Poster: Biology & Disease Mgmt: Chemical Control
Effect of kasugamycin application on bacterial resistance to kasugamycin and cross resistance with other antibiotics
S. GEBBEN (1), S. Gebben (2), G. McGhee (2), G. Sundin (2) (1) Michigan State University, U.S.A.; (2) Michigan State University, U.S.A.
Kasugamycin (Ks) is a an alternative option to the use of streptomycin for the control of bacterial plant diseases and it has been shown to be as effective as streptomycin in controlling fire blight, caused by Erwinia amylovora. However, there remains a concern that Ks application in orchards will select for Ks resistance that could be linked with other resistance genes that are active against antibiotics used in human medicine. To monitor for this possibility, we assessed the effect of the use of Ks (Kasumin 2L) in orchard systems on the level of resistance to Ks and five other antibiotics (streptomycin, ampicillin, gentamicin, cefotaxime, and tetracycline). Two sets of leaf and soil samples were collected (treated and non-treated with Ks) from a total of 23 orchards (5 different tree hosts from 7 states). Samples were processed in the laboratory and dilution plated onto King’s B medium with or without Ks amendment. Bacterial population sizes were determined per sample and up to 15 gram-negative colonies growing on Ks-amended medium per sample (a total of 1,038 isolates) were used in antibiotic resistance screening. Although the bacterial population sizes were larger on Ks-amended medium from soil compared to leaf samples, there were no differences in populations from Ks treated vs. non-treated sites. Similarly, there was no difference in levels of resistance to the five antibiotics tested between Ks-treated and non-treated sites.