EFFECTS OF COLD STRESS ON THE ANTIMICROBIAL DRUG-RESISTANCE OF ESCHERICHIA-COLI OF THE INTESTINAL FLORA OF SWINE

Faecal samples were initially collected from pigs of different age gro ups, over periods considered to be seasonally normal and stable (basel ine), and during times in which drastic drops in environmental tempera ture (cold stress) occurred. Baseline bacterial resistance to ampicill in and tetracycline were significantly higher (P < 0.05) in younger th an in older pigs. Also, when animals were exposed to excessively cold conditions, there was a significant (P < 0.05) increase in ampicillin and tetracycline resistance in Escherichia coli for animals of all age groups. These results may indicate that factors other than feeding or use of antibiotics may play a role in establishing or maintaining the antibiotic resistance microflora of pigs, especially in those operati ons where animals are maintained outdoors, with minimal protection aga inst extreme weather conditions.