Occurrence and distribution of species of Enterobacteriaceae in selected Ethiopian traditional dairy products: A contribution to epidemiology

A total of 316 samples of traditional milk and milk products (66 milk, 52 Ergo – naturally fermented milk, 66 butter, 66 buttermilk and 66 Ayib, Ethiopian cottage cheese); 20 samples of cleaning water and 20 samples of udder swabs were collected in the central highlands of Ethiopia to assess the occurrence and distribution of enteric bacteria. A total of 534 isolates distributed among 10 genera and 20 species were identified. Klebsiella, Escherichia and Enterobacter were the dominant genera in their order of abundance with Escherichia coli, the most prevalent species. Erwinia, Klyuvera and Providentia were the least abundant genera. Most of the genera/species identified were isolated predominantly from milk samples followed by butter and buttermilk during the dry season and from milk, buttermilk and butter during the wet season in order of their abundance. The overall mean aerobic mesophilic, coliform and enterobacterial counts of dairy products were 8.3, 4.5 and 5.2 log cfu mL⁻¹ or g⁻¹, respectively. Ergo samples had 0.7 more log cfu of aerobic mesophilic count than butter samples. Coliform and enterobacterial counts were generally lower in samples of fermented milk products than milk with the largest difference being 1.2 log cfu mL⁻¹ for coliform and 1 log cfu mL⁻¹ for enterobacteria between milk and Ergo samples. The highest and lowest coliform counts were 5.2 and 3.9 log cfu mL⁻¹ or g⁻¹ in samples collected from cooperative centers and smallholder producers, respectively. The knowledge of the enteric bacterial properties of traditional dairy products is essential for the improvement of quality and preservation of the products thereby provide a wholesome product to the consumer with minimum health risk.