Experimental comparison of excision and swabbing microbiological sampling methods for carcasses

• Published in: Journal of food protection 2005, Vol.68 (10), p.2163-2168
• Main Authors: Pepperell, R, Reid, C.A, Solano, S.N, Hutchison, M.L, Walters, L.D, Johnston, A.M, Buncic, S
• Format: Article
• Language: English
• Subjects: Abattoirs - standards; Animals; beef carcasses; Biological and medical sciences; Cattle; Colony Count, Microbial - methods; Common Agricultural Policy; Consumer Product Safety; Escherichia coli; Escherichia coli K12 - isolation & purification; excision; Food Contamination - analysis; Food industries; Food Inspection - methods; Food Microbiology; Fundamental and applied biological sciences. Psychology; HACCP; international cooperation; lamb carcasses; Meat - microbiology; Meat and meat product industries; methodology; microbial detection; pig carcasses; plate count; Pseudomonas fluorescens; Pseudomonas fluorescens - isolation & purification; quality control; sampling; Sheep; standard operating procedures; Swine
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028X-68.10.2163

Bovine sides, ovine carcasses, and porcine carcasses were individually inoculated by dipping in various suspensions of a marker organism (Escherichia coli K-12 or Pseudomonas fluorescens), alone or in combination with two meat-derived bacterial strains, and were sampled by two standard methods: cotton wet-dry swabbing and excision. The samples were examined for bacterial counts on plate count agar (PCA plate counts) and on violet red brilliant green agar (VRBGA plate counts) by standard International Organization for Standardization methods. Average bacterial recoveries by swabbing, expressed as a percentage of the appropriate recoveries achieved by excision, varied widely (2 to 100%). Several factors that potentially contributed to relatively low and highly variable bacterial recoveries obtained by swabbing were investigated in separate experiments. Neither the difference in size of the swabbed area (10, 50, or 100 cm2 on beef carcasses) nor the difference in time of swabbing (20 or 60 min after inoculation of pig carcasses) had a significant effect on the swabbing recoveries of the marker organism used. In an experiment with swabs preinoculated with the marker organism and then used for carcass swabbing, on average, 12% of total bacterial load was transferred inversely (i.e., from the swab to the carcass during the standard swabbing procedure). In another experiment, on average, 14% of total bacterial load was not released from the swab into the diluent during standard swab homogenization. Use of custom-made swabs with abrasive butts, around which metal pieces of pan scourers were wound, markedly increased PCA plate count recoveries from noninoculated lamb carcasses at commercial abattoirs compared with cotton swabs. In spite of the observed inferiority of the cotton wet-dry swabbing method compared with the excision method for bacterial recovery, the former is clearly preferred by the meat industry because it does not damage the carcass. Therefore, further large-scale evaluation of the two carcass sampling methods has been undertaken under commercial conditions and reported separately.