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Comparison of number of Streptococcus uberis calculated on a volume or weight basis in sand and sawdust bedding
M T Gabler1, J K Reneau, R J Farnsworth
1Department of Animal Science, College of Agriculture, University of Minnesota, St Paul 55108, USA.
Objective:
To determine a method for comparing counts of Streptococcus uberis in sand and sawdust and account for the influence of weight or volume of the bedding material.
Sample Population:
2 sources of kiln-dried sawdust and 2 sources of washed sand.
Procedures:
Sterilized bedding material (100 ml) was weighed and uniformly distributed in an aluminum pan. Each sterilized bedding material was inoculated with a mean of 3.6 X 10(6) (experiment 1) or 2.4 X 10(7) (experiment 2) colony-forming units (CFU) of S uberis/ml of bedding material. Without allowing time for replication of S uberis, inoculated bedding materials were washed with sterile saline (0.9% NaCl) solution. A 200-ml aliquot of wash solution was serially diluted up to 2,500 times with additional saline solution and inoculated on plates containing tryptose agar with 5% sheep blood. After incubation for 48 hours, number of CFU of S uberis was counted. This procedure was replicated 19 and 16 times for each bedding material in experiments 1 and 2, respectively.
Results:
Evaluation of Bonferroni 95% confidence intervals revealed significant differences for counts of S uberis calculated on a weight basis between sand and sawdust.
Conclusions And Clinical Relevance:
Comparison of counts of S uberis determined on a volume basis for sand and sawdust accentuates to a lesser degree the weight difference of the bedding materials and ensures a more appropriate comparison of number of S uberis.
