resistant to most antibiotics. No previous cases of F. indologenes corneal ulcer have been reported in the literature. The natural habitat of Flavobacteria is soil, water, plants, and foodstuffs. In the hospital environment, these bacteria exist in water systems and on wet surfaces. They are not part of the normal ocular flora.

Risk assessment of opportunistic bacterial pathogens in drinking water

This study was undertaken to examine quantitatively the risks to human health posed by heterotrophic plate count (HPC) bacteria found naturally in ambient and potable waters. There is no clear-cut evidence that the HPC bacteria as a whole pose a public health risk. Only certain members are opportunistic pathogens. Using the four-tiered approach for risk assessment from the National Academy of Sciences, hazard identification, dose-response modeling, and exposure through ingestion of drinking water were evaluated to develop a risk characterization, which estimates the probability of infection for individuals consuming various levels of specific HPC bacteria. HPC bacteria in drinking water often include isolates from the following genera: Pseudomonas, Acinetobacter, Moraxella, Aeromonas, and Xanthomonas. Other bacteria that are commonly found are Legionella and Mycobacterium. All these genera contain species that are opportunistic pathogens which may cause serious diseases. For example, the three nonfermentative gram-negative rods most frequently isolated in the clinical laboratory are (1) Pseudomonas aeruginosa, (2) Acinetobacter, and (3) Xanthomonas maltophilia. P. aeruginosa is a major cause of hospital-acquired infections with a high mortality rate. Aeromonas is sometimes associated with wound infections and suspected to be a causative agent of diarrhea. Legionella pneumophila causes 4%-20% of cases of community-acquired pneumonia and has been ranked as the second or third most frequent cause of pneumonia requiring hospitalization. The number of cases of pulmonary disease associated with Mycobacterium avian is rapidly increasing and is approaching the incidence of M. tuberculosis in some areas. Moraxella can cause infections of the eye and upper respiratory tract. The oral infectious doses are as follows in animal and human test subjects: P. aeruginosa, 10(8)-10(9); A, hydrophila, > 10(10); M. avium, 10(4)-10(7); and X. maltophilia, 10(6)-10(9). The infectious dose for an opportunistic pathogen is lower for immunocompromised subjects or those on antibiotic treatment. These bacteria have been found in drinking water at the following frequencies: P. aeruginosa, < 1%-24%; Acinetobacter, 5%-38%; X. maltophilia, < 1%-2%; Aeromonas, 1%-27%; Moraxella, 10%-80%; M. avium, < 1%-50%; and L. pneumophila, 3%-33%. These data suggest that drinking water could be a source of infection for some of these bacteria. The risk characterization showed that risks of infection from oral ingestion ranged from a low of 7.3 x 10(-9) (7.3/billion) for low exposures to Aeromonas to higher risks predicted at high levels of exposure to Pseudomonas of 9 x 10(-2) (98/100). This higher risk was only predicted for individuals on antibiotics. Overall, the evidence suggests that specific members of HPC bacteria found in drinking water may be causative agents of both hospital- and community-acquired infections. However, the case numbers may be very low and the risks represent levels generally less than 1/10,000 for a single exposure to the bacterial agent. Future research needs include (1) determining the seasonal concentrations of these bacteria in drinking water, (2) conducting adequate dose-response studies in animal subjects or human volunteers, (3) determining the health risks for an individual with multiple exposures to the opportunistic pathogens, and (4) evaluating the increase in host susceptibility conferred by antibiotic use or immunosuppression.

Fungal infections

Fungal infections have increased in frequency in the last decades because of the growing number of immunocompromised patients who survive longer periods of time than in the past, the widespread use of immunosuppressive drugs, a large aging population with increased numbers of malignancies, and the spread of AIDS. Although fungi are present everywhere, some mycoses predominate in the tropics, not only in view of warm temperature and humid climate, which favor their growth, but also because of inadequate hygienic and working conditions brought about by poverty. Mycotic diseases in the brain are usually secondary to infections elsewhere in the body, usually the lungs, less often from other extracranial sites, and in the vast majority of the cases spread via blood circulation. Only occasionally they result from direct extensions from infections of the sinuses or bone, and less frequently from prosthetic heart valves. Candida may be endogenous in origin, inhabiting the digestive tract. Most fungi cause basal meningitis or intraparenchymal abscesses. Direct extension from the cribriform plate cause necro-hemorrhagic lesions in the base of the frontal lobe. Although fungi are common in our environment, few are pathogenic. In this paper mycotic infections are divided into opportunistic and pathogenic; although most of the latter have also been described in immunosuppressed patients, some of those caused by opportunistic organisms, have also occurred in the absence of predisposing factors.

[Early postoperative infections after liver transplantation--pathogen spectrum and risk factors]

Infections occurring during the early postoperative phase after liver transplantation result in a significant rise in morbidity and mortality. The records of 279 orthoptic transplantations performed in 248 patients were analyzed retrospectively. 55.6% of all patients suffered from one or more episodes of bacterial and/or fungal infection during their postoperative hospitalisation. The median onset of bacterial/fungal infection was on day 7 after transplantation. Enterococci (42 episodes), Pseudomonas aeruginosa (38 episodes), staphylococci (37 episodes), Escherichia coli (17 episodes) and Candida albicans (11 episodes) were the most frequently detected organisms. 74 (29.8%) patients developed viral infections. 20 patients (8.1%) showed infection with cytomegalovirus (CMV), 32 patients (12.9%) with herpes simplex virus (HSV) and 6 patients (2.4%) with varicella zoster virus (VZV). 14 patients (5.6%) developed infection with both CMV and VZV. Triple infection with CMV, HSV and VZV occurred in one patient. Statistical analysis of potential risk factors showed a significant influence of blood volume replacement (p < 0.001) and occurrence of at least one rejection period (p < 0.02) for major bacterial/fungal infection and immunosuppression (p < 0.001), cold ischemic time (p < 0.04), occurrence of at least one rejection period (p < 0.005) and blood volume replacement (p < 0.04) for viral infection.

Chronic viral hepatitis enhances the risk of infection but not acute rejection in renal transplant recipients

To assess the impact of chronic viral hepatitis on host immune response, we analyzed the incidence of acute rejection and the frequency of infections in 86 patients infected with hepatitis B and C viruses and had developed clinical evidence of chronic liver disease and 1283 control patients who were transplanted at our center during the same period, but had no evidence of chronic viral hepatitis. To compare the mean number of rejections and the mean number of infections between the two groups, we used multivariate linear regression analysis, which allowed us to adjust simultaneously for the effects of 10 other risk variables with potential impact on graft rejection and posttransplant infection. During a mean follow up of 5.3+/-5.2 years, 62% of hepatitis patients and 54% of control patients had experienced an acute rejection (P=NS). The mean rejections/patient in the hepatitis group was 1.3+/-0.14 versus 1.03+/-0.03 in control (P=NS). In the linear regression analysis, the number of acute rejections in the hepatitis group was 0.16 higher than in control (P=NS). With reference to infection, 84% of hepatitis patients experienced an infectious complication in the posttransplant period, compared with 75% in the control (P=0.05). The mean number of infections/patient was 5.7+/-0.73 in the hepatitis group compared with 3.9+/-0.14 in the control group (P=0.002). The linear regression model had shown that the hepatitis group had a relative increase of 1.18 infections/pt, compared with control. Of the different sites of infection, the hepatitis group had a significant increase in bloodstream (0.48+/-0.08 vs. 0.25+/-0.02) P=0.003; pulmonary (0.60+/-0.09 vs. 0.38+/-0.03) P=0.03; and CNS infections (0.08+/-0.03 vs. 0.02+/-0.004) P=0.05 compared with control. Among the different microorganisms causing infection, the hepatitis patients had a significant increase in gram negative bacterial infections compared with the control group (74% vs. 61%) P=0.04. Our data suggest that chronic viral hepatitis is associated with a significant increase in overall infections, and that of potentially fatal infections involving CNS, lungs and bloodstream. Since there is no significant increase in the rate of graft rejection, one could consider a cautious reduction in the doses of maintenance immunosuppressive agents in renal transplant patients with chronic viral hepatitis. The reduced immunosuppression may in turn lower the death rate from sepsis and progressive hepatic failure.

Veillonella parvula bacteremia without an underlying source

Veillonella parvula is an anaerobic gram-negative coccus that is part of the normal human flora. It has rarely been identified as a pathogen in humans, and the most frequently reported infection caused by V. parvula is osteomyelitis. We report a case of bacteremia unrelated to a central venous catheter and without an underlying source of infection.

Case of bacterial endophthalmitis caused by an Agrobacterium radiobacter-like organism

A case of postsurgical endophthalmitis caused by Agrobacterium radiobacter in a 70-year-old male is reported. A. radiobacter organisms are normally environmental bacteria but may occasionally be opportunistic pathogens. Infection in this case occurred after the patient was discharged following routine cataract surgery. The infection cleared after empiric therapy intraocular administration of vancomycin and gentamicin.

Penicillium brevicompactum as the cause of a necrotic lung ball in an allogeneic bone marrow transplant recipient

The non-Candida, non-Aspergillus fungal infections are being reported with increasing frequency in BMT patients. One of these agents is Penicillium which has rarely been implicated as a pathogen in these patients. Only a few cases of isolated fungemias have been reported to date. We present the first documented case of invasive lung infection due to Penicillium brevicompactum in an allogeneic BMT recipient. As this case shows, the diagnosis of non-Candida, non-Aspergillus fungal infections may be incorrect if only histologic findings are available, mainly because misdiagnosis with other more common fungus can occur. A positive culture is required in order to make an accurate diagnosis.

[Empirical antimicrobial therapy in neutropenic patients]

Infectious complications emerge in more than 80% of neutropenic patients after intensive antineoplastic therapy. Empirical antimicrobial intervention is mandatory, and initial administration of an antipseudomonal betalactam in combination with an aminoglycoside represents the most widely applied standard regimen. At least in patients with short-term neutropenia, also an initial betalactam monotherapy is accepted. Symptoms of skin or venous-catheter-related infection should prompt the addition of a glycopeptide, whereas in case of lung infiltrates, amphotericin B should be administered at least after 96 h. of nonresponse to the antibiotic first-line therapy. In nonresponders with persisting fever of unknown origin, carbapenems or fluoroquinolones in combination with a glycopeptide might be considered for second-line treatment. The supplementation of a recombinant hematopoietic growth factor [G-CSF or GM-CSF] shows no significant benefit and should be restricted to controlled clinical studies. In case of good clinical response, the established antimicrobial treatment regimen should be continued for at least seven days in persistently neutropenic patients.

Epidemiology of nosocomial fungal infections

This paper briefly reviews the current knowledge of the epidemiology and modes of transmission of nosocomial fungal infections and some of the therapeutic options for treating these diseases. In the mid-1980s, many institutions reported that fungi were common pathogens in nosocomial infections. Most, if not all, hospitals care for patients at risk for nosocomial fungal infections. The proportion in all nosocomial infections reportedly caused by Candida spp. increased from 2% in 1980 to 5% in 1986 to 1989. Numerous studies have identified common risk factors for acquiring these infections, most of which are very common among hospitalized patients; some factors act primarily by inducing immunosuppression (e.g., corticosteroids, chemotherapy, malnutrition, malignancy, and neutropenia), while others primarily provide a route of infection (e.g., extensive burns, indwelling catheter), and some act in combination. Non-albicans Candida spp., including fluconazole-resistant C. krusei and Torulopsis (C.) glabrata, have become more common pathogens. Newer molecular typing techniques can assist in the determination of a common source of infection caused by several fungal pathogens. Continued epidemiologic and laboratory research is needed to better characterize these pathogens and allow for improved diagnostic and therapeutic strategies.

Severe anal condylomata acuminata following high-dose chemotherapy and autologous hematopoietic stem cell transplantation: a case report

We report the case of a 37 years old male patient who developed severe anal condylomata acuminata after high-dose chemotherapy and autologous hematopoietic stem cell transplantation for follicular non-Hodgkin's lymphoma. Anal warts were particularly disabling, refractory to the treatment and finally imposed diversion colostomy. The role of cellular immunodeficiency observed after high-dose chemotherapy and autologous hematopoietic stem cell transplantation as etiology of anal condylomata is discussed.

Plasmodium vivax malaria after autologous bone marrow transplantation: an unusual complication

We report the case of unusually early infection by Plasmodium vivax after autologous bone marrow transplantation in a 20-year-old female from Bangladesh affected by acute myelogenous leukemia in first complete remission (CR) who underwent autologous bone marrow transplantation in our center. During the aplastic phase she became febrile; broad spectrum antibiotics and antifungal therapy were without effect. Blood smears were examined and Plasmodium vivax was detected despite a very low number of red cells infected. Cloroquine therapy for 3 days was given followed by primaquine for 2 weeks in order to avoid possible cloroquine resistance. Fever disappeared within 48 h from initial treatment and the patient was discharged having completely recovered at day +30. Primary malaria infection in non-endemic areas is a very rare event. In this particular case, after excluding primary infection or blood transfusion-mediated infection, malaria was attributed to a recrudescence of a primary unidentified infection.

Tuberculosis in bone marrow transplant recipients: report of two cases and review of the literature

Over a 6 year period we have seen two cases of tuberculosis among 118 allogeneic and 237 autologous bone marrow (BMT) or peripheral blood transplants. Both patients had received an HLA-identical related allogeneic BMT. The first case suffered from extensive chronic graft-versus-host disease (GVHD) and developed pulmonary tuberculosis 19 months after BMT. An open-lung biopsy was required to establish the diagnosis, and response to antituberculosis agents was complete, with no relapse at 49 months post-BMT. The second patient received a CD4+ T lymphocyte-depleted BMT, was receiving steroids for acute GVHD and developed rapid-onset meningeal tuberculosis on day +107 post-BMT. Despite initial severe neurologic deterioration, response to antituberculosis agents was good, and she remains alive and well 11 months from BMT. Review of the scant literature on this topic reveals that this is a relatively rare infection in BMT recipients despite their often severely immunosuppressed condition, occurring mainly in recipients of T cell-depleted allogeneic grafts or those who develop GVHD.

Intestinal water and electrolyte absorption and secretion

Diarrhea is a frequent complication of small bowel transplantation in patients and experimental models. Although there are many potential causes, the underlying basis for most are not fully understood. Improved therapeutic approaches will come about through better understanding of mechanisms of bowel adaptation and regulation.

Phaeohyphomycosis caused by Exophiala dermatitidis following intra-articular steroid injection

A patient with long-standing rheumatoid arthritis presented with a painful pigmented chronic nodule on the dorsum of the right hand, at the site of intra-articular steroid injections undertaken 5 years previously. Histology showed pigmented fungal elements consistent with phaeohyphomycosis. Cultures yielded black yeast-like colonies, identified as Exophiala dermatitidis and sensitive to itraconazole and amphotericin. A 1-month course of itraconazole resulted in marked clinical improvement but surgical excision and skin grafting were required for complete resolution. Phaeohyphomycosis has been related to inoculation injury but association with intra-articular steroid injection appears hitherto to be unreported.

[Bacteremia caused by Alcaligenes (Achromobacter) xylosoxidans. Description of 3 cases and review of the literature]

BACKGROUND

Alcaligenes (Achromobacter) xylosoxidans occasionally cause infections, mainly in immunocompromised hosts.

METHODS

Three cases of bacteremia due to A. xylosoxidans observed at the Fundación Jiménez Díaz between 1985-1994 were described. Moreover, 38 single cases of bacteremia due to A. xylosoxidans and 21 episodes associated with outbreak were reviewed by using computerized bibliography data base MEDLINE (1970-december 1994).

RESULTS

From 41 patients with bacteremia (including our 3 cases) reviewed, 27 were immunosuppressed hosts (twenty had neoplasia disease). The most common clinical presentation was primary bacteremia (11 cases, 27%) and pneumonia (10, 24%), followed by catheter-associated bacteremia (8, 20%), meningitis (4), bacteremia from abdominal cavity (4), endocarditis (3) and pyelonephritis (1). The mortality rate was higher (39%), specially in patients whom were a intensive care unit acquisition (87%), and illness with endocarditis (100%). No patient with catheter-related bacteremia died. All of 21 outbreak episodes of bacteremia had a autolimited form and low mortality (4.8%).

CONCLUSION

A. xylosoxidans is a microorganism with demonstrated capacity of cause bacteremia, mainly in immunocompromised hosts, with high mortality rates. Sometimes, it causes outbreaks of bacteremia with low mortality.

Photoaccentuated erythroderma associated with CD4+ T lymphocytopenia: successful treatment with 5-methoxypsoralen and UVA, interferon alfa-2b, and extracorporeal photopheresis

We describe a 53-year-old HIV-negative white man who had chronic CD4+ T lymphocytopenia and photoaccentuated erythroderma with lymphoma-like histologic changes. The erythroderma completely responded to 5-methoxypsoralen and UVA (PUVA), interferon alfa-2b, and extracorporeal photopheresis. During therapy opportunistic skin infections, including tinea corporis, warts, and disseminated molluscum contagiosum, developed. Although the patient met the current definition of idiopathic CD4+ T lymphocytopenia (ICTL), we cannot rule out the possibility that this peripheral CD4+ T lymphocytopenia resulted from sequestration of CD4+ T lymphocytes in erythrodermic skin.