Prevalence and antimicrobial resistance of escherichia coli O157:H7 and salmonella, and the prevalence of staphylococcus aureus in dairy cattle and camels under pastoral production system

Authors: HUNDUMA, DIRIBA - Arsi University; AMENU, KEBEDE - Addis Ababa University; DESTA, HIWOT - International Livestock Research Institute Ethiopia; GRACE, DELIA - International Livestock Research Institute Ethiopia; Agga, Getahun; KERRO DEGO, OUDESSA - University Of Tennessee

Submitted to: Antibiotics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2023
Publication Date: 12/27/2023
Citation: Hunduma, D., Amenu, K., Desta, H., Grace, D., Agga, G.E., Kerro Dego, O. 2023. Prevalence and antimicrobial resistance of escherichia coli O157:H7 and salmonella, and the prevalence of staphylococcus aureus in dairy cattle and camels under pastoral production system. Antibiotics. 13(1). Article 26. https://doi.org/10.3390/antibiotics13010026.
DOI: https://doi.org/10.3390/antibiotics13010026

Interpretive Summary: Salmonella and Escherichia coli O157:H7 are two important human pathogens that could be acquired through unpasteurized milk and milk products. Specially it is critical to study their occurrence in dairy animals, cows and camels in developing countries particularly in pastoral communities with poor infrastructure for milk handling. Under such resource poor communities, milk is consumed without pasteurization, a practice that can expose people to milk borne pathogens. In this study we assessed the burden of these two pathogens in the fecal and milk samples collected from lactating dairy cows and camels. The antimicrobial resistance of the pathogens was also determined. E. coli O157: H7 occurred in four and three percent of the cow fecal and milk samples, respectively. Salmonella was detected in eight and four percent of cow feces and milk samples, respectively. E. coli O157:H7 was detected from a single fecal sample, and all milk samples were negative. Salmonella was detected from three percent of fecal and one percent of milk samples from camels. All E. coli O157: H7 and Salmonella isolates both from cows and camels were resistant to at least one antimicrobial. All isolates were susceptible ciprofloxacin and nalidixic acid which are critically important to human medicine. All E. coli O157:H7 and one-fifths of Salmonella cattle isolates were multidrug resistant, respectively. The lower burden of the two pathogens and corresponding lower antimicrobial resistance in the camels compared to cows could be attributed to their browsing nature. This study provides information necessary to educate the pastoral community to boil milk before consumption to safeguard the public especially children who are the most vulnerable to infections caused by these pathogens and often require antibiotic treatment.

Technical Abstract: Escherichia coli O157: H7 and Salmonella are common milk borne pathogens compromising the microbiological safety of raw milk. However, studies reporting on the occurrence of the pathogens in the developing countries like Ethiopia especially in pastoral production system are scarce. This study was conducted to assess the occurrence and determine the antimicrobial resistance of the two pathogens in milk and feces of lactating cows and camels raised under extensive pastoral animal production systems. We collected milk and fecal samples from lactating cows (n=154) and camels (n=158). Samples were analyzed for the pathogens using bacteriological culture following concentration by using immunomagnetic separation beads and identified using biochemical and latex agglutination tests. The bacterial isolates were tested for antimicrobial resistance (AMR) against nine antimicrobial agents. Fecal- and milk-prevalence of E. coli O157: H7 in the cows were 3.9% and 2.6%, respectively. Salmonella was detected in 8.4% and 3.9% of feces and milk samples, respectively in the cows. In camels, E. coli O157: H7 was detected from a single fecal sample, and all milk samples were negative. Salmonella was detected from 2.5% of fecal and 1.3% of milk samples from camels. All E. coli O157: H7 (n=11) and Salmonella (n=25) isolates, of both species and sample types, were resistant to at least one antimicrobial. All isolates were susceptible to the quinolones (ciprofloxacin and nalidixic acid). While all E. coli O157:H7 were susceptible, 4% of the Salmonella isolates showed reduced susceptibility to chloramphenicol. All of E. coli O157:H7 isolates (n=10) from cattle multidrug resistance (MDR; resistance to =3 antimicrobial classes) with 70% being resistant to three antimicrobial classes. On the other hand, only 21.1% (4/19) of Salmonella isolates from cattle were MDR. In conclusion, the presence of E. coli O157:H7 and Salmonella in lactating cows and camels is important consideration for the public health. Consumption of raw milk and close animal contact in the pastoral communities are two important exposures to these foodborne pathogens specially in children. Public education, personal and milk hygiene practices can reduce direct or milk-borne transmission of pathogens to humans through consumption of raw milk.