A precise and simple isodose-volume-based verification method for HDR and LDR brachytherapy plans.

PURPOSE: The American Association of Physicists in Medicine (AAPM) code of practice for brachytherapy physics recommends performing an independent treatment time calculation. For this we implemented an easy to use isodose-based verification method for HDR (high-dose-rate) and LDR (low-dose-rate) brachytherapy plans. MATERIAL AND METHODS: Dose-volume-based methods have been developed for Ir-192-based high-dose-rate (HDR) and I-125 prostate low-dose-rate (LDR) brachytherapy. They allow checking the integral dwell time or activity when the volume of a suitable isodose is known. The verification method was validated for 55 clinical HDR and 243 clinical LDR plans. RESULTS: For HDR brachytherapy, the mean absolute difference between the estimated and calculated integral dwell time was 0.8% ± 1.0% (n = 30) with a single-source path and 2.7% ± 1.1% (n = 25) for multiple source paths. The corresponding value for LDR brachytherapy was 1.8% ± 2.0% (n = 243). In HDR brachytherapy, the verification method depends slightly on the plan class when considering one or more than one source paths. Good agreement between the estimated and calculated integral dwell times was obtained based on the 2 Gy isodose. Unlike HDR brachytherapy, the parameters used in the verification method for LDR brachytherapy plan verification strongly depend on the type of seed distribution. So, we recommend using an isodose at the prescribed dose for prostate HDR therapy. CONCLUSIONS: Isodose-based verification methods are precise, do not presuppose dedicated tools, and are simple to implement in clinical practice.

Measurements of isocenter path characteristics of the gantry rotation axis with a smartphone application.

PURPOSE: For stereotactic radiosurgery, the AAPM Report No. 54 [AAPM Task Group 42 (AAPM, 1995)] requires the overall stability of the isocenter (couch, gantry, and collimator) to be within a 1 mm radius. In reality, a rotating system has no rigid axis and thus no isocenter point which is fixed in space. As a consequence, the isocenter concept is reviewed here. It is the aim to develop a measurement method following the revised definitions. METHODS: The mechanical isocenter is defined here by the point which rotates on the shortest path in the room coordinate system. The path is labeled as "isocenter path." Its center of gravity is assumed to be the mechanical isocenter. Following this definition, an image-based and radiation-free measurement method was developed. Multiple marker pairs in a plane perpendicular to the assumed gantry rotation axis of a linear accelerator are imaged with a smartphone application from several rotation angles. Each marker pair represents an independent measuring system. The room coordinates of the isocenter path and the mechanical isocenter are calculated based on the marker coordinates. The presented measurement method is by this means strictly focused on the mechanical isocenter. RESULTS: The measurement result is available virtually immediately following completion of measurement. When 12 independent measurement systems are evaluated, the standard deviations of the isocenter path points and mechanical isocenter coordinates are 0.02 and 0.002 mm, respectively. CONCLUSIONS: The measurement is highly accurate, time efficient, and simple to adapt. It is therefore suitable for regular checks of the mechanical isocenter characteristics of the gantry and collimator rotation axis. When the isocenter path is reproducible and its extent is in the range of the needed geometrical accuracy, it should be taken into account in the planning process. This is especially true for stereotactic treatments and radiosurgery.

The Swiss IMRT dosimetry intercomparison using a thorax phantom.

PURPOSE: In 2008, a national intensity modulated radiation therapy (IMRT) dosimetry intercomparison was carried out for all 23 radiation oncology institutions in Switzerland. It was the aim to check the treatment chain focused on the planning, dose calculation, and irradiation process. METHODS: A thorax phantom with inhomogeneities was used, in which thermoluminescence dosimeter (TLD) and ionization chamber measurements were performed. Additionally, absolute dosimetry of the applied beams has been checked. Altogether, 30 plan-measurement combinations have been used in the comparison study. The results have been grouped according to dose calculation algorithms, classified as "type a" or "type b," as proposed by Kntis et al. ["Comparison of dose calculation algorithms for treatment planning in external photon beam therapy for clinical situations," Phys. Med. Biol. 51, 5785-5807 (2006)]. RESULTS: Absolute dosimetry check under standard conditions: The mean ratio between the dose derived from the single field measurement and the stated dose, calculated with the treatment planning system, was 1.007 +/- 0.010 for the ionization chamber and 1.002 +/- 0.014 (mean+/- standard deviation) for the TLD measurements. IMRT Plan Check: In the lung tissue of the planning target volume, a significantly better agreement between measurements (TLD, ionization chamber) and calculations is shown for type b algorithms than for type a (p <0.001). In regions outside the lungs, the absolute differences between TLD measured and stated dose values, relative to the prescribed dose, [(Dm-Ds)/Dprescribed], are 1.9 +/- 0.4% and 1.4 +/- 0.3%, respectively. These data show the same degree of accuracy between the two algorithm types if low-density medium is not present. CONCLUSIONS: The results demonstrate that the performed intercomparison is feasible and confirm the calculation accuracies of type a and type b algorithms in a water equivalent and low-density environment. It is now planned to offer the intercomparison on a regular basis to all Swiss institutions using IMRT techniques.

Topological methods for the comparison of structures using LDR-brachytherapy of the prostate as an example.

The dose coverage of low dose rate (LDR)-brachytherapy for localized prostate cancer is monitored 4-6 weeks after intervention by contouring the prostate on computed tomography and/or magnetic resonance imaging sets. Dose parameters for the prostate (V100, D90 and D80) provide information on the treatment quality. Those depend strongly on the delineation of the prostate contours. We therefore systematically investigated the contouring process for 21 patients with five examiners. The prostate structures were compared with one another using topological procedures based on Boolean algebra. The coincidence number C(V) measures the agreement between a set of structures. The mutual coincidence C(i, j) measures the agreement between two structures i and j, and the mean coincidence C(i) compares a selected structure i with the remaining structures in a set. All coincidence parameters have a value of 1 for complete coincidence of contouring and 0 for complete absence. The five patients with the lowest C(V) values were discussed, and rules for contouring the prostate have been formulated. The contouring and assessment were repeated after 3 months for the same five patients. All coincidence parameters have been improved after instruction. This shows objectively that training resulted in more consistent contouring across examiners.

Mechanical examinations on dental implants with porous titanium coating.

Due to its good biocompatibility, porous titanium is an interesting material for biomedical applications. Bone tissue can grow inside the porous structure and maintain a long and stable connection between the implant and the human bone. To investigate its long term stability, the mechanical behavior of porous titanium was tested under static and dynamic conditions and was compared to human bone tissue. A promising application of this material is the coating of dental implants. A manufacturing technique was developed and implants were produced. These implants were fatigue tested according to modified ISO 14801 and the micro structural change was examined. The fatigue test was statically modeled using finite element analysis (FEA). The results show that the implants resist a continuous load which is comparable to the loading conditions in the human jaw. The experiments show that the porous titanium has bone-like mechanical properties. Additionally the porous titanium shows an anisotropic behavior of its mechanical properties depending on the alignment of the pores. Finally, other potential applications of porous titanium are outlined.

Intra-individual comparison between open and 2-portal endoscopic release in clinically matched bilateral carpal syndrome.

Based upon bilateral carpal tunnel syndrome (CTS) we undertook a prospective randomised intra-individual comparison between open (OR) and 2-portal endoscopic release (2-PER) to establish if there is any demonstrable advantage in undertaking either technique in a 1 year follow-up. Ten patients with bilateral CTS were enrolled in this study and underwent a 2-PER on the one and an OR with two minimised incisions on the contralateral hand. Both hands were examined pre- and postoperatively after 2, 4, 6 and 12 weeks and after 6 and 12 months, respectively. Preoperatively both hands revealed statistically no significant differences in all the parameters recorded. Comparing both techniques no significant differences could be detected in the follow-up period. Nevertheless, both techniques showed significant improvements in the severity of symptoms and pain, in sensory nerve testing and in electro-diagnostic parameters, when comparing pre- with postoperative data after 1 year. The endoscopic approach revealed no distinct advantages over the open technique not only in the late but also in the early postoperative follow-up period when performing intra-individual comparison. Considering the higher complication rate and costs when performing 2-PER the OR with two minimised incisions seems to be a good alternative in order to keep the recovery period as short as possible.

Influence of autogenous leucocytes and Escherichia coli on sperm motility parameters in vitro.

Urogenital infections are considered important factors in male infertility. In this in vitro study we have evaluated the impact of leucocytes in association with an artificial infection with Escherichia coli on the motility of human spermatozoa. Ejaculates and blood samples were obtained from healthy donors with normal semen parameters. Ejaculates were prepared by swim-up technique and five fractions were isolated for incubation. Leucocyte subtypes were separated from blood samples by gradient centrifugation. Purified sperm suspensions were adjusted to a concentration of 20 x 106 ml-1 and incubated with lymphocytes/ monocytes, polymorphonuclear granulocytes (PMN), and E. coli. Samples were incubated for up to 6 h at 37 degrees C. Motility analysis was performed using a computer-assisted sperm analyzer (CASA). Spermatozoa incubated with 3 x 106 PMN ml-1 revealed a significant (P=0.003) decrease in progressive motility after 2 h. This decrease remained weakly significant (P=0.024) after 4 and 6 h. Lymphocytes and monocytes had no effect on sperm motility. Spermatozoa incubated with granulocytes and E. coli demonstrated highly significant alterations in motility after 4 and 6 h of incubation (P < 0.001). The PMN indicate an effect on motility of spermatozoa under experimental conditions. However, the results suggest that bacteria are the primary agents that interfere with sperm motility.

Experimental Escherichia coli epididymitis in rats: a model to assess the outcome of antibiotic treatment.

OBJECTIVE: To assess the effect of initial antimicrobial therapy with a new highly potent quinolone (sparfloxacin) on the outcome of infection, especially acute and chronic inflammation, in a rat model of unilateral Escherichia coli epididymitis. MATERIALS AND METHODS: The study included 60 Sprague-Dawley rats, each of which received 0.1 mL of an E. coli (0:6 strain) suspension (106 colony forming units/mL) injected into the right ductus deferens. At 24 h after infection an oral antimicrobial treatment with sparfloxacin was initiated in half of the animals. The rats were killed 14 days, 3 and 6 months after infection, and both epididymes and the prostate gland cultured to re-isolate E. coli. To evaluate the grade of inflammation in both epididymes, histological variables, including acute and chronic inflammation and scar formation, were evaluated and a total inflammatory score, representing the sum of all variables, computed. RESULTS: Whereas antimicrobial therapy eradicated the pathogen, in untreated animals the pathogen was detectable for up to 6 months after infection in the infected epididymis and/or the prostate gland, while the contralateral epididymis was sterile. The inflammatory reaction in the infected epididymis was significantly less in treated animals (P < 0.001). Subclinical nonbacterial inflammation was present in the contralateral epididymis. CONCLUSIONS: Although adequate antimicrobial treatment eradicated the pathogen and reduced the grade of epididymal damage, inflammation was not avoided. Subclinical inflammation of the contralateral epididymis may contribute to impaired fertility. These results indicate that an inflammatory reaction initiated by bacteria might persist as a nonbacterial process despite early therapy, or by bacteria undetectable by conventional culture techniques, and may compromise male fertility.

[Colonisation of the airways with ureaplasma urealyticum as a risk factor for bronchopulmonary dysplasia in VLBW infants?]. / Chronische Atemstörung sehr kleiner Frühgeborener: Besiedlung mit Ureaplasma urealyticum als ätiologischer Faktor?

BACKGROUND: Chronic inflammatory processes contribute to the pathogenesis of bronchopulmonary dysplasia (BPD). We hypothesized colonisation with Ureaplasma urealyticum (Uu) as a possible reason for an increased risk of developing prolonged oxygen dependency > 28 days in very low birth weight (VLBW) infants. PATIENTS AND METHODS: From January 1998 to November 1999 pharyngeal swabs were prospectively obtained and tested for Uu at birth and then weekly in VLBW infants. The following variables were compared between Uu-positive and Uu-negative infants: prenatal corticosteroids, maternal infections, mode of delivery, gestational age, birth weight, gender distribution, RDS, surfactant therapy, maximum inspiratory oxygen concentration during the first 24 and 48 hours, duration of oxygen supplementation beyond day 28, PDA, and weight differences during the first week of life. RESULTS: Of a total of 74 infants, 17 were found to be Uu-positive. The latter group showed a lower mean gestational age (29; 25 - 37 vs. 28; 24 - 34 WOG; p = 0.02) and a longer duration of oxygen supplementation after day 28 (0; 0 - 121 vs. 5; 0 - 134 d; p = 0.02). All other variables did not differ significantly between both groups. Multivariate analyses identified the variables birth weight and colonisation with Uu as risk factors for a longer period of oxygen dependency after day 28 (p < 0.01; p = 0.05). CONCLUSION: These data indicate a correlation between the colonisation with Uu and prolonged oxygen dependency > 28 days.

Escherichia coli-induced alterations of human spermatozoa. An electron microscopy analysis.

This study evaluated if the negative influence of Escherichia coli on the motility of human spermatozoa is a consequence of E. coli-induced ultrastructural alterations. Suspensions of spermatozoa were artificially infected with E. coli from a serotyped, pathogenic strain and incubated at 37 degrees C for 6 h. After incubation, spermatozoa were fixed in glutaraldehyde, stained with osmium tetroxide and ruthenium red and embedded in Spurr(R)-resin followed by ultramicrotomy. The sections were analysed subsequently by use of transmission electron microscopy. Uninfected suspensions of spermatozoa in medium and bacterial suspensions served as controls. Negative contrast technique was performed to facilitate visualization of ultrastructural details of the bacterial capsule after experimental exposure to spermatozoa. Electron microscopic evaluation revealed multiple and profound alterations in the ultrastructure of spermatozoa such as membrane defects and cytoplasmic vacuoles exclusively in spermatozoa of infected samples (> 90%). Morphological alterations involved all superficial structures of spermatozoa, in particular the plasma membrane of the mid-piece and neck as well as the inner and outer acrosomal membrane of the acrosome, indicating that morphological defects account for the immobilization of spermatozoa by E. coli. The results suggest that E. coli infection of ejaculates results in immobilization and impaired acrosomal function in human spermatozoa, findings that support the indication for antimicrobial chemotherapy in symptomatic and silent infections that affect the ejaculate.

Outcome of antibiotic therapy with ciprofloxacin in chronic bacterial prostatitis.

Chronic bacterial prostatitis (CBP) is a rare infection of the prostate with Escherichia coli being the predominant causative pathogen. Appropriate antimicrobial therapy is mandatory for cure. We report on our experience with a 4-week regimen of ciprofloxacin in 40 men suffering from CBP due to E. coli. Follow-up was conducted over a period of 12 to 24 months. The microbiological work-up included an analysis of expressed prostatic secretions (EPS) and semen. Eradication of the pathogen in EPS was achieved in 92% of patients 3 months after therapy and in about 70 to 80% of patients evaluated 12 and 24 months after treatment, respectively. Treatment failure was not associated with the presence of prostatic calculi, as assessed by transrectal ultrasonography. After successful therapy, mean EPS pH decreased significantly from 7.95 to 7.35. Significant bacteriospermia with E. coli was detected in 21/22 (95.5%) patients before treatment and in 6/22 (27.3%) patients 6 months after therapy. Our data reconfirm ciprofloxacin as an excellent antimicrobial agent in the therapy of CBP. However, eradication of the pathogen is unpredictable and cannot be achieved in every case. Further studies should correlate microbiological treatment success with symptomatic relief, as assessed by standardised questionnaires.

Diagnosis and therapeutic management of 18 patients with prostatic abscess.

OBJECTIVES: Our retrospective study aimed to analyze the findings and therapeutic strategies in 18 men who were admitted to our department as outpatient emergency cases with prostatic abscess. METHODS: During the period 1985 to 1997, prostatic abscess was diagnosed in 18 patients (mean age 48 years, range 20 to 68) on the basis of evidence of fluctuation at digital rectal examination and transrectal ultrasound (TRUS) findings. Diagnostic workup included analysis of midstream urine and abscess fluid for leukocytes and pathogens. Therapeutic options were conservative treatment and/or draining procedures. RESULTS: Predisposing diseases were found in 13 men. Fluctuation at digitorectal palpation was present in 15 patients. In 3 patients, diagnosis was based on TRUS. All men demonstrated leukocytes in their midstream urine. Causative pathogens in midstream urine were found in 11 patients. In 3 men, additional microbiologic evaluation of abscess fluid revealed uncommon pathogens. All patients received antibiotic treatment. Nine men with monofocal abscess less than 1 cm in diameter were treated with antibiotic therapy and a suprapubic catheter. Surgical drainage (transperineal or transrectal puncture, partly guided by TRUS, or transurethral unroofing) was performed in 12 patients and included 3 patients in whom conservative treatment failed. CONCLUSIONS: Our data confirm the importance of predisposing factors in the pathogenesis of prostatic abscess. Medical history and analysis of midstream urine indicated a diagnosis that was confirmed by digital palpation. In some cases, TRUS may improve diagnosis and treatment. Although both operative and conservative therapy strategies appear feasible, prostatic abscess chiefly requires individually selected drainage procedures.

Alterations of bacterial clearance induced by propofol.

BACKGROUND: The purpose of the study was to investigate the potential influence of the anaesthetic agent propofol on immune function in terms of systemic clearance and organ distribution of injected Escherichia coli in a rabbit model. METHODS: Defined numbers of E. coli (1.3 x 10(8) colony-forming units, CFU) were injected intravenously 1 h after starting a 4-h infusion of the anaesthetic propofol (2 ml.kg-1.h-1, Disoprivan 1%; n = 6)) or after saline application (n = 6). As propofol is formulated in a 10% lipid emulsion, the lipid vehicle Intralipid (2 ml.kg-1.h-1; n = 6) alone was investigated in a separate group. Parameters monitored were arterial pressure and rates of bacterial elimination from the blood. Three hours after bacterial injection, the animals were killed, and tissue samples of liver, spleen, lung, and kidney were collected for microbiological examinations. RESULTS: Compared to saline-treated animals, infusion of propofol induced increased accumulation of E. coli in lung and spleen, thus reflecting reticuloendothelial system dysfunction. CONCLUSION: As the lipid emulsion by itself induced the same effects, the impaired immune function due to propofol is thought to be attributed to its solvent Intralipid.

Microbiology of male urethroadnexitis: diagnostic procedures and criteria for aetiologic classification.

Common pathogens and unconventional, fastidious bacteria, viruses, parasites, and fungi are causative agents in male urethroadnexitis. Uropathogens and sexually transmitted organisms must be considered. Diagnostic procedures and criteria for aetiologic classification in cases of balanitis, urethritis, prostatitis, epididymitis, and orchitis are described and evaluated.

Influence of different uropathogenic microorganisms on human sperm motility parameters in an in vitro experiment.

The influence of different uropathogenic microorganisms (E. coli, enterococcus, Pseudomonas aeruginosa, Staphylococcus saprophyticus, Candida albicans) on human sperm motility was studied in vitro with a computer-assisted sperm analyser (CASA). Native ejaculates were prepared with the swim-up technique and adjusted to 22 x 10(6) spermatozoa ml-1. The sperm suspension was artificially infected with microorganisms in concentrations varying from 2 x 10(3) to 2 x 10(7). Sperm motility was examined directly after incubation, 2, 4 and 6 h later using the Mika motion analysis, a computer-based, automatic motility analysis. Former results with E. coli (serotype 06) could be confirmed that a significant inhibitory effect on sperm motility was associated with bacterial growth. Experiments with the enterococcus strain and Staphylococcus saprophyticus indicated no significant influence on sperm motility parameters. Tests with Pseudomonas aeruginosa showed a decrease of progressive motility according to time, but not to different bacterial concentrations. A significant inhibitory effect of Candida albicans was only detected in the samples with the initial bacterial concentration of 2 x 10(7) microorganisms ml-1.

Influence of urogenital infections on sperm functions.

Many studies have examined the impact of genital tract infections on male fertility; however, the effect of bacteriospermia on sperm quality is still controversial. Bacterial infections are more frequently found in semen samples from asymptomatic infertile patients than in those from fertile men. Bacteriospermia is also a common problem of male partners from couples undergoing IVF. Therefore, the effects of microorganisms on human sperm acrosome reaction of oocytes have been studied in vitro and in vivo. Incubation of spermatozoa with Escherichia coli or Mycoplasma hominis in vitro resulted in reduced sperm motility and inducibility of acrosome reaction (delta AR) after exposure to calcium ionophore A23187. To show possible effects of E. coli and mycoplasma species on sperm functions in vivo, data from 488 patients were evaluated, in whose ejaculates microbiological examinations and determinations of acrosome reaction after exposure to low temperature had been performed. U. urealyticum and E. coli were found in semen samples from 52 and 31 men, respectively. M. hominis was only present in a minor number of samples and was not included in this study. Semen concentrations of E. coli and U. urealyticum ranged between 500-100,000 cfu x ml-1 and 100-80,000 cfu x ml-1. No correlation was found between delta AR and concentration of bacteria (Spearman rank correlation coefficient, E. coli: r-0.081, P = 0.6644; U. urealyticum: r = -0.081, P = 0.5698). In 69% of cases with U. urealyticum infection and reduced inducibility of acrosome reaction, this sperm function was normal after antibiotic therapy. However, improvement of acrosomal function may only be due to intra-individual variations of acrosome reaction. While E. coli and mycoplasma species affect sperm functions in vitro, the present data and a review of the literature fail to demonstrate similar effects in vivo.

Ankylosing spondylitis and infections of the female urogenital tract.

Thirty-two female patients with confirmed ankylosing spondylitis (AS) and 33 women of similar age with pure ileitis terminalis Crohn were examined for genitourinary infection. Urethral syndrome was found in 15 out of 32 patients with AS: 11 of them had urethritis and 4 urethritis associated with vaginitis. Five women of the control group suffered from urethritis. In all cases with genitourinary infection, Chlamydia trachomatis was isolated. By comparing the AS-patients (urogenital infection group and the non-infected group) with regard to other present clinical parameters, it was found, as expected, that the erythrocyte sedimentation rate in the 1st hour was significantly higher in the infected group. In addition, the infected patients had a significantly higher incidence of enthesopathy, involvement of the spinal column, and higher C-reactive protein values (CRP > or = 5 mg/l). A family history of AS was equally present. Other clinical parameters, such as inflammatory involvement of the joints and HLA-B27 correlation, did not differ significantly between infected and non-infected patients.

Experimental genital tract infection with Chlamydia psittaci (GPIC agent) in male rats.

The course of experimental chlamydial infection of the male genital tract was studied. Inoculation of the Chlamydia psittaci agent of guinea pig inclusion conjunctivitis (GPIC agent) into the vas deferens of rats resulted in chlamydial infection of the epididymis, testis and the prostate gland. The inflammatory response was most prominent at 14 days after infection. Chlamydiae were recovered from the epididymides and the prostate glands for up to 90 and 60 days post inoculation, respectively. Histopathological changes associated with chlamydial infection of the epididymis or prostate gland were characterized by intratubular and interstitial purulent inflammation. Chlamydia-specific IgM- and IgG-antibodies were found in sera of nearly all infected animals. Results of this study indicate that this animal model may be useful to study the pathogenesis, immune responses and sequelae of chlamydial infections of the male genital tract.

Tissue penetration of sparfloxacin in a rat model of experimental Escherichia coli epididymitis.

The epididymal, testicular, and prostatic tissue penetration of sparfloxacin, a new quinolone, was assessed in a rat model of acute epididymitis. Seventy-two hours after injection of 0.1 ml (10(6) cfu/ml) of an Escherichia coli suspension into the right epididymis via the right ductus deferens, a single oral dose of sparfloxacin 50 mg/kg body weight was administered. One, 2, 4, 8, 12, and 24 h after administration the animals were sacrificed and the sparfloxacin concentrations and "areas under the curve" (AUC0-24) in both epididymides, both testes, the prostate gland and in the serum were measured by bioassay. The highest mean AUC0-24 was found in the prostate gland, followed by left epididymis, right epididymis, serum, right testis, and left testis (190, 79, 60, 28, 12, and 9 mg/kg x h, respectively). Though there was no statistically significant difference in the sparfloxacin concentration of both epididymides (p = 0.09), the mean AUC0-24 was significantly higher in the non-infected left epididymis (p < 0.0001). The AUC0-24 and sparfloxacin concentrations of the right infected epididymis were significantly higher than those observed in the serum (p < 0.0001). In both testes, the AUC0-24 and sparfloxacin concentrations were lower than in the serum (p < 0.0001), however, the concentration exceeded the MIC tenfold for approximately 20 h. It is concluded that the pharmacokinetic properties of sparfloxacin (good in vitro activity, high penetration into the prostate gland, testes, infected and non-infected epididymides) make this drug a recommendable choice for the initial treatment of acute epididymitis caused by E. coli.

Impaired bacterial clearance after activation of the complement and coagulation systems.

The aim of this study was to investigate the influence of the activation of the complement and coagulation systems on bacterial clearance and killing capacity of the reticuloendothelial system in rabbits. To enable quantification of the clearance process, defined numbers of exogenous Escherichia coli (1.3 x 10(8) colony-forming units) were injected intravenously, after complement activation with inulin-activated rabbit serum (n = 6), after complete defibrination with the snake toxin ancrod (n = 6), and in sham-operated animals (controls, n = 6). During the following 180 min observation period, parameters monitored were arterial pressure, fibrinogen, blood gases, and bacterial counts in blood and tissue samples of liver, kidney, spleen, and lung. Defibrination produced a significant delay in blood clearance (p < .05) compared with controls, coupled with up to four times higher bacterial counts in organ homogenates. Complement activation did not affect bacterial elimination kinetics, but was associated with accumulation of E. coli in lung and kidney (up to 100-fold of control values, p < .001). The impaired bacterial clearance associated with increased organ colonization after activation of the complement and coagulation systems reflect reticuloendothelial system dysfunction, thus pointing toward a weaker resistance against bacterial infection.