¹Department of Pharmaceutical Microbiology, Faculty of Pharmacy, Ankara University, Yenimahalle, 06560 Ankara, Turkey DOI : 10.29228/jrp.31 The result of a crucial rise in the prevalence of antibiotic resistance of bacteria, and the development of an inadequate number of new antibiotics, over the last decade a marked increase in interest in the studies of phages has been observed. It was aimed to determine the commercial preparation including Pyo-bacteriophage and Intesti-bacteriophage and compare their efficiency with isolated bacteriophage vB_Pa01 against carbapenem resistant Pseudomonas aeruginosa. Susceptibility to the bacteriophages present in each cocktail was tested using the spot test. A total of 126 carbapenem-resistant P. aeruginosa isolates were included in this test. Bacteriophage susceptibilities of each isolate were tested by spot test method. Confluent, semi confluent, opaque lysis was considered a sensitivity. The absence of any lysis is reported as resistance. The lytic activity of the bacteriophage was found 46% (58/126) Pyo-bacteriophage and 36.5% (46/126) Intesti-bacteriophage and 63.5% (80/126) vB_Pa01 bacteriophage. The most effective bacteriophage preparation was the vB_Pa01 bacteriophage (63.5%) and the least effective one was Intesti-bacteriophage (36.5%). 95 (75.4%) of 126 carbapenem resistant. This is the first study that investigated two commercial bacteriophage cocktails against carbapenem resistant P. aeruginosa. The higher efficacy of vB_Pa01 bacteriophage is promising for creating an alternative preparation especially in the treatment of infections caused by MDR pathogens that are difficult to treat. Keywords : Bacteriophage; carbapenem resistant Pseudomonas aeruginosa; commercial bacteriophage cocktail; lytic activity