The viral content ratio between abdomen and head is informative of the relative efficiency with which Bemisia tabaci populations transmit begomoviruses. [P.12]

Begomoviruses (family Geminiviridae) are transmitted by the whitefly Bemisia tabaci in a circulative non propagative manner. B. tabaci is a species complex composed of at least 24 morphocryptic species which differ in host range, insecticide resistance, endosymbionts and virus transmission. Begomoviruses are supposed to cross the gut barrier at the midgut level and salivary gland barrier in the principal salivary gland (PSG) cells because of the highest virus concentrations in these organs. Thus, the critical steps of the virus circulation in the insect body are (i) the exit of virion from the midgut, (ii) their preservation in the hemocoel and (iii) their entry in the PSG. Thus, we proposed that the efficiency of viral transfer from midgut to PSG may be assessed by measuring the viral content in both compartments and that the deduced viral content ratio may be correlated to viral transmission efficiency by the vector. Our predicition was tested with two invasive B. tabaci species, Middle East-Minor Asia 1 (MEAM1), and Mediterranean (MED), and three begomoviruses: the invasive species Tomato yellow leaf curl virus-Mild (TYLCV-Mld), Tomato leaf curl Comoros virus (ToLCKMV), indigenous from Mayotte and R4, a recombinant between TYLCV and ToLCKMV. In a first approach, PSG and midgut were separated by a cross section through the prothorax and viral loads were estimated in both sections by measuring viral DNA using real time PCR. As the midgut of B. tabaci was reported to be sometimes pushed through the diaphragm separating the abdomen and the thorax, the estimation of the viral content ratio between PSG and midgut may be biased by thorax sectioning. The simple cross sectioning was however validated because the ratio determined with such sections and the ratio determined after a careful gut dissection was similar. Using the simple cross section, the viral content ratio between head and abdomen was higher for MEAM1 than for Med for the three begomoviruses. As predicted, the transmission efficiency was higher with MEAM1 than Med Q2 for the three viruses. These results indicate that viral content ratio may be a reliable predictor of the relative transmission efficiency between different B. tabaci populations. Measuring transmission efficiency is time consuming, involves technically difficult experiments with acquisition and inoculation steps and needs specialized cage and containment equipment. However measuring viral content ratios needs only a few cages for the acquisition step, a binocular lens and an access to the commonly used qPCR machines. This approach might be extended to estimate the relative transmission efficiency of other circulative non propagative viruses. (Résumé d'auteur

Xanthomonas albilineans is able to move outside of the sugarcane xylem despite its reduced genome and the absence of a Hrp type III secretion system.

Xanthomonas albilineans, the causal agent of leaf scald disease of sugarcane, is a pathogen that experienced genome reduction during its speciation. Additionally, this xanthomonad is notably missing the Hrp type III secretion system and the xanthan gene cluster that are commonly found in pathogenic Xanthomonas species. X. albilineans was up to now considered as limited to the xylem of sugarcane. However, recently published studies suggested that X. albilineans was able to invade tissues other than the xylem of sugarcane leaves but the occurrence of X. albilineans outside the xylem has not been clearly proven. In this study, we used confocal microscopy and transmission electron microscopy to investigate the localization of this pathogen in diseased leaves and stalks of sugarcane. Three sugarcane cultivars with different levels of resistance to leaf scald were inoculated with the green fluorescent protein labelled X. albilineans strains XaFL07-1 (from Florida) and GPE PC73 (from Guadeloupe). Sections of sugarcane leaves and stalks were examined 8-60 days after inoculation in order to localize X. albilineans in the different plant tissues. Confocal microscopy observation of symptomatic leaves confirmed the presence of the pathogen in the protoxylem and the metaxylem, however, X. albilineans was also observed in the phloem, the parenchyma and the bulliform cells of the leaves. Similarly, the protoxylem and the metaxylem of infected sugarcane stalks were invaded by X. albilineans. Surprisingly, the pathogen was also observed in apparently intact storage cells of the stalk and in the intercellular spaces between these cells. Several of these observations made by confocal microscopy have been confirmed by transmission electron microscopy. X. albilineans can therefore no longer be considered as a xylem-limited pathogen. To our knowledge, this is the first description of a plant pathogenic bacterium invading apparently intact non-vascular plant tissue and multiplying in parenchyma cells. The mechanisms and virulence factors used by X. albilineans to enter and invade different tissues of sugarcane remain to be identified. (Résumé d'auteur

Genetic variation and relationships among Turkish water buffalo populations

The genetic variation and relationships among six Turkish water buffalo populations,typical of different regions was assessed using a set of twenty-six heterologous (bovine) microsatellite markers. Between 7 and 17 different alleles were identified per microsatellite in a total of 254 alleles. The average number of alleles across all loci in all the analyzed populations was found to be 12.57. The expected mean heterozygosity (HE) per population was between 0.5 and 0.58. Significant departures from Hardy-Weinberg equilibrium were observed for 44 locus-population combinations. Population differentiation was analyzed by estimation of the FST index (values ranging from 0.053 to 0.123) among populations. In the PCA analysis the Merzifon population showed the highest differentiation compared to the others. Also some individuals of the Danamandira population appeared clearly separated. Instead Afyon, Coskun, Pazar and Thural populations represented one single cluster. The assignment of individuals to their source populations, performed using the Bayesian clustering approach implemented in STRUCTURE 2.2 software, has evidenced a high differentiation of Merzifon and Danamandira populations as well. The results of this study could be useful for the development of conservation strategies of the Turkish buffalo

Surface polysaccharides and quorum sensing are involved in the attachment and survival of Xanthomonas albilineans on sugarcane leaves

Xanthomonas albilineans, the causal agent of sugarcane leaf scald, is a bacterial plant pathogen that is mainly spread by infected cuttings and contaminated harvesting tools. However, some strains of this pathogen are known to be spread by aerial means and are able to colonize the phyllosphere of sugarcane before entering the host plant and causing disease. The objective of this study was to identify the molecular factors involved in the survival or growth of X. albilineans on sugarcane leaves. We developed a bioassay to test for the attachment of X. albilineans on sugarcane leaves using tissue-cultured plantlets grown in vitro. Six mutants of strain XaFL07-1 affected in surface polysaccharide production completely lost their capacity to survive on the sugarcane leaf surface. These mutants produced more biofilm in vitro and accumulated more cellular poly-β-hydroxybutyrate than the wild-type strain. A mutant affected in the production of small molecules (including potential biosurfactants) synthesized by non-ribosomal peptide synthetases (NRPSs) attached to the sugarcane leaves as well as the wild-type strain. Surprisingly, the attachment of bacteria on sugarcane leaves varied among mutants of the rpf gene cluster involved in bacterial quorum sensing. Therefore, quorum sensing may affect polysaccharide production, or both polysaccharides and quorum sensing may be involved in the survival or growth of X. albilineans on sugarcane leaves. (Résumé d'auteur

Persistent pulmonary congestion before discharge predicts rehospitalization in heart failure: a lung ultrasound study

BACKGROUND: B-lines evaluated by lung ultrasound (LUS) are the sonographic sign of pulmonary congestion, a major predictor of morbidity and mortality in patients with heart failure (HF). Our aim was to assess the prognostic value of B-lines at discharge to predict rehospitalization at 6 months in patients with acute HF (AHF). METHODS: A prospective cohort of 100 patients admitted to a Cardiology Department for dyspnea and/or clinical suspicion of AHF were enrolled (mean age 70 ± 11 years). B-lines were evaluated at admission and before discharge. Subjects were followed-up for 6-months after discharge. RESULTS: Mean B-lines at admission was 48 ± 48 with a statistically significant reduction before discharge (20 ± 23, p 15) (log rank χ(2) 20.5, p 15 before discharge (hazard ratio [HR] 11.74; 95 % confidence interval [CI] 1.30-106.16) was an independent predictor of events at 6 months. CONCLUSIONS: Persistent pulmonary congestion before discharge evaluated by ultrasound strongly predicts rehospitalization for HF at 6-months. Absence or a mild degree of B-lines identify a subgroup at extremely low risk to be readmitted for HF decompensation

Ultrasound Lung Comets versus cardiac natriuretic peptides in patients with acute dyspnoea

Background: Acute shortness of breath as a presenting symptom is a frequent challenge for physicians. The main differential diagnosis is between cardiac and non-cardiac origin of dyspnoea. Natriuretic peptides levels have been used to successfully aid in the diagnosis of congestive heart failure (CHF) in patients presenting with dyspnoea. Ultrasound lung comets (ULCs) are a useful chest sonography sign of increased extravascular lung water. Aim: To assess the concordance rate between ULCs and cardiac natriuretic peptides. Methods: 275 patients (87 females; age 70?14 yrs) admitted with dyspnoea (NYHA class II, III or IV) to a Cardiology-Pneumology or Emergency Department were evaluated. Cardiac peptides assessment and chest sonography, scanning along the intercostal spaces, were performed in all (within 3 hours) and independently analyzed. NT-proBNP values &#8805;157 ng/l, BNP &#8805;100 ng/l and ULCs &#8805;5 were considered abnormal, according to pre-determined cut-offs. Results: Abnormal values of natriuretic peptides were found in 251 patients, while ULCs were present in 220 patients. The total number of discordant cases was 36 (13%), with a concordance rate of 87%. The dominant source of discordance was due to abnormal natriuretic peptides and absence of ULCs (34 patients, see figure): in these patients the mean hospitalization time was significantly lower than in patients with abnormal cardiac peptides and presence of ULCs (7.8?3.7 vs 10.9?6 days, p<.001). Conclusions: ULCs findings are in broad concordance with natriuretic peptides values. Being natriuretic peptides analysis not always available, especially in peripheral Emergency Departments, ULCs assessment could be a plausible alternative to identify CHF in patients with acute dyspnoea

Dynamic changes and prognostic value of pulmonary congestion by lung ultrasound in acute and chronic heart failure: a systematic review

Aims: Pulmonary congestion is an important finding in patients with heart failure (HF) that can be quantified by lung ultrasound (LUS). We conducted a systematic review to describe dynamic changes in LUS findings of pulmonary congestion (B-lines) in HF and to examine the prognostic utility of B-lines in HF. Methods and results: We searched online databases for studies conducted in patients with chronic or acute HF that used LUS to assess dynamic changes or the prognostic value of pulmonary congestion. We included studies in adult populations, published in English, and conducted in ≥25 patients. Of 1327 identified studies, 13 (25–290 patients) met the inclusion criteria: six reported on dynamic changes in LUS findings (438 patients) and seven on the prognostic value of B-lines in HF (953 patients). In acute HF, B-line number changed within as few as 3 h of HF treatment. In acute HF, ≥15 B-lines on 28-zone LUS at discharge identified patients at a more than five-fold risk for HF readmission or death. Similarly, in ambulatory patients with chronic HF, ≥3 B-lines on five- or eight-zone LUS marked those at a nearly four-fold risk for 6-month HF hospitalization or death. Conclusions: Lung ultrasound findings change rapidly in response to HF therapy. This technique may represent a useful and non-invasive method to track dynamic changes in pulmonary congestion. Furthermore, residual congestion at the time of discharge in acute HF or in ambulatory patients with chronic HF may identify those at high risk for adverse events

The prognostic value of ultrasound lung comets in patients with pulmonary hypertension

Background: Ultrasound Lung Comets (ULCs) consist of multiple comet tails originating from thickened interlobular septa, due to water or connective tissue accumulation. Therefore they are detectable in patients with several lung diseases. Aim: To assess the prognostic value of ULCs in patients with pulmonary hypertension. Materials and methods: 33 in-hospital patients (age 67?13 years, 16 females) admitted to the Pneumology Division of Clinical Physiology in Pisa with diagnosis of idiopathic or secondary pulmonary hypertension were evaluated upon admission with a comprehensive 2D and Doppler echocardiography, and chest sonography with ULCs assessment. A patient ULC score was obtained by summing the number of comets from each of the scanning spaces in the anterior right and left hemithorax, from second to fifth intercostal spaces. By echocardiography, we measured Tricuspid Annular Plane Systolic Excursion (TAPSE) as an index of right ventricular function, and Pulmonary Artery Systolic Pressure (PASP) from tricuspid regurgitant jet velocity. Results: During the follow-up, 16 events occurred: 4 deaths, 12 new admission for the worsening of symptoms or respiratory function. A ROC analysis identified 14 ULCs as the best diagnostic cut-off to predict events with 94 % sensitivity and 71 % specificity. The 9-months event-free survival was higher in patients with no ULCs and lower in patients with ULCs (see Figure). There was a weak significant correlation between ULCs and PAPs (r=.541, p<.001) and no correlation between ULCs and TAPSE (r=.088, p=ns). Conclusion: ULCs are a simple, user-friendly, radiation-free bedside sign of thickened lung interlobular septa, adding a useful information for straightforward prognostic stratification of patients with pulmonary hypertension