Their report, published in the Journal of the American Medical Association, said the "superbug" -- the l9A strain -- could only be killed by levofloxacin -- an antibiotic approved for adults only.

The two partners in the private practice Legacy Pediatrics, in Rochester, N.Y., had preformed an ear tap or typanocentesis -- the puncturing of the eardrum to relieve pain and drain fluid. The l9A strain was confirmed when the fluid also was tested by the University of Rochester Medical Center.

"Children with the new strain of superbug represented a small subset of those in our practice, but the results are worrisome, especially since there are no new antibiotics in the pipeline for ear infections in children," Dr. Michael Pichichero, of Legacy Pediatrics, said in a statement. "While we must be careful not to create undue alarm, the potential exists for newly evolved strains to spread to the ears of more children."