Antibiotic- and metal-resistantö öAöeörööoömöoönöaös isolated from environmental sources

Aeromonas is a ubiquitous aquatic bacterium that causes serious infections in both cold- and warm-blooded animals, including humans. Clinical isolates of the organism have shown an increasing incidence of antibiotic and antimicrobial drug resistances since the widespread use of antibiotics began. The genes for antibiotic resistance and metal resistance are frequently carried on the same plasmids, imparting both characteristics to the host bacterium. When there are either antibiotics or metals present in the environment, both markers are co-selected. Two hundred eighty-three Aeromonas isolates belonging to eleven different species were isolated from several streams and both urban and rural playa lakes in Lubbock, TX and New Mexico. The minimal inhibitory concentrations of seven metals, six antibiotics, and two synthetic drugs were determined. Low incidences of trimethoprim resistance, mercury resistance, and arsenite resistance were found. Antibiotic and metal resistances were not linked in almost all of the Aeromonas isolates. Plasmids were isolated from selected strains of the arsenite- and mercury-resistant organisms and transformed into Escherichia coli XLl-Blue MRP', showing that the resistance genes were carried on plasmids. From the data, it was concluded that mercury and arsenite resistance could be transferred to other organisms in natural environments.