In this paper, we introduce a sectorial episode of the form C r, where C is a set of events and r is an event. The sectorial episode C r means that every event of C is followed by an event r. Then, by formulating the support and the confidence of sectorial episodes, in this paper, we design the algorithm Sect to extract all of the sectorial episodes that are frequent and confidential from a given event sequence by traversing it just once. Finally, by applying the algorithm Sect to bacterial culture data, we extract sectorial episodes representing drugresistant change.