Bacterial sampling techniques on beef, pork, and lamb adipose tissue

Effects of experience with swabbing procedures on the numbers of bacteria recovered from carcasses by swabbing with sponges

Each carcass in groups of 25 pig, cattle, or bison carcasses was sampled by five people: two or three people experienced with carcass sampling and two or three without previous experience. Each person sampled a different randomly selected site on a dressed carcass side by swabbing an undelimited area of approximately 100 cm(2) with a moistened synthetic sponge. The numbers of aerobic bacteria, coliform bacteria, and Escherichia coli recovered from each sample were determined. The mean log and log mean values were calculated for each set of 25 counts for each group of bacteria from pig carcasses and each set of 25 aerobic counts from cattle and bison carcasses from the samples obtained by each person. Values for the log of the total number recovered were calculated for all the sets of counts from samples obtained by each person. Most of the corresponding statistics for each set of counts of the same type for samples obtained by five people from the same group of carcasses differed by less than 0.5 log unit. These findings indicate that the numbers of bacteria recovered from carcasses by swabbing with sponges are unlikely to differ substantially as a result of samples being collected by different people using the same procedure.

Sampling methods for microbiological analysis of red meat and poultry carcasses

Microbiological analysis of carcasses at slaughterhouses is required in the European Union for evaluating the hygienic performance of carcass production processes as required for effective hazard analysis critical control point implementation. The European Union microbial performance standards refer exclusively to the excision method, even though swabbing using the wet/dry technique is also permitted when correlation between both destructive and nondestructive methods can be established. For practical and economic reasons, the swab technique is the most extensively used carcass surface-sampling method. The main characteristics, advantages, and limitations of the common excision and swabbing methods are described here.

Microbiological sampling of meat cuts and manufacturing beef by excision or swabbing

Groups of 25 beef or pork loin primal cuts or of pieces of stored or not stored manufacturing beef were sampled by excision and by swabbing with cotton wool, sponge, and gauze. Total aerobic counts, coliforms, and Escherichia coli from each sample were enumerated. Values for the mean log10, log10 mean, and/or the log10 total numbers recovered were calculated for each set of 25 bacterial counts. Those statistics indicated that, for product sampled without storage, swabbing with cotton wool or sponge recovered about 30%, and swabbing with gauze recovered about 10% of the bacteria recovered by excision sampling; but that for product sampled after storage, swabbing with cotton wool or sponge recovered about 50% and swabbing with gauze recovered about 15% of the bacteria recovered by excision sampling. However, the incidences of samples positive for coliforms and E. coli were less for stored than for nonstored product with all methods of sampling. The findings indicate that the conditions of meat surfaces, the handling of product, and the state of the microflora might all affect the numbers of bacteria recovered by any sampling technique. Thus, the relationship between the numbers recovered by excision or any selected swabbing technique may differ for different types of noncomminuted, raw meat product.

Microbiological sampling of carcasses by excision or swabbing

Groups of 25 carcasses were obtained by random selection of carcasses at the end of each of eight commercial processes for the dressing or cooling of carcasses. Samples were collected from six groups of pig or beef carcasses by excision or swabbing with sponge, gauze, or cotton wool, with one sample obtained by each of the four methods from a separate, randomly selected site on each carcass. Total aerobic counts, coliforms, and Escherichia coli from each sample were enumerated. Values for the mean log10, log10 mean, and log10 total numbers recovered were calculated for each set of total aerobic counts. Those statistics indicated that the numbers of bacteria recovered by excision or swabbing with sponge or gauze were similar, while the numbers recovered by swabbing with cotton wool were at the lower end of or below the range of the numbers recovered by the other methods. The numbers of coliforms or E. coli recovered from carcasses by sampling areas up to 100 cm2 were too few for the estimation of log mean numbers. Sampling of two groups of carcasses by swabbing with gauze indicated that each 10-fold increase in the area sampled, from 10 to 1,000 cm2, approximately doubled the number of samples from which coliforms or E. coli were recovered. Sampling of six groups of carcasses from one process indicated that the sizes of swabs and volumes of diluent used for processing swabs did not have to be increased proportionally to the area of carcass surface sampled to recover numbers of E. coli proportional to the sampled area. It therefore appears that carcass sampling techniques can be varied widely without compromising the recovery of bacteria, and that the relative efficiencies with which bacteria are recovered by different techniques can be assessed by sampling each carcass in a group of 25 by each of the methods to be compared.