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Abstract
Integrons are a genetic element, similar to transposons, that mediate multiple drug resistance. This genetic element has the potential for acquiring "new" antibiotic resistance genes through the recombination of these genes into the integrons integration site attI. An integrase gene, intI1, a signature of class 1 integrons, mediates this recombination event. My hypothesis is that the integron serves as a vehicle for exchange of drug resistance genes and their eventual dissemination within microflora in the farm, including their final disposition into food-born pathogens like Salmonella and Campylobacter.|This study examines the prevalence of class 1 integrons in gram- negative bacteria in chicken litter from two poultry farms. Litter was collected from two farms participating in this study. Samples were collected at the time of chick placement (time 0), as well as at 2, 4, and 6 weeks following chick placement. Gram- negative enterics were isolated from the poultry litter on MacConkey agar. Isolated colonies were screened by Southern colony blot for intI. Those colonies that screened positive in the Southern blot were further analyzed by 53 PCR amplifying the integrons and cassettes as well as speciation of the colonies. A second Southern blot was performed after the PCR to screen for aadA1 (aminoglycoside resistance). The number of gram- negatives with intI consistently increased, although varying in the actual percentages. The lowest percentage was 12% and the maximum found was 68%. The amplified PCR products displayed a vast array of cassette combinations and sizes. Most samples showed 1 band that was 1 Kb. However, as many as 8 bands was found and sizes ranged from 600bp to 4 Kb. The class 1 integrons were present among a diverse number of genera, species, and genetic types. E. coli was the most prevalent organism found. It was hypothesized that the 1 Kb band was for aadA1. All samples with a 1 Kb band screened positive in the Southern blot for aadA1. My results indicate that integrons are not confined to veterinary or human pathogens, but are present among the normal microflora of the poultry farm as well.