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Antibiotic-free pig production does not guarantee higher levels of consumer protection
Raleigh (aho/lme) – In the lay press, an association is commonly made between the use of antibiotics in pigs and the occurrence of antibiotic-resistant Salmonella in both live animals and pigmeat. But according to scientists at North Carolina State University, this view may not be entirely correct. In a study recently published in the Journal of Food Protection, they compared the prevalence and antibiotic resistance of Salmonella from conventional and “antibiotic-free” production systems. A total of 889 pigs and 743 carcasses were sampled in the study.
Salmonella prevalence was found to be significantly higher in pigs and carcasses from antibiotic-free syst-ems (15.2%) than from conventional systems (4.2%).
Antibiotic resistance was detected against 10 of the 12 antibiotics tested. Resistance was most commonly found against tetracycline (80%), streptomycin (43.4%) and sulfamethoxazole (36%). Frequency of resistance to all these antibiotics (except tetracycline) was higher among conventional farms.
A total of 28 resistance patterns were detected. A resistance pattern with streptomycin, sulfamethoxazole and tetracycline was the most common; the proportion of isolates with this pattern was virtually identical in the two types of production system (19.5%).
A pentaresistance pattern with ampicillin, chloramphenicol, streptomycin, sulfamethoxazole and tetracycline was strongly associated with antibiotic-free systems. Multidrug resistances of this type can make it more difficult to treat Salmonella infections in humans.
The study shows there is no justification for the commonly-held view that antibiotic-free production is associated with a lower prevalence of Salmonella and less antibiotic resistance. Multidrug-resistant Salmonella can occur in antibiotic-free production systems as well, sometimes more often than in conventional systems.
Gebreyes WA, Thakur S, Morrow WEM. Comparison of prevalence, antimicrobial resistance, and occurrence of multidrug-resistant Salmonella in antimicrobial-free and conventional pig production. J Food Prot 2006; 69 (4): 743-8
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