Characterization Of Multi-Drug Resistant Enterobacter SPP. In Camp Creek, IA

Abstract

Antibiotics are vital in fighting bacterial infections and are necessary in effectively raising livestock in close quarters and high numbers. They are widely used and relatively little restrictions are placed on their use. Misdiagnosis and overuse has led to bacteria evolving resistance mechanisms to avoid the effects of the antibiotics. These bacteria propagate easily and transfer their resistance genes to other, antibiotic sensitive bacterial strains in certain aquatic systems. Such inter- and intraspecies transfer of antibiotic resistance is a major environmental and health risk. Therefore, we investigated the Camp Creek in Iowa to determine (i) the extent of antibiotic resistance in Enterobacter spp. and (ii) beef cattle ranching as a potential source contributing to the antibiotic resistant bacteria at this site. Greater bacterial loads were identified in samples from upstream of the cattle ranch suggesting they are not contributing bacteria or selective pressures for antibiotic resistance to the creek. We tested Enterobacter spp. for resistance against tetracycline, penicillin, ampicillin, erythromycin, chloramphenicol, kanamycin, and streptomycin and found resistance to all except the last two drugs. All isolates tested also exhibited multidrug resistance. Further research is needed to determine specific mechanisms of the multidrug resistant phenotype. Samples stored in liquid broth in the absence of any antibiotic lost resistance to tetracycline after 12 weeks, suggesting an extrachromosomal location for this trait. We conclude that reducing effluent levels of antibiotics would be necessary and sufficient to control such plasmid borne tetracycline resistance in Enterobacter spp.