Cross-contamination during transportation and slaughter of poultry plays an important role for Campylobacter, according to researchers.

The study investigated the prevalence of Campylobacter in birds from three farms at different ages and corresponding carcasses and poultry products, as well as the effect of certain stages in the poultry slaughter process.

Campylobacter-infected flocks may be a source of the bacteria for corresponding carcasses but cross-contamination is a big factor, according to a study published in the journal Foods.

Samples from broiler flocks at the farm and their carcasses and poultry meat were collected between May and June 2014. Slaughterhouse environment and processing equipment were also sampled.

Three poultry broiler farms in the North of Spain were seleced. The first farm had two houses, one with a capacity of 24,500 birds and the other holding 35,500 birds. The second farm had one house with 31,000 birds and the third farm had one house with 35,000 birds.

Samples from the same flock at different ages were taken at each farm. A total of 160 samples from three broiler flocks were collected.

Broilers from the three farms were slaughtered on the same day. Those from the third farm, which were Campylobacter negative at the farm level, were slaughtered before positive flocks from the other two farms.

Samples from poultry meat were taken at the processing plant. The breast, legs, and wings were seleced as they are the most widely consumed parts.

Samples were taken from the scalding water, defeathering machine, water used for washing final carcasses (before refrigeration), and from work tables at the processing plant. They were taken at the beginning of production when surfaces and equipment were clean and disinfected, and in the middle and end of the working day before cleaning and disinfection.

Campylobacter was not detected in birds under two weeks of age from two of the three farms that became colonized with the pathogen during the growing period.

Campylobacter spp. was detected in the first two farms in 35 and 42-day-old broilers but was not found in birds from the third farm.

The two houses on the first farm were positive on day 35. Significant differences in Campylobacter counts were found between the seven and 14-day-old and the 35 and 42-day-old broilers in the first two farms and between the 35 and 42-day-old broilers in the first two farms. Researchers said the age of broilers could be associated with an increased risk of Campylobacter in poultry flocks.

Birds were analyzed for Campylobacter spp. on the same day, they were transported to the slaughterhouse for processing (day 42). Those from the third farm were negative before being taken there.

All samples of birds from this farm at the slaughterhouse and processing plant were Campylobacter-positive suggesting the poultry carcasses were cross-contaminated during the transportation and slaughter process.

After defeathering, Campylobacter spp. was detected in all carcasses from the first farm. After evisceration, it was down to 80 percent positive samples. After chilling, it was detected in 90 percent of the carcasses. In the processing plant, it was found in 73.33 percent of samples.

Campylobacter spp. was detected in all carcasses from the second farm after defeathering, evisceration and after refrigeration. After washing, it decreased to 60 percent of samples positive. In the processing plant, it was detected in all samples.

All carcasses analyzed after defeathering were Campylobacter-positive, even in those from negative farms. This high prevalence could be explained by the previous stage, scalding, as the temperature was only 52 degrees Celsius, said researchers.

In products from the first farm, Campylobacter spp. was detected in 60 percent, 100 percent and 60 percent of the legs, breast, and wings, respectively. It was found in all poultry meat portions analyzed from the second farm. All meat samples from the third farm were Campylobacter positive.

Campylobacter was detected in transport crates after cleaning and disinfection. All equipment and environment samples analyzed by PCR were Campylobacter negative at the beginning of the working day after cleaning and disinfection.

However, in the middle and the end of the working day, it was detected in the scalding water and the defeathering machine. Campylobacter was only found on the working table at the end of the day.