Person: Álvarez Sánchez, Julio
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First Name
Julio
Last Name
Álvarez Sánchez
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Veterinaria
Department
Sanidad Animal
Area
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62 results
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Item Evaluation of a new enzyme-linked immunosorbent assay for the diagnosis of tuberculosis in goat milk(Research in Veterinary Science, 2020) Roy, A.; Infantes-Lorenzo, J.A.; Dominguez, M.; Moreno, I.; Pérez Sancho, Marta; García Benzaquén, Nerea; García-Seco Romero, María Teresa; Álvarez Sánchez, Julio; Romero Martínez, Beatriz; Gortázar, C.; Juan Ferré, Lucía De; Domínguez Rodríguez, Lucas José; Bezos Garrido, JavierCaprine tuberculosis (TB) is a zoonosis with sanitary and economic repercussions. Caprine TB control programs are based on a test and cull strategy using the intradermal tuberculin tests and slaughterhouse surveillance. However, this approach is not always feasible and may have a limited sensitivity under specific circumstances. In this study, performance of a new experimental test based on the P22 protein complex (P22 ELISA) was evaluated in two TB-infected herds using milk and serum samples and compared with cell-based diagnostic tests. Samples from a low (n = 62, herd 1) and a high (n = 52, herd 2) TB prevalence herd were selected. Moreover, bulk tank milk samples from both herds were analysed using the P22 ELISA. At the end of the study, a group of animals (n = 21) was euthanized and subjected to post-mortem analysis and bacteriological culture. Significant differences (p < .001) on the qualitative and quantitative (ODs) results were observed between herds using both serum and milk samples in the P22 ELISA. The correlation observed in the quantitative results obtained in serum and milk samples was very strong in animals from flock 2 (rs = 0.91) and moderate in animals from flock 1 (rs = 0.46). Among the slaughtered animals, the P22 ELISA detected a higher proportion of lesion-culture positive animals than cell-based diagnostic tests (61.9 and 66.7% using milk and serum samples, respectively). The P22 ELISA using milk samples demonstrated a similar sensitivity compared with serum samples, suggesting it might be a valuable test for TB control in dairy goats.Item Epidemiological investigation of bovine tuberculosis herd breakdowns in Spain 2009/2011(PLoS ONE, 2014) Guta, Sintayehu; Casal, Jordi; Napp, Sebastian; Saez, Jose Luis; Garcia Saenz, Ariadna; Perez de Val, Bernat; Romero Martínez, Beatriz; Alvarez, Julio; Allepuz, Alberto; Álvarez Sánchez, JulioWe analyzed the most likely cause of 687 bovine tuberculosis (bTB) breakdowns detected in Spain between 2009 and 2011 (i.e., 22% of the total number of breakdowns detected during this period). Seven possible causes were considered: i) residual infection; ii) introduction of infected cattle from other herds; iii) sharing of pastures with infected herds; iv) contiguous spread from infected neighbor herds; v) presence of infected goats in the farm; vi) interaction with wildlife reservoirs and vii) contact with an infected human. For each possible cause a decision tree was developed and key questions were included in each of them. Answers to these key questions lead to different events within each decision tree. In order to assess the likelihood of occurrence of the different events a qualitative risk assessment approach was used. For this purpose, an expert opinion workshop was organized and ordinal values, ranging from 0 to 9 (i.e., null to very high likelihood of occurrence) were assigned. The analysis identified residual infection as the most frequent cause of bTB breakdowns (22.3%; 95%CI: 19.4-25.6), followed by interaction with wildlife reservoirs (13.1%; 95%CI: 10.8-15.8). The introduction of infected cattle, sharing of pastures and contiguous spread from infected neighbour herds were also identified as relevant causes. In 41.6% (95%CI: 38.0-45.4) of the breakdowns the origin of infection remained unknown. Veterinary officers conducting bTB breakdown investigations have to state their opinion about the possible cause of each breakdown. Comparison between the results of our analysis and the opinion from veterinary officers revealed a slight concordance. This slight agreement might reflect a lack of harmonized criteria to assess the most likely cause of bTB breakdowns as well as different perceptions about the importance of the possible causes. This is especially relevant in the case of the role of wildlife reservoirs.Item Molecular epidemiology of Types I/III strains of Mycobacterium avium subspecies paratuberculosis isolated from goats and cattle(Veterinary Microbiology, 2006) Juan Ferré, Lucía De; Álvarez Sánchez, Julio; Aranaz Martín, Alicia; Rodríguez Bertos, Antonio Manuel; Romero Martínez, Beatriz; Bezos Garrido, Javier; Mateos García, Ana Isabel; Domínguez Rodríguez, Lucas JoséMolecular characterization of Mycobacterium avium subsp. paratuberculosis (M. a. paratuberculosis) isolates classifies them into three groups: cattle or Type II, sheep or Type I, and intermediate or Type III. To avoid problems associated with characterization of extremely slow growth strains, PCR-based techniques that divide the M. a. paratuberculosis strains in two main groups (cattle or Type II, and sheep or Types I/III) can be performed. The objectives of this study were to characterize the M. a. paratuberculosis isolates identified by different PCR-based tests (IS1311-PCR and restriction endonuclease analysis, PCR test based on a DNA sequence difference, and a PCR aimed at three Type I-specific loci), and to determine the clinical and epidemiological implications of Types I/III M. a. paratuberculosis strains in livestock. One hundred and fifty-eight M. a. paratuberculosis strains from domestic ruminants were analyzed. One hundred and six M. a. paratuberculosis isolates (61 from goats and 45 from cattle) were classified as Type II strains; and 52 (29 from cows, 20 from goats, and three from sheep) were included in the Types I/III. The Types I/III M. a. paratuberculosis strains were associated to Spanish native breeds. The majority of these animals had not been in direct or indirect contact with sheep flocks infected with M. a. paratuberculosis. This fact should be taken into account when implementing paratuberculosis control programs.Item Effect of a recent intradermal test on the specificity of P22 ELISA for the diagnosis of caprine tuberculosis(Frontiers in Veterinary Science, 2024) Romero Martínez, Beatriz; Juan Ferré, Lucía De; Domínguez Rodríguez, Lucas José; Álvarez Sánchez, Julio; Bezos Garrido, Javier; Velasco, Carlos; Ortega, Javier; Domínguez, Mercedes; Ricón, Jaime; Moreno, InmaculadaCaprine tuberculosis (TB) is a zoonotic disease caused by members of the Mycobacterium tuberculosis complex. TB eradication programs in goats are based on the single and comparative intradermal tuberculin tests (SITT and CITT, respectively). Antibody-based diagnostic techniques have emerged as potential diagnostic tools for TB. P22 ELISA has been previously evaluated using samples collected after the intradermal tuberculin tests to maximize the sensitivity, a phenomenon known as booster effect. However, there is no information available on whether the use of this diagnostic strategy could lead to a decrease of its specificity (Sp). The aim of the present study was to elucidate the interference effect of a recent CITT on the Sp of the P22 ELISA in serum and milk samples collected at different times after the CITT from a TB-free herd (n = 113). The number of reactors to P22 ELISA was significantly higher (p < 0.01) on serum samples collected 15 days post-CITT compared to day 0, showing a decrease in Sp from 99.1% (95% CI; 95.2–99.8%) to 88.5% (95% CI; 81.3–93.2%). The number of reactors and the quantitative values of P22 ELISA were significantly higher (p < 0.01) in serum samples compared to milk. No significant (p > 0.05) changes in the Sp of the P22 ELISA were observed throughout the different time samplings using milk No significant (p > 0.05) changes were observed on days 30 and 60 post-CITT. In conclusion, the booster effect strategy may significantly decrease the Sp of P22 ELISA in TB-free herds when serum samples are used but not when milk is tested.Item Epidemiological factors associated with the exposure of cattle to Coxiella burnetii in the Madrid region of Spain(The Veterinary Journal, 2012) Álvarez Sánchez, Julio; Perez, A.; Mardones, F.O.; Pérez Sancho, Marta; García-Seco Romero, María Teresa; Pagés, E.; Mirat, F.; Díaz, R.; Carpintero, J.; Domínguez Rodríguez, Lucas JoséDomestic ruminants are considered to be the major source of Coxiella burnetii, the causative agent of Q fever. Even though Q fever is considered to be present worldwide, its distribution in many areas and countries remains unknown. Here, a serological assay was used to estimate the seroprevalence of C. burnetii in cattle in the Madrid region of Spain, to assess its spatial distribution, and to identify risk factors associated with positive results. Ten animals from each of 110 herds (n=1100) were randomly selected and analyzed using an ELISA test. In addition, epidemiological information, at both the herd and individual level, was collected. Variables for which an association with test results was detected in a bivariate analysis were included as predictors (main effects) in a multivariable logistic regression model. Herd and individual seroprevalences were 30% (95% CI=22.2-39.1) and 6.76% (95% CI=5.42-8.41), respectively, and a strong spatial dependence was identified at the first neighbour level using the Cuzick-Edwards test. Production type (dairy >beef >bullfighting) and age of animals (old vs. young) were the only variables significantly associated (P<0.05) with positive serological results at the herd and individual levels, respectively. These results indicate that cattle are exposed to C. burnetii in the Madrid region The high herd seroprevalence found in dairy herds (75%) indicates a higher risk of infection (probably for management reasons) whereas no C. burnetii positive bullfighting herds were identified.Item Accuracy of Tests for Diagnosis of Animal Tuberculosis: Moving Away from the Golden Calf (and towards Bayesian Models)(Transboundary and Emerging Diseases, 2023) Álvarez Sánchez, Julio; Pozo Piñol, Pilar; Gómez-Buendía, Alberto; Picasso-Risso, Catalina; Branscum, Adam; Pérez, AndrésThe last decades have seen major efforts to develop new and improved tools to maximize our ability to detect tuberculosis-infected animals and advance towards the objective of disease control and ultimately eradication. Nevertheless, there is still uncertainty regarding test performance due to the wide range of specificity and especially sensitivity estimates published in the scientific literature. Here, we performed a systematic review of the literature on studies that evaluated the performance of tuberculosis diagnostic tests used in animals through Bayesian Latent Class Models (BLCMs), which do not require the application of a (fallible) reference procedure to classify animals as infected with tuberculosis or not. BLCM-based sensitivity and specificity estimates deviated from those obtained using a reference procedure for certain antemortem tests: an overall lower sensitivity of skin tests and serology and a higher sensitivity of interferon-gamma (IFN-γ) assays was reported. In the case of postmortem diagnostic tests, sensitivity estimates from BLCMs were similar to estimates from studies based on other methodologies. For specificity, the range of BLCM-based estimates was narrower than those based on a reference test, reaching values close to 100% (but lower in the case of IFN-γ assays). In conclusion, Bayesian methods have been increasingly applied for the evaluation of tuberculosis diagnostic tests in animals, yielding results that differ (sometimes substantially) from previously reported test performance in the literature, particularly for in vivo tests and sensitivity estimates. Newly developed models that allow adjustment for relevant factors (e.g., age, breed, region, and herd size) can contribute to the generation of more unbiased estimates of test performance. Nevertheless, although BLCMs for tuberculosis do not require the use of an imperfect reference procedure and are therefore not influenced by its limited performance, they require careful implementation, and transparent systematic reporting should be the norm.Item The expression of aminoglycoside resistance genes in integron cassettes is not controlled by riboswitches(Nucleic Acids Research, 2022) Hipólito, Alberto; García Pastor, Lucía; Trigo da Roza, Filipa; Kieffer, Nicolas; Vergara, Ester; Jové, Thomas; Escudero García-Calderón, José Antonio; Blanco Torres, Paula; Álvarez Sánchez, JulioRegulation of gene expression is a key factor influencing the success of antimicrobial resistance determinants. A variety of determinants conferring resistance against aminoglycosides (Ag) are commonly found in clinically relevant bacteria, but whether their expression is regulated or not is controversial. The expression of several Ag resistance genes has been reported to be controlled by a riboswitch mechanism encoded in a conserved sequence. Yet this sequence corresponds to the integration site of an integron, a genetic platform that recruits genes of different functions, making the presence of such a riboswitch counterintuitive. We provide, for the first time, experimental evidence against the existence of such Ag-sensing riboswitch. We first tried to reproduce the induction of the well characterized aacA5 gene using its native genetic environment, but were unsuccessful. We then broadened our approach and analyzed the inducibility of all AgR genes encoded in integrons against a variety of antibiotics. We could not observe biologically relevant induction rates for any gene in the presence of several aminoglycosides. Instead, unrelated antibiotics produced mild but consistently higher increases in expression, that were the result of pleiotropic effects. Our findings rule out the riboswitch control of aminoglycoside resistance genes in integrons.Item Los Oligoquetos terrícolas de la Península Ibérica(2015) Álvarez Sánchez, JulioItem Transmission of Similar Mcr-1 Carrying Plasmids among Different Escherichia coli Lineages Isolated from Livestock and the Farmer(Antibiotics, 2021) Viñes, Joaquim; Cuscó, Anna; Napp, Sebastian; Alvarez, Julio; Sáez Llorente, José Luis; Rosàs Rodoreda, Montserrat; Francino, Olga; Migura García, Lourdes; Álvarez Sánchez, JulioColistin use has mostly been stopped in human medicine, due to its toxicity. However, nowadays, it still is used as a last-resort antibiotic to treat hospital infections caused by multi-drug resistant Enterobacteriaceae. On the contrary, colistin has been used in veterinary medicine until recently. In this study, 210 fecal samples from pigs (n = 57), calves (n = 152), and the farmer (n = 1) were collected from a farm where E. coli harboring mcr-1–mcr-3 was previously detected. Samples were plated, and mcr-genes presence was confirmed by multiplex-PCR. Hybrid sequencing which determined the presence and location of mcr-1, other antibiotic resistance genes, and virulence factors. Eighteen colistin resistant isolates (13 from calves, four from pigs, and one from the farmer) contained mcr-1 associated with plasmids (IncX4, IncI2, and IncHI2), except for two that yielded mcr-1 in the chromosome. Similar plasmids were distributed in different E. coli lineages. Transmission of mcr-1 to the farmer most likely occurred by horizontal gene transfer from E. coli of calf origin, since plasmids were highly similar (99% coverage, 99.97% identity). Moreover, 33 virulence factors, including stx2 for Shiga toxin E. coli (STEC) were detected, highlighting the role of livestock as a reservoir of pathotypes with zoonotic potential.Item Once bitten twice shy: Risk factors associated with bovine tuberculosis recurrence in Castilla y León, Spain(Research in Veterinary Science, 2023) Grau, Anna; Nácar, Jesús; Sáez-Lorente, José Luis; Mínguez, Olga; Pozo Piñol, Pilar; Bezos Garrido, Javier; Romero Martínez, Beatriz; Álvarez Sánchez, JulioPersistence of bovine tuberculosis (bTB) in cattle herd remains a major challenge in disease elimination due to the ineffectual removal of all infected animals in a bTB breakdown. Characterization of herds with a higher probability of experiencing further bTB breakdowns can help to implement specific risk-based policies for disease control and eradication. Here, our aim was to identify herd- and breakdown-level risk factors in bTB infected herds in Castilla y Leon, Spain, associated with a decreased time to recurrence and an increased risk of recurrence using a mixed effects Cox proportional hazards model and a multivariable logistic regression model, respectively. Results revealed that location (province), herd size and number of incoming animals/contacts were good predictors of a decreased time to bTB recurrence and an increased risk of becoming a recurrent herd. Additionally, the duration of the previous outbreak and the number of IFN-γ herd-tests applied in it were associated with increased odds of (an early) recurrence. Risk factors identified here can be used for early identification of herds in which bTB eradication may be more challenging and that should thus be subjected to increased control efforts. The characterization of high-risk herds may help to minimize the risk of reinfection and emphasize early detection and removal of bTB positive animals in the herd.