It could mean 2 things...1) penicillin resistance developed by the organism causing it 2) second infection by some other organism...if you have more than 5 episodes per year of tonisillitis, then consider getting them removed by undergoing a 'tonsillectomy' to prevent further recurrences..if not ask your doctor for a repeat checkup and do a culture sensitivity test from the tonsil surface to see what organism is responsible for the infection and which antibiotic is best suited to eliminate it.