A fusion protein including a phage tail-spike protein ΦAB6TSP and a signal indicator is provided. Also, a method of detecting bacteria having pseudaminic acid (Pse) is provided, including steps of contacting a sample with a phage tail-spike protein ΦDAB6TSP; and detecting a signal from the sample. The fusion protein and the method of detecting bacteria can be applied to a set of practical diagnosis and therapeutic alternative against Pse-coated antibiotic resistant pathogenic bacteria.