1. INTRODUCTION Klebsiella pneumoniae (K. pneumoniae), is a Gram-negative bacterium belongs to the Enterobacteriaceae family. It is an important opportunistic pathogen and a frequent cause of urinary tract infections (UTIs) and pneumonia (Podschun and Ullmann, 1998). It is the second Gram negative causative agent of UTI (Schembri et al., 2005). UTIs represent one of the most common diseases encountered in medical practice. There is a growing concern regarding antimicrobial resistance worldwide, particularly in K. pneumoniae and other causative agents of UTIs (Rashed et al., 2008). The predominant mechanism for resistance to β-lactam antibiotics in gramnegative bacteria is the production of β-lactamase. In addition, production of extendedspectrum β-lactamases (ESBLs) is another important mechanism which is responsible for resistance to the third-generation cephalosporins (Paterson et al., 2003). ESBLs are plasmid mediated enzymes that are able to hydrolyse a wide variety of penicillins and cephalosporins (Turner, 2005). ESBLs are more prevalent in K. pneumoniae than in any other Enterobacterial species. K. pneumoniae isolates usually carry a chromosomal βlactamase, most commonly SHV (Haeggman et al., 2004) and the plasmid variants have probably derived from the chromosomal SHV genes (Chaves et al., 2001). Plasmid-mediated SHV-type ESBLs are wide spread in clinical isolates of K. pneumoniae (Ryoo et al., 2005).