How Effective is Sponge Sampling for Removing Bacteria from Beef Carcasses

Removal of bacteria by sponging carcass surfaces is a common, non-destructive sampling method. The proportion of bacteria removed by sponging was measured as a percentage of those on the sponge plus those on the excised carcass surface beneath the sponged area. For a total of ten experienced operators working at five abattoirs, the mean proportion of bacteria removed at each site was 39.1% (rump), 39.9% (flank) and 33.7% (brisket). The standard deviation at each site was relatively high (28.5, 21.3 and 17.4%, respectively), reflecting the wide variation of recovery among operators (2.3-93.1%). To determine the proportion that could be removed by continued sponging, numbers of bacteria were counted after each of five sequential spongings, together with those remaining on the excised site after homogenizing of tissue by stomaching. The proportion of bacteria recovered by sequential sponging varied between 11.1 and 97.4% and, with one exception, larger proportions were recovered from the first sponge. The present study demonstrates that sponge sampling, while convenient, is a highly variable means of removing bacteria for enumeration.