Enumeration of total coliforms and Escherichia coli on broiler chickens by whole carcass rinsing and an alternative scrape method

An experiment was conducted to compare the whole carcass rinse method (WCR) versus scraping the breast skin or back skin for enumeration of total coliforms and E. coli. In each of two replicate trials, four pre-chill broiler carcasses were collected from two different commercial processing plants. WCR was conducted on each carcass using 400 mL 1% peptone and 1 min of shaking. After the WCR, a blunt edge stainless steel blade was used to scrape an area measuring approximately 80 square cm of the breast (front) skin. A similar area was scraped on the back of the carcass. After scraping, the blades were placed in plastic tubes and vigorously shaken for 3 sec in 30 mL 1% peptone. One mL of rinsate from the WCR and each scrape blade tube was plated to determine total coliforms and E. coli. Results are reported as log cfu/mL. Mean total coliform WCR counts (5.1) were significantly higher (P<0.05) than back scrapes (2.8), which were higher than front scrapes (2.2). Mean E. coli WCR counts (4.5) were higher than back scrapes (2.4), which were higher than front scrapes (1.6). There were no significant differences in counts due to the plant of origin. WCR counts were higher than scrape counts due to the difference in surface area sampled. When adjusted for surface area, mean total coliform back scrape count was 4.2, compared to WCR count of 5.1. Higher back scraping counts (vs. front) suggest that either more total bacteria are present on the back of the carcass or more bacteria on the back are loosened and recovered after scraping.