Background: Approximately 80% of nosocomial infections are caused by strains of Klebsiella pneumoniae. Resistance to -lactam antibiotics is a result of expression of extended-spectrum -lactamase (ESBL) genes. Recently, phage therapy has gained increasing attention due to its many advantages over chemotherapy. Objectives: The aim of this study was to isolate ESBL-positive Klebsiella pneumoniae strains from different types of wounds, and a lytic bacteriophage against them. Methods: During a two-year period from January 2013 to February 2015, in a cross-sectional study, 41 K. pneumoniae strains were isolated from 193 categories of infected wounds at three hospitals in Isfahan, Iran. Phenotypic and genotypic methods were used to detect the ESBL-positive strains. A lytic phage against K. pneumoniae was isolated, and its host range, morphology, thermal and pH stability, saline stress, and estimated genome size were determined. Results: Of the 41 K. pneumoniae isolates, 18 were ESBL-producing and 36 carried antibiotic-resistance genes. A total of 36 out of 41 isolated samples carried one or more resistance genes. The results showed that the differences between phenotypic and genotypic identification methods were significant (P = 0.0001). The SHV, CTX-M, and TEM genes were detected in 29, 10, and 9 isolates of the tested bacteria, respectively. No bacteria contained both the SHV and the CTX-M genes. The frequency of the SHV gene was significantly higher than that of the other genes (P = 0.0001). The phage’s morphology features placed it in the Myoviridae family. Only 38 out of 41 clinical isolates were susceptible to the phage. Phage titers were completely preserved after one hour of incubation at 30°C and 40°C, and they were stable at different pH values. The phage’s survival decreased when the salt concentration was increased. Conclusions: The high rate of isolation of antibiotic-resistant strains of K. pneumoniae was consistent with other studies. As the phage was virule
