Browsing by Author "Timsit, Edouard"

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    Assessment and Impacts of Newborn Beef Calf Vigour
    (2016) Homerosky, Elizabeth Rose; Kastelic, John; Windeyer, Claire; Timsit, Edouard; Pajor, Edmond
    Modified APGAR scores, intended to identify compromised calves with reduced vigour, yield inconsistent results and are not widely adopted. Data were collected from 77 newborn beef calves to determine calving characteristics and clinical examination parameters associated with abnormal blood parameters and a calf’s ability to consume colostrum by 4 h after birth. Calves born to primiparous dams, with increased calving difficulty, a weak suckle reflex, or incomplete tongue withdrawal, had decreased blood pH and increased L-lactate at 10 min after birth (P<0.05). Calves with a weak suckle reflex were 41.6 times more likely to fail to consume colostrum by 4 h compared to calves with a strong suckle reflex (P<0.0001). Calves that failed to consume colostrum by 4 h were 2.8 times more likely to be treated prior to weaning (P=0.03). In conclusion, good newborn beef calf vigour is a vital survival characteristic that helps ensure timely colostrum consumption, contributing to long-term health.
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    Bacterial Respiratory Microbiota and its Role in Respiratory Health in Beef Cattle
    (2020-08-12) McMullen, Christopher A.; Orsel, Karin; Timsit, Edouard; van der Meer, Frank; Alexander, Trevor W.
    Bovine respiratory disease (BRD) is one of the most significant diseases facing the North American beef industry. Mounting concern over the role mass medication with antibiotics in beef production may play in antimicrobial resistance has elevated pressure on the industry to develop novel techniques and approaches for controlling BRD. This includes approaches that involve modulation of the bovine respiratory tract microbiota. The overall aim of this thesis was to investigate the role of respiratory bacterial microbiota in respiratory health and disease in beef cattle. Four studies were designed to assess different features of the respiratory microbiota using a targeted amplicon (16S rRNA gene) sequencing approach. In the first study, the bacterial microbiotas present along the entire cattle respiratory tract were described to determine which upper respiratory tract niches may contribute the most to the composition of the lung microbiota. In the second study, evolution of the nasopharyngeal bacterial microbiota of beef calves was characterized from the time of spring processing to a targeted 40 days after arrival at the feedlot. In the third study, nasopharyngeal bacterial microbiotas of beef feedlot calves raised without the use of antimicrobials that were either healthy or diagnosed with BRD were characterized and compared. In the fourth study, the progression of the nasopharyngeal and tracheal bacterial microbiotas of beef calves during the development of BRD were described. The findings of all studies were summarized and discussed. Although the nasopharynx was confirmed to likely be the most important location that should be targeted in bovine respiratory microbiota research, it appears the role of the respiratory bacterial microbiota in cattle health and disease is more complex than originally anticipated. Indeed, no common patterns of change in community composition over time, including over large periods of time and during the development of clinical BRD, were observed. These findings may affect how we research the role of the bovine microbiota in respiratory health, as well as how we design and implement novel methods for controlling, preventing, and diagnosing BRD in beef cattle.
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    Characterization of Antimicrobial and Metal Resistance in Contemporary and Historical clinical isolates of Histophilus somni from Feedlot cattle in Alberta
    (2016) Bhatt, Krishna; Liljebjelke, Karen; Windeyer, Claire; Timsit, Edouard; Storey, Douglas
    This study was conducted to determine antimicrobial and metal resistance, associated resistant genes, and mobile genetic elements in contemporary (2012-2016, n=63) and historical (1980’s, n=31) clinical isolates of Histophilus somni from feedlot cattle in Alberta. A significant increase in antimicrobial resistance was observed in the contemporary isolates compared to the historical (P<0.001). Sixty-two percent of the contemporary isolates exhibited multidrug resistance (resistance to 3 drug classes). Sixty-eight percent and 52% of the contemporary isolates showed tolerance to copper and zinc concentrations above one millimolar, respectively. Multicopper oxidase and cation efflux pump genes associated with copper and zinc tolerance and tet(H) gene associated with oxytetracycline resistance were identified. We identified integrative conjugative element carrying antimicrobial, copper, and zinc resistance genes, which indicates the possibility of co-selection of antimicrobial resistance due to copper and zinc selection pressure, and the dissemination of resistance by horizontal gene transfer.
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    Erratum to: The nasopharyngeal microbiota of beef cattle before and after transport to a feedlot
    (2017-04-20) Holman, Devin B; Timsit, Edouard; Amat, Samat; Abbott, D. W; Buret, Andre G; Alexander, Trevor W
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    The nasopharyngeal microbiota of beef cattle before and after transport to a feedlot
    (2017-03-22) Holman, Devin B; Timsit, Edouard; Amat, Samat; Abbott, D. W; Buret, Andre G; Alexander, Trevor W
    Abstract Background The nasopharyngeal (NP) microbiota plays an important role in bovine health, comprising a rich and diverse microbial community. The nasopharynx is also the niche for potentially pathogenic agents which are associated with bovine respiratory disease (BRD), a serious and costly illness in feedlot cattle. We used 14 beef heifers from a closed and disease-free herd to assess the dynamics of the NP microbiota of cattle that are transported to a feedlot. Cattle were sampled prior to transport to the feedlot (day 0) and at days 2, 7, and 14. Results The structure of the NP microbiota changed significantly over the course of the study, with the largest shift occurring between day 0 (prior to transport) and day 2 (P < 0.001). Phylogenetic diversity and richness increased following feedlot placement (day 2; P < 0.05). The genera Pasteurella, Bacillus, and Proteus were enriched at day 0, Streptococcus and Acinetobacter at day 2, Bifidobacterium at day 7, and Mycoplasma at day 14. The functional potential of the NP microbiota was assessed using PICRUSt, revealing that replication and repair, as well as translation pathways, were more relatively abundant in day 14 samples. These differences were driven mostly by Mycoplasma. Although eight cattle were culture-positive for the BRD-associated bacterium Pasteurella multocida at one or more sampling times, none were culture-positive for Mannheimia haemolytica or Histophilus somni. Conclusions This study investigated the effect that feedlot placement has on the NP microbiota of beef cattle over a 14-d period. Within two days of transport to the feedlot, the NP microbiota changed significantly, increasing in both phylogenetic diversity and richness. These results demonstrate that there is an abrupt shift in the NP microbiota of cattle after transportation to a feedlot. This may have importance for understanding why cattle are most susceptible to BRD after feedlot placement.
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    Topography of the respiratory tract bacterial microbiota in cattle
    (2020-06-10) McMullen, Christopher; Alexander, Trevor W; Léguillette, Renaud; Workentine, Matthew; Timsit, Edouard
    Abstract Background Bacterial bronchopneumonia (BP) is the leading cause of morbidity and mortality in cattle. The nasopharynx is generally accepted as the primary source of pathogenic bacteria that cause BP. However, it has recently been shown in humans that the oropharynx may act as the primary reservoir for pathogens that reach the lung. The objective was therefore to describe the bacterial microbiota present along the entire cattle respiratory tract to determine which upper respiratory tract (URT) niches may contribute the most to the composition of the lung microbiota. Methods Seventeen upper and lower respiratory tract locations were sampled from 15 healthy feedlot steer calves. Samples were collected using a combination of swabs, protected specimen brushes, and saline washes. DNA was extracted from each sample and the 16S rRNA gene (V3-V4) was sequenced. Community composition, alpha-diversity, and beta-diversity were compared among sampling locations. Results Microbiota composition differed across sampling locations, with physiologically and anatomically distinct locations showing different relative abundances of 1137 observed sequence variants (SVs). An analysis of similarities showed that the lung was more similar to the nasopharynx (R-statistic = 0.091) than it was to the oropharynx (R-statistic = 0.709) or any other URT sampling location. Five distinct metacommunities were identified across all samples after clustering at the genus level using Dirichlet multinomial mixtures. This included a metacommunity found primarily in the lung and nasopharynx that was dominated by Mycoplasma. Further clustering at the SV level showed a shared metacommunity between the lung and nasopharynx that was dominated by Mycoplasma dispar. Other metacommunities found in the nostrils, tonsils, and oral microbiotas were dominated by Moraxella, Fusobacterium, and Streptococcus, respectively. Conclusions The nasopharyngeal bacterial microbiota is most similar to the lung bacterial microbiota in healthy cattle and therefore may serve as the primary source of bacteria to the lung. This finding indicates that the nasopharynx is likely the most important location that should be targeted when doing bovine respiratory microbiota research. Video abstract.
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    Upper and lower respiratory tract microbiota in horses: bacterial communities associated with health and mild asthma (inflammatory airway disease) and effects of dexamethasone
    (2017-08-23) Bond, Stephanie L; Timsit, Edouard; Workentine, Matthew; Alexander, Trevor; Léguillette, Renaud
    Abstract Background The microbial composition of the equine respiratory tract, and differences due to mild equine asthma (also called Inflammatory Airway Disease (IAD)) have not been reported. The primary treatment for control of IAD in horses are corticosteroids. The objectives were to characterize the upper and lower respiratory tract microbiota associated with respiratory health and IAD, and to investigate the effects of dexamethasone on these bacterial communities using high throughput sequencing. Results The respiratory microbiota of horses was dominated by four major phyla, Proteobacteria (43.85%), Actinobacteria (21.63%), Firmicutes (16.82%), and Bacteroidetes (13.24%). Fifty genera had a relative abundance > 0.1%, with Sphingomonas and Pantoea being the most abundant. The upper and lower respiratory tract microbiota differed in healthy horses, with a decrease in richness in the lower airways, and 2 OTUs that differed in abundance. There was a separation between bacterial communities in the lower respiratory tract of healthy and IAD horses; 6 OTUs in the tracheal community had different abundance with disease status, with Streptococcus being increased in IAD horses. Treatment with dexamethasone had an effect on the lower respiratory tract microbiota of both heathy and IAD horses, with 8 OTUs increasing in abundance (including Streptococcus) and 1 OTU decreasing. Conclusions The lower respiratory tract microbiota differed between healthy and IAD horses. Further research on the role of Streptococcus in IAD is warranted. Dexamethasone treatment affected the lower respiratory tract microbiota, which suggests that control of bacterial overgrowth in IAD horses treated with dexamethasone could be part of the treatment strategy.