The antibiotic resistance patterns of gram-negative fecal bacteria from pigs in three herds with different histories of antibiotic exposure were examined. In general, smaller proportions of antibiotic-resistant or multiply resistant fecal isolates (P < 0.05) were obtained from pigs in a herd not exposed to antimicrobial agents for 154 months than from pigs in a herd continuously exposed to antimicrobial agents at subtherapeutic doses or from pigs in a herd exposed only to therapeutic doses of antimicrobial agents. The proportions of antibiotic-resistant and multiply resistant strains were greater among isolates from pigs in the therapeutic herd than in the non-antibiotic-exposed herd (P < 0.05). The proportion of antibiotic-resistant isolates in the non-lactose-fermenting population was greater than that in the lactose-fermenting population, regardless of herd. The results suggest that any form of antimicrobial exposure will increase the prevalence of antimicrobial and multiple resistance of fecal bacteria.
|Number of pages
|Applied and Environmental Microbiology
|Published - 1989
ASJC Scopus subject areas
- Food Science
- Applied Microbiology and Biotechnology