Specific Detection of Human BK Polyomavirus in Urine Samples of Immunocompromised Patients

A semiquantitative PCR assay for the detection of BK virus in urine was developed using primers for BK virus that specifically amplified BK but not JC virus. DNA was extracted from urine through treatment with proteinase K followed by DNA precipitation with sodium acetate. Semiquantitation was achieved by amplifying serial dilutions (1:1, 1:10, 1:100, and 1:1,000) of the urine specimens. Each assay included both positive (stock BK virus and previously positive patient urine) and negative (no template) controls. A urine sample was interpreted as positive if any of the serial dilutions showed amplification of the DNA fragment of the expected size. For some patient-derived samples, amplification of the expected-size fragment was achieved with a dilute template whereas no amplification was achieved with a concentrated template. This was attributed to interfering substances in the urine. PCR results were compared with urine cytology and shown to be more sensitive. Validation studies were performed at the University of Nebraska Medical Center, utilizing a separate qualitative PCR assay that detects both BK and JC virus and distinguishes between them by restriction enzyme digestion patterns. Of 46 urine samples analyzed using both methods, 22 were positive by both assays, 18 were negative by both assays, 5 were positive only by the Nebraska method, and 1 was positive only by our method. In comparison with the Nebraska PCR, our PCR assay had a sensitivity of 81% and specificity of 95%. For twenty-one (43%) of 49 immunocompromised patients, tests were postive when specimens were submitted because of clinical suspicion of BK virus infection

Genetic Diversity of Human Pathogenic Members of the Fusarium oxysporum Complex Inferred from Multilocus DNA Sequence Data and Amplified Fragment Length Polymorphism Analyses: Evidence for the Recent Dispersion of a Geographically Widespread Clonal Lineage and Nosocomial Origin

Fusarium oxysporum is a phylogenetically diverse monophyletic complex of filamentous ascomycetous fungi that are responsible for localized and disseminated life-threatening opportunistic infections in immunocompetent and severely neutropenic patients, respectively. Although members of this complex were isolated from patients during a pseudoepidemic in San Antonio, Tex., and from patients and the water system in a Houston, Tex., hospital during the 1990s, little is known about their genetic relatedness and population structure. This study was conducted to investigate the global genetic diversity and population biology of a comprehensive set of clinically important members of the F. oxysporum complex, focusing on the 33 isolates from patients at the San Antonio hospital and on strains isolated in the United States from the water systems of geographically distant hospitals in Texas, Maryland, and Washington, which were suspected as reservoirs of nosocomial fusariosis. In all, 18 environmental isolates and 88 isolates from patients spanning four continents were genotyped. The major finding of this study, based on concordant results from phylogenetic analyses of multilocus DNA sequence data and amplified fragment length polymorphisms, is that a recently dispersed, geographically widespread clonal lineage is responsible for over 70% of all clinical isolates investigated, including all of those associated with the pseudoepidemic in San Antonio. Moreover, strains of the clonal lineage recovered from patients were conclusively shown to genetically match those isolated from the hospital water systems of three U.S. hospitals, providing support for the hypothesis that hospitals may serve as a reservoir for nosocomial fusarial infections