Characterization of resistance patterns and detection of apramycin resistance genes in Escherichia coli isolated from swine exposed to various environmental conditions

• Published in: International journal of food microbiology Vol. 89; no. 1; pp. 11 - 20
• Main Authors: Mathew, Alan G, Arnett, Debbie B, Cullen, Patricia, Ebner, Paul D
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.12.2003; Elsevier
• Subjects: Animal Husbandry - methods; Animals; Anti-Bacterial Agents - pharmacology; Antibiotic resistance; Apramycin; apramycin sulfate; Biological and medical sciences; Colony Count, Microbial - veterinary; DNA, Bacterial - analysis; Drug Resistance, Bacterial - genetics; Escherichia coli; Escherichia coli - classification; Escherichia coli - drug effects; Escherichia coli - genetics; Escherichia coli Infections - drug therapy; Escherichia coli Infections - microbiology; Escherichia coli Infections - veterinary; Feces - microbiology; Food industries; Food microbiology; Fundamental and applied biological sciences. Psychology; Meat and meat product industries; Microbial Sensitivity Tests - veterinary; Nebramycin - analogs & derivatives; Nebramycin - pharmacology; Polymerase Chain Reaction - veterinary; Random Allocation; Stress; Swine; Swine Diseases - drug therapy; Swine Diseases - microbiology; Swine; Escherichia coli; Apramycin; Stress; Antibiotic resistance; Farming animal; Environmental factor; Antimicrobial agent; Characterization; Antibiotic; Vertebrata; Meat animals; Mammalia; Sensitivity resistance; Bacteria; Artiodactyla; Animal production; Ungulata; Enterobacteriaceae
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/S0168-1605(03)00124-7

Weaned pigs were separated into eight treatments including a control without exposure to apramycin; a control with exposure to apramycin; and apramycin plus either cold stress, heat stress, overcrowding, intermingling, poor sanitation, or intervention with oxytetracycline, to determine the effects of management and environmental conditions on antibiotic resistance among indigenous Escherichia coli. Pigs exposed to apramycin sulfate received that antibiotic in the feed at a concentration of 150 g/ton for 14 days. Environmental treatments were applied 5 days following initial antibiotic administration and maintained throughout the study. Fecal samples were obtained on day 0 (prior to antibiotic treatment) and on days 2, 7, 14, 28, 64, 148, and 149. E. coli were isolated and tested for resistance to apramycin using a minimum inhibitory concentration (MIC) broth microdilution method. Macrorestriction profiling, arbitrarily primed PCR, PCR targeting a gene coding for apramycin resistance, and DNA hybridization were used to characterize genetic elements of resistance. Increased ( P<0.0001) resistance to apramycin was noted in E. coli from all treatment groups administered apramycin. MICs of isolates from control pigs receiving apramycin returned to pretreatment levels following removal of the antibiotic, whereas isolates from cold stress, overcrowding, and oxytetracycline groups expressed greater ( P<0.05) MICs through day 64, before returning to pretreatment levels. Genetic analysis indicated that all resistant isolates carried the aac(3)IV gene sequence and this sequence was found in a variety of E. coli isotypes. Our data indicate that E. coli resistance to apramycin is increased upon exposure to various stressors.