Assessment of carcass contamination with E. coli O157 before and after washing with water at abattoirs in Nigeria

The study was carried out to assess the level of beef carcass contamination with Escherichia coli including O157 strains before and after washing with water. Samples of water used for washing carcasses were collected and thirty beef carcasses were swabbed within a period of one month in each of three abattoirs located in North-Western states of Nigeria. E. coli were enumerated as indicator organisms. Using conventional biochemical tests, the isolation rate of E. coli in the 120 swab samples collected in each abattoir from external and internal surfaces of the carcasses was 58.3% at Kano abattoir, 70.8% at Sokoto abattoir, while 76.7% was recorded at Zango abattoir. E. coli counts from external and internal surfaces of the carcasses were enumerated as mean log and ranged between 4.3 Log(10) and 4.6 Log(10) cfu/cm(2) before washing, while the values were 4.6 Log(10) and 4.9 Log(10) cfu/cm(2) after washing. Data analysis revealed that the increase in E. coli counts after washing carcasses with water was statistically significant (P<0.05) in all the abattoirs. However, there was no statistically significant difference (P>0.05) between the 3 abattoirs in mean log of E. coli counts from external surfaces of carcass after washing. E. coli O157 was identified from both the water and surfaces of carcasses using Latex agglutination kit. A prevalence of 2.8% of E. coli O157 was detected in 360 swab samples from 90 beef carcasses examined. E. coli counts from water used in washing carcasses were between 22 and 120 cfu/100 ml. Of the 72 water samples, 3(4.2%) were positive for E. coli O157. In conclusion, there was increased contamination of carcasses during processing and water used in washing carcasses might have contributed to carcass contamination in all the abattoirs studied due to use of non-potable water.