Antibiotic resistance of Escherichia coli and Salmonella from apparently healthy slaughtered cattle and pigs, and diseased animals in Zambia.

Escherichia (E.) coli and Salmonella (S.) choleraesuis (subsp. choleraesuis and subsp. salamae) from apparently healthy slaughtered cattle and pigs in 1989 in Zambia, were examined for antibiotic resistance and the presence of conjugative R plasmid. Salmonella strains from diseased animals (cattle, chickens, leopards, lions and warthogs) were similarly tested. The majority of the cattle had been nomadically kept in so-called "traditional farms" while all the pigs were from commercial farms. More pigs (39%; 41/105) harboured drug-resistant E. coli than cattle (6.7%; 7/105). Moreover, the number of drug-resistant E. coli was higher among strains from pigs (31.2%; 49/157) than cattle (4.2%; 7/167). For both cattle and pigs, drug resistance was more frequently observed against tetracycline, streptomycin, sulfadimethoxine and ampicillin than other antibiotics and the single resistance pattern occurred most frequency, especially among pig E. coli strains. Drug-resistant Salmonella was recorded in 3.6% (1/28) of strains from slaughtered cattle and 31.3% (10/32) of those from diseased animals. Drug-resistant E. coli from pigs and cattle carried R plasmid at high frequency.