Vaccine and immunotherapeutic interventions.

PURPOSE OF REVIEW: As we enter the fourth decade in HIV epidemic, advances in understanding HIV pathogenesis and development of potent and safer antiretroviral drugs have been spectacular. More than 30 antiviral drugs have been registered and the impact of combination antiviral therapy on morbidity and mortality has been dramatic. However, despite long-term virus suppression, HIV invariably rebounds after interruption of therapy. Long-term antiviral therapy does not cure HIV infection nor does it induce restoration/development of virus-specific immune responses capable of controlling HIV replication. Therefore, development of immune-based interventions is needed to restore effective defenses that can lead to HIV functional cure and ultimately eradication. RECENT FINDINGS: Therapeutic vaccination and immune interventions that generate de-novo or that boost preexisting HIV-specific T-cell responses are being investigated as a potential means to achieve a 'functional HIV cure'. One major hurdle in the quest of an HIV cure is control and elimination of the HIV latent reservoir. Several immune interventions that target the latent reservoir have been tried in recent years. In parallel, several therapeutic vaccination strategies have been developed and tested in early clinical studies. Recent encouraging studies show for the first time that vaccination can have an impact on HIV load. SUMMARY: This review summarizes the main immune interventions evaluated over the last years. Ways to improve them, as well as challenges in monitoring/evaluating effects of such strategies, are being discussed. In addition, clinical efficacy and potential clinical benefits of immunotherapeutic interventions are particularly difficult to measure. This review highlights current assays used and their shortcoming.

A novel technique using echocardiography to evaluate venous cannula performance perioperatively in CPB cardiac surgery.

OBJECTIVE: Transthoracic echocardiography (TTE) has been used clinically to disobstruct venous drainage cannula and to optimise placement of venous cannulae in the vena cava but it has never been used to evaluate performance capabilities. Also, little progress has been made in venous cannula design in order to optimise venous return to the heart lung machine. We designed a self-expandable Smartcanula (SC) and analysed its performance capability using echocardiography. METHODS: An epicardial echocardiography probe was placed over the SC or control cannula (CTRL) and a Doppler image was obtained. Mean (V(m)) and maximum (V(max)) velocities, flow and diameter were obtained. Also, pressure drop (DeltaP(CPB)) was obtained between the central venous pressure and inlet to venous reservoir. LDH and Free Hb were also compared in 30 patients. Comparison was made between the two groups using the student's t-test with statistical significance established when p<0.05. RESULTS: Age for the SC and CC groups were 61.6+/-17.6 years and 64.6+/-13.1 years, respectively. Weight was 70.3+/-11.6 kg and 72.8+/-14.4 kg, respectively. BSA was 1.80+/-0.2 m(2) and 1.82+/-0.2 m(2), respectively. CPB times were 114+/-53 min and 108+/-44 min, respectively. Cross-clamp time was 59+/-15 min and 76+/-29 min, respectively (p=NS). Free-Hb was 568+/-142 U/l versus 549+/-271 U/l post-CPB for the SC and CC, respectively (p=NS). LDH was 335+/-73 mg/l versus 354+/-116 mg/l for the SC and CC, respectively (p=NS). V(m) was 89+/-10 cm/s (SC) versus 63+/-3 cm/s (CC), V(max) was 139+/-23 cm/s (SC) versus 93+/-11 cm/s (CC) (both p<0.01). DeltaP(CPB) was 30+/-10 mmHg (SC) versus 43+/-13 mmHg (CC) (p<0.05). A Bland-Altman test showed good agreement between the two devices used concerning flow rate calculations between CPB and TTE (bias 300 ml+/-700 ml standard deviation). CONCLUSIONS: This novel Smartcanula design, due to its self-expanding principle, provides superior flow characteristics compared to classic two stage venous cannula used for adult CPB surgery. No detrimental effects were observed concerning blood damage. Echocardiography was effective in analysing venous cannula performance and velocity patterns.

Tillage Management and Soil Organic Matter, 2005

Tillage systems play a significant role in agricultural production throughout Iowa and the Midwest. It has been well documented that increased tillage intensities can reduce soil organic matter in the topsoil due to increased microbial activity and carbon (C ) oxidation. The potential loss of soil organic matter due to tillage operations is much higher for high organic matter soils than low organic matter soils. Tillage effects on soil organic matter can be magnified through soil erosion and loss of soil productivity. Soil organic matter is a natural reservoir for nutrients, buffers against soil erosion, and improves the soil environment to sustain soil productivity. Maintaining soil productivity requires an agriculture management system that maintains or improves soil organic matter content. Combining cropping systems and conservation tillage practices, such as no-tillage, strip-tillage, or ridge-tillage, are proven to be very effective in improving soil organic matter and soil quality.

APRIL is critical for plasmablast survival in the bone marrow and poorly expressed by early-life bone marrow stromal cells.

The persistence of serum IgG antibodies elicited in human infants is much shorter than when such responses are elicited later in life. The reasons for this rapid waning of antigen-specific antibodies elicited in infancy are yet unknown. We have recently shown that adoptively transferred tetanus toxoid (TT)-specific plasmablasts (PBs) efficiently reach the bone marrow (BM) of infant mice. However, TT-specific PBs fail to persist in the early-life BM, suggesting that they fail to receive the molecular signals that support their survival/differentiation. Using a proliferation-inducing ligand (APRIL)- and B-cell activating factor (BAFF) B-lymphocyte stimulator (BLyS)-deficient mice, we demonstrate here that APRIL is a critical factor for the establishment of the adult BM reservoir of anti-TT IgG-secreting cells. Through in vitro analyses of PB/plasma cell (PC) survival/differentiation, we show that APRIL induces the expression of Bcl-X(L) by a preferential binding to heparan sulfate proteoglycans at the surface of CD138(+) cells. Last, we identify BM-resident macrophages as the main cells that provide survival signals to PBs and show that this function is slowly acquired in early life, in parallel to a progressive acquisition of APRIL expression. Altogether, this identifies APRIL as a critical signal for PB survival that is poorly expressed in the early-life BM compartment.

Geochemical and geothermal study of springs in the Ossola-Simplon Region

Geological, hydrogeological and geochemical surveys were carried out in the Piedilago area (Ossola-Simplon region) in order to investigate the geothermal resources present in this area. Following these surface exploration efforts an exploratory geothermal well of 248 m was drilled in 1991. It discharges a thermal water with temperatures up to 43 degrees C and calcium (sodium) sulphate composition with a TDS close to 1350 mg/l. Chemical geothermometers suggest a reservoir temperature close to 45 degrees C indicating that the well virtually produces the pure uncooled thermal water. The Piedilago ex-ample is here considered as the departure point to establish both general criteria for further geothermal investigations in young mountains chains and taking into consideration all the available data on geology and fluid geochemistry of thermal systems in the Ossola-Simplon region, to constrain a geothermal model for the Lower Pennine Zone.

High incidence of childhood hemolytic uremic syndrome in Switzerland is associated with indicators of livestock farming intensity

Background: Hemolytic-uremic syndrome (HUS) is a multisystem disorder associated with significant morbidity and mortality. Typically, HUS is preceded by an episode of (bloody) diarrhea mostly due to Shiga-toxin (Stx) producing Escherichia coli (STEC). The main reservoir for STEC is the intestine of healthy ruminants, mostly cattle, and recent studies have revealed an association between indicators of livestock density and human STEC infection or HUS, respectively. Nationwide data on HUS in Switzerland have been established through the Swiss Pediatric Surveillance Unit (SPSU) [Schifferli et al. Eur J Pediatr. 2010; 169:591-8]. Aims: Analysis of age-specific incidence rate of childhood HUS and possible association of Shiga-toxin associated HUS (Stx-HUS) with indicators of livestock farming intensity. Methods: Epidemiological and ecological analysis based on the SPSU data (1997-2003) and the database of the Swiss Federal Statistical Office (data on population and agriculture). Results: One hundred-fourteen cases were registered, 88% were ≤5 years old. The overall annual incidence rate was 1.42 (0.60-1.91) and 4.23 (1.76-6.19) per 100000 children ≤5 and ≤16 years, respectively (P = 0.005). Stx-HUS was more frequent compared to cases not associated with STEC (P = 0.002). The incidence rate for Stx-HUS was 3.85 (1.76-5.65) in children ≤5, compared to 0.27 (0.00-0.54) per 100'000 children 5-16 years (P = 0.002), respectively. The incidence rate of cases not associated with STEC infection did not significantly vary with age (P = 0.107). Compared to data from Scotland, Canada, Ireland, Germany, England, Australia, Italy, and Austria the annual incidence rate of HUS in young children is highest in Switzerland. Ecological analysis revealed strong association between the incidence rate of Stx-HUS and indicators of rural occupation (agricultural labourer / population, P = 0.030), farming intensity (livestock breeding farms / population, P = 0.027) and cattle density (cattle / cultivated area, P = 0.013). Conclusions: Alike in other countries, HUS in Switzerland is mostly associated with STEC infection and affects predominantly young children. However, the incidence rate is higher compared to countries abroad and is significantly correlated with indicators of livestock farming intensity. The present data support the impact of direct and indirect contact with animals or fecal contaminants in transmission of STEC to humans.

Desarrollo de herramientas para la consulta de mensajería en integraciones realizadas con Mirth Connect

Proyecto consistente en el desarrollo de una herramienta web que permita consultar la mensajería procesada por el motor de integración Mirth de manera que puedan reflejarse los resultados de canales relacionados.

Water chemistry and isotope composition of the Acquarossa thermal system, Ticino, Switzerland

The thermal springs of Acquarossa and the nearby mineral springs of Soia have outlet temperatures of 12 degrees to 25 degrees C, TDS of 2290 to 3000 mg/kg and Ca-SO4 to Ca-SO4-HCO3 composition. Chemical geothermometers suggest reservoir temperatures close to 60 degrees C. P-CO2 values at depth are estimated to range from 0.3 to 2 bar. delta D and delta(18)O values indicate a meteoric origin and recharge elevations of 1600 +/- 150 m above sea level (a.s.l.) for these thermal and mineral waters. All these waters discharge from the overturned limb of the Simano nappe, probably dose to the contact between basement and underlying cover rocks. They therefore represent rain waters that descend slowly, heat at depth and locally rise relatively quickly to the surface, preserving part of their physical and chemical characteristics. (C) 1999 CNR. Published by Elsevier Science Ltd. All rights reserved.

Modes of acquisition of health literacy skills in informal learning contexts

In this article we try to analyze the learning processes of health literacy skills in informal contexts. We intend to broaden the understanding of the learning process beyond the formal contexts, thus contributing to the elucidation of health professionals on how individuals acquire and manage their knowledge in health matters. Given our goal, we use an analytic corpus constituted by one hundred autobiographical narratives written between 2006 and 2011, in educational contexts but with recognized potential for use in different scientific fields, including health. The results reveal the existence of three different types of modes of learning health literacy skills in informal context: : i) learning that takes place in action, in achieving daily tasks; ii) learning processes that result from problem solving; iii) learning that occurs in an unplanned manner, resulting from accidental circumstances and, in some cases, devoid of intentionality.

Vacuum assisted venous drainage does not increase trauma to blood cells.

Although gravity drainage has been the standard technique for cardiopulmonary bypass (CPB), the development of min imally invasive techniques for cardiac surgery has renewed interest in using vacuum assisted venous drainage (VAVD) Dideco (Mirandola, Italy) has modified the D903 Avant oxygenator to apply a vacuum to its venous reservoir. The impact of VAVD on blood damage with this device is analyzed. Six calves (mean body weight, 71.3 +/- 4.1 kg) were con nected to CPB by jugular venous and carotid arterial cannu lation, with a flow rate of 4-4.51 L/min for 6 h. They were assigned to gravity drainage (standard D903 Avant oxygen ator, n = 3) or VAVD (modified D903 Avant oxygenator, n = 3). The animals were allowed to survive for 7 days. A standard battery of blood samples was taken before bypass, throughout bypass, and 24 h, 48 h, and 7 days after bypass. Analysis of variance was used for repeated measurements. Thrombocyte and white blood cell counts, corrected by hematocrit and normalized by prebypass values, were not significantly different between groups throughout all study periods. The same holds true for hemolytic parameters (lactate dehydrogenase [LDH] and plasma hemoglobin). Both peaked at 24 hr in the standard and VAVD groups: LDH, 2,845 +/- 974 IU/L vs. 2,537 +/- 476 IU/L (p = 0.65), respectively; and plasma hemoglobin, 115 +/- 31 mg/L vs. 89 +/- 455 mg/L (p = 0.45), respectively. In this experimental setup with prolonged perfusion time, VAVD does not increase trauma to blood cells in comparison with standard gravity drainage.

Amoeba/amoebal symbiont genetic transfers: lessons from giant virus neighbours.

Free-living amoebae serve as hosts for a variety of amoebae-resisting microorganisms, including giant viruses and certain bacteria. The latter include symbiotic bacteria as well as bacteria exhibiting a pathogenic phenotype towards amoebae. Amoebae-resisting bacteria have been shown to be widespread in water and to use the amoebae as a reservoir, a replication niche, a protective armour as well as a training ground to select virulence traits allowing survival in the face of microbicidal effects of macrophages, the first line of defense against invading pathogens. More importantly, amoebae play a significant role as a melting pot for genetic exchanges. These ecological and evolutionary roles of amoebae might also be at play for giant viruses and knowledge derived from the study of amoebae-resisting bacteria is useful for the study and understanding of interactions between amoebae and giant viruses. This is especially important since some genes have spread in all domains of life and the exponential availability of eukaryotic genomes and metagenomic sequences will allow researchers to explore these genetic exchanges in a more comprehensive way, thus completely changing our perception of the evolutionary history of organisms. Thus, a large part of this review is dedicated to report current known gene exchanges between the different amoebae-resisting organisms and between amoebae and the internalized bacteria.

Hidrossedimentologia e disponibilidade hídrica da bacia hidrográfica da Barragem de Poilão

TEIXEIRA, José João Lopes. Departamento de Engenharia Agrícola, Centro de Ciências Agrárias da Universidade Federal do Ceará, Agosto de 2011. Hidrossedimentologia e disponibilidade hídrica da bacia hidrográfica da Barragem de Poilão, Cabo Verde. Orientador: José Carlos de Araújo. Examinadores: George Leite Mamede, Pedro Henrique Augusto Medeiros. O Arquipélago de Cabo Verde, situado na costa ocidental africana, sofre influência do deserto de Saara tornando o clima caraterizado por pluviometria muito baixa e distribuída irregularmente no espaço e no tempo. As chuvas são muito concentradas, gerando grandes escoamentos para o mar. O aumento da disponibilidade hídrica requer além da construção e manutenção de infraestrutura de captação e conservação de águas pluviais, uma gestão eficiente destes recursos. Atualmente, constitui um dos eixos estratégicos da política do estado de Cabo Verde, a captação, armazenamento e mobilização de águas superficiais através de construção de barragens. Estudos do comportamento hidrológico e sedimentológico do reservatório e da sua bacia de contribuição constituem premissas básicas para um ótimo dimensionamento, gestão e monitoramento da referida infraestrutura. É neste sentido que o presente estudo objetivou sistematizar informações hidrológicas e sedimentológicas da bacia hidrográfica da Barragem de Poilão (BP) e apresentar proposta operacional de longo prazo. A área de estudo ocupa 28 km² a montante da Bacia Hidrográfica da Ribeira Seca (BHRS) na Ilha de Santiago. A altitude da bacia varia de 99 m, situada na cota da barragem, até 1394 m. Para o estudo, foram utilizados e sistematizados, série pluviométrica de 1973 a 2010, registos de vazão instantânea do período 1984 a 2000 e registos agroclimáticos da área de estudo (1981 a 2004). Para o preenchimento das falhas tanto dos escoamentos como da descarga sólida em suspensão, foi utilizado o método de curva chave. Para estimativa de produção de sedimentos na bacia, aplicou-se a Equação Universal de Perda de Solo (USLE) e a razão de aporte de sedimentos (SDR). O índice de retenção de sedimentos no reservatório foi estimado pelo método de Brune e a distribuição de sedimento pelo método empírico de redução de área descrito por Borland e Miller e, revisado por Lara. Para gerar e simular curvas de vazão versus garantia foi utilizado código computacional VYELAS, desenvolvido por Araújo e baseado na abordagem de Campos. Também foi avaliada a redução da vazão de retirada do período 2006 a 2026, provocado pelo assoreamento do reservatório. Concluiu-se que em média a precipitação anual é de 323 mm, concentrando-se 73% nos meses de agosto e setembro; a bacia de contribuição apresenta como valor um número de curva (CN) de 76, com abstração inicial (Ia) de 26 mm, coeficiente de escoamento de 19% e uma vazão anual afluente de 1,7 hm³(cv= 0,73); a disponibilidade hídrica para uma garantia de 85% é avaliada em 0,548 hm³/ano e não 0,671 hm³/ano como indica o projeto original. Com uma descarga sólida estimada em 22.185 m³/ano conclui-se que até o ano de 2026, a capacidade do reservatório reduz a uma taxa de 1,8 % ao ano, devido ao assoreamento, provocando uma redução de 41% da disponibilidade hídrica inicial. Nessa altura, as perdas por evaporação e sangria serão da ordem de 81% da vazão afluente de entrada no reservatório. Na base desses resultados se apresentou proposta de operação da BP.

Parachlamydia acanthamoebae, an emerging agent of pneumonia.

Parachlamydia acanthamoebae is a Chlamydia-like organism that easily grows within Acanthamoeba spp. Thus, it probably uses these widespread free-living amoebae as a replicative niche, a cosmopolite aquatic reservoir and a vector. A potential role of P. acanthamoebae as an agent of lower respiratory tract infection was initially suggested by its isolation within an Acanthamoeba sp. recovered from the water of a humidifier during the investigation of an outbreak of fever. Additional serological and molecular-based investigations further supported its pathogenic role, mainly in bronchiolitis, bronchitis, aspiration pneumonia and community-acquired pneumonia. P. acanthamoebae was shown to survive and replicate within human macrophages, lung fibroblasts and pneumocytes. Moreover, this strict intracellular bacterium also causes severe pneumonia in experimentally infected mice, thus fulfilling the third and fourth Koch criteria for a pathogenic role. Consequently, new tools have been developed for the diagnosis of parachlamydial infections. It will be important to routinely search for this emerging agent of pneumonia, as P. acanthamoebae is apparently resistant to quinolones, which are antibiotics often used for the empirical treatment of atypical pneumonia. Other Chlamydia-related bacteria, including Protochlamydia naegleriophila, Simkania negevensis and Waddlia chondrophila, might also cause lung infections. Moreover, several additional novel chlamydiae, e.g. Criblamydia sequanensis and Rhabdochlamydia crassificans, have been discovered and are now being investigated for their human pathogenicity.

Role and regulation of polyphosphate in leishmania parasites

Le protozoaire unicellulaire Leishmania est l'agent responsable de la leishmaniose, une maladie parasitaire humaine qui se manifeste par des lésions de la peau, se résolvant le plus souvent spontanément, jusqu'à des lésions viscérales fatales. Le parasite est transmis de l'insecte à l'hôte mammifère lors d'un repas sanguin de la mouche des sables et y réside respectivement sous formes extra- et intracellulaires. On estime que cette maladie touche environ 12 millions de personnes dans 98 pays. Etant donné que les médicaments disponibles à ce jour sont faiblement efficaces et/ou hautement toxiques, il est indispensable de consolider les connaissances sur le fonctionnement et la survie du parasite pour pouvoir développer de nouvelles stratégies de traitements et de préventions. Tous les organismes vivants, dont Leishmania, contiennent du polyphopshate (polyP). Cette molécule chargée négativement est constituée de trois jusqu'à plusieurs centaines de résidus de phosphates reliées par des liaisons à haute énergie. Le polyP sert donc de source d'énergie et de réservoir de phosphate; dans certaines espèces, il joue aussi un rôle dans l'adaptation au stress et la virulence de pathogènes. Ceci nous a amené à étudier le rôle du polyP dans le parasite Leishmania. L'enzyme responsable de la synthèse de polyP a été identifié récemment dans la levure : il s'agit de la chaperone de transport vacuolaire 4 (Vtc4). Nous avons identifié un homologue de Vtc4 chez les Trypanosomatidae, et avons donc décidé d'examiner sa fonction dans le métabolisme du polyP chez Leishmania. En éliminant l'expression de Vtc4 chez L. major et L. guyanensis, nous avons pu démontrer qu'il est indispensable pour la production de polyP chez Leishmania. De plus, nous avons constaté que ces parasites possèdent des chaînes de polyP allant de trois jusqu'à environ 300 résidus de phosphate. Le taux de polyP dans la cellule est précisément régulé et varie entre un très haut niveau durant la phase proliférative des promastigotes à un niveau bas en phase stationnaire tardive, alors que l'expression de Vtc4p reste stable. Dans les amastigotes intracellulaires, seulement des petites quantités de polyP et de Vtc4p sont détectées. En outre, l'absence de Vc4p et de polyP n'a pas d'effet significatif sur les infections in vivo de souris, ce qui indique que le polyP n'est pas nécessaire au développement de la leishmaniose. Ceci suggère que Vtc4p n 'est pas une bonne cible pour le développement de nouveaux traitements contre Leishmania. "Néanmoins, la présence du polyP favorise fortement la survie du parasite suite à un choc de température (37°C) et aide ainsi à sa persistance intracellulaire pendant les premiers jours d'infection de macrophages. En résumé, nos résultats indiquent que si le polyP a peu d'importance pendant l'infection et le développement de la leishmaniose chez la souris, il est par contre crucial pour l'adaptation à des situations de stress comme l'augmentation de la température. Le fait que le polyP a été conservé dans tous les organismes durant l'évolution suggère toutefois que cette molécule joue un rôle fondamental. Etant donné que l'absence de polyP n'a pas d'effet sur la survie des amastigotes, il pourrait être plus important dans la forme promastigote infectant la mouche des sables. - The unicellular protozoan parasite Leishmania is the causative agent of the human disease leishmaniasis, which can range from self-healing skin lesions to fatal visceral lesions. The parasite is transmitted from the insect vector to the mammalian host when the sand fly takes its blood meal and exists in an extra- and an intracellular form, respectively. The disease is estimated to affect 12 million people in 98 countries and currently available drug treatments are of relatively low potency and/or high toxicity. Thus, investigating parasite survival mechanisms and parasite adaptation to the two host environments contributes to the general understanding of Leishmania propagation and might therefore help to develop future treatments or preventions. All living cells, including Leishmania, contain a negatively charged polymer of a few up to several hundred phosphate residues. These so-called polyphosphates (polyPs) serve as an energy source and phosphate reservoir. In some organisms, polyP is also involved in adaptation to stresses and virulence of pathogens. Therefore we were interested in investigating the importance of polyP in Leishmania parasites. Recently, an eukaryotic enzyme responsible for polyP synthesis has been identified as the vacuolar transporter chaperone 4 (Vtc4) in yeast. We, and others, found a Vtc4 homologue in trypanosomatids and decided to examine its potential function in polyP metabolism. By generating VTC4 knock-out cell lines in L. major and Vtc4 knock-down cell lines in L. guyanensis, we were able to demonstrate that Vtc4p is responsible for the total amount of cellular polyP. We also observed that Leishmania polyP chain length ranges from a few up to around 300 residues and that its level is tightly regulated. PolyP abundance is highest during the logarithmic proliferating phase of promastigotes and decreases in the stationary phase, while Vtc4 protein expression remains stable during both phases. In the intracellular amastigote form, only low amounts of polyP and Vtc4p were detectable. Furthermore, absence of Vtc4p and polyP did not have a significant effect on in vivo mouse infections, indicating that polyP is not necessary for Leishmania disease progression. This suggests that Vtc4p would be a poor drug target against Leishmania infection. However, presence of the polymer strongly supported parasite survival during heat shock (37°C) and thereby promoted intracellular persistence during the first days of macrophage infections. Taken together, we found that polyP has little importance in Leishmania {in vivo) infection but that it plays a crucial role during adaptation to stress, such as heat shock. Given that polyP has been preciously conserved in all organisms during evolution it seems to play a fundamental role. Since absence of polyP does not affect amastigote survival, it might be significant for promastigote existence in the sand fly vector.

New record of Pterotaenia fasciata (Wiedemann) (Diptera, Ulidiidae) in Brazil, a probably mechanical vector of enteric bacteria

Pterotaenia fasciata is commonly recorded in rural areas in Argentina, but during a Diptera survey study developed in a reservoir which retains storm water from polluted canals in an urban area of Taboão da Serra municipality, SP, Brazil, we could capture P. fasciata adults. Enteric bacteria Escherichia coli T. Escherich, 1885 and Proteus sp. were isolated from P. fasciata collected in traps inside the reservoir and around it. Fecal coliforms and E. coli were found in the water of the reservoir. These records suggest that a high abundance of this species at urban areas with inadequate sewage canals should reveal these muscoid dipterans as mechanical vectors of enteric bacteria.