Evaluation of a cup scrub technique for quantification of the microbial flora on bovine skin

A cup-scrub technique devised for sampling the human skin surface microflora was evaluated in cattle. Scrub samples from bovine skin contained clumps of squama and bacterial microcolonies which were progressively broken down by shaking. This was accelerated in the presence of ballotini beads but aggregations of bacteria were still present after prolonged agitation. Vigorous shaking, particularly with beads, decreased the viability of the bacteria and optimum viable counts were obtained after manual shaking for half a minute. Immersion in buffered detergent, wash and diluting fluids for up to 2 h promoted release of bacteria from microcolonies but decreased the viability of aerobic and anaerobic pleomorphic rods and a Bacillus strain. There was no significant effect on strains of Micrococcaceae. Prolonged exposure of bacteria from scrub samples to these fluids can thus lead to both quantitative and qualitative alterations in the counts obtained, although these effects may be masked by the continuing release of bacteria from microcolonies. The cup-scrub technique provides a convenient means of quantifying changes in the bovine skin microflora but results obtained from different studies should only be compared if closely similar techniques are used.