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Biomedical subjects

R Frei

Publications and source records attributed to R Frei.

At least 19 recordsLinked to original sources
PubMed2006

Improved anchorage in osteoporotic vertebrae with new implant designs.

The goal of our study was to evaluate two newly developed implant designs and their behavior in terms of subsidence in lumbar vertebral bodies under cyclic loading. The new implants were evaluated in two different configurations (two small prototypes vs. one large prototype with similar load-bearing area) in comparison to a conventional screw-based implant (MACS TL). A pool of 13 spines with a total of 65 vertebrae was used to establish five testing groups of similar bone mineral density (BMD) distribution with eight lumbar vertebrae each. In additional to BMD assessment via dual-energy X-ray absorptiometry, cancellous BMD and structural parameters were determined using a new generation in vivo 3D-pQCT. The specimens were loaded sinusoidally in force control at 1 Hz for 1000 cycles at three load levels (100, 200, and 400 N). A survival analysis using the number of cycles until failure (Cox regression with covariates) was applied to reveal differences between implant groups. All new prototype configurations except the large cylinder survived significantly longer than the control group. The number of cycles until failure was significantly correlated with the structural parameter Tb.Sp. and similarly with the cancellous BMD for three of five implants. In both large prototypes the cycle number until failure significantly correlated with the preoperative distance to the upper endplates. Although the direct relationship between bone structure or density and mechanical breakage behavior cannot be conclusively proven, all the prototypes adapted for poor bone structure performed better than the comparable conventional implant.

Aged↗
PubMed2006

[More haste less speed].

A 36 year old Portuguese man was admitted to our hospital with diffuse malaise, 25 kg weight loss in the past 6 months and night sweats. The diagnostic workup revealed hyperthyroidism due to graves disease and a mass lesion in the upper anterior mediastinum. Because of the uncertain dignity of the tumor a thoracoscopic thymectomy was performed. Histologically we found a thymic hyperplasia without any signs of malignancy. If systematically searched, thymic hyperplasia is often found with graves disease, however, this association is not widely appreciated and is not mentioned in general text books. The pathophysiology of thymic hyperplasia in graves disease is not fully understood. Immunological mechanisms seem to play an important role, since TSH receptors have been found on human thymic epithelial cells. Thyreostatic therapy leeds to spontaneous shrinkage of the thymic gland. Awareness of thymic hyperplasia in the differential diagnosis of an anterior mediastinal mass lesion is essential, since it prevents further invasive diagnostic procedures that might cause unnecessary morbidity.

Adult↗
PubMed2006

Course and outcome of Staphylococcus aureus bacteraemia: a retrospective analysis of 308 episodes in a Swiss tertiary-care centre.

Staphylococcus aureus bacteraemia (SAB) is associated with substantial morbidity and mortality worldwide. The charts of adult patients with SAB who were hospitalised in a Swiss tertiary-care centre between 1998 and 2002 were studied retrospectively. In total, 308 episodes of SAB were included: 2% were caused by methicillin-resistant strains; 49% were community-acquired; and 51% were nosocomial. Bacteraemia without focus was the most common type of community-acquired SAB (52%), whereas intravenous catheter-related infection predominated (61%) among nosocomial episodes of SAB. An infectious diseases (ID) specialist was consulted in 82% of all cases; 83% received appropriate antibiotic treatment within 24 h of obtaining blood cultures. Overall hospital-associated mortality was 20%. Community-acquired SAB was associated independently with a higher mortality rate than nosocomial SAB (26% vs. 13%; p 0.009). Independent risk-factors for a fatal outcome were age (p < 0.001), immunosuppression (p 0.007), alcoholism (p < 0.001), haemodialysis (p 0.03), acute renal failure (p < 0.001) and septic shock (p < 0.001). Consultation with an ID specialist was associated with a better outcome in univariate analysis (p < 0.001). Compared with a previous retrospective analysis performed at the same institution between 1980 and 1986, there was a 140% increase in community-acquired SAB, a 60% increase in catheter-related SAB, and a 14% reduction in mortality. In conclusion, mortality in patients with SAB remained high, despite effective antibiotic therapy. Patients with community-acquired SAB were twice as likely to die as patients with nosocomial SAB. Consultation with an ID specialist may reduce mortality in patients with SAB.

Adult↗
PubMed2006

Antimicrobial prophylaxis to prevent surgical site infections in a rural sub-Saharan hospital.

A prospective cohort study was performed to collect baseline data concerning surgical site infections (SSIs) and antimicrobial prophylaxis (AMP) in a remote sub-Saharan district hospital. The SSI rate of 22% was high. Most (88%) of the patients received prophylaxis after incision, and only 5% within the 30-min period before incision. Of all pathogens isolated from SSIs, 60% were resistant to the agent administered. The antibiotics given most frequently were chloramphenicol (60%), aminopenicillins (23%) and benzylpenicillin (15%). Staphylococcus aureus (36%), Escherichia coli (5%) and enterococci (4%) were the pathogens isolated most commonly from SSIs.

Adolescent↗
PubMed2005

Water birth: is the water an additional reservoir for group B streptococcus?

OBJECTIVE: Water birth became popular in the last years, despite the fact that many questions like the risk of infection for the newborn remain unanswered. Group B streptococcal (GBS) infections in the newborn remain a challenge in obstetrics and neonatology. METHOD: We conducted a prospective trial to study the impact of water birth on the colonization rate of the bath water and, more importantly, the GBS-colonization rate of the newborn. RESULT: After water birth the bath water was significantly more often colonized with GBS than after immersion followed by a delivery in bed. The newborns, however, showed no difference in GBS colonization and there was even a trend towards less GBS colonization of the newborn after a water delivery. CONCLUSION: Regarding GBS colonization of the newborn during water birth there might be a wash out effect, which protects the children during the delivery.

Baths↗
PubMed2005

Value of smear and PCR in bronchoalveolar lavage fluid in culture positive pulmonary tuberculosis.

At present, further investigations are needed in patients with suspected pulmonary tuberculosis (TB) and either negative sputum smear or without sputum. The aim of the present study was to analyse the yield of bronchoalveolar lavage fluid (BALF) smear and PCR in patients with confirmed pulmonary TB. Patients with a positive culture for Mycobacterium tuberculosis complex in sputum or BALF were analysed over 5 yrs. In total, 90 out of 230 (39%) patients with culture-positive pulmonary TB had a positive sputum smear, and 120 patients underwent bronchoscopy. BALF smear was positive in 56 (47%), BALF PCR in 93 (78%) patients, and BALF smear and/or PCR was positive in 83%. In total, 71 patients who underwent bronchoscopy and had complete clinical records were further analysed. BALF (smear or Mycobacterium tuberculosis complex-PCR) allowed a rapid diagnosis in 10 (59%) out of 17 patients who had a negative sputum smear, and 49 (91%) out of 54 patients without sputum production. Of these 71 patients, 12 (17%) were only culture positive. Rapid diagnosis of pulmonary TB by smear and/or PCR was made in 190 out of 210 patients (90%) in sputum or BALF. In conclusion, combined use of bronchoalveolar lavage fluid smear and Mycobacterium tuberculosis complex-PCR has a good diagnostic yield in patients with sputum smear-negative tuberculosis or without sputum production.

Adult↗
PubMed2004

New implant designs for fracture fixation in osteoporotic bone.

Screws are one of the limiting factors for fixation of implants, particularly in poor bone quality. A class of new implants with an implant-bone-interface optimized regarding load transition by increasing the peripheral area might improve the anchorage of implants in osteoporotic bone. However, the shape of these implants requires new technologies for insertion. The goal of the work presented here was to analyze the relevant parameters regarding implant geometry and to demonstrate the effect of new procedures for their insertion. The investigation was divided into three parts: 1) implant design optimisation, 2) efficiency of cortical bone ablation, and 3) implant insertion technology. Finite element analysis (FEA) was performed to investigate the influence of the number of lobes, the radius of the outer curvature and additional milling to remove any sharp changes of section around the lobe. Opening of the cortical bone with an Er:YAG laser was studied using calf cortex from 2 to 7 mm thickness. The effect of a) pulse energy and pulse duration, b) cortical thickness, c) wet or dry boundary conditions on volume and geometry of ablated bone, time required to penetrate the cortical bone and local bone tissue damage was quantified. Pneumatic and ultrasound based insertion were compared in the third experiment. The cortical bone was prepared in the following ways: a) no opening, b) predrilling of three holes (1 mm diameter each) and c) exact pre-cutting of the whole contour. Increasing the radius of the outer curvature from 2 to 5 mm reduces the peak stresses during loading in all planes in the implant as well as in the adjacent cortical bone by about 30-40%. An increase in the number of lobes from two to three decreases the mean peak stress by about 46% (alpha < 0.001) and the range between the minimal and maximal peak stresses for different loading directions by about 83%. Penetration of cortical bone with an Er:YAG laser was possible up to a cortical thickness of 6 mm with fewer than 100 pulses. The ablation rate per pulse increased more with increasing duration than with increasing energy. Signs of bone damage such as melting were only visible when high pulse energies and durations were used. Insertion of the prototype was possible with all devices, but only when the whole contour was cut out of the cortical bone. However, the use of the ultrasound vibrator led to heating up of the tissue fluid and subsequently to water evaporation and tissue damage. Insertion of the prototype was possible with both pneumatic vibrators, but only when the whole contour was cut out of the cortical bone. New implant designs may lead to reduced stress peaks in the surrounding bone and might be inserted with the help of new insertion technologies, namely laser cutting of cortical bone and pneumatic vibration. Further studies are required to optimize these technologies prior to clinical use.

Animals↗
PubMed2003

Emergence of a teicoplanin-resistant small colony variant of Staphylococcus epidermidis during vancomycin therapy.

Small colony variants of Staphylococcus aureus can cause persistent and recurrent infections. There are only a few reports of small colony variants of coagulase-negative staphylococci. Herein a case of infection with a teicoplanin-resistant small colony variant of Staphylococcus epidermidis is presented. The small colony variant was isolated from blood cultures of a patient with acute leukaemia and therapy-induced neutropenia who was treated with vancomycin for catheter-associated bloodstream infection. Despite removal of the catheter and adequate antibiotic therapy, the infection did not clear and the patient died 20 days after continuous antibiotic therapy.

Aged↗
PubMed2003

[Reliability and general practice value of 2 rapid Streptococcus A tests].

Rapid streptococcal-A-antigen detection assays have good specificity (over 90 percent) but moderate sensitivity (between 80 and 90 percent), when the tests are compared with a standard throat culture. Contradictory results have been found for one of the more recent tests, the optical immune assay Strep A OIA MAX, while for 6 years, we have been using the immune assay Strep A Plus. Results of the optical immunoassay and the conventional immune assay Strep A Plus were compared in 65 patients with acute pharyngitis. A standard culture was used as reference and confirmed by enhanced broth culturing and nucleic acid hybridization assay (Gen-Probe) when the two detection assays produced contradictory results. While both assays were equally sensitive (78.3%), Strep A OIA MAX and Strep A Plus had a similar specificity of 95.2% and 100%, respectively. Four and nine steps were required for Strep A Plus and for Strep A OIA MAX test procedures, respectively with results being available in 4-5 min and in 9-10 min, respectively. We conclude that both rapid immunoassays have a similar reliability while the handling of the Strep A Plus is much simpler than the handling of the Strep A OIA MAX. Neither rapid immunoassays are sensitive enough to eliminate the need for backup cultures.

Adolescent↗
PubMed2003

Molecular typing of methicillin-resistant Staphylococcus aureus: can PCR replace pulsed-field gel electrophoresis?

Pulsed-field gel electrophoresis (PFGE) is considered the "gold standard" for molecular typing of methicillin-resistant Staphylococcus aureus (MRSA). However, the method is time-consuming and expensive, and its discriminatory power may not be necessary in outbreak situations. We used a rapid multiplex PCR-based method with published primers and compared the results with those obtained by PFGE. A total of 75 clinical isolates were typed: 59 strains originated from our prospectively collected clinical strains and were epidemiologically unrelated; 16 strains came from an outbreak that was epidemiologically well defined in time and space. A primer mix of the spa gene, the coa gene, and the hypervariable region adjacent to mecA gene was used for multiplex PCR. Both PFGE and PCR clustered the 75 strains into 41 different genotypes. Concordance of the results was 100% for strains originating from the outbreak. Overall, both methods produced concordant results in 72% of cases. A total of 16% were clustered together by PFGE, but not by PCR and 12% were clustered together by PCR but not by PFGE, respectively. The turnaround time was only 8 h for PCR but 5 days for PFGE. This PCR-based method is excellent for rapid and inexpensive typing of MRSA in an outbreak setting, but the discriminatory power and reproducibility are still insufficient to replace PFGE in longitudinal studies in the endemic setting.

Bacterial Typing Techniques↗
PubMed2002

Impaired sensory function in heterozygous P0 knockout mice is associated with nodal changes in sensory nerves.

Mice heterozygously deficient in the major myelin component P0 are an established model of an inherited neuropathy and show signs of myelin degeneration in motor nerves. Unlike the case in patients, the sensory nerves are only mildly affected in the mouse mutants and do not show features indicative of myelin degeneration. Unexpectedly, by applying established behavioral tests, we found sensory deficits, as reflected by raised withdrawal thresholds to mechanical and thermal stimuli, whereas behavioral signs of a painful neuropathy were not detectable. By electron microscopy of longitudinal sections of sensory nerves, we found abnormalities in nodes of Ranvier comprising enlarged nodal gaps and poorly developed nodal Schwann cell microvilli. These alterations might be causally linked to the sensory deficits in the absence of profound myelin degeneration in the sensory nerves of the mutants.

Animals↗
PubMed2002

Clustering of bloodstream infections during maggot debridement therapy using contaminated larvae of Protophormia terraenovae.

BACKGROUND: The treatment of human wounds with fly larvae is an ancient procedure recently reintroduced into medical practice under the term of biosurgery. The crucial technical problem of biosurgery is asepsis of the larvae. PATIENTS AND METHODS: Since February 1999, we conducted a prospective observational study on the use of maggot debridement therapy in the management of ulcers refractory to standard treatment. RESULTS: During the first 5 months we observed five bloodstream infections (four with Providencia stuartii and one with Candida albicans) in 24 patients (21%) treated with maggots. The blood isolates could be traced back to contaminated maggots. Accordingly, the disinfecting procedure of the maggots was optimized and the fly species was changed from Protophormia terraenovae to Phaenicia (Lucilia) sericata. With the new procedure, no case of sepsis occurred in 45 patients treated between January 2000 and December 2001 (p < 0.005). CONCLUSION: Despite promising benefits, maggot debridement therapy can be threatened by serious infectious complications. With an appropriate disinfecting procedure, maggots free of pathogens can be obtained. Provided the maggots have been effectively disinfected, their application on chronic ulcers seems to be safe.

Aged↗
PubMed2002

Invasive pulmonary aspergillosis: effects of early resection in a neutropenic rat model.

OBJECTIVE: Invasive pulmonary aspergillosis is frequent in neutropenic patients. Usually localized in the beginning, the disease spreads and mortality is high despite antifungal treatment. The role of early adjuvant surgery is not clear. Surgery may help to confirm fungal disease, may control fungal disease locally and may prevent systemic spreading. This study examines effects of early resection on survival and dissemination in a rat model of localized invasive pulmonary aspergillosis. METHODS: Forty persistently neutropenic male albino rats were challenged with standardized conidial aspergillus inoculum injected into peripheral lung tissue of the right upper lobe under direct vision. Animals were divided into four groups. Twenty animals were treated with amphotericin B at 1 mg/kg per day beginning 48 h after inoculation, 20 animals were left untreated. In each group half the animals underwent early resection of localized invasive aspergillosis by lobectomy. Animals were checked daily and mortality was recorded up to 28 days after which surviving animals were sacrificed. RESULTS: Significantly higher survival was observed in resected animals in the non-Am B groups (survival: 10 +/- 19% without early resection and 50 +/- 32% with early resection; P = 0.044). However, early resection did not lead to improved survival in animals treated with amphotericin B (survival 70 +/- 29% without early resection and 50 +/- 32% with early resection; P = 0.316). CONCLUSIONS: In this rat model of localized invasive pulmonary aspergillosis effects of early resection on survival could be demonstrated only in animals not receiving amphotericin B treatment.

Amphotericin B↗
PubMed2002

Molecular epidemiology of predominant clones and sporadic strains of methicillin resistant Staphylococcus aureus in Switzerland and comparison with European epidemic clones.

OBJECTIVE: To assess the molecular epidemiology and risk factors of predominant clones and sporadic strains of methicillin-resistant Staphylococcus aureus (MRSA) in Swiss hospitals and to compare them with European strains of epidemic clones. MATERIAL AND METHODS: One-year national survey of MRSA cases. Analysis of epidemiological and molecular typing data (PFGE) of MRSA strains. RESULTS: In 1997, 385 cases of MRSA were recorded in the five Swiss university hospitals and in 47 community hospitals. Half of the cases were found in Geneva hospitals where MRSA was already known to be endemic. Molecular typing of 288 isolates (one per case) showed that 186 (65%) belong to four predominant clones, three of which were mostly present in Geneva hospitals. In contrast, the fourth clone (85 cases) was found in 23 hospitals (in one to 16 cases per hospital). The remaining 35% of the strains were clustered into 62 pulsed field gel electrophoresis types. They accounted for one to five patients per hospital and were defined as sporadic. Multivariate analysis revealed no independent risk factors for harboring a predominant versus a sporadic strain, except that transfer from a foreign hospital increases the risk of harboring a sporadic strain (OR, 42; 95% CI, 5-360). CONCLUSION: While cases with predominant clones were due to the local spread of these clones, most sporadic cases appear to be due to the continuous introduction of new strains into the country. With the exception of a transfer from a hospital outside Switzerland, no difference in the clinical or epidemiological characteristics was observed between patients harboring a predominant clone and those with a sporadic strain.

Anti-Bacterial Agents↗
PubMed2001

Derivation and validation of guidelines for stool cultures for enteropathogenic bacteria other than Clostridium difficile in hospitalized adults.

CONTEXT: The yield of in-hospital stool cultures performed more than 72 hours after admission is low, and a commonly used policy dictates that laboratories reject these cultures to save costs. However, enteropathogenic bacteria other than Clostridium difficile (EPB) may cause nosocomial illness that would be missed by use of such a "3-day rule." OBJECTIVE: To develop guidelines for hospital use of stool cultures that are sensitive to clinically relevant cases of sporadic and epidemic nosocomial diarrhea. DESIGN: Five-part study that incorporated a derivation sample based on retrospective chart review and a prospective cohort study (including cost savings analysis), and a validation sample based on retrospective chart review. SETTING: Four European academic health care centers. PATIENTS: Derivation sample: 1735 adult inpatients from whom 3416 stool cultures were obtained during a 19-month period (1995-1997) and 68 adult inpatients for whom EPB were grown from stool cultures during a 10-year period (1988-1998); validation sample: 65 patients with sporadic isolation of EPB (1993-1998), 56 patients involved in 2 nosocomial Salmonella outbreaks (1992 and 1997), and 330 patients who had stool cultures performed (1998). MAIN OUTCOME MEASURE: Performance of derived criteria in detecting pathogenic bacteria and outbreaks and reducing total number of stool cultures performed. RESULTS: Stool cultures grew EPB in 3.3% of samples obtained </=72 hours after admission and 0.5% of samples obtained thereafter (P<.001). Isolation of EPB >72 hours after admission was not associated with clinical symptoms or signs but was associated with community-acquired diarrhea (24%), age 65 years or older with preexisting comorbid disease (25%), neutropenia (13%), HIV infection (10%), and nondiarrheal manifestations of enteric infections (16%). Twelve percent were asymptomatic carriers. These characteristics were used to create criteria for selecting patients for whom stool cultures would be indicated. These criteria were applied post hoc to a series of 1025 stool cultures; the number of stool cultures would have been reduced by 52% and no clinically significant cases would have been missed. Annual savings to a 355-bed institution would be approximately $7800 for reagent costs and 75 hours of technician time. In the validation samples, only 2 patients of 65 who had EPB would not have been identified, and neither required treatment. If the 3-day rule had been applied, 52 cases would not have been identified, 28 of which required antibiotic treatment. CONCLUSION: Our modified 3-day rule for use in selecting cases for stool culture is sensitive to sporadic and epidemic cases of nosocomial diarrhea in hospitalized adults.

Adult↗