Comparison of Antibiotic Resistance in Aeromonas
Isolated
from Fish Collected from Heavy Metal Contaminated and
Uncontaminated Streams: Effect of Fish Trophic Status
ABSTRACT
Antibiotic resistance is a significant public health problem. An understanding of the mechanisms and factors that affect the acquisition and dissemination of antibiotic resistance traits is crucial if we expect to abate this trend. We have previously shown that antibiotic resistance increases along heavy metal contamination gradients. Aeromonas spp. cause bacterial septicemia on fish and can be readily isolated from most fish with or without lesions. We hypothesized that Aeromonas isolated from fish collected in a heavy metal contaminated stream would have higher incidences of antibiotic resistant (AR) Aeromonas than fish collected from more pristine streams. Over 780 fish were collected on the Savannah River Site, Aiken, SC. Fish species included redbreast and spotted sunfishes, largemouth bass and bullhead catfishes. Lesions were recorded. Samples were obtained by swabbing and subsequent streaking and replicated onto a series of plates each containing one of the following antibiotics: Kanamycin, Streptomycin, Tetracycline, Ciprofloxacin, Chloramphenicol, and Gentamycin. Over 4200 isolates were screened. Within a fish species, there were no statistically significant differences in the proportion of AR Aeromonas between the two streams. However there were significantly more AR bacteria on fishes associated with stream sediments, i.e., bullheads vs. sunfish or bass. Our hypothesis was not supported but we have shown that some fish have more AR bacteria on their surfaces than other fishes. Specifically, bottom-dwelling fish have more AR bacteria presumably from sediments than do water column fish. These data have far reaching public health implications.
