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Abstract

Objective—To develop an in vitro fluorometric assay to assess Pasteurella haemolytica adherence to bovine respiratory and epithelial cells and compare adherence of single strains of P haemolytica serovars A1 and A2 (PhA1 and PhA2, respectively).

Sample Population—Monolayers of bovine turbinate and Madin Darby bovine kidney (MDBK) cells.

Procedure—To determine optimal inoculum concentration and incubation time, various concentrations of P haemolytica were labeled with fluorescein isothiocyanate and incubated with monolayers of bovine cells for various times. Bovine cells were washed to remove nonadherent bacteria, and percentage of bacteria adhered (percentage of adherence) was estimated fluorometrically. Percentage of adherence of PhA1 was compared with that of PhA2.

Results—The optimal inoculum concentration that resulted in measurable fluorescence of adherent bacteria was 1 × 108 colony-forming units/ml, and the optimal incubation time was 45 minutes. Percentage of adherence of PhA1 to MDBK and turbinate cells was significantly greater than that determined for PhA2.

Conclusions—The in vitro fluorometric assay is a timeefficient, inexpensive, and labor-saving method for evaluation of P haemolytica adherence to bovine cells. The concentration of bacteria used to inoculate bovine cells in this assay is similar to that typically used in other types of in vitro adherence assays. The predominance of PhA1 over PhA2 during the early stages of bovine respiratory disease may be attributable to the ability of PhA1 to adhere more avidly to nasopharyngeal tissue. (Am J Vet Res 2000;61:129–132)

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in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate the tensile strength, elongation, and degradation of 4 monofilament absorbable suture materials that undergo degradation by hydrolysis in specimens of canine urine with various physical characteristics.

Sample Population—4 monofilament absorbable sutures (polydioxanone, poliglecaprone 25, polyglyconate, and glycomer 631).

Procedure—Voided urine was collected from 6 healthy dogs, pooled, filter-sterilized, and prepared to provide 5 media: sterile neutral (pH, 7.0), sterile acidic (pH, 6.2), sterile basic (pH, 8.8), Escherichia coli-inoculated, and Proteus mirabilis-inoculated urine. Ten strands of each suture material were immersed in each of the media for 0 to 28 days. Tensile strength and elongation of each suture material were evaluated by use of a texture analyzer on days 0, 1, 3, 7, 10, 14, 21, and 28.

Results—Reduction in tensile strength was detected for all materials in all urine specimens over time. Polyglyconate and polydioxanone had superior tensile strengths in sterile neutral and E coli-inoculated urine, and polydioxanone retained the greatest tensile strength throughout the study period. All suture materials disintegrated before day 7 in P mirabilis-inoculated urine.

Conclusions and Clinical Relevance—Polydioxanone, polyglyconate, and glycomer 631 may be acceptable for urinary bladder closure in the presence of sterile neutral and E coli-contaminated urine. Tensile strength of poliglecaprone 25 in urine may be unacceptable by the critical healing time for bladder tissue (14 to 21 days). During bladder surgery, exposure of suture material that degrades via hydrolysis to urine containing Proteus spp should be minimized. Am J Vet Res (2004;65:847–853)

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in American Journal of Veterinary Research

Abstract

Objective—To develop and validate an ex vivo model for study of adherence of Mannheimia haemolytica (formerly Pasteurella haemolytica) to respiratory tract mucosa of cattle and to use this model to confirm adherence of M haemolytica serovar 1 (Mh1) to several relevant respiratory mucosal surfaces.

Sample Population—Excised nasal, nasopharyngeal, turbinate, and tonsillar mucosal tissue from the bovine upper respiratory tract.

Procedure—Mh1 was radiolabeled by use of tritiated leucine. Various concentrations of labeled bacteria were incubated with bovine upper respiratory tract tissues for various times. Tissue was washed to remove nonadherent bacteria, and percentage of bacteria adhered (percentage of adherence) was estimated using radioactivity. Using an optimal inoculum concentration and incubation time, percentage of Mh1 adherence was compared on nasal, nasopharyngeal, turbinate, and tonsillar mucosal tissue, and adherence to nasopharyngeal tissue was confirmed by scanning and transmission electron microscopy.

Results—The optimal Mh1 inoculum concentration was 1 × 107 colony forming units/ml and incubation time was 3 hours. Percentage of adherence of Mh1 to nasopharyngeal tissue was greater than adherence to other tissue types.

Conclusions and Clinical Relevance—The ex vivo model maintained the functional and structural integrity of bovine upper respiratory tract mucosa, as confirmed by light and electron microscopy. Electron microscopy revealed participation of epithelial cell cilia and surface mucus in adherence of Mh1 to nasopharyngeal tissue. Adherence of Mh1 was confirmed in repeated assays, indicating that this organism adheres to upper respiratory tract mucosa of cattle. (Am J Vet Res 2001;62:805–811)

Full access
in American Journal of Veterinary Research