545 research outputs found
Simulation Approach for Timing Analysis of Genetic Logic Circuits
Constructing
genetic logic circuits is an application of synthetic
biology in which parts of the DNA of a living cell are engineered
to perform a dedicated Boolean function triggered by an appropriate
concentration of certain proteins or by different genetic components.
These logic circuits work in a manner similar to electronic logic
circuits, but they are much more stochastic and hence much harder
to characterize. In this article, we introduce an approach to analyze
the threshold value and timing of genetic logic circuits. We show
how this approach can be used to analyze the timing behavior of single
and cascaded genetic logic circuits. We further analyze the timing
sensitivity of circuits by varying the degradation rates and concentrations.
Our approach can be used not only to characterize the timing behavior
but also to analyze the timing constraints of cascaded genetic logic
circuits, a capability that we believe will be important for design
automation in synthetic biology
Disseminated Microsporidiosis Due to Encephalitozoon hellem: Pulmonary Colonization, Microhematuria, and Mild Conjunctivitis in a Patient with AIDS
Four genera of microsporidia have been associated with disease in humans, which predominantly affects immunocompromised persons. Systemic infection with a newly characterized microsporidian species, Encephalitozoon hellem, was recently reported in a patient with AIDS. This article describes a second patient with AIDS and disseminated E. hellem infection. In this case the parasite was detected in sputum, urine, and conjunctival swab specimens. Apart from recurrent mild conjunctivitis and asymptomatic microhematuria, the patient had no findings or symptoms that could be related to this parasite. Specifically, no microsporidian-associated pulmonary pathology was documented. Detection of E. hellem in the patient's sputum may have epidemiological implications in that this finding suggests transmission of microsporidia by the aerosol route. Because the patient died of unrelated complications, it remains unknown whether he was an asymptomatic carrier of microsporidia or whether microhematuria heralded early microsporidian disease, with the onset of cellular damage in the urinary trac
Disseminated Microsporidiosis in an Immunosuppressed Patient
We report a case of disseminated microsporidiosis in a patient with multiple myeloma who had received an allogeneic stem cell transplant requiring substantial immunosuppression. The causative organism was identified as Tubulinosema acridophagus, confirming this genus of microsporidia as a novel human pathogen
Status of the effectiveness of contact lens disinfectants in Malaysia against keratitis-causing pathogens
The aim of this study was (i) to assess the antimicrobial effects of contact lens disinfecting solutions marketed
in Malaysia against common bacterial eye pathogens and as well as eye parasite, Acanthamoeba castellanii,
and (ii) to determine whether targeting cyst wall would improve the efficacy of contact lens disinfectants. Using
ISO 14729 Stand-Alone Test for disinfecting solutions, bactericidal and amoebicidal assays of six different
contact lens solutions including Oxysept®, AO SEPT PLUS, OPTI-FREE® pure moist®, Renu® fresh™,FreshKon® CLEAR and COMPLETE RevitaLens™ were performed using Manufacturers Minimum recommended disinfection time (MRDT). The efficacy of contact lens solutions was determined against keratitis-
causing microbes, namely: Pseudomonas aeruginosa, Methicillin-resistant Staphylococcus aureus, Streptococcus
pyogenes, Streptococcus pneumoniae, and Acanthamoeba castellanii. In addition, using chlorhexidine
as an antiamoebic compound and cellulase enzyme to disrupt cyst wall structure, we determined whether combination of both agents can enhance efficacy of marketed contact lens disinfectants against A. castellanii trophozoites and cysts, in vitro. The results revealed that all contact lens disinfectants tested showed potent bactericidal effects exhibiting 100% kill against all bacterial species tested. In contrast, none of the contact lens disinfectants had potent effects against Acanthamoeba cysts viability. When tested against trophozoites, two disinfectants, Oxysept Multipurpose and AO-sept Multipurpose showed partial amoebicidal effects. Using chlorhexidine as an antiamoebic compound and cellulase enzyme to disrupt cyst wall structure, the findings revealed that combination of both agents in contact lens disinfectants abolished viability of A. castellanii cysts and trophozoites. Given the inefficacy of contact lens disinfectants tested in this study, these findings present a significant concern to public health. These findings revealed that targeting cyst wall by using cyst wall degrading molecules in contact lens disinfecting solutions will enhance their efficacy against this devastating eye infection
Primary Amebic Meningoencephalitis Caused by Naegleria fowleri, Karachi, Pakistan
We report 13 cases of Naegleria fowleri primary amebic meningoencephalitis in persons in Karachi, Pakistan, who had no history of aquatic activities. Infection likely occurred through ablution with tap water. An increase in primary amebic meningoencephalitis cases may be attributed to rising temperatures, reduced levels of chlorine in potable water, or deteriorating water distribution systems
Prevalence of intestinal microsporidiosis in Human Immunodeficiency Virus-infected patients with diarrhea in major United States cities
To determine the prevalence of intestinal microsporidiosis in HIV-infected patients, we performed a prospective study of HIV-infected patients with diarrheal illnesses in three US hospitals and examined an observational database of HIV-infected patients in 10 US cities. Among 737 specimens from the three hospitals, results were positive for 11 (prevalence 1.5%); seven (64%) acquired HIV through male-to-male sexual contact, two (18%) through male-to-male sexual contact and injection drug use, and one (9%) through heterosexual contact; one (9%) had an undetermined mode of transmission. Median CD4 count within six months of diagnosis of microsporidiosis was 33 cells/µL (range 3 to 319 cells/µL). For the national observational database (n = 24,098), the overall prevalence of microsporidiosis was 0.16%. Prevalence of microsporidiosis among HIV-infected patients with diarrheal disease is low, and microsporidiosis is most often diagnosed in patients with very low CD4+ cell counts. Testing for microsporidia appears to be indicated, especially for patients with very low CD4+ cell counts.Para determinar a prevalência de microsporidiose intestinal em pacientes infectados pelo HIV foi realizado um estudo prospectivo em três hospitais dos Estados Unidos da América do Norte (EUA) e analizada uma base de dados nacional composta de dados coletados de pacientes infectados pelo HIV em 10 cidades dos EUA. De um total de 737 amostras de fezes de pacientes infectados pelo HIV que apresentavam diarréia, amostras de 11 pacientes (prevalência de 1,5%) foram positivas para microsporídios. Todos os positivos eram do sexo masculino e, entre eles, sete (64%) pacientes adquiriram a infecção pelo HIV através de relação homossexual, dois (18%) através de relação sexual e drogas injetáveis e um (9%) através de contato heterosexual, enquanto que em um paciente o modo de transmissão do HIV não foi determinado. A contagem média de linfócitos CD4 realizada até seis meses do diagnóstico de microsporidiose foi de 33 células/microlitro (3 a 319 células/microlitro). A análise da base de dados nacional (n = 24.098) mostrou uma prevalência de microsporidiose de 0,16%. A prevalência de microsporidiose em pacientes HIV-positivos com diarréia é baixa. Entretando, como a microsporidiose é mais frequentemente diagnosticada em pacientes com contagens de CD4 muito baixas, a indicação de pesquisa de microsporídios é justificada, especialmente para estes pacientes
National Outbreak of Acanthamoeba Keratitis Associated with Use of a Contact Lens Solution, United States
Premarket standardized testing for Acanthamoeba spp. is warranted
Fatal Naegleria fowleri Meningoencephalitis, Italy
We report the first case of primary amebic meningoencephalitis in Italy, in a 9-year-old boy. Clinical course was fulminant, and diagnosis was made by identifying amebas in stained brain sections and by indirect immunofluorescence analysis. Naegleria fowleri was characterized as genotype I on the basis of polymerase chain reaction test results
Successful Treatment of Disseminated Acanthamoeba sp. Infection with Miltefosine
We report on an HIV-negative but immunocompromised patient with disseminated acanthamoebiasis, granulomatous amoebic encephalitis, and underlying miliary tuberculosis and tuberculous meningitis. The patient responded favorably to treatment with miltefosine, an alkylphosphocholine. The patient remained well with no signs of infection 2 years after treatment cessation
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