Potentiel de systèmes de culture bactériologique à la ferme et validation de la cytologie pour le diagnostic de l’endométrite chez la vache laitière en période post-partum

L’endométrite est une maladie affectant les performances en reproduction chez la vache laitière. Elle est définie par la présence d’inflammation excessive au niveau de l’utérus durant la période post-partum. Le traitement antibiotique sous forme d’infusion intra-utérine est l’une des approches curatives les plus utilisées et améliore les performances de reproduction subséquentes. Considérant les enjeux modernes en lien avec l’antibiorésistance et la réduction de l’utilisation d’antibiotiques en productions animales, il est justifiable de remettre en question l’utilisation d’une méthode diagnostique de l’endométrite basée uniquement sur la présence d’inflammation en vue de déterminer si un traitement antibiotique doit être utilisé. En ce sens, l’objectif principal de ce projet de recherche était de valider l’exactitude des résultats de milieux de culture bactériologique utilisés à la ferme (Tri-plate et Petrifilm) en se basant sur ceux obtenus en laboratoire diagnostique. Un objectif secondaire était de vérifier la concordance entre les résultats bactériens de laboratoire et ceux cytologiques. Pour ce faire, une étude observationnelle transversale a été réalisée au sein de deux troupeaux laitiers commerciaux faisant partie de la clientèle de la Clinique ambulatoire bovine de la Faculté de médecine vétérinaire de l’Université de Montréal. Un total de 189 vaches en période post-partum (30 à 43 jours de lactation) ont été enrôlées de façon systématique afin de recueillir 2 échantillons utérins à partir de cytobrosses lors d’un même examen. La première cytobrosse était utilisée pour inoculer directement le milieu de culture Tri-plate et ensuite être envoyée au laboratoire du Service diagnostic de la FMV de l’Université de Montréal pour culture bactérienne aérobique. La seconde cytobrosse était utilisée pour l’analyse cytologique (proportion de cellules polymorphonucléaires; PMNL), puis était diluée dans 1 ml de solution saline pour inoculer le milieu Petrifilm. Après une période d’incubation de 24h, le décompte de colonies était fait pour chaque milieu de culture. À partir de ces données, les analyses statistiques ont été complétées dans le but d’optimiser la sommation de sensibilité et spécificité (Se+Sp) des deux milieux de culture en fonction des résultats du laboratoire de référence. Pour le milieu Tri-plate, le seuil de ˃ 90 colonies a permis d’obtenir la Se+Sp maximale, soit 167,7. Pour le milieu Petrifilm, le seuil de ˃100 colonies a donné la Se+Sp maximale, soit 129. En ce qui concerne la concordance entre le diagnostic cytologique et bactériologique, les résultats de notre projet montrent que 64,3% des vaches positives au niveau cytologique (˃6% PMNL) se sont avérées négatives à la culture bactérienne, démontrant un manque de concordance. En conclusion, les résultats de notre étude supportent la faisabilité et le potentiel de la culture bactérienne d’échantillons de l’endomètre à la ferme. Notre projet met également en évidence que l’utilisation d’un dépistage cytologique de l’endométrite afin d’utiliser un traitement antibiotique puisse causer un manque d’optimisation dans l’efficacité des traitements. Il semble donc pertinent que d’autres projets soient complétés afin d’approfondir le dépistage bactériologique de l’endométrite et d’analyser le potentiel diagnostique de celui-ci.Endometritis is a disease affecting reproductive performance in dairy cows. It is defined by the presence of excessive inflammation in the uterine body during the postpartum period. From a curative point of view, the use of antibiotic treatment in the form of intrauterine infusion is one of the most widely used methods which has a beneficial effect on subsequent reproductive performance in positive cases of endometritis. Considering the modern issues concerning the use of antibiotics in animal production, the use of a diagnostic method based on the presence of inflammation in order to administer antibiotic treatment is questionable. In that sense, the main objective of this research project was to validate the accuracy of the results of bacteriological culture medium used on the farm (Tri-plate and Petrifilm) based on the ones from diagnosis laboratory. A secondary objective was to verify the concordance between the bacterial and cytological results. To do this, a cross-sectional observational study was set up within two commercial dairy herds followed by the bovine outpatient clinic of the Faculty of Veterinary Medicine of the Université de Montréal. A total of 189 cows in the postpartum period (30 to 43 days in milk) were systematically enrolled in order to collect 2 uterine samples from cytobrush during the same examination. The first cytobrush was used to directly inoculate the Tri-plate medium and then be sent to the reference laboratory (Diagnostic service of the FVM of the Université de Montréal) for aerobic bacterial analysis. The second cytobrush was initially used to make a microscopic smear for cytological analysis (polymorphonuclear cell proportion (PMNL)) and subsequently diluted in 1 ml of saline to inoculate the Petrifilm medium. After an incubation period of 24 hours, the colony count was made for each culture medium. From these data, statistical analyses were completed in order to optimize the summation of sensitivity and specificity (Se + Sp) of the two culture medium according to the results of the reference laboratory. For the Tri-plate medium, the cutoff of ˃ 90 colonies resulted in the maximum Se + Sp, which was 167.7. For the Petrifilm medium, the threshold of ˃100 colonies gave the maximum Se + Sp, which was 129. Regarding the concordance between the cytological and bacterial diagnosis, the results of our project show that 64.3% of cows positive for cytological criteria (˃6% PMNL) were found to be negative from a bacterial point of view. In conclusion, this study shows that Tri-plate and Petrifilm medium used on-farms were best to reproduce the results obtained by laboratory analysis using 90 and 100 colony threshold respectively. Our results also support a lack of agreement between cytological and bacterial diagnosis. It therefore seems relevant that other projects are completed in order to deepen the bacterial screening for endometritis and to analyze its diagnostic potential

Validation of On-Farm Bacteriological Systems for Endometritis Diagnosis in Postpartum Dairy Cows

The objective of this study was to validate the accuracy of the results of on-farm bacteriological culture media (Tri-plate and Petrifilm) from endometrial samples compared with the ones from the diagnostic laboratory. A cross-sectional observational study was set up within two dairy herd clients of the Université de Montréal. A total of 189 cows in the postpartum period were systematically enrolled to collect two uterine samples from cytobrushes during the same examination. The first cytobrush was used to inoculate the Tri-plate medium directly and then was sent to the reference laboratory for aerobic bacterial culture. The second cytobrush was used to make a microscopic smear for cytological analysis (proportion of polymorphonuclear cells) and subsequently diluted in 1 mL of saline to inoculate the Petrifilm medium. From these data, statistical analyses were computed to optimize the summation of sensitivity and specificity of the two systems compared with the results of the reference laboratory. For the Tri-plate and Petrifilm media, the cutoffs of ˃90 and ˃100 colonies gave the maximum sum of sensitivity and specificity, respectively. In conclusion, Tri-plate media was best at reproducing the results obtained by laboratory analysis using a threshold of >90 colonies

Standardization and validation of ATP luminometry as a diagnostic tool to assess the cleanliness of feeding equipment in preweaning calves

ABSTRACT: The objective of this cross-sectional study was to standardize a reliable and repeatable swabbing technique using ATP luminometry (light emission proportional to the amount of ATP with result provided in relative light units [RLU]) to describe the cleanliness of various feeding equipment used for preweaning calves in dairy farms. A total of 7 Québec commercial dairy herds were selected conveniently. Following visual hygiene scoring, the cleanliness of every available piece of feeding equipment was assessed using direct surface swabbing for buckets and nipples with Hygiena UltraSnap swabs. A liquid rinsing technique was used for esophageal feeders, bottles, and automatic milk feeders (AMF) with UltraSnap, AquaSnap, and MicroSnap swabs. To validate direct swabbing technique of buckets, a stage within and between operators was realized, as well as a conventional bacterial culture. A total of 519 swab samples were obtained from 201 pieces of equipment. The median (interquartile range) contamination in RLU for a bottle, esophageal feeder, AMF, bucket and nipple was 2 (1;6), 2 (0;12), 52 (19;269), 886 (128;7,230) and 899 (142;6,928), respectively. The direct swabbing technique, which consists in swabbing directly the surface of an equipment, showed excellent correlation for intrarater reliability (intraclass correlation (ICC) = 0.93; 95% CI: 0.88–0.96). The interoperator (2 sessions with 3 different operators) reliability also showed high correlation (ICC = 0.88; 95% CI: 0.78–0.94 for the first session, and ICC = 0.89; 95% CI: 0.79–0.95 for the second session). Luminometer values were positively associated with the visual score of esophageal feeders, AMF and buckets. A positive correlation between bacterial culture and direct swabbing of buckets was also found for the UltraSnap (rs = 0.653; 95% CI: 0.283–0.873; P = 0.0003) and MicroSnap (rs = 0.569, 95% CI: 0.309–0.765; P = 0.002). This study describes a standardized and practical on-farm swabbing technique for assessing the hygienic status of feeding equipment by luminometry, which can be integrated in the investigation of preweaning dairy calves problems