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Abstract: Mycoplasma bovis is an etiologic agent of pneumonia, arthritis, and otitis in young calves, such as those found in the special-fed veal industry. We conducted a blinded, controlled trial of two commercially available M. bovis bacterin vaccines for the prevention of respiratory disease in calves associated with M. bovis infection. Calves were randomly assigned to a subcutaneous treatment of vaccine A (n =50), adjuvant A (n =50), vaccine B (n =50), or 0.9% sterile saline solution (n =50) beginning at 27 days of age. Upper-respiratory tract colonization was not impacted by vaccination status. Vaccine A significantly reduced the presence of lung lesions (p =0.0325), however there was no significant reduction of M. bovis in lung lesions. Vaccine B did not significantly reduce total lung lesions or M. bovis-specific lung lesions. The relative risk was determined to be 0.56, 1.0, and 1.36 for vaccine A, adjuvant A, and vaccine B, respectively. There was no association between the total specific antibody isotype (IgM, IgG1, IgG2, IgA) concentrations or M. bovis antibodies and the M. bovis-associated morbidity in the veal calves. Under the field conditions of this study, observed vaccine efficacy for vaccine A and vaccine B was 44% and less than 1%, respectively. [Copyright &y& Elsevier]

Healthy calves (n = 96, 1 to 9 weeks old) from a dairy herd in central Pennsylvania were examined each month over a five-month period for fecal shedding of ceftiofur-resistant gram-negative bacteria. Ceftiofur-resistant Escherichia coli isolates (n = 122) were characterized by antimicrobial resistance (disk diffusion and MIC), serotype, pulsed-field gel electrophoresis subtypes, beta-lactamase genes, and virulence genes. Antibiotic disk diffusion assays showed that the isolates were resistant to ampicillin (100%), ceftiofur (100%), chloramphenicol (94%), florfenicol (93%), gentamicin (89%), spectinomycin (72%), tetracycline (98%), ticarcillin (99%), and ticarcillin-clavulanic acid (99%). All isolates were multidrug resistant and displayed elevated MICs. The E. coli isolates belonged to 42 serotypes, of which O8:H25 was the predominant serotype (49.2%). Pulsed-field gel electrophoresis classified the E. coli isolates into 27 profiles. Cluster analysis showed that 77 isolates (63.1%) belonged to one unique group. The prevalence of pathogenic E. coli was low (8%). A total of 117 ceftiofur-resistant E. coli isolates (96%) possessed the blaCMY2 gene. Based on phenotypic and genotypic characterization, the ceftiofur-resistant E. coli isolates belonged to 59 clonal types. There was no significant relationship between calf age and clonal type. The findings of this study revealed that healthy dairy calves were rapidly colonized by antibiotic-resistant strains of E. coli shortly after birth. The high prevalence of multidrug-resistant nonpathogenic E. coli in calves could be a significant source of resistance genes to other bacteria that share the same environment. [ABSTRACT FROM AUTHOR]