Experimental models in the investigation of device-related infections

There has been an increasing concern with the problem of device-related infections, ever since foreign materials such as metal or plastic began to be used in implant surgery. The prophylaxis and treatment of such infections is difficult to evaluate in clinical studies, because placebo-controlled prophylaxis trials are thought to be unethical, and no single centre has enough patients for comparative treatment studies. For this reason different experimental models have been developed to study aspects of device-related infections. In this review, these infection models are presented. Different applications of the tissue-cage guinea pig model are summarized. This model allows the study of pathogenesis, natural course, prophylaxis, and treatment of device-related infection. In addition, by using this infection model, novel microbiological in-vitro tests could be developed, and questions of biocorn-patibility analyse

Radio frequency tank eigenmode sensor for propellant quantity gauging

A method for measuring the quantity of fluid in a tank may include the steps of selecting a match between a measured set of electromagnetic eigenfrequencies and a simulated plurality of sets of electromagnetic eigenfrequencies using a matching algorithm, wherein the match is one simulated set of electromagnetic eigenfrequencies from the simulated plurality of sets of electromagnetic eigenfrequencies, and determining the fill level of the tank based upon the match

Phagosome-lysosome fusion is a calcium-independent event in macrophages.

Phagosome-lysosome membrane fusion is a highly regulated event that is essential for intracellular killing of microorganisms. Functionally, it represents a form of polarized regulated secretion, which is classically dependent on increases in intracellular ionized calcium ([Ca2+]i). Indeed, increases in [Ca2+]i are essential for phagosome-granule (lysosome) fusion in neutrophils and for lysosomal fusion events that mediate host cell invasion by Trypanosoma cruzi trypomastigotes. Since several intracellular pathogens survive in macrophage phagosomes that do not fuse with lysosomes, we examined the regulation of phagosome-lysosome fusion in macrophages. Macrophages (M phi) were treated with 12.5 microM bis-(2-amino-S-methylphenoxy) ethane-N,N,N',N',-tetraacetic acid tetraacetoxymethyl ester (MAPT/AM), a cell-permeant calcium chelator which reduced resting cytoplasmic [Ca2+]; from 80 nM to < or = 20 nM and completely blocked increases in [Ca2+]i in response to multiple stimuli, even in the presence of extracellular calcium. Subsequently, M phi phagocytosed serum-opsonized zymosan, staphylococci, or Mycobacterium bovis. Microbes were enumerated by 4',6-diamidino-2-phenylindole, dihydrochloride (DAPI) staining, and phagosome-lysosome fusion was scored using both lysosome-associated membrane protein (LAMP-1) as a membrane marker and rhodamine dextran as a content marker for lysosomes. Confirmation of phagosome-lysosome fusion by electron microscopy validated the fluorescence microscopy findings. We found that phagosome-lysosome fusion in M phi occurs noramlly at very low [Ca2+]i (< or = 20 nM). Kinetic analysis showed that in M phi none of the steps leading from particle binding to eventual phagosome-lysosome fusion are regulated by [Ca2+]i in a rate-limiting way. Furthermore, confocal microscopy revealed no difference in the intensity of LAMP-1 immunofluorescence in phagolysosome membranes in calcium-buffered vs. control macrophages. We conclude that neither membrane recognition nor fusion events in the phagosomal pathway in macrophages are dependent on or regulated by calcium

Pathogenesis of implant-associated infection: the role of the host

Implanted devices are mainly used to improve impaired function or to replace missing anatomic structures. They are made of synthetic material or devitalized biological structures. In contrast to vital transplants, they are not rejected by the body. However, the host reacts against these foreign bodies, a process which can be designated as biocompatibility. The interaction of the device with adjacent granulocytes and complement not only induces various degrees of inflammation but also impairs local microbial clearance. Foreign surfaces are a preferred target for bacterial adherence. While adhering bacteria are highly resistant to the bactericidal activity of phagocytes, they are also resistant to most antimicrobial agents. Certain bacteria may reside within host cells, and hence, evade host defense mechanisms by persisting intracellularly around implants. Nanotechnology minimizes clotting activation and bacterial adhesion by intravascular devices. Furthermore, surface coating with appropriate substances favorably influences biocompatibility as well as susceptibility to infection. In the future, "Microsystems Technology” deployed as intelligent device may decrease the risk of implant failure due to infectio

Infectious Complications in Drug Addicts: Seven-Year Review of 269 Hospitalized Narcotics Abusers in Switzerland

In a retrospective survey of patients hospitalized in the Department of Medicine of the University Hospital, Basel, Switzerland, from 1980 to 1986, we found 269 patients with history of past or current drug abuse. The charts of these patients were analyzed for infectious complications according to defined criteria. Heroin was the principal drug consumed by 95%. In 127patients (47%) at least one infectious complication was diagnosed. In 125(31%) of 404 admissions, the infectious problem was the main reason for hospitalization. Among the 269 patients, 217 infective episodes occurred. Pulmonary infections were the most frequently occurring (52 episodes). There were 44 cases of viral hepatitis, 30 of human immunodeficiency virus infection, and 25 of minor genital infections. Bone and joint infections and sepsis/endocarditis werediagnosed in seven cases each. The overall mortality was 4.1%; however, only three of the 11 deaths were attributed to infections. Intravenous drug addiction is complicated by a high morbidity because of infections that were seldom lethal during the observed perio