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Biomedical subjects

Daniel Vargas

Publications and source records attributed to Daniel Vargas.

11 recordsLinked to original sources
PubMed2005

The epidemiology of intestinal microsporidiosis in patients with HIV/AIDS in Lima, Peru.

We studied microsporidiosis in human immunodeficiency virus-positive patients in 2 Lima hospitals. Of 2652 patients, 66% were male, 6% received antiretroviral therapy (ART), and the median CD4 lymphocyte count was 131 cells/microL. Sixty-seven patients (3%) had microsporidiosis; stool specimens from 56 were identified as having Enterocytozoon bieneusi of 10 different genotypes. The 2 most common genotypes, Peru-1 and Peru-2, were not associated with significant increases in chronic diarrhea; other genotypes were associated with a 4-fold increased risk. Risk factors for E. bieneusi infection segregated by genotype: contact with duck or chicken droppings and lack of running water, flush toilet, or garbage collection with genotype Peru-1 and watermelon consumption with other genotypes. Shortened survival was associated with low CD4 lymphocyte count (P<.0001), no ART (P<.0001), and cryptosporidiosis (P=.004) but not with microsporidiosis (P=.48). Our data suggest the possibility of zoonotic E. bieneusi transmission and an association with poor sanitary conditions.

AIDS-Related Opportunistic Infections↗
PubMed2005

Musculoskeletal infection imaging: past, present, and future.

Imaging plays a key role in the evaluation of patients with known or suspected musculoskeletal infection. Although conventional radiograph still remains as the initial imaging approach, it has low sensitivity and specificity in the setting of acute infection. Magnetic resonance is highly sensitive for the detection of acute osteomyelitis and septic arthritis. Computed tomography is usually reserved for guided interventional procedures (eg, aspiration or drainage) and for evaluation of sinus tracts in chronic infections. Ultrasound is useful for fluid detection in joints and soft tissues but limited in bone assessment. Nuclear medicine, with the different radiotracers currently available, is highly sensitive for the diagnosis of acute osteomyelitis. Newer radiotracers are being developed that promise high sensitivity and specificity for the detection of these pathologies.

Journal Article↗
PubMed2005

Neuroimaging in drug and substance abuse part II: opioids and solvents.

The central nervous system is one of the primary targets for the detrimental effects of drugs of abuse. Diagnostic imaging, especially MRI, plays an important role in the detection of complications associated with drug abuse. We present the imaging findings associated with the abuse of opioids and other morphine derivatives, as well, as solvents. Of the morphine derivatives, heroin is the most commonly abused. Several CNS pathologic effects have been described in association with its abuse. These include neurovascular complications such as microvascular ischemic changes or ischemic stroke. A rare form of leukoencephalopathy has been described in those abusers who inhale heroin vapors. Other neurologic complications include atrophy and various infectious processes. Solvent inhalation is a common practice among adolescents and young adults secondary to its ease of access and low cost. The most important component of industrial solvents is toluene. Complications of toluene abuse may be either acute, showing no neuroradiological changes, or chronic, characterized by cerebral and cerebellar demyelination as well as atrophy.

Administration, Inhalation↗
PubMed2005

Neuroimaging in drug and substance abuse part I: cocaine, cannabis, and ecstasy.

Multiple neurological complications of cocaine abuse have been described including both ischemic and hemorrhagic cerebrovascular events, atrophy in the case of chronic abuse, and an increase in incidence of congenital malformations in the setting of maternal use. The abuse of cannabis may cause a number of neurovascular changes that, in turn, may result in ischemic events, however, a direct connection between these has not been fully established. The use of MDMA (ecstasy), a popular recreational drug, has been related to ischemic and hemorrhagic cerebrovascular events, as well as atrophy. Neuroimaging studies are vital in the assessment of the extent of neurologic damage in these patients.

Atrophy↗
PubMed2005

PET and SPECT in drug and substance abuse.

The use of imaging in the evaluation of the brain under the influence of drugs has evolved into a functional assessment of its processes. It has been shown that SPECT and PET imaging studies demonstrate selected areas that are affected by multiple drugs among substance abusers. This paper illustrates examples of different drugs and how their effect on the brain may be portrayed by imaging applications. The developing "road maps" that we have obtained possess multidimensional applications. They can be useful to confirm specific diseases, clarify diagnosis wherein the clinical picture is not observed, aid in the development of new treatment evaluations and also provide researchers a better insight in the detection and functionality of dementia and specific mental illnesses processes.

Brain Diseases↗
PubMed2004

Microscopic observation drug susceptibility assay, a rapid, reliable diagnostic test for multidrug-resistant tuberculosis suitable for use in resource-poor settings.

There is an urgent need for new tools to improve our ability to diagnose tuberculosis (TB) and multidrug-resistant TB (MDR-TB) in resource-poor settings. In a retrospective analysis undertaken in a region with a high incidence of TB, we evaluated the performance of the microscopic observation drug susceptibility assay (MODS), a novel assay developed in Perú which uses an inverted light microscope and culture in Middlebrook 7H9 broth to detect mycobacterial growth. MODS detected 94.0% of 1,908 positive sputum cultures, whereas Lowenstein-Jensen (LJ) culture detected only 86.9% (P < 0.001). The median time to culture positivity was 8 days (compared to 16 days for the same 208 samples by LJ culture; P < 0.001, Wilcoxon signed rank test). The results obtained by direct susceptibility testing using MODS demonstrated excellent concordance for isoniazid and rifampin and the detection of multidrug resistance with those obtained by indirect colorimetric methods: the microplate Alamar Blue assay (MABA) and the tetrazolium microplate assay (TEMA) (agreement, 95, 98, and 94%; kappa values, 0.8, 0.7, and 0.7, respectively). The concordance of the susceptibility testing results for ethambutol and streptomycin was poor. MODS is a novel assay which can detect the organisms responsible for TB and MDR-TB directly from sputum inexpensively, rapidly, and effectively. A comprehensive prospective evaluation of MODS is under way in Perú, and independent validation in nonresearch laboratories should be undertaken at the earliest opportunity.

Antitubercular Agents↗
PubMed2004

Purification of Enterocytozoon bieneusi spores from stool specimens by gradient and cell sorting techniques.

A three-step method for the purification of Enterocytozoon bieneusi spores from stool specimens was developed. The primary process of purification of the spores from bacterial contaminants involved Percoll gradient centrifugation followed by additional separation using cesium chloride density gradient centrifugation. The cesium chloride-isolated spores were further purified using a flow cytometer with cell sorting capabilities. Sorting was performed without the use of antibodies, fluorochromes, or dyes, leaving the sorted spores in their native state, which appears to be less destructive for spores. When quantified by flow cytometry using tubes with known numbers of highly fluorescent polystyrene beads, the sorted material showed a slight decrease in light scatter characteristics compared with the slightly larger Encephalitozoon species spores. Although the overall recovery of the E. bieneusi spores was low, calcofluor and Gram chromotrope staining, indirect immunofluorescence assay, and transmission electron microscopy revealed that the sorted material was highly purified and contained large numbers of E. bieneusi spores and relatively few bacteria and other debris. The sorted material appeared to be sufficiently pure and could be used for in vitro culture and for the development of a variety of diagnostic reagents as well as in studying the genome of E. bieneusi and host-parasite interactions.

Cell Separation↗
PubMed2003

Cryptosporidium species and genotypes in HIV-positive patients in Lima, Peru.

Cryptosporidium parasites from a cross-sectional study conducted in two national hospitals in Lima, Peru were genetically characterized to determine the diversity of Cryptosporidium spp. in HIV-positive people. A total of 2,672 patients participated in this study and provided 13,937 specimens. Cryptosporidium oocysts were detected by microscopy in 354 (13.3%) of the patients. Analysis of 951 Cryptosporidium-positive specimens from 300 patients using a small subunit rRNA-based PCR-RFLP tool identified 6 genotypes; Cryptosporidium hominis was the species most frequently detected (67.5%), followed by C. meleagridis (12.6%) and C. parvum (11.3%). Cryptosporidium canis (4.0%), C. felis (3.3%), and Cryptosporidium pig genotype (0.5%) were also found. These findings indicate that C. hominis is the predominant species in Peruvian HIV-positive persons, and that zoonotic Cryptosporidium spp. account for about 30% of cryptosporidiosis in these patients.

AIDS-Related Opportunistic Infections↗
PubMed2003

A molecular biologic study of Enterocytozoon bieneusi in HIV-infected patients in Lima, Peru.

A cross-sectional study was conducted to examine the genotype distribution of Enterocytozoon bieneusi in HIV-infected patients who visited two government hospitals in Lima, Peru from January 2000 through March 2003. Microsporidia were detected by microscopy in 105 (3.9%) of 2,672 patients. A total of 212 stool samples from 89 microsporidia-positive patients were genotyped by sequence analysis of the internal transcribed spacer (ITS) region of the rRNA gene. A 392-bp fragment containing the complete ITS region was amplified and sequenced. Multiple alignments and phylogenetic analysis of these ITS sequences identified 11 distinct genotypes of E. bieneusi (Peru-1 to Peru-11), 6 of which were new genotypes not reported before. The remaining 5 genotypes had nucleotide sequences identical to those previously reported in humans, cats, pigs, and wild mammals. All the 11 E. bieneusi-genotypes identified are genetically related, and members of the group have been previously found in humans, domestic animals, and some wild mammals. Thus, there is a high genetic diversity of E. bieneusi in humans in Peru, and zoonotic transmission is possible if humans are in close contact with infected animals.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Diagnosis of sputum-scarce HIV-associated pulmonary tuberculosis in Lima, Peru.

Sputum induction, bronchoalveolar lavage, or gastric aspiration are often needed to produce adequate diagnostic respiratory samples from people with HIV in whom tuberculosis is suspected. Since these procedures are rarely appropriate in less-developed countries, we compared the performances of a simple string test and the gold-standard sputum induction. 160 HIV-positive adults under investigation for tuberculosis, and 52 asymptomatic HIV-positive control patients underwent the string test followed by sputum induction. The string test detected tuberculosis in 14 patients in whom this disease was suspected; sputum induction detected only eight of them (McNemar's test, p=0.03). These preliminary data suggest that the string test is safe and effective for retrieval of useful clinical specimens for diagnosis of pulmonary tuberculosis, and is at least as sensitive as sputum induction.

AIDS-Related Opportunistic Infections↗