The Microvascular Network Density and Morphology Affect the Radiotherapy Outcome at the Microscale Level: A Computational Analysis

PURPOSE/OBJECTIVE(S)

Half of the cancer patients are treated with radiotherapy to obtain tumor control while minimizing radiation toxicity. In this context, hypoxia is known to determine treatment resistance, driving tumor relapse after treatment. Therefore, we investigated the role of microvasculature density and morphology in shaping the tissue oxygen distribution and consequently affecting the treatment outcome.

MATERIALS/METHODS

We developed an advanced computational model to describe oxygen delivery in the vascular network and the surrounding tissue. A peculiar aspect of the model is its mesoscale mixed-dimensional approach, which allows the explicit inclusion of vascular network geometry and the description of the red blood cells' effect. The oxygen delivery is modeled considering both diffusive and convective phenomena. A 30 × 2GyRBE treatment is delivered in silico simulating photons, protons, and carbon ions. First, we estimated the surviving fraction by the classical linear quadratic model modified to account for the oxygen effect. Then, leveraging the 3D description of the surviving fraction at the microenvironment scale, we compute the local tumor control probability (LTCP) in different oxygenation states (reference, acute hypoxia, high oxygen consumption).

RESULTS

We report correlations between the LTCP and the hypoxic volume fractions (with pO2 lower than 1 mmHg) starting with photons. These hypoxic regions are present locally, even in highly vascularized tissue, if the network is not uniformly distributed, as it might be in cancer. They are also present in tissue with low microvascular density, even with regular morphology. Interestingly, the domain considered is comparable to or smaller than the clinical imaging standard voxel dimension, and the average oxygen partial pressure in the tissue region fails to spot treatments with low LTCP, questioning whether these hypoxia areas are visible clinically via imaging. Protons have a similar effect, highlighting a similar behavior across the oxygenation levels at the microscale level. Finally, carbon ions seem more effective than photons and protons in the presence of hypoxia due to the lower oxygen effect at high LET. For this reason, the treatment with carbon ions results in high LTCPs, whatever vascular network is considered (density and morphology differences).

CONCLUSION

These results show the effect of microvascular density and regularity on the radiotherapy outcome and they help us understand how the microvascular network morphology affects tumor oxygenation and the radiotherapy outcome.

Supplementation of honey bee production colonies with a native beneficial microbe mixture

Honey bee colonies form a complex superorganism, with individual and social immune defences that control overall colony health. Sometimes these defences are not enough to overcome infections by parasites and pathogens. For that reason, several studies have been conducted to evaluate different strategies to improve honey bee health. A novel alternative that is being studied is the use of beneficial microbes. In a previous study, we isolated and characterised bacterial strains from the native gut microbiota of honey bees. Four Apilactobacillus kunkeei strains were mixed and administered in laboratory models to evaluate their potential beneficial effect on larvae and adult bees. This beneficial microbe mixture was safe; it did not affect the expression of immune-related genes, and it was able to decrease the mortality caused by Paenibacillus larvae infection in larvae and reduced the Nosema ceranae spore number in infected adult honey bees. In the present study, we aimed to delve into the impact of the administration of this beneficial microbe mixture on honey bee colonies, under field conditions. The mixture was administered in sugar syrup using lyophilised bacterial cells or fresh cultures, by aspersion or sprayed and feeder, once a week for three consecutive weeks, in autumn or spring 2015, 2017 and 2019. Colony strength parameters were estimated before the administration, and one and three months later. Simultaneously different samples were collected to evaluate the infection levels of parasites and pathogens. The results showed that administering the beneficial microbe mixture decreased or stabilised the infection by N. ceranae or Varroa destructor in some trials but not in others. However, it failed to improve the colony's strength parameters or honey production. Therefore, field studies can be a game-changer when beneficial microbes for honey bees are tested, and meticulous studies should be performed to test their effectiveness.

Relevance of iron metabolic genes in biofilm and infection in uropathogenic Proteus mirabilis

The microorganisms are found in the environment, forming sessile communities embedded in an extracellular matrix of their own production, called biofilm. These communities have a great relevance in the clinical context, since they are associated with infections caused by biofilm in medical implants, such as urinary catheters. The development of biofilms is a complex process where a great diversity of genes participate. The present work is based on the study of genes related to iron metabolism and its implication in the development of P. mirabilis biofilms and pathogenicity. For this study, two mutant strains defective in biofilm formation were selected, generated by the interruption of genes that encoded non-heme ferritin and TonB-dependent receptor. The mutations influence on the development of the biofilm was evaluated by different approaches. The complexity of the biofilm was analyzed using Confocal Laser Microscopy and image analysis. The mutants infectivity potential was assessed in two experimental mice models of urinary tract infection. The results obtained in the present work show us the role of the ferritin and a TonB-associated porin protein over the initial and later stages of biofilm development. Moreover, in the ascending UTI mouse model, both mutants failed to colonize the urinary tract. In CAUTI models, ferritin mutant damaged the bladder similarly to wild type but the Ton-B mutant was unable to generate infection in the urinary tract. The results obtained in the present work confirm the relevant role that iron metabolism genes have in P. mirabilis biofilm development and for infection in the urinary tract.

Impact of Nutritional Stress on Honeybee Gut Microbiota, Immunity, and Nosema ceranae Infection

Honeybees are important pollinators, having an essential role in the ecology of natural and agricultural environments. Honeybee colony losses episodes reported worldwide and have been associated with different pests and pathogens, pesticide exposure, and nutritional stress. This nutritional stress is related to the increase in monoculture areas which leads to a reduction of pollen availability and diversity. In this study, we examined whether nutritional stress affects honeybee gut microbiota, bee immunity, and infection by Nosema ceranae, under laboratory conditions. Consumption of Eucalyptus grandis pollen was used as a nutritionally poor-quality diet to study nutritional stress, in contraposition to the consumption of polyfloral pollen. Honeybees feed with Eucalyptus grandis pollen showed a lower abundance of Lactobacillus mellifer and Lactobacillus apis (Firm-4 and Firm-5, respectively) and Bifidobacterium spp. and a higher abundance of Bartonella apis, than honeybees fed with polyfloral pollen. Besides the impact of nutritional stress on honeybee microbiota, it also decreased the expression levels of vitellogenin and genes associated to immunity (glucose oxidase, hymenoptaecin and lysozyme). Finally, Eucalyptus grandis pollen favored the multiplication of Nosema ceranae. These results show that nutritional stress impacts the honeybee gut microbiota, having consequences on honeybee immunity and pathogen development. Those results may be useful to understand the influence of modern agriculture on honeybee health.

Effect of the administration of Lactobacillus spp. strains on neonatal diarrhoea, immune parameters and pathogen abundance in pre-weaned calves

Neonatal calf diarrhoea is one of the challenges faced by intensive farming, and probiotics are considered a promising approach to improve calves' health. The objective of this study was to evaluate the effect of potential probiotic lactobacilli on new-born dairy calves' growth, diarrhoea incidence, faecal score, cytokine expression in blood cells, immunoglobulin A (IgA) levels in plasma and faeces, and pathogen abundance in faeces. Two in vivo assays were conducted at the same farm in two annual calving seasons. Treated calves received one daily dose of the selected lactobacilli (Lactobacillus reuteri TP1.3B or Lactobacillus johnsonii TP1.6) for 10 consecutive days. A faecal score was recorded daily, average daily gain (ADG) was calculated, and blood and faeces samples were collected. Pathogen abundance was analysed by absolute qPCR in faeces using primers directed at Salmonella enterica, rotavirus, coronavirus, Cryptosporidium parvum and three Escherichia coli virulence genes (eae, clpG and Stx1). The faecal score was positively affected by the administration of both lactobacilli strains, and diarrhoea incidence was significantly lower in treated calves. No differences were found regarding ADG, cytokine expression, IgA levels and pathogen abundance. Our findings showed that oral administration of these strains could improve gastrointestinal health, but results could vary depending on the calving season, which may be related to pathogen seasonality and other environmental effects.

Impact of nutritional stress on the honeybee colony health

Honeybees Apis mellifera are important pollinators of wild plants and commercial crops. For more than a decade, high percentages of honeybee colony losses have been reported worldwide. Nutritional stress due to habitat depletion, infection by different pests and pathogens and pesticide exposure has been proposed as the major causes. In this study we analyzed how nutritional stress affects colony strength and health. Two groups of colonies were set in a Eucalyptus grandis plantation at the beginning of the flowering period (autumn), replicating a natural scenario with a nutritionally poor food source. While both groups of colonies had access to the pollen available in this plantation, one was supplemented with a polyfloral pollen patty during the entire flowering period. In the short-term, colonies under nutritional stress (which consumed mainly E. grandis pollen) showed higher infection level with Nosema spp. and lower brood and adult bee population, compared to supplemented colonies. On the other hand, these supplemented colonies showed higher infection level with RNA viruses although infection levels were low compared to countries were viral infections have negative impacts. Nutritional stress also had long-term colony effects, because bee population did not recover in spring, as in supplemented colonies did. In conclusion, nutritional stress and Nosema spp. infection had a severe impact on colony strength with consequences in both short and long-term.

Probiotic properties of native Lactobacillus spp. strains for dairy calves

The use of native microorganisms with probiotic capacity is an alternative tool for the treatment and prevention of several diseases that affect animals, such as neonatal calf diarrhoea. The selection of probiotic strains within a collection is based on different in vitro and in vivo assays, which predict their potential. The aim of this study was to characterise a group of native Lactobacillus spp. strains isolated from faeces of healthy calves using an in vitro approach and to assess their ability to colonise the gastrointestinal tract (GIT) of calves. Native Lactobacillus spp. strains were evaluated on their capacity to survive low pH conditions and bile salts presence, biofilm formation and adhesion to both mucus and Caco-2 cells. Based on the in vitro characterisation, four strains (Lactobacillus johnsonii TP1.1, Lactobacillus reuteri TP1.3B, L. johnsonii TP1.6 and Lactobacillus amylovorus TP8.7) were selected to evaluate their capacity to colonise and persist in the GIT of calves. The assessment of enteric persistence involved an in vivo assay with oral administration of probiotics and quantification in faeces of the administered bacterial species with real-time quantitative PCR (qPCR). The study was conducted using 15 calves (1-month-old) which were divided into five groups of three animals, four of which were treated with four different selected strains and one was the control group. Strains TP1.3B and TP1.6 managed to persist in treated animals until ten days after the end of the administration period, indicating that they could be promising candidates for the design of probiotics for calves.

Lactobacillus kunkeei strains decreased the infection by honey bee pathogens Paenibacillus larvae and Nosema ceranae

Due to their social behaviour, honey bees can be infected by a wide range of pathogens including the microsporidia Nosema ceranae and the bacteria Paenibacillus larvae. The use of probiotics as food additives for the control or prevention of infectious diseases is a widely used approach to improve human and animal health. In this work, we generated a mixture of four Lactobacillus kunkeei strains isolated from the gut microbial community of bees, and evaluated its potential beneficial effect on larvae and adult bees. Its administration in controlled laboratory models was safe for larvae and bees; it did not affect the expression of immune-related genes and it was able to decrease the mortality associated to P. larvae infection in larvae and the counts of N. ceranae spores from adult honey bees. These promising results suggest that this beneficial microorganism's mixture may be an attractive strategy to improve bee health. Field studies are being carried out to evaluate its effect in naturally infected colonies.

Characterization of Nosema ceranae Genetic Variants from Different Geographic Origins

In recent years, large-scale colony losses of honey bees (Apis mellifera) have been reported and the infection with the microsporidia Nosema ceranae has been involved. However, the effect of N. ceranae at the colony level and its role in colony losses vary in different geographic areas. This difference may be related to the presence of multiple N. ceranae genetic variants resulting in different biological consequences. In this study, we analyzed the genetic diversity of 75 N. ceranae samples obtained from 13 countries and Hawaii through inter-sequence single repetition (ISSR) and evaluated if two of these genetic variants triggered different immune responses when infecting Apis mellifera iberiensis. The genetic diversity analysis showed that 41% of the samples had the same DNA amplification pattern, including samples from most European countries except Spain, while the remaining samples showed high variability. Infection assays were performed to analyze the infection levels and the immune response of bees infected with N. ceranae from Spain and Uruguay. The infected bees presented similar infection levels, and both isolates downregulated the expression of abaecin, confirming the ability of the microsporidia to depress the immune response. Only N. ceranae from Uruguay downregulated the expression level of imd compared to control bees. On the other hand, both genetic variants triggered different expression levels of lysozyme. As imd and lysozyme play important roles in the response to pathogens, these results could reflect differences in the biological consequences of N. ceranae variants in A. mellifera infection.

Theory and application of arterial tissue in-host remodelling

A central therapeutic goal in many applications of modern Biomedicine is the reconstruction of the diseased arterial sections via robust and viable tissue equivalents. In-host remodelling is an emerging technology that exploits the remodelling ability of the host to regenerate tissue. We develop a general theoretical framework of growth and remodeling of arterial tissue starting from a synthetic, degradable, acellularized graft and we demonstrate the potential of mechanistic models to guide the development and assisting in the design of arterial tissue engineered constructs.

Modelling mass and heat transfer in nano-based cancer hyperthermia

We derive a sophisticated mathematical model for coupled heat and mass transport in the tumour microenvironment and we apply it to study nanoparticle delivery and hyperthermic treatment of cancer. The model has the unique ability of combining the following features: (i) realistic vasculature; (ii) coupled capillary and interstitial flow; (iii) coupled capillary and interstitial mass transfer applied to nanoparticles; and (iv) coupled capillary and interstitial heat transfer, which are the fundamental mechanisms governing nano-based hyperthermic treatment. This is an improvement with respect to previous modelling approaches, where the effect of blood perfusion on heat transfer is modelled in a spatially averaged form. We analyse the time evolution and the spatial distribution of particles and temperature in a tumour mass treated with superparamagnetic nanoparticles excited by an alternating magnetic field. By means of numerical experiments, we synthesize scaling laws that illustrate how nano-based hyperthermia depends on tumour size and vascularity. In particular, we identify two distinct mechanisms that regulate the distribution of particle and temperature, which are characterized by perfusion and diffusion, respectively.

A computational model of drug delivery through microcirculation to compare different tumor treatments

Starting from the fundamental laws of filtration and transport in biological tissues, we develop a computational model to capture the interplay between blood perfusion, fluid exchange with the interstitial volume, mass transport in the capillary bed, through the capillary walls and into the surrounding tissue. These phenomena are accounted at the microscale level, where capillaries and interstitial volume are viewed as two separate regions. The capillaries are described as a network of vessels carrying blood flow. We apply the model to study drug delivery to tumors. The model can be adapted to compare various treatment options. In particular, we consider delivery using drug bolus injection and nanoparticle injection into the blood stream. The computational approach is suitable for a systematic quantification of the treatment performance, enabling the analysis of interstitial drug concentration levels, metabolization rates and cell surviving fractions. Our study suggests that for the treatment based on bolus injection, the drug dose is not optimally delivered to the tumor interstitial volume. Using nanoparticles as intermediate drug carriers overrides the shortcomings of the previous delivery approach. This work shows that the proposed theoretical and computational framework represents a promising tool to compare the efficacy of different cancer treatments.

Simulation of oxygen transfer in stented arteries and correlation with in-stent restenosis

Computational models are used to study the combined effect of biomechanical and biochemical factors on coronary in-stent restenosis, which is a postoperative remodeling and regrowth pathology of the stented arteries. More precisely, we address numerical simulations, on the basis of Navier-Stokes and mass transport equations, to study the role of perturbed wall shear stresses and reduced oxygen concentration in a geometrical model reconstructed from a real porcine artery treated with a stent. Joining in vivo and in silico tools of investigation has multiple benefits in this case. On one hand, the geometry of the arterial wall and of the stent closely correspond to a real implanted configuration. On the other hand, the inspection of histological tissue samples informs us on the location and intensity of in-stent restenosis. As a result, we are able to correlate geometrical factors, such as the axial variation of the artery diameter and its curvature; the numerical quantification of biochemical stimuli, such as wall shear stresses; and the availability of oxygen to the inner layers of the artery, with the appearance of in-stent restenosis. This study shows that the perturbation of the vessel curvature could induce hemodynamic conditions that stimulate undesired arterial remodeling.

Numerical treatment of boundary conditions to replace lateral branches in hemodynamics

In this paper, we discuss a technique for weakly enforcing flow rate conditions in computational hemodynamics. In particular, we study the effectiveness of cutting lateral branches from the computational domain and replacing them with non-perturbing boundary conditions to simplify the geometrical reconstruction and the numerical simulation. All these features are investigated both in the case of rigid and compliant walls. Several numerical results are presented to discuss the reliability of the proposed method.

Development of 3D architecture of uropathogenic Proteus mirabilis batch culture biofilms-A quantitative confocal microscopy approach

This work studies the development of the 3D architecture of batch culture P. mirabilis biofilms on the basis of morpho-topological descriptors calculated from confocal laser scanning microscopy (CLSM) stacks with image processing routines. A precise architectonical understanding of biofilm organization on a morpho-topological level is necessary to understand emergent interactions with the environment and the appearance of functionally different progeny swarmer cells. P. mirabilis biofilms were grown on glass coverslips for seven days on LB broth and subjected to in situ immunofluorescence. Confocal image stacks were deconvolved prior to segmentation of regions of interest (ROI) that identify individual bacteria and extracellular material, followed by 3D reconstruction and calculation of different morpho-topological key descriptors. Results showed that P. mirabilis biofilm formation followed a five stage process: (i) reversible adhesion to the surface characterized by slow growth, presence of elongated bacteria, and absence of extracellular material, (ii) irreversible bacterial adhesion concomitant to decreasing elongation, and the beginning of extracellular polymer production, (iii) accelerated bacterial growth concomitant to continuously decreasing elongation and halting of extracellular polymer production, (iv) maturation of biofilm defined by maximum bacterial density, volume, minimum elongation, maximum extracellular material, and highest compaction, and (v) decreased bacterial density and extracellular material through detachment and dispersion. Swarmer cells do not play a role in P. mirabilis biofilm formation under the applied conditions. Our approach sets the basis for future studies of 3D biofilm architecture using dynamic in vivo models and different environmental conditions that assess clinical impacts of P. mirabilis biofilm.

Changes in the aerobic vaginal bacterial mucous load after treatment with intravaginal sponges in anoestrous ewes: effect of medroxiprogesterone acetate and antibiotic treatment use

Intravaginal sponges (IS) impregnated with progestagens are widely used for oestrous synchronization in ewes. As progestogens depress the immuno response, the first aim was to determine whether medroxiprogesterone acetate (MAP) content affects the vaginal bacteria number (VBN) in IS-treated anoestrous ewes. The second aim was to compare the effectiveness of different antibiotic treatments to control the VBN increase caused by IS. In both experiments, IS were inserted during 14 days in anoestrous ewes. In the first, 11 ewes received commercial sponges (50 mg MAP), and 10 ewes received placebo sponges. For the second experiment, IS were inserted in three groups (n = 12/group), containing oxytetracycline im (20 mg/kg); injected into the sponge (0.02 mg), or control (no antibiotic). At sponge withdrawal, all ewes received 300 UI eCG. Mucous samples were collected from the vagina before sponge insertion, at sponge withdrawal, 24, 48 and 72 h later, and the VBN (colony-forming units per ml; CFU/ml) was counted after 48-h incubation. Medroxiprogesterone content did not affect VBN (log CFU/ml: 4.3 ± 0.2 vs 4.4 ± 0.2 with and without MAP, respectively). Bacterial number increased from 3.5 ± 0.2 at sponge insertion to 6.9 ± 0.1 at sponge withdrawal (p < 0.0001) and decreased the following day to 4.3 ± 0.2 (p < 0.0001). In the second experiment, VBN increased at sponge withdrawal (p < 0.0001) in all groups and decreased the following day (p < 0.0001). The CFU/ml at sponge withdrawal was lower in ewes treated with antibiotics (p < 0.0001), being even lower when local rather than systemic antibiotic was administered (log CFU/ml: 3.3 ± 1.8 vs 7.2 ± 1.8). The day of oestrous VBN was similar for all treatments and similar to that observed before sponge insertion. We concluded that MAP does not influence the increase in VBN, as the main effect is provoked by the sponge device itself, and local antibiotic treatment resulted in a lower bacterial growth than systemic treatments.

Expansion and drug elution model of a coronary stent

The present study illustrates a possible methodology to investigate drug elution from an expanded coronary stent. Models based on finite element method have been built including the presence of the atherosclerotic plaque, the artery and the coronary stent. These models take into account the mechanical effects of the stent expansion as well as the effect of drug transport from the expanded stent into the arterial wall. Results allow to quantify the stress field in the vascular wall, the tissue prolapse within the stent struts, as well as the drug concentration at any location and time inside the arterial wall, together with several related quantities as the drug dose and the drug residence times.

Phenotypic and genotypic characterization of Paenibacillus larvae isolates

Paenibacillus larvae is the causative agent of American Foulbrood (AFB), a severe disease of honeybees (Apis melifera). The aim of this work was to develop a strategy for the subtyping and the epidemiological analysis of P. larvae. Phenotypic characterisation, susceptibility to several antibiotics, electrophoresis of whole bacterial proteins, rep-PCR, ribotyping and DGGE were assessed using a collection of P. larvae isolates from different Uruguayan and Argentinean locations. Results indicated that there are two P. larvae genotypes circulating in Uruguay ERIC I-BOX A (worldwide distributed) and ERIC I-BOX C (exclusively detected in Argentina until this study). These results suggest that P. larvae isolates had moved between Argentina and Uruguay, probably through the Uruguay River. Patterns of whole bacterial proteins, DGGE and ribotyping did not improve the P. larvae intraspecific discrimination. Antibiotic susceptibility assays showed that 100% isolates were OTC-sensitive and 22% (belonging to ERIC I-BOX A group) were sulfisoxazole-resistant. This work may contribute to the elucidation of basic aspects related to the epidemiology of AFB in Uruguay and in the region.

Mathematical and numerical models for transfer of low-density lipoproteins through the arterial walls: a new methodology for the model set up with applications to the study of disturbed lumenal flow

In this work we introduce and discuss several mathematical models, based on partial differential equations, devised to study the coupled transport of macromolecules as low-density lipoproteins in the blood stream and in the arterial walls. These models are accurate provided that a suitable set of physical parameters characterizing the physical properties of the molecules and of the wall layers are available. Here we turn our attention on this aspect, and propose a new methodology to compute the physical parameters needed for the model set up, starting from available in vivo measurements. Then, we focus on the study of the accumulation of low-density lipoproteins in vascular districts featuring a highly disturbed flow. Our results demonstrate that mathematical models whose set up procedure benefits from an experimental feedback provide reliable information not only qualitatively, but also quantitatively. Their application to geometrically perturbed vascular districts (as for example a severe stenosis) shows that geometrical parameters such as curvature and variations of the lumenal section strongly influence the accumulation of low-density lipoproteins within the wall. For instance, in a stenotic segment with 75% area constriction, the LDL concentration at the lumenal side of the wall is about 10% higher than for the undisturbed segment.

Complete heart block associated with lupus in a dog

A 5-year-old Poodle-cross was initially presented for exercise intolerance and difficulty in chewing and yawning. Some months later it acutely developed lethargy referable to complete heart block. Further investigations before and after permanent pacemaker implantation demonstrated Coombs-positive immune-mediated haemolytic anaemia, presumptive masticatory myositis and hypoadrenocorticism, suggesting the possibility of multisystem auto-immune disease. A diagnosis of systemic lupus erythematosus (SLE) was made based on these findings and a positive anti-nuclear antibody titre. It was thought that immune-mediated destruction of cardiac conduction tissues was responsible for the development of atrioventricular conduction block. Glucocorticoid deficiency was corrected using cortisone replacement therapy. SLE was controlled successfully for 10 months using azathioprine monotherapy until signs, subsequently shown to be due to subacute bacterial endocarditis, resulted in the death of the patient. Lupus should be considered as a potential underlying aetiology in dogs that develop heart block.

New aspects of the role of MR/P fimbriae in Proteus mirabilis urinary tract infection

Proteus mirabilis, a common cause of urinary tract infection (UTI), produces a number of different fimbriae including mannose-resistant Proteus-like fimbriae (MR/P). The precise role of different P. mirabilis fimbriae in ascending UTI has not yet been elucidated. In this study, a clinical isolate of P. mirabilis and an isogenic mutant unable to express MR/P were tested using different experimental approaches. They were tested for their ability to cause infection in an ascending co-infection model of UTI and in a haematogenous model in the mouse. In both models, the mutant was less able than the wild-type strain to colonise the lower and upper urinary tracts although infectivity was not abolished. In vitro adherence to uroepithelial cells was also assessed. Significant differences in adherence between both strains were observed at 1 h but not at 15 min post infection. We have also shown that a wild-type strain carries two copies of the mrpA gene. These data reinforce the importance of MR/P fimbriae in P. mirabilis UTI although other virulence factors may be necessary for efficient colonisation and development of infection.

Virulence of a Proteus mirabilis ATF isogenic mutant is not impaired in a mouse model of ascending urinary tract infection

Proteus mirabilis, a common cause of urinary tract infection, produces a number of different fimbriae, including ambient temperature fimbriae (ATF). These fimbriae are optimally expressed at 23 degrees C and their contribution to urinary tract infection has so far remained unknown. In the present study, a clinical isolate of P. mirabilis and an isogenic allelic replacement mutant unable to express ATF were tested for their ability to cause infection in the ascending urinary tract infection model in mice. The atf mutant colonised the urinary tract as well as the wild-type strain and was also able to outcompete the wild-type strain in a co-challenge experiment. Different non-clinical P. mirabilis isolates showed a reactive AtfA band after Western blot analysis using a polyclonal rabbit AtfA antiserum. These data together suggest that ATF does not play a role in P. mirabilis urinary tract infection.

Growth, cellular differentiation and virulence factor expression by Proteus mirabilis in vitro and in vivo

A uropathogenic strain of Proteus mirabilis was grown in vitro in human and mouse urine and brain-heart infusion broth (BHIB) and in vivo in subcutaneous open chambers (SOC) in mice, intraperitoneal diffusion chambers (IPC) in rats and by ascending urinary tract infection in mice in order to compare growth pattern, cellular differentiation and expression of virulence factors. Although the growth rate was slower in vivo than in vitro, the extent of growth was similar after 24 h. PR mirabilis differentiated into filamentous swarmer cells in all in-vitro culture conditions, but no filamentous cells were observed in either of the in-vivo chamber models. Transurethrally infected mice showed a rapid release or loss of filamentous cells and these could not be seen in kidney or bladder homogenates 7 days after infection. Bacteria showed increasing haemagglutination titres for fresh and tanned red blood cells after subculturing in BHIB, but bacteria grown in vivo did not show haemagglutination. An increasing resistance to normal serum was found when bacteria were grown in vivo. Significant haemolytic activity was detected with bacteria grown in BHIB and IPC, but almost no activity was found when bacteria had grown in urine. These findings improve the understanding of the role of P. mirabilis uropathogenic virulence factors in vivo.

Defined mutants of Proteus mirabilis lacking flagella cause ascending urinary tract infection in mice

A clinical isolate of Proteus mirabilis (Pr 990) and an isogenic non-flagellate allelic replacement mutant (Pr M9) were tested for their ability to cause infection in the ascending mouse model of urinary tract infection. Wild-type Pr 990 differentiates into swarmer cells in brain-heart infusion broth. Pr M9 neither has flagella nor does it apparently differentiate into swarmer cells after subculturing. The infectivity of both strains from an initial culture and the sixth subculture was assessed in the ascending urinary tract infection mouse model. Infection was ascertained by determining colony forming units from kidney and bladder homogenates from individual mice 7 days after inoculation. In all cases the nonflagellate mutant Pr M9 was at least as infective as Pr 990. Using bacteria from the first culture, Pr M9 infected 61.5% and Pr 990 infected 45.5% of mice tested. The levels of viable counts were similar between the Pr M9 and the Pr 990 infections. Using bacteria from the sixth subculture, Pr M9 infected 75% and Pr 990 infected 76.5% of mice tested. Again viable counts were similar. Pr 990 increased in infectivity from the first to the sixth subculture, whereas Pr M9 did not, but this may be a reflection of the high initial rate of infectivity with first culture Pr M9. These results suggest that neither flagella nor swarmer cells are required for P. mirabilis infectivity in ascending urinary tract infections in mice.

Flagellate and non-flagellate Proteus mirabilis in the development of experimental urinary tract infection

Three isolates of Proteus mirabilis from symptomatic human urinary tract infections (UTI) were tested for their ability to cause renal infection in mice. All three strains were fimbriated as tested by hemagglutination. One of the strains, Pr 988, did not possess flagella, whereas the other two did and were capable of swarming on solid rich media. We compared the capacity of these strains to infect mice in both the ascending and hematogenous mouse UTI models. Infection was assessed by counting viable bacteria in kidney and bladder homogenates in ascending UTI or by the presence of abscesses in the hematogenously inoculated mice. All three strains were able to infect mice in both UTI models. These results suggest that flagella are not absolutely necessary for virulence in these experimental models.

Influence of occlusal splints on bilateral anterior temporal EMG activity during swallowing of saliva in patients with craniomandibular dysfunction

A full-arch maxillary stabilization occlusal splint was made for each of 10 patients with craniomandibular dysfunction. These splints were divided into three sections (one anterior and two posterior). This procedure allowed variation in the anteroposterior centric localization of occlusal contacts, thus permitting the recording of the EMG effects produced by the different occlusal splint sections. The integrated EMG activity was recorded from the right and left anterior temporal muscles during swallowing of saliva in habitual occlusion and with the different occlusal splint sections inserted. EMG activity during swallowing of saliva was significantly lower with the different occlusal splints than in habitual occlusion. This supports the rationale for diurnal wear of the occlusal splint. No differences in EMG activity were found during swallowing of saliva when different sections of the occlusal splints were used. This fact points out the possibility for therapeutic use of different occlusal splints for improving swallowing function.

Antigenic and immunogenic activity of flagella and fimbriae preparations from uropathogenic Proteus mirabilis

The antigenic and immunogenic activities of fimbriae and flagella from three uropathogenic strains of Proteus mirabilis were compared. Flagella were obtained by mechanical treatment and fimbriae were isolated from cells by heat shock, ammonium sulfate precipitation, sodium deoxycholate and urea treatment, and gel filtration. Both preparations inoculated to mice demonstrated high antigenicity. Titers up to 1:80,000 were determined by an enzyme-linked immunosorbent assay either against the homologous or heterologous strains. When immunized mice were challenged with homologous or heterologous hematogenous infecting doses, a good cross protection was achieved only when fimbriae were used as antigens. Cross-reactivity found between the three fimbriae antisera, and the presence of common proteins in sodium dodecyl sulfate polyacrylamide gel electrophoresis patterns of fimbriae, should validate the study of these proteins to determine the existence of a shared adhesin.

[Colo-vesical fistulas in acute pathology of the colon]

A survey of the relevant literature and a statement of the acute diseases of the colon giving rise to urological complications are followed by a short account of the subjective and objective symptoms of colo-vesical fistulae. An assessment is also made of the advantages of careful diagnostic, clinical and instrumental appraisal. The classic management of such fistulae is described, and the main features of the surgical technique required are illustrated. Successful employment of total parenteral therapy in 13 cases of enteric fistula (including 2 colo-vesical cases) at the University of Genoa "R" Surgical Clinic is reported. The indications, contraindications and complications associated with this method are explained. The modalities whereby a gradual transition is made to feeding per os are described and the results obtained are evaluated.