Background: Food-borne infectious diseases cause huge economic loses, lowered quality of life and, in extreme cases, losses of lives. In general, these are global problems but the magnitudes differ. Pathogens involved include those of the genera Salmonellae, Escherichia, Campylobacter, Yersinia, Listeria, and Staphylococci. Infections follow consumption of contaminated foods or animal to human and human to human transmissions. Contaminated dairy products are among the top sources of food-borne infections. Most such infections come from unpasteurized dairy products, but pasteurized products are sometimes implicated. These occur because of either faulty pasteurization or due to post-pasteurization contaminations. Many factors hamper control of such infectious pathogens, including lack of vaccines, the presence of asymptomatic healthy carriers, existence of broad host range pathogens (with the hosts serving as reservoirs), resistance of pathogens to ordinary disinfectants, the long contamination-prone processes from production to consumption and increased frequency of resistance of pathogens to antibiotics. The antibiotic resistance property is hazardous in itself (whether with or without the contaminants being pathogenic) considering the potential for interspecies transfer of these resistance traits (be they chromosomal or plasmid-borne) to commensal or pathogenic bacteria in clinical settings and/or in the food chain. In low income countries, the problems are further compounded by the limited capacity for accurate diagnosis, overlap of symptoms, and the resulting (hit-or-miss) empirical treatment. Here, samples of dairy products were purchased from Addis Ababa supermarkets. The samples were subjected to enrichment and selective cultures to test the presence of and isolate gram-negative bacteria. The isolates were characterized by biochemical and molecular methods.
Results: All milk samples harboured gram-negative bacilli, which are likely to constitute hazard to public health. Moreover, all of the isolates exhibited intermediate-level or higher resistance to two or more clinically relevant antibiotics. Sequence alignment showed the isolates to be most closely related to Salmonella enterica.
Conclusion: This work found high level of contamination in all sampled milk. The reason(s) for this burden of contamination (either ineffective pasteurization or post-pasteurization contamination) need to be elucidated for meaningful targeted control.