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Biomedical subjects

Peter C Iwen

Publications and source records attributed to Peter C Iwen.

13 recordsLinked to original sources
PubMed2006

Mucor circinelloides was identified by molecular methods as a cause of primary cutaneous zygomycosis.

A case of primary cutaneous zygomycosis caused by Mucor circinelloides is described. Histopathology showed typical hyphae along with chlamydospores. The isolate was identified by molecular and phenotypic methods. The utility of sequence analysis of the internal transcribed spacer region is highlighted; however, further studies are needed to assess species genetic heterogeneity.

Aged, 80 and over↗
PubMed2006

First report of Mycobacterium nebraskense as a cause of human infection.

Newly described nontuberculous Mycobacterium species have emerged as causes of opportunistic infection in compromised patients. This report describes the first case of Mycobacterium nebraskense isolated from a patient with a history of emphysema and details the need for adequate diagnostic capabilities to manage patients with infections caused by slow-growing pathogens.

Aged, 80 and over↗
PubMed2006

Geographic factors contributing to a high seroprevalence of West Nile virus-specific antibodies in humans following an epidemic.

Sera of 624 blood donors were evaluated to determine seroprevalence of West Nile virus (WNV) antibodies following the 2003 WNV epidemic in Nebraska. Geographic factors contributing to differences in WNV seropositivity were evaluated. The overall prevalence of WNV in Nebraska was higher than reported previously in other U.S. locations (9.5% WNV immunoglobulin G seroprevalence rate), with the highest prevalence identified in the western part of the state (19.7%), followed by the central (13.8%) and the eastern (4.2%) parts. Regions of the state with the highest WNV-positive mosquito rates correlated with the highest human WNV seroprevalence rates. The results showed that both the western and central parts of the state, where mosquito positivity rates were highest, had significantly higher seroprevalence rates than the eastern region. Additional studies are needed to determine whether the high prevalence rates in Nebraska will be reflected in other states and what impact environmental and geographical factors may have on future outbreaks of WNV infection.

Animals↗
PubMed2005

Molecular identification of Rhizomucor pusillus as a cause of sinus-orbital zygomycosis in a patient with acute myelogenous leukemia.

Sinus-orbital zygomycosis caused by Rhizomucor pusillus in a patient with acute myelogenous leukemia is described. Identification was achieved by sequencing of the internal transcribed spacer (ITS) regions of the rRNA gene and by expression of zygospores in mating. This report highlights the value of ITS sequencing as a diagnostic tool for the identification of R. pusillus and expands the understanding of infection types caused by this zygomycete.

DNA, Fungal↗
PubMed2005

Computational approach involving use of the internal transcribed spacer 1 region for identification of Mycobacterium species.

The rapid and reliable identification of clinically significant Mycobacterium species is a challenge for diagnostic laboratories. This study evaluates a unique sequence-dependent identification algorithm called MycoAlign for the differential identification of Mycobacterium species. The MycoAlign system uses pan-Mycobacterium-specific primer amplification in combination with a customized database and algorithm. The results of testing were compared with conventional phenotypic assays and GenBank sequence comparisons using the 16S rRNA target. Discrepant results were retested and evaluated using a third independent database. The custom database was generated using the hypervariable sequences of the internal transcribed spacer 1 (ITS-1) region of the rRNA gene complex from characterized Mycobacterium species. An automated sequence-validation process was used to control quality and specificity of evaluated sequence. A total of 181 Mycobacterium strains (22 reference strains and 159 phenotypically identified clinical isolates) and seven nonmycobacterial clinical isolates were evaluated in a comparative study to validate the accuracy of the MycoAlign algorithm. MycoAlign correctly identified all referenced strains and matched species in 94% of the phenotypically identified Mycobacterium clinical isolates. The ITS-1 sequence target showed a higher degree of specificity in terms of Mycobacterium identification than the 16S rRNA sequence by use of GenBank BLAST. This study showed the MycoAlign algorithm to be a reliable and rapid approach for the identification of Mycobacterium species and confirmed the superiority of the ITS-1 region sequence over the 16S rRNA gene sequence as a target for sequence-based species identification.

Base Sequence↗
PubMed2004

Utilization of the relative complexity measure to construct a phylogenetic tree for fungi.

The relative complexity measure (RCM) is a new approach to evaluate relatedness of DNA sequences which eliminates the requirement to align sequences prior to analysis, a step required with standard reference methods. The value of the RCM approach to generate distance matrices for use in phylogenetic analysis of organisms has not been determined. This study compared RCM with the algorithmic and tree searching reference methods for phylogenetic analysis using fungal sequences. Sequences of the cytochrome b gene and the 18S rDNA gene were obtained from the GenBank database to determine feasibility of this method for phylogenetic relatedness. The RCM approach was also used to construct a phylogenetic tree using internal transcribed spacer (ITS) sequences from 23 medically relevant fungal species. The robustness of the RCM and reference approaches was determined by comparing the topology of seven medically relevant fungi within the phylogenetic trees generated after progressive removal of 10, 20, 30, 40 and 50% of the nucleotide bases from either the 5' or 3' end of the three genomic target sequences. The results demonstrated that the RCM method was equivalent to the reference methods for construction of phylogenetic trees from cytochrome b and 18S rDNA gene sequences. The phylogenetic tree constructed using the ITS sequence generated no contradictory topology. The RCM generated trees retained the appropriate topology after removal of up to 50% of the cytochrome b sequence, 40% of the ITS sequence, and 30% of the 18S gene target sequence. Comparatively, the reference methods failed to maintain topology after only a 10% sequence deletion for each genomic target. The results showed the RCM to be a reliable and robust computational approach for use in the construction of fungal phylogenetic trees without the requirement for prior sequence alignment.

Algorithms↗
PubMed2004

Zygomycosis.

Zygomycosis is an invasive mycotic disease caused by fungi in the class Zygomycetes. Within this class, the most common species associated with infection include Absidia corymbifera, Apophysomyces elegans, Cunninghamella bertholletiae, Rhizomucor pusillus, Rhizopus microsporus var. rhizopodiformis, and Rhizopus arrhizus. These fungi all produce characteristic hyphal forms in tissue that are variable in width, produce haphazard branching, and lack septation. Although these fungi are ubiquitous in the environment, they are opportunists causing invasive disease in compromised hosts with a high mortality even when aggressive antifungal therapy and surgical intervention are utilized. Clinically, the disease most often affects the sinus with or without pulmonary involvement; direct extension from sinuses into cerebral tissue is not uncommon. This article describes the general clinical features of zygomycosis, with an emphasis on management in the setting of immunosuppression.

Journal Article↗
PubMed2004

Mycobacterium nebraskense sp. nov., a novel slowly growing scotochromogenic species.

The characterization of a novel slowly growing, scotochromogenic Mycobacterium species is reported. This previously undescribed mycobacterial species was isolated from five different patients with symptomatic pulmonary infections. All isolates were acid-fast-positive and the mycolic acid profiles were unique and supported placement into the genus Mycobacterium. Phenotypic characteristics of each strain included optimal growth after 3 weeks at a temperature range of 30-35 degrees C, yellow pigmentation after incubation in the dark and production of a heat-stable catalase. The 16S rRNA gene and internal transcribed spacer 1 sequences were identical for all five strains, but distinct from all known mycobacterial species. Phylogenetic analysis based on the 16S rRNA gene sequence placed the novel species within the slowly growing mycobacteria group in close proximity to Mycobacterium malmoense, Mycobacterium avium, Mycobacterium kansasii and Mycobacterium scrofulaceum. These data support the conclusion that the related five described organisms represent a novel Mycobacterium species, for which the name Mycobacterium nebraskense sp. nov. is proposed, with the type strain UNMC-MY1349(T) (=ATCC BAA-837(T)=DSM 44803(T)).

Catalase↗
PubMed2003

Molecular detection and typing of fungal pathogens.

A major goal of molecular testing is to develop a cost-effective as well as sensitive and specific assay that can detect microbial DNA in clinical samples early in the course of disease. Additionally, the ability to analyze the genetic relatedness of fungi on a timelier basis using molecular methods will have a positive impact on epidemiologic investigating. As technology advances, it seems apparent that commercially available molecular assays will become available in the near future for the management of patients with suspected fungal infections.

DNA, Fungal↗
PubMed2003

PCR rapidly detects methicillin-resistant staphylococci periprosthetic infection.

Optimal treatment of methicillin-resistant staphylococcal periprosthetic infections is predicated on rapid and reliable detection of these organisms. Culture has served as the gold standard for identification of these organisms despite shortcomings with sensitivity and processing time. The objective of the current study was to investigate a polymerase chain reaction assay aimed at rapid genomic detection of methicillin-resistance in staphylococci (mecA gene). The feasibility of the molecular approach first was validated using a septic arthritis model consisting of 73 synovial fluid samples inoculated with methicillin-resistant staphylococci and four negative controls. MecA polymerase chain reaction then was done on 35 clinical samples from 18 patients obtained at the time of revision arthroplasty. Results of the polymerase chain reaction were compared with culture. MecA polymerase chain reaction successfully predicted the presence of methicillin-resistant staphylococci in the septic arthritis model. In the clinical samples studied, the polymerase chain reaction results were concordant with culture results in 34 of the 35 samples tested. The one discordant result represented a false-positive culture result. The molecular assay was processed in less than 5 hours compared with 2 to 3 days for culture. Detection of methicillin-resistant staphylococci involved in periprosthetic infections by the polymerase chain reaction is a rapid and reliable approach.

Arthritis, Infectious↗
PubMed2003

Effects of sterilizing gamma irradiation on bloodspot newborn screening tests and whole blood cyclosporine and tacrolimus measurements.

Sterilizing irradiation of the US mail has been proposed as a method to prevent delivery of viable anthrax spores. Because newborn screening samples (bloodspots) and cyclosporine and tacrolimus specimens (whole blood) are delivered routinely through the mail, we studied whether sterilizing gamma irradiation could affect these test results. Specimens were exposed to 18 kGy gamma irradiation (100 hours x 18,000 rad/h), a "kill dose" for Bacillus pumilus spore strips. Irradiation had no significant effect on whole blood cyclosporine or tacrolimus results, but it had a degradative effect on bloodspot phenylalanine, hemoglobins, biotinidase, galactose-1-phosphate uridyltransferase, thyroxine, and thyrotropin. Such irradiation potentially could cause false-negative results for the detection of phenylketonuria and likely would lead to an increase in secondary testing for hemoglobin variants, but it is unlikely to lead to false-negative or false-positive results for the remaining newborn screening tests. These experiments cannot rule out possible greater effects by larger doses or other types of irradiation.

Anthrax↗
PubMed2002

Delayed diagnosis of osseous blastomycosis in two patients following environmental exposure in nonendemic areas.

Blastomycosis generally results from inhalation of Blastomyces dermatitidis conidia following exposure to contaminated soil in an endemic area. Primary infections commonly involve the lungs, although secondary dissemination to other body sites may occur. We describe 2 cases of osseous blastomycosis in people living outside the endemic areas. Both patients reported exposure to soilfollowing injury to the knee from occupational activities. Mold isolated from each case was identified as B dermatitidis by micromorphologic characteristics including yeast conversion testing and by a positive AccuProbe Blastomyces dermatitidis test (GenProbe, San Diego, CA). Retrospective review of histologic slides, initially reported as negative, identified rare poorly staining, broad-based budding yeast forms in each case. Both patients were treated successfully with itraconazole with no evidence of recurrent infection after 1 year These cases illustrate the importance of considering blastomycosis in the differential diagnosis of bony lesions, even though the patient may live outside an endemic area for B dermatitidis.

Adult↗