Bovine Airway Models: Approaches for Investigating Bovine Respiratory Disease

Relationship between capsule production and biofilm formation by Mannheimia haemolytica, and establishment of a poly-species biofilm with other Pasteurellaceae

Mannheimia haemolytica is one of the bacterial agents responsible for bovine respiratory disease (BRD). The capability of M. haemolytica to form a biofilm may contribute to the development of chronic BRD infection by making the bacteria more resistant to host innate immunity and antibiotics. To improve therapy and prevent BRD, a greater understanding of the association between M. haemolytica surface components and biofilm formation is needed. M. haemolytica strain 619 (wild-type) made a poorly adherent, low-biomass biofilm. To examine the relationship between capsule and biofilm formation, a capsule-deficient mutant of wild-type M. haemolytica was obtained following mutagenesis with ethyl methanesulfonate to obtain mutant E09. Loss of capsular polysaccharide (CPS) in mutant E09 was supported by transmission electron microscopy and Maneval's staining. Mutant E09 attached to polyvinyl chloride plates more effectively, and produced a significantly denser and more uniform biofilm than the wild-type, as determined by crystal violet staining, scanning electron microscopy, and confocal laser scanning microscopy with COMSTAT analysis. The biofilm matrix of E09 contained predominately protein and significantly more eDNA than the wild-type, but not a distinct exopolysaccharide. Furthermore, treatment with DNase I significantly reduced the biofilm content of both the wild-type and E09 mutant. DNA sequencing of E09 showed that a point mutation occurred in the capsule biosynthesis gene wecB. The complementation of wecB in trans in mutant E09 successfully restored CPS production and reduced bacterial attachment/biofilm to levels similar to that of the wild-type. Fluorescence in-situ hybridization microscopy showed that M. haemolytica formed a poly-microbial biofilm with Histophilus somni and Pasteurella multocida. Overall, CPS production by M. haemolytica was inversely correlated with biofilm formation, the integrity of which required eDNA. A poly-microbial biofilm was readily formed between M. haemolytica, H. somni, and P. multocida, suggesting a mutualistic or synergistic interaction that may benefit bacterial colonization of the bovine respiratory tract.

Measurement of Human and Bovine Exhaled Breath Condensate pH Using Polyaniline-Modified Flexible Inkjet-Printed Nanocarbon Electrodes

The collection, processing, and electrochemical analysis of exhaled breath condensate (EBC) from healthy human and animal subjects is reported on. EBC is a biospecimen potentially rich in biomarkers of respiratory disease. The EBC pH was analyzed potentiometrically using a disposable polyaniline (PANI)-modified inkjet-printed (IJP) carbon electrode. Comparison measurements were performed using a commercial screen-printed carbon (SPC) electrode. The PANI-modified electrodes exhibited reproducible and near-Nernstian responses for pH values between 2 and 9 with slopes from -50 to -60 mV/dec. The PANI-modified IJP carbon electrode exhibited a faster response time and superior reproducibility to the modified SPC electrode. In proof-of-concept studies, the healthy human EBC pH was found to be 6.57 ± 0.09 and the healthy bovine EBC pH was 5.9 ± 0.2. All pH determined using the PANI-modified electrodes were in good agreement with the pH determined using a micro glass pH electrode. An RTube device was used to collect EBC from humans while a modified device was used to collect EBC from calves in the field. EBC volumes of 0.5-2 mL for 5-6 min of tidal breathing were collected from healthy animals. The pH of EBC from healthy calves (17 animals) depends on their age from 1 to 9 weeks with values ranging from 5.3 to 7.2. A distinct alkaline shift was observed for many animals around 20 days of age. The bovine EBC pH also depends on the ambient temperature and humidity at the time of collection. The results indicate that the PANI-modified IJP carbon electrodes outperform commercial SPC and provide reproducible and accurate measurement of pH across various biospecimen types.

Development and characterization of an immortalized nasopharyngeal epithelial cell line to explore airway physiology and pathology in yak (Bos grunniens)

Airway epithelial cells play a crucial role in investigating the physiological and pathological mechanisms of the respiratory tract in yaks, a species whose unique respiratory system has garnered extensive interest. Despite this growing interest, there currently are no available airway epithelial cell lines from yaks, underscoring the crucial need to establish a yak respiratory epithelial cell line. Therefore, our objective was to isolate a population of primary yak nasopharyngeal epithelial cells (pYNE) and transform them into immortalized yak nasopharyngeal epithelial cells (iYNE), assessing their suitability as an in vitro model. Employing a combined method of physical elimination and differential adhesion, we successfully isolated a population of high-purity pYNE, and developed an iYNE line through pCI-neo-hTERT plasmid transfection. Karyotype and transmission electron microscopy analyses confirmed that pYNE and iYNE share identical morphologies and structures. Gel electrophoresis and real-time PCR analyses demonstrated that pYNE and iYNE expressed similar levels of KRT18 and CDH1 genes (p ≥ 0.541). Notably, iYNE expressed a significantly high level of TERT gene expression (p < 0.001). Immunofluorescence analysis demonstrated that both cell types expressed Pan-Cytokeratin, ZO-1, and E-cadherin proteins. Furthermore, immunoblotting analysis indicated significantly higher levels of hTERT and Ki67 proteins in iYNE (p < 0.001), and similar levels of Cluadin-3 and Occludin proteins (p ≥ 0.103). Proliferation curve analysis highlighted iYNE's serum-dependency and significantly enhanced proliferation capacities (p < 0.001). Additionally, pYNE and iYNE cells demonstrated comparable susceptibilities to infectious bovine rhinotracheitis virus (IBRV). These findings collectively suggest that the developed iYNE retains the evaluated physiological characteristics of pYNE, making it an appropriate in vitro model. This advancement will facilitate further investigation into the respiratory physiological and pathological mechanisms in yaks.

When the solution becomes the problem: a review on antimicrobial resistance in dairy cattle

Antibiotics' action, once a 'magic bullet', is now hindered by widespread microbial resistance, creating a global antimicrobial resistance (AMR) crisis. A primary driver of AMR is the selective pressure from antimicrobial use. Between 2000 and 2015, antibiotic consumption increased by 65%, reaching 34.8 billion tons, 73% of which was used in animals. In the dairy cattle sector, antibiotics are crucial for treating diseases like mastitis, posing risks to humans, animals and potentially leading to environmental contamination. To address AMR, strategies like selective dry cow therapy, alternative treatments (nanoparticles, phages) and waste management innovations are emerging. However, most solutions are in development, emphasizing the urgent need for further research to tackle AMR in dairy farms.

Role of biofilms in antimicrobial resistance of the bacterial bovine respiratory disease complex

An increase in chronic, non-responsive bovine respiratory disease (BRD) infections in North American feedlot cattle is observed each fall, a time when cattle are administered multiple antimicrobial treatments for BRD. A number of factors are responsible for BRD antimicrobial treatment failure, with formation of biofilms possibly being one. It is widely accepted that biofilms play a role in chronic infections in humans and it has been hypothesized that they are the default lifestyle of most bacteria. However, research on bacterial biofilms associated with livestock is scarce and significant knowledge gaps exist in our understanding of their role in AMR of the bacterial BRD complex. The four main bacterial species of the BRD complex, Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, and Mycoplasma bovis are able to form biofilms in vitro and there is evidence that at least H. somni retains this ability in vivo. However, there is a need to elucidate whether their biofilm-forming ability contributes to pathogenicity and antimicrobial treatment failure of BRD. Overall, a better understanding of the possible role of BRD bacterial biofilms in clinical disease and AMR could assist in the prevention and management of respiratory infections in feedlot cattle. We review and discuss the current knowledge of BRD bacteria biofilm biology, study methodologies, and their possible relationship to AMR.

Investigation of the safety and protective efficacy of an attenuated and marker M. bovis-BoHV-1 combined vaccine in bovines

Bovine respiratory disease (BRD) is one of the most common diseases in the cattle industry worldwide; it is caused by multiple bacterial or viral coinfections, of which Mycoplasma bovis (M. bovis) and bovine herpesvirus type 1 (BoHV-1) are the most notable pathogens. Although live vaccines have demonstrated better efficacy against BRD induced by both pathogens, there are no combined live and marker vaccines. Therefore, we developed an attenuated and marker M. bovis-BoHV-1 combined vaccine based on the M. bovis HB150 and BoHV-1 gG-/tk- strain previously constructed in our lab and evaluated in rabbits. This study aimed to further evaluate its safety and protective efficacy in cattle using different antigen ratios. After immunization, all vaccinated cattle had a normal rectal temperature and mental status without respiratory symptoms. CD4+, CD8+, and CD19+ cells significantly increased in immunized cattle and induced higher humoral and cellular immune responses, and the expression of key cytokines such as IL-4, IL-12, TNF-α, and IFN-γ can be promoted after vaccination. The 1.0 × 108 CFU of M. bovis HB150 and 1.0 × 106 TCID50 BoHV-1 gG-/tk- combined strain elicited the most antibodies while significantly increasing IgG and cellular immunity after challenge. In conclusion, the M. bovis HB150 and BoHV-1 gG-/tk- combined strain was clinically safe and protective in calves; the mix of 1.0 × 108 CFU of M. bovis HB150 and 1.0 × 106 TCID50 BoHV-1 gG-/tk- strain was most promising due to its low amount of shedding and highest humoral and cellular immune responses compared with others. This study introduces an M. bovis-BoHV-1 combined vaccine for application in the cattle industry.

Investigation of the Optimal Immunization Dose and Protective Efficacy of an Attenuated and Marker M. bovis-Bovine Herpesvirus Type 1 Combined Vaccine in Rabbits

Bovine respiratory disease (BRD) is one of the most common diseases in the cattle industry; it is a globally prevalent multifactorial infection primarily caused by viral and bacterial coinfections. In China, Mycoplasma bovis (M. bovis) and bovine herpesvirus type 1 (BoHV-1) are the most notable pathogens associated with BRD. Our previous study attempted to combine the two vaccines and conducted a preliminary investigation of their optimal antigenic ratios. Based on this premise, the research extended its investigation by administering varying vaccine doses in a rabbit model to identify the most effective immunization dosage. After immunization, all rabbits in other immunization dose groups had a normal rectal temperature without obvious clinical symptoms. Furthermore, assays performed on the samples collected from immunized rabbits indicated that there were increased humoral and cellular immunological reactions. Moreover, the histological analysis of the lungs showed that immunized rabbits had more intact lung tissue than their unimmunized counterparts after the challenge. Additionally, there appears to be a positive correlation between the protective efficacy and the immunization dose. In conclusion, the different immunization doses of the attenuated and marker M. bovis HB150 and BoHV-1 gG-/tk- combined vaccine were clinically safe in rabbits; the mix of 2.0 × 108 CFU of M. bovis HB150 and 2.0 × 106 TCID50 BoHV-1 gG-/tk- strain was most promising due to its highest humoral and cellular immune responses and a more complete morphology of the lung tissue compared with others. These findings determined the optimal immunization dose of the attenuated and marker M. bovis HB150 and BoHV-1 gG-/tk- combined vaccine, laying a foundation for its clinical application.

The Safety and Protective Efficacy Evaluation of an Attenuated M. bovis-BoHV-1 Bivalent Vaccine in Rabbits

Bovine respiratory disease (BRD) is a global prevalent multifactorial infection primarily caused by viral and bacterial coinfections. In China, Mycoplasma bovis (M. bovis) and bovine herpesvirus type 1 (BoHV-1) are the predominant pathogens associated with BRD. Our previous study involved the development of attenuated M. bovis HB150 and BoHV-1 gG-/tk- vaccine strains, which were thoroughly assessed for their safety profiles and protective efficacy in cattle. In this study, we applied a combination of vaccines in varying ratios and used a rabbit model to determine the safety and protective efficacy. We used PCR/RT-PCR to detect the postimmunization and challenge shedding of M. bovis and BoHV-1. Additionally, we measured antibody titers and the expression of IFN-β and TNF-α to evaluate the humoral and cellular immune responses, respectively. Furthermore, we performed a histopathological analysis to assess lung damage. Our study provides evidence of the safety and effectiveness of the bivalent M. bovis-BoHV-1 vaccine in rabbits, particularly when applying a combination of 1.0 × 108 CFU of M. bovis HB150 and 1.0 × 106 TCID50 of the BoHV-1 gG-/tk- strain. The bivalent vaccine significantly enhanced both the long-term antibody immune response and cellular protection against the M. bovis and BoHV-1 challenge. These findings provide a valuable model for the potential application in cattle.