Search PubMed⌕ Search

Biomedical subjects

D A Relman

Publications and source records attributed to D A Relman.

At least 37 records · Page 2Linked to original sources
PubMed1999

Molecular approaches for identification of infectious agents in Wegener's granulomatosis and other vasculitides.

The primary symptoms of many vasculitides resemble those of infectious diseases. Patients with Wegener's granulomatosis usually seek medical care for respiratory tract symptoms resembling those caused by infection or allergy. In addition, vasculitis is a well-documented manifestation of infection by some known microbial agents. There have been relatively few controlled studies, however, seeking to identify infectious agents as the triggering factors in systemic vasculitides. Molecular methods offer powerful approaches for the identification of infectious agents in diseases of previously unknown origin. These methods include broad-range amplification of microbial nucleic acid sequences and comparative or subtractive methods, such as differential display and representational difference analysis. Host gene expression profiles (using DNA-chip technology) may also provide clues as to the possible infectious cause of an idiopathic disease. Furthermore, the application of molecular methods may reveal pathologic mechanisms and novel therapeutic strategies for the vasculitides.

Granulomatosis with Polyangiitis↗
PubMed1998

Culture-negative endocarditis caused by Bartonella henselae.

A 4-year-old girl presented with clinical evidence of infective endocarditis involving her aortic valve, but blood cultures were sterile. Serologic studies and analysis of resected valve by immunohistochemistry and polymerase chain reaction established the diagnosis of Bartonella henselae endocarditis. Clinicians should be aware that B. henselae can cause apparent culture-negative endocarditis in children.

Antibodies, Bacterial↗
PubMed1998

Cyclospora.

Although Cyclospora infection has been documented in humans worldwide since at least 1977, it is only in the past 2 years that this organism has come into prominence as a result of major foodborne outbreaks in the United States and Canada. Cyclospora causes significant gastrointestinal disease in immunocompetent and immunocompromised hosts and can be successfully treated with trimethoprim-sulfamethoxazole. The infection is under-recognized because our methods for diagnosis are rudimentary and insensitive. The mechanisms by which the parasite causes disease, the range of animal hosts, and the natural reservoir are unknown. Cyclospora is a unique coccidian parasite that has just begun to emerge; as yet, we have no clue as to where it comes from or where it hides.

Animals↗
PubMed1998

PCR analysis of T. whippelii DNA in a case of Whipple's disease: effect of antibiotics and correlation with histology.

A 58-yr-old man developed severe weight loss, arthralgias, and diarrhea. Endoscopic examination of the stomach and duodenum revealed thickened folds of duodenal mucosa. Biopsy of the gastric mucosa was negative, whereas duodenal biopsy revealed blunted epithelial villi and PAS-positive foamy macrophages within the lamina propria. Bacilli typical of those associated with Whipple's disease were found by electron microscopy. The diagnosis was confirmed by polymerase chain reaction (PCR) assay, which detected a portion of the 16S ribosomal RNA gene sequence corresponding to the Whipple bacillus (Tropheryma whippelii) in duodenum, stomach, and liver biopsies before therapy. T. whippelii DNA was eliminated from all tissues tested within 3 months of starting antibiotic treatment, but the histological improvement lagged behind the clinical and molecular evidence of improvement.

Actinobacteria↗
PubMed1998

Filamentous hemagglutinin of Bordetella bronchiseptica is required for efficient establishment of tracheal colonization.

Adherence to ciliated respiratory epithelial cells is considered a critical early step in Bordetella pathogenesis. For Bordetella pertussis, the etiologic agent of whooping cough, several factors have been shown to mediate adherence to cells and cell lines in vitro. These putative adhesins include filamentous hemagglutinin (FHA), fimbriae, pertactin, and pertussis toxin. Determining the precise roles of each of these factors in vivo, however, has been difficult, due in part to the lack of natural-host animal models for use with B. pertussis. Using the closely related species Bordetella bronchiseptica, and by constructing both deletion mutation and ectopic expression mutants, we have shown that FHA is both necessary and sufficient for mediating adherence to a rat lung epithelial (L2) cell line. Using a rat model of respiratory infection, we have shown that FHA is absolutely required, but not sufficient, for tracheal colonization in healthy, unanesthetized animals. FHA was not required for initial tracheal colonization in anesthetized animals, however, suggesting that its role in establishment may be dedicated to overcoming the clearance action of the mucociliary escalator.

Adhesins, Bacterial↗
PubMed1998

Improved amplification of microbial DNA from blood cultures by removal of the PCR inhibitor sodium polyanetholesulfonate.

Molecular methods are increasingly used to identify microbes in clinical samples. A common technical problem with PCR is failed amplification due to the presence of PCR inhibitors. Initial attempts at amplification of the bacterial 16S rRNA gene from inoculated blood culture media failed for this reason. The inhibitor persisted, despite numerous attempts to purify the DNA, and was identified as sodium polyanetholesulfonate (SPS), a common additive to blood culture media. Like DNA, SPS is a high-molecular-weight polyanion that is soluble in water but insoluble in alcohol. Accordingly, SPS tends to copurify with DNA. An extraction method was designed for purification of DNA from blood culture media and removal of SPS. Blood culture media containing human blood and spiked with Escherichia coli was subjected to an organic extraction procedure with benzyl alcohol, and removal of SPS was documented spectrophotometrically. Successful amplification of the extracted E. coli 16S rRNA gene was achieved by adding 5 microliter of undiluted processed sample DNA to a 50-microliter PCR mixture. When using other purification methods, the inhibitory effect of SPS could be overcome only by dilution of these samples. By our extraction technique, even uninoculated blood culture media were found to contain bacterial DNA when they were subjected to broad-range 16S rRNA gene consensus PCR. We conclude that the blood culture additive SPS is a potent inhibitor of PCR, is resistant to removal by traditional DNA purification methods, but can be removed by a benzyl alcohol extraction protocol that results in improved PCR performance.

Bacteria↗
PubMed1998

Infectious agents and the etiology of chronic idiopathic diseases.

At the end of the nineteenth century, the field of microbiology was born, and the infectious nature of many previously unexplained diseases was illuminated as powerful new technology was applied. At the end of the twentieth century, the etiology of myriad chronic diseases remains unexplained. We have argued that many of these diseases have clinical, epidemiological, and pathological features that suggest a role for microbes in their pathogenesis. Although definitive evidence of microbial disease causation is lacking, we believe that new technologies, such as sequence-based microbial identification, will successfully be applied to many of these chronic idiopathic diseases in the near future. As novel pathogens and previously described pathogens are revealed as the causative agents for some of these conditions, new diagnostic, preventive, and therapeutic modalities may emerge, transforming some diseases from idiopathic and chronic, to infectious and curable.

Arteriosclerosis↗
PubMed1997

Diagnosis and monitoring of Whipple disease by polymerase chain reaction.

BACKGROUND: Whipple disease is a chronic, multisystem disorder associated with infection with Tropheryma whippelii, an organism that has not yet been grown on artificial media. In some cases, the diagnosis of Whipple disease is uncertain if it is based on histology alone. Although antibiotic regimens of various durations have been used, the disease recurs in about one third of cases. No test for cure is available. OBJECTIVE: To develop a test that is more sensitive and specific than histologic examination to diagnose Whipple disease and monitor the effects of antibiotic therapy. DESIGN: Retrospective, laboratory-based evaluations of stored tissue specimens. PATIENTS: 30 patients with clinically diagnosed, histologically confirmed Whipple disease and 8 patients in whom Whipple disease was clinically suspected but who did not have definitive histologic evidence. MEASUREMENTS: Pretreatment and post-treatment biopsy specimens of the small bowel and lymph node were tested by polymerase chain reaction for the presence of T. whippeli DNA. RESULTS: Results on PCR were positive in 29 of the 30 specimens from patients with histologically confirmed disease (sensitivity, 96.6%; specificity, 100%) and in 7 of the 8 specimens from patients in whom disease was clinically suspected. Small-bowel biopsy specimens were obtained after treatment from 17 patients (median duration of follow-up, 119 months); specimens from 12 of these patients had positive results on PCR. When these cases were correlated with therapeutic outcome, it was found that 7 of the 12 patients had clinical relapse during subsequent follow-up or had never responded to treatment (positive predictive value, 58% [95% CI, 28% to 85%]). In contrast, none of the 5 patients whose post-treatment biopsy specimens had negative results on PCR had relapse (negative predictive value, 100% [CI, 48% to 100%]; P = 0.044). No correlation was found between post-treatment histology and clinical outcome (P > 0.2). CONCLUSIONS: Polymerase chain reaction is highly sensitive and specific when used to confirm the diagnosis of Whipple disease, to identify inconclusive and suspicious cases, and to monitor response to therapy. A negative result on PCR may predict a low likelihood of clinical relapse; a positive test result that remains positive despite therapy may be associated with a poor clinical outcome. Histopathologic evaluation of post-treatment specimens does not predict clinical cure or relapse.

Actinobacteria↗
PubMed1997

Polymerase chain reaction-based detection of Tropheryma whippelii in central nervous system Whipple's disease.

Whipple's disease of the central nervous system (CNS) may be associated with normal intestinal histology as a result of minimal or patchy involvement. The diagnosis is difficult and is frequently made post mortem. We studied 6 patients with clinically suspected CNS Whipple's disease; 2 had oculomasticatury myorhythmia (OMM) fitting criteria for a diagnosis of definite CNS Whipple's disease. One of the 2 had duodenal histology highly suggestive of Whipple's disease the other 5 patients had normal duodenal histology. DNA was extracted from paraffin-embedded duodenal tissues in all patients and frozen pontine tissue in 1. Two primer pairs (W3F-W4R, W3F-W2R) were used in separate polymerase chain reactions (PCRs) to amplify fragments of Tropberyma whippelii 16S rDNA from these tissue samples. PCR amplicons were detected only in the duodenal tissues from the 2 patients with OMM. The sequences of these amplicons were identical to the corresponding region of the previously published Tropheryma whippelii 16S rDNA sequence. PCR-based assays of intestinal or brain tissue may be of value for confirming, and possibly refuting, a clinical diagnosis of CNS Whipple's disease in a patient with any combination of dementia, supranuclear gaze palsy, hypothalamic manifestations, myoclonus, seizures, ataxia, or OMM, especially when tissue histology is unrevealing.

Actinobacteria↗
PubMed1997

Emerging infections and newly-recognised pathogens.

Clinicians and microbiologists have for many years relied on growth and characterisation of micro-organisms in the laboratory as the major method for their detection and identification, but reliance upon microbial growth in the laboratory has probably significantly limited our ability to recognise important pathogenic micro-organisms. The traditional methods are often slow, non-specific and insensitive, and sometimes discriminate poorly among microbial species and strains. It is now known that the evolutionary ancestry and interrelationships of all living organisms can be reliably inferred from sequences in their genetic material. Highly conserved sequences characterise broad phylogenetic groups and variable sequences allow specific identification. Sequence-based methods combined with DNA amplification methods, such as the polymerase chain reaction (PCR), have led to powerful molecular identification techniques such as consensus nucleic acid amplification and representational difference analysis. These methods allow one to detect and isolate informative gene sequences from occult microbial pathogens in human tissues. Sequence-based methods are often quicker, more sensitive and more specific than traditional methods not only in detecting known microbial pathogens, but also in identifying previously-uncharacterised micro-organisms. Widespread, organised use of these methods will reveal new emerging microbial pathogens, implicate microbes in the aetiology of poorly-understood chronic inflammatory diseases and significantly expand our understanding of microbial diversity.

Humans↗
PubMed1997

Bordetella pertussis infection of human monocytes inhibits antigen-dependent CD4 T cell proliferation.

Human monocytes and macrophages bind Bordetella pertussis through multiple specific receptor-ligand interactions; however, the effect of these interactions on monocyte and macrophage function is not well understood. In an in vitro system, B. pertussis infection of human monocytes significantly impaired T cell proliferation to exogenous antigen at MOIs as low as 1.0. B. pertussis isogenic mutant strains deficient in filamentous hemagglutinin or adenylate cyclase toxin were incapable of proliferation inhibition, suggesting that these virulence-associated factors are essential for this activity. B. pertussis-induced monocyte death alone did not explain these results, nor did differences in intracellular survival. In addition, B. pertussis infection did not significantly alter monocyte phagocytosis of complement-opsonized latex particles, indicating that B. pertussis infection does not globally impair monocyte functions in this system. These results suggest that B. pertussis may be capable of subverting cellular immune defenses in an infected host.

Adenylate Cyclase Toxin↗