Optical Density Ratio Research Articles

1779. Comparison of Two Zika IgM Antibody Capture Enzyme-linked Immunosorbent Assays (MAC-ELISA) in Symptomatic Patients from Dominican Republic, 2016

BackgroundZika virus (ZIKV) is a Flavivirus transmitted to humans by Aedes mosquitos. To assess the clinical presentation in 434 symptomatic patients (64 men, 370 women [65 pregnant; 305 nonpregnant]) during a ZIKV outbreak in the Dominican Republic (DR) in 2016, we evaluated clinical symptoms, ZIKV by qualitative detection of ZIKV RNA and ZIKV IgM by two MAC-ELISA assays, one from CDC and performed by the Florida Department of Health, Jacksonville, FL and one from InBios International Inc., Seattle, WA (Zika Virus Detect).MethodsThe Aptima ZIKV assay (Hologic, San Diego, CA) was used to detect ZIKV by transcription-mediated amplification RT–PCR in serum, plasma, or urine. Corresponding clinical symptomology reports were reviewed for all 434 patients. The results from the two MAC-ELISA assays were evaluated by linear regression analysis. The two MAC-ELISA assays were reported as optical density (OD) ratios from a sample with three different antigens (P/N ratio for CDC Zika MAC-ELISA and Zika Immune Status Ratio or ISR for InBios Zika Virus Detect MAC-ELISA).ResultsThere was a biphasic increase in ZIKV detection in April and late May/June 2016 in the 434 symptomatic patients. All 434 had one or more of four symptoms including rash, fever, conjunctivitis, and arthralgia. Linear regression analysis (log scale) of results from subject samples tested on the two MAC-ELISAs (282 total) revealed a slope of 1.172, y-intercept of 0.1584 and R2 of 0.587. In 88 RT–PCR-negative patients, 48 (54.5%) were positive by both MAC-ELISAs; 27 (30.7%) were negative by both MAC-ELISAs and 13 (14.7%) had discrepant results with a sensitivity of 85% for the InBios MAC-ELISA. The InBios also detected IgM in 54.4% of samples that were positive for ZIKV by RT–PCR attributable to errors in determining the days post symptom onset.ConclusionIn 2016 there was a biphasic spike of ZIKV-positive infections in 434 symptomatic men and women tested in DR. Both linear regression analysis and our comparative analysis in the ZIKV RT–PCR-positive and negative cohorts demonstrate that the InBios Zika Virus Detect MAC-ELISA provides diagnostic results comparable to the CDC Zika MAC-ELISA. Disclosures All authors: No reported disclosures.

Fundus-simulating phantom for calibration of retinal vessel oximetry devices

Retinal vessel oxygen supply is important for retinal tissue metabolism. Commonly used retinal vessel oximetry devices are based on dual-wavelength spectral measurement of oxyhemoglobin and deoxyhemoglobin. However, there is no traceable standard for reliable calibration of these devices. In this study, we developed a fundus-simulating phantom that closely mimicked the optical properties of human fundus tissues. Microchannels of precisely controlled topological structures were produced by soft lithography to simulate the retinal vasculature. Optical properties of the phantom were adjusted by adding scattering and absorption agents to simulate different concentrations of fundus pigments. The developed phantom was used to calibrate the linear correlation between oxygen saturation (SO2) level and optical density ratio in a dual-wavelength oximetry device. The obtained calibration factors were used to calculate the retinal vessel SO2 in both eyes of five volunteers aged between 24 and 27 years old. The test results showed that the mean arterial and venous SO2 levels after phantom calibration were coincident with those after empirical value calibration, indicating the potential clinical utility of the produced phantom as a calibration standard.

OPTICAL DENSITY RATIO OF THE SUBRETINAL FLUID IN CHOROIDAL MELANOMA AND METASTASIS.

To investigate the optical density (OD) characteristics and clinical relevance of subretinal fluid in choroidal melanoma and choroidal metastasis. Medical records of patients with choroidal melanoma and choroidal metastasis who underwent optical coherence tomography examinations at diagnosis before any intervention and whose optical coherence tomography scans showed sufficient subretinal fluid for sampling were reviewed. The highest quality B-scan containing subretinal fluid was analyzed. Optical density measurements obtained using ImageJ and optical density ratios (ODRs) were calculated as subretinal fluid OD divided by vitreous OD. Patient details and diagnosis were masked during measurements. Nonparametric tests for independent samples were used to detect differences in ODR between groups. Of the 39 cases of choroidal tumors that met the inclusion criteria, 14 were diagnosed as metastases and 25 as malignant melanoma. There were no significant differences between the groups in age, optical coherence tomography acquisition and parameters of quality, and vitreous OD. Optical density ratio values were significantly lower in metastases cases (mean 0.68, SD ±0.18) than in melanoma cases (0.95 ± 0.33, P = 0.006). Receiver operating characteristic curve analysis yielded an optimal cutoff of ODR = 0.771 (sensitivity = 78.6%, specificity = 72.0%). Optical density ratio can serve as an additional test to differentiate between choroidal melanoma and choroidal metastases.

A rapid method for post-antibiotic bacterial susceptibility testing.

Antibiotic susceptibility testing is often performed to determine the most effective antibiotic treatment for a bacterial infection, or perhaps to determine if a particular strain of bacteria is becoming drug resistant. Such tests, and others used to determine efficacy of candidate antibiotics during the drug discovery process, have resulted in a demand for more rapid susceptibility testing methods. Here, we have developed a susceptibility test that utilizes chemiluminescent determination of ATP release from bacteria and the overall optical density (OD600) of the bacterial solution. Bacteria release ATP during a growth phase or when they are lysed in the presence of an effective antibiotic. Because optical density increases during growth phase, but does not change during bacterial lysing, an increase in the ATP:optical density ratio after the bacteria have reached the log phase of growth (which is steady) would indicate antibiotic efficacy. Specifically, after allowing a kanamycin-resistant strain of Escherichia coli (E.coli) to pass through the growth phase and reach steady state, the addition of levofloxacin, an antibiotic to which E. coli is susceptible, resulted in a significant increase in the ATP:OD600 ratio in comparison to the use of kanamycin alone (1.80 +/- 0.50 vs. 1.12 +/- 0.28). This difference could be measured 20 minutes after the addition of the antibiotic, to which the bacteria are susceptible, to the bacterial sample. Furthermore, this method also proved useful with gram positive bacteria, as the addition of kanamycin to a chloramphenicol-resistant strain of Bacillus subtilis (B. subtilis) resulted in an ATP:OD600 ratio of 2.14 +/- 0.26 in comparison to 0.62 +/- 0.05 for bacteria not subjected to the antibiotic to which the bacteria are susceptible. Collectively, these results suggest that measurement of the ATP:OD600 ratio may provide a susceptibility test for antibiotic efficacy that is more rapid and quantitative than currently accepted techniques.

A novel pooled milk test strategy for the herd level diagnosis of Dictyocaulus viviparus

Current diagnostic methods for detecting the presence or absence of Dictyocaulus viviparus in dairy herds, are insensitive when based on detection of antibody levels in bulk tank milk (BTM). Here we present a novel technique to confirm the presence of the parasite based on a pooled-milk sample from 10 randomly selected first – lactation heifers (FLH). This study was run in two parts. First, a longitudinal study was performed to look at infection dynamics in milk samples across the grazing season using a prototype ELISA developed by Svanova (Boehringer-Ingelheim, Uppsala). We identified that mean ODR values in milk samples from FLH was significantly higher than that for older cows (0.13 versus 0.07 respectively, p < 0.001) suggesting that samples from the FLH cohort should be pooled to produce the test. Second, the pooled – milk test was evaluated on a cross-sectional survey of UK dairy herds (n = 25 grazing and n = 25 zero-grazing herds) to evaluate test performance under field conditions. The optical density ratio (ODR) cut-off value for our pooled-milk test using 10 FLH milk samples was optimal at a value of 0.16. Pooling 10 FLH samples created a sensitivity and specificity of 66.7% and 95.5% respectively. In comparison, whole-herd BTM samples had a maximum sensitivity of 37.5% and specificity of 63.6% at an ODR cut-off of 0.18. The area under the curve according to receiver-operative-characteristic (ROC) analysis was high for the 10-heifer test (0.87) but poor for the whole herd BTM testing (0.45). This study provides a more sensitive diagnostic test strategy for the screening of D.viviparus in dairy herds. Testing herds at the end of a grazing season would facilitate the planning of effective control measures, such as the use of the lungworm vaccination or strategic deworming, for the following grazing season. This may prove to be a useful test strategy for the diagnosis of a variety of parasitic diseases of livestock.

Higher DNA Yield for Epidemiological Studies: A Better Method for DNA Extraction from Blood Clot.

Blood clots can be used to extract DNA, but they are not as widely used as whole blood or buffy coats. This is due not only because of the relatively low DNA yields and quality obtained from blood clots, but also because sampling prior to DNA extraction is more difficult. To solve these problems, we compared several clot liquefaction methods, determined the four most feasible methods, and subsequently performed a comparative analysis among them. We compared the yields and optical density ratios of the resulting DNA samples and assessed their integrity using agarose gel electrophoresis, polymerase chain reaction, and next-generation sequencing (NGS). Each of the four methods has advantages and disadvantages. But in general, higher yields of DNA with better quality and integrity were obtained using the high-shear homogenization method than using the other three methods. Additionally, this method is cost-effective and feasible at large operational scales. The DNA yields and A260/280 ratios were optimal and stable, the operation time and labor costs were acceptable, and the success rate of NGS applications was 99.74%. Furthermore, we developed a simple and rapid method for cleaning the homogenizer head to remove residual samples. According to our experimental results, our cleaning method effectively eliminated the risk of cross-contamination caused by the homogenizer head. We recommend high-shear homogenization as a superior method for clot liquefaction. We believe that this method is worthy of large-scale application as it can improve the efficiency of DNA extraction from clots, thus reducing labor and economic costs.

Low intensity ultrasound mechanical index as a parameter affecting of ability of proliferation and collagene type 1 expression of cells

Introduction: Mechanical index (MI) is used for quantifying acoustic cavitation and the relationship between acoustic pressure and the frequency. In this study, modeling of the MI was applied to provide treatment protocol and to understand the effective physical processes on reproducibility and gene expression of fibroblast cells. Skin damage can occur of burn, cuts, abrasions and ulcers to varying degrees of severity. Fibroblasts are the major cell type in connective tissue and are critical for tissue restoration and remodeling after injury. Therapeutic ultrasound is commonly used to enhance the repair of tissue injuries and reduce associated pain. It was noted that these effects required specific exposure conditions . So in this study, MI of threshold 0.2 in water and heigher (0.4) and lower (0.1) than it were investigatrd on the proliferation and collagene type 1 expression of fibroblast. Materials and Methods: The acoustic pressure and MI equations are modeled and solved to estimate optimal MI for 1MHz and 40 kHz frequencies. Radial and axial acoustic pressure distribution was extracted. mechanical index of 0.10, 0.20, 0.40 that were compared with control and sham groups in continuous mode. The mature guniea pig skin was cut into small pieces (1mm2) and explanted in Medium. fibroblast cells isolated and growed of the skin explant after 25 days. The proliferation was calculated as a ratio of optical density (OD) of cells in MTT assay and type1 collagene expression was quantified with real time PCR utilizing SYBR. Results: The optical density(OD) of experimental groups was normalized to that of corresponding 80000 groups at the day of 5th. Increasing reproducibility in the group of 0.21 mechanical index had the maximum reproducible (0.62±0.05) compared to control group (0.38±0.03). Fold change of expreesion level of fibroblast cells in 0.2 mechanical index has been achieved 4.35 ±0.03 compared to the control group. Conclusion: Low intensity ultrasound with 0.20 MI is more effective on the proliferation rate and type1 collagene of Fibroblast cells. This model provides proper treatment planning in vitro and in vivo by estimating the cavitation phenomenon. Finally, the effect of low intensity ultrasound based on MI in the best limit obtained and suggested to used in skin wound healing, cell therapy and transplant.

Risk factors for the presence of Fasciola hepatica antibodies in bulk-milk samples and their association with milk production decreases, in Cuban dairy cattle

BackgroundWorldwide, Fasciola hepatica infection causes high production losses in the livestock industry. Recently, studies have analyzed the association between measurements of F. hepatica infection intensity and herd management practices. The aim of the present study, the first of its kind in a subtropical region, was to evaluate associations between F. hepatica bulk-tank milk ELISA results with herd management factors and milk yield in dairy herds, in Camagüey, Cuba. The SVANOVIR® F. hepatica-AB ELISA was used to measure F. hepatica antibody levels in a random sample of 516 dairy herds during the period of May–July of 2014. Farm management practice data were collected using a questionnaire.ResultsWith 82% of the herds testing positive, the results indicate that F. hepatica is very widespread in this area. Reductions in milk production of 18 and 32% were observed in herds with Optical Density Ratios (ODR) of 0.3–0.6 and > 0.6, respectively, when compared to herds with ODR < 0.3. Overall, the longer the milking cows were put out to pasture, the higher the levels of anti-parasite antibodies. Co-grazing with sheep and goats also significantly increased the risk of high ODR.ConclusionsOur data show a widespread occurrence of the parasite as well as a major potential impact of the infection on the Cuban development goal of becoming self-sufficient in milk production. Our risk factor analysis suggests that the prevention of infection around water sources, and the separation of cattle from small ruminants could be useful control measures. This is the first epidemiological survey of F. hepatica abundance, and associated reductions in milk yield, in dairy herds in Cuba.

Retinal oximetry and systemic arterial oxygen levels.

Retinal oximetry and systemic arterial oxygen levels.

Bulk tank milk ELISA to detect IgG1 prevalence and clustering to determine spatial distribution and risk factors of Fasciola hepatica-infected herds in Mexico.

Fasciola hepatica is a helminth parasite that causes huge economic losses to the livestock industry worldwide. Fasciolosis is an emerging foodborne zoonotic disease that affects both humans and grazing animals. This study investigated the associations between climatic/environmental factors (derived from satellite data) and management factors affecting the spatial distribution of this liver fluke in cattle herds across different climate zones in three Mexican states. A bulk-tank milk (BTM) IgG1 enzyme-linked immunosorbent assay (ELISA) test was used to detect F. hepatica infection levels of 717 cattle herds between January and April 2015. Management data were collected from the farms by questionnaire. The parasite's overall herd prevalence and mean optical density ratio (ODR) were 62.76% and 0.67, respectively. The presence of clustered F. hepatica infections was studied using the spatial scan statistic. Three marked clusters in the spatial distribution of the parasite were observed. Logistic regression was used to test three models of potential statistical association from the ELISA results using climatic, environmental and management variables. The final model based on climatic/environmental and management variables included the following factors: rainfall, elevation, proportion of grazed grass in the diet, contact with other herds, herd size, parasite control use and education level as significant predictors. Geostatistical kriging was applied to generate a risk map for the presence of parasites in dairy herds in Mexico. In conclusion, the spatial distribution of F. hepatica in Mexican cattle herds is influenced by multifactorial effects and should be considered in developing regionally adapted control measures.

Development of a high-throughput assay to detect antibody inhibition of low pH induced conformational changes of influenza virus hemagglutinin.

Many broadly neutralizing antibodies (bnAbs) bind to conserved areas of the hemagglutinin (HA) stalk region and can inhibit the low pH induced HA conformational changes necessary for viral membrane fusion activity. We developed and evaluated a high-throughput virus-free and cell-free ELISA based low pH induced HA Conformational Change Inhibition Antibody Detection Assay (HCCIA) and a complementary proteinase susceptibility assay. Human serum samples (n = 150) were tested by HCCIA using H3 recombinant HA. Optical density (OD) ratios of mAb HC31 at pH 4.8 to pH 7.0 ranged from 0.87 to 0.09. Our results demonstrated that low pH induced HA conformational change inhibition antibodies (CCI) neutralized multiple H3 strains after removal of head-binding antibodies. The results suggest that HCCIA can be utilized to detect and characterize CCI in sera, that are potentially broadly neutralizing, and serves as a useful tool for evaluating universal vaccine candidates targeting the HA stalk.

P2Y12 shRNA treatment decreases SGC activation to relieve diabetic neuropathic pain in type 2 diabetes mellitus rats.

Diabetic neuropathic pain is a common complication of type 2 diabetes mellitus (DM). Activation of satellite glial cells (SGCs) in the dorsal root ganglia (DRG) plays a crucial role in neuropathic pain through the release of proinflammatory cytokines. The P2Y12 receptor is expressed in SGCs of the DRG. In this study, our aim was to investigate the role of the P2Y12 receptor on the pathological changes in diabetic neuropathic pain. The present study showed that diabetic neuropathic pain increased mechanical and thermal hyperalgesia in type 2DM model rats. The results showed that the expression levels of P2Y12 messenger RNA (mRNA) and protein in DRG SGCs were increased in DM model rats compared with control rats. Glial fibrillary acidic protein (GFAP) and interleukin-1β (IL-1β) expression levels in the DRG were increased in DM rats. Upregulation of GFAP is a marker of SGC activation. Targeting the P2Y12 receptor by short hairpin RNA (shRNA) decreased the upregulated expression of P2Y12 mRNA and protein, coexpression of P2Y12 and GFAP, the expression of GFAP, IL-1β, and tumor necrosis factor-receptor 1in the DRG of DM rats, and relieved mechanical and thermal hyperalgesia in DM rats. After treatment with the P2Y12 receptor shRNA, the enhancing integrated OPTICAL density (IOD) ratios of p-P38 MAPK to P38 mitogen activated protein kinase (MAPK) in the DM rats treated with P2Y12 shRNA were significantly lower than that in the untreated DM rats. Therefore, P2Y12 shRNA treatment decreased SGC activation to relieve mechanical and thermal hyperalgesia in DM rats.

Ostertagia ostertagi antibodies in bulk tank milk from dairy cattle in Italy: A nation-wide survey.

The objective of this study was to investigate the exposure to Ostertagia ostertagi in dairy cattle herds across Italy through measurement of antibody concentration in the bulk tank milk (BTM) and to evaluate the possible effect of regions, seasons and pasture management practices on the level of exposure to the parasite. The O. ostertagi antibody levels in milk were determined using a commercial ELISA kit (SVANOVIR® O. ostertagi-Ab) and expressed as optical density ratio (ODR). From March 2015 to September 2017, BTM samples were collected in 1209 dairy cattle farms located in 15 regions of Northern, Central and Southern Italy. As reported in previous studies, BTM samples were classified in three different categories according to the level of exposure to O. ostertagi as follows: (i) positive with ODR values >0.60; (ii) negative with ODR values <0.30 and (iii) grey zone with ODR values between 0.30 and 0.60. Finally, differences in ODR values between regions, seasons and herd management practices were studied using the one-way analysis of variance. The overall mean ODR revealed a value of 0.49 in Italy; in particular, dairy cattle farms located in Southern Italy showed the highest O. ostertagi BTM ODR values than the other regions (p < 0.05). The ODR values ranged from 0.45 in autumn to 0.53 in spring and the seasonal difference was significant (p < 0.05). Furthermore, a positive association was found between the ODR values and the access to pasture; herds with access to pasture showed significantly higher titres (p < 0.0001) of O. ostertagi antibodies in milk (mean ODR = 0.63) than in those in total-confinement housing (mean ODR = 0.42). This study, the first of its kind in Italy, will provide a quantitative assessment exposure to O. ostertagi of Italian dairy herds and represents a significant step forward in evidence-based medicine for dairy veterinarians, advisors and farmers.

Isolation of high-quality RNA from intervertebral disc tissue via pronase predigestion and tissue pulverization.

The isolation of high‐quality RNA from the intervertebral disc and especially from the nucleus pulposus is challenging due to the low cellularity and high proteoglycan content of this tissue. In this study, we report a simple modification of the standard guanidinium thiocyanate‐phenol‐chloroform extraction method, which involves enzymatic predigestion of the tissue prior to standard RNA isolation. Yield, purity and integrity of RNA isolated from bovine nucleus pulposus, inner annulus fibrosus and outer annulus fibrosus were compared among complete matrix digestion, predigestion and pulverization, pulverization alone, and pulverization followed by on‐column purification. With predigestion, the average yield of RNA obtained from bovine nucleus pulposus was 8.82 ± 2.05 ng/mg of wet tissue with 260/280 and 260/230 optical density ratios of 1.91 ± 0.15 and 1.84 ± 0.30, respectively. RIN analysis indicated that RNA quality was best preserved with the predigestion method (RNA integrity number > 7), and the extracted RNA was suitable for real‐time polymerase chain reaction. This method is of importance for gene expression studies on intervertebral disc development, degeneration and repair, and we anticipate that it may be further applied to other tissues rich in proteoglycans.

Combining ODR and Blood Vessel Tracking for Artery-Vein Classification and Analysis in Color Fundus Images.

PurposeThis study aims to develop a fully automated algorithm for artery–vein (A-V) and arteriole-venule classification and to quantify the effect of hypertension on A-V caliber and tortuosity ratios of nonproliferative diabetic retinopathy (NPDR) patients.MethodsWe combine an optical density ratio (ODR) analysis and blood vessel tracking (BVT) algorithm to classify arteries and veins and arterioles and venules. An enhanced blood vessel map and ODR analysis are used to determine the blood vessel source nodes. The whole vessel map is then tracked beginning from the source nodes and classified as vein (venule) or artery (arteriole) using vessel curvature and angle information. Fifty color fundus images from NPDR patients are used to test the algorithm. Sensitivity, specificity, and accuracy metrics are measured to validate the classification method compared to ground truths.ResultsThe combined ODR-BVT method demonstrates 97.06% accuracy in identifying blood vessels as vein or artery. Sensitivity and specificity of A-V identification are 97.58%, 97.81%, and 95.89%, 96.68%, respectively. Comparative analysis revealed that the average A-V caliber and tortuosity ratios of NPDR patients with hypertension have 48% and 15.5% decreases, respectively, compared to that of NPDR patients without hypertension.ConclusionsAutomated A-V classification has been achieved by combined ODR-BVT analysis. Quantitative analysis of color fundus images verified robust performance of the A-V classification. Comparative quantification of A-V caliber and tortuosity ratios provided objective biomarkers to differentiate NPDR groups with and without hypertension.Translational RelevanceAutomated A-V classification can facilitate quantitative analysis of retinal vascular distortions due to diabetic retinopathy and other eye conditions and provide increased sensitivity for early detection of eye diseases.

Herd-level seroprevalence of Fasciola hepatica and Ostertagia ostertagi infection in dairy cattle population in the central and northeastern Poland

BackgroundFasciola hepatica and Ostertagia ostertagi infections are widespread in cattle population of Europe, however data on their prevalence in Poland are only fragmentary. Therefore, the cross-sectional study was carried out to determine the herd-level seroprevalence of F. hepatica and O. ostertagi infection in dairy cattle population in the central and north-eastern provinces Poland, and to identify basic local risk factors for these infections. In total, 598 herds were enrolled, 394 (65.9%) in the north-eastern province and 204 (34.1%) in the central province. In each herd the questionnaire survey was conducted and bulk-tank milk (BTM) sample was collected and screened using two indirect immunoenzymatic tests. Optical density ratio (ODR) was regarded as the quantitative proxy of exposure to either of the two parasites.ResultsBoth Fasciola and Ostertagia ELISA ODR in the north-eastern province was significantly higher than ODR in the central province. At the cut-off value of ODR = 0.27 the true herd-level seroprevalence of F. hepatica was 79.6% (95% CI: 74.0%, 84.3%) in the north-eastern province and 13.0% (95% CI: 5.3%, 21.7%) in the central province. At the cut-off of ODR = 0.50151 of 188 herds (80.3%, 95% CI: 74.1%, 85.4%) were seropositive for O. ostertagi in the north-eastern province and only 70 of 136 herds (51.5%, 95% CI: 43.1%, 59.7%) were seropositive in the central province. Location of a herd in the north-eastern province, longer grazing period practiced in a herd and > 50%-share of grazing grass in roughage were all positively related to the increase in exposure to both parasites. Moreover, the use of hay or haylage as main roughage proved to be positively related to the increase in exposure to F. hepatica.ConclusionsF. hepatica and O. ostertagi are widespread in cattle population in Poland, however their occurrence at a herd-level varies between different regions of Poland. This diversity can only partly be explained by different herd management, and appears linked to environmental and climate conditions typical for these regions.

Bulk tank milk prevalence and production losses, spatial analysis, and predictive risk mapping of Ostertagia ostertagi infections in Mexican cattle herds.

This study investigated the prevalence, production losses, spatial clustering, and predictive risk mapping in different climate zones in five states of Mexico. The bulk tank milk samples obtained between January and April 2015 were analyzed for antibodies against Ostertagia ostertagi using the Svanovir ELISA. A total of 1204 farm owners or managers answered the questionnaire. The overall herd prevalence and mean optical density ratio (ODR) of parasite were 61.96% and 0.55, respectively. Overall, the production loss was approximately 0.542kg of milk per parasited cow per day (mean ODR = 0.92, 142 farms, 11.79%). The spatial disease cluster analysis using SatScan software indicated that two high-risk clusters were observed. In the multivariable analysis, three models were tested for potential association with the ELISA results supported by climatic, environmental, and management factors. The final logistic regression model based on both climatic/environmental and management variables included the factors rainfall, elevation, land surface temperature (LST) day, and parasite control program that were significantly associated with an increased risk of infection. Geostatistical kriging was applied to generate a risk map for the presence of parasite in dairy cattle herds in Mexico. The results indicate that climatic and meteorological factors had a higher potential impact on the spatial distribution of O. ostertagi than the management factors.

Diagnosis of bovine dictyocaulosis by bronchoalveolar lavage technique: A comparative study using a Bayesian approach

Bovine dictyocaulosis is a pulmonary parasitic disease present in temperate countries, with potential important clinical and economic impacts. The Baermann technique is routinely used despite its low sensitivity in adult cows. Recently developed serological tests seem to offer better sensitivity, but validations of these tests in field conditions are few. We aimed to study two non-previously evaluated diagnosis methods of dictyocaulosis based on bronchoalveolar lavage sampling (BAL), which allows finding lungworm stages in the lungs as well as determination of eosinophilia. We compared them to the Baermann technique and serological tests. As no gold standard was available, we performed a Bayesian analysis by the simultaneous use of latent class and mixture models. The study was carried out during the 2015 pasture season on 60 adult cows originating from 11 herds with clinical signs of dictyocaulosis, and 10 apparently healthy cows originating from the teaching herd of VetAgro Sup, in France. Prevalence of infection was highly variable among herds with clinical signs (10–90%). Despite a maximal specificity (100%), the sensitivity of parasitological methods was low (7.4% for the Baermann sedimentation and 24.7% for the examination of BAL fluids). Better results were observed with serology (Se = 74.9%, Sp = 85.5%) with an optimal cut-off value estimated at 0.397 for the optical density ratio. Even better results were obtained with the count of eosinophil in BAL (Se = 89.4%, Sp = 85.2%) with an optimal cut-off value estimated at 4.77% for the eosinophil proportion. The BAL is a relevant diagnostic method of dictyocaulosis for practitioners due to the opportunity to perform two analyses (direct parasitic research and the eosinophil count) and to its good sensitivity and specificity.

22. Immune Response to Stenotrophomonas maltophilia in Cystic Fibrosis Patients

Background: Stenotrophomonas maltophilia is one of the most common multidrug-resistant organisms isolated from the cystic fibrosis (CF) respiratory tract but it is unknown how it influences the long term clinical outcomes of CF patients.&#x0D; &#x0D; Objective/Hypothesis: To characterize the immune response to S. maltophilia and its association with clinical outcomes in CF patients over time. &#x0D; Methods: This was a longitudinal study from 2007-2014 of CF patients followed at The Hospital for Sick Children and St. Michael’s Hospital. All patients were classified as: 1) those with chronic S. maltophilia: ³2 positive cultures/year, 2) intermittent S. maltophilia: 1 positive sputum culture/year, and 3) no S. maltophilia cultures/year with and without chronic P. aeruginosa. IgG/IgA/IgM serologic responses were measured in serial sera samples by ELISA using whole cell S. maltophilia antigen. Results were calculated as the ratio of the average serum sample optical density to the average optical density of the negative control wells. Antibody levels for each patient were compared longitudinally to their rate of decline in FEV1 % predicted, body mass index, and rate of hospitalization.&#x0D; &#x0D; Results: S. maltophilia antibody levels were measured in 350 sera samples from 113 CF patients. Median baseline antibody levels were 1.56 (range 0.996-5.15) in chronic patients, 1.09 (range 0.907-3.79) in intermittent patients, and 1.12 (range 0.737-4.86) in patients with no S. maltophilia. &#x0D; Conclusions:&#x0D; Preliminary data suggests antibody levels to be significantly higher in patients with chronic S. maltophilia, and no significant difference between intermittent S. maltophilia and no S. maltophilia.

Automated classification and quantitative analysis of arterial and venous vessels in fundus images.

It is known that retinopathies may affect arteries and veins differently. Therefore, reliable differentiation of arteries and veins is essential for computer-aided analysis of fundus images. The purpose of this study is to validate one automated method for robust classification of arteries and veins (A-V) in digital fundus images. We combine optical density ratio (ODR) analysis and blood vessel tracking algorithm to classify arteries and veins. A matched filtering method is used to enhance retinal blood vessels. Bottom hat filtering and global thresholding are used to segment the vessel and skeleton individual blood vessels. The vessel tracking algorithm is used to locate the optic disk and to identify source nodes of blood vessels in optic disk area. Each node can be identified as vein or artery using ODR information. Using the source nodes as starting point, the whole vessel trace is then tracked and classified as vein or artery using vessel curvature and angle information. 50 color fundus images from diabetic retinopathy patients were used to test the algorithm. Sensitivity, specificity, and accuracy metrics were measured to assess the validity of the proposed classification method compared to ground truths created by two independent observers. The algorithm demonstrated 97.52% accuracy in identifying blood vessels as vein or artery. A quantitative analysis upon A-V classification showed that average A-V ratio of width for NPDR subjects with hypertension decreased significantly (43.13%).