SPREAD AND IDENTIFICATION OF STREPTOMYCIN RESISTANT ISOLATES IN NEW YORK

The aminoglycoside antibiotic streptomycin is the most widely used antibiotic for the control of fire blight, caused by the bacterium Erwinia amylovora. In several countries use of streptomycin is prohibited or highly regulated due to concerns about antibiotic resistance development. Streptomycin resistance has been identified throughout the western United States and has developed independently in Canada, New Zealand, Israel and Lebanon. Streptomycin has been routinely applied in New York State for the past 50 years with no recorded resistance development. In 2002 and 2003, resistant isolates were identified in two related orchards in Wayne County, NY. Resistance developed due to the acquisition of the strA-strB gene cluster, previously characterized in populations of streptomycin resistant E. amylovora found in Michigan. Infected trees originated in Michigan and it is likely bacteria were imported on infected nursery stock. The movement of infested plant material poses a great threat to the continued use of streptomycin as a routine application to control fire blight. The importation of resistant isolates into countries that currently do not have endemic E. amylovora populations could seriously impede eradication measures.