IntroductionMicrobial resistance through extended-spectrum beta-lactamase (ESBL) was first reported in the early1980s in Europe and then in the United States soon after the introduction of third- generation cephalosporins to clinical practice (Hassan and Abdalhamid, 2014). The enzyme β- lactamase continues to be the leading cause of resistance to betalactam antibiotics in gram-negative bacteria. There has been an increased incidence and prevalence of ESBL enzymes that hydrolyze and cause resistance to oxyimino-cephalosporins and aztreonam (Versalovic et al, 2011). More than 300 different ESBL variants have been described (Ahmed et al, 2013). Although temoneira (TEM) and sulphydryl variable (SHV) variants are the most common ESBLs, strains expressing CTX-M ESBL have begun to emerge ( Ahmed et al, 2013).The dominant enzyme variants until the late 1990s were TEM,SHV and OXA( Livermore and Hawkey, 2004; Livermore et al, 2007). New families of ESBLs have emerged (6), including families of pseudomonas extended-resistance (PER) and Vietnamese extended-spectrum beta– lactamase (VEB) ( Stürenburg and Mack, 2003). VEB and PER variants are rare and are valuable for study. PER-1 was first detected in Pseudomonas aeruginosa (Nordmann et al, 1993) and later in Salmonella enteric and Acinetobacter isolates. PER-2, which shows 86% homology to PER-1, has been reported in S. enterica, E. coli, Klebsiella pneumoniae, Proteus mirabilis, and Vibrio cholera O1 El Tor (Bauernfeind et al, 1996; Petroni et al , 2002).The blaSHV genes are responsible for the production of SHV þ-lactamases , large families ofenzymes with evolutionary affinity. Of the 172 enzyme types in the SHV family, 45are extended-spectrum þ-lactamases on transferable elements such as plasmids and transposons (Al-Jasser, 2006;Shah et al, 2004) . This localization of bla genes can facilitate horizontal spreading of antibioticresistance among bacterial strains (El Salabi and Walsh, 2013).K. pneumonia resides in the intestinal tract of about 40% of humans and animals. It is an opportunistic human pathogen, meaning that under certain conditions it can cause disease. For example, nosocomial infections are those contracted by hospitalized patients in a weakened state (Manikandan and Amsath, 2013). K. pneumoniae causes recurrent cough and acute exacerbation of chronic obstructive pulmonary disease defined as presence of increased sputum volume, purulence and dyspnea and is responsible for 30-50% of exacerbations (Madhavi, 2012). K. pneumoniaeis naturally resistant to ampicillin, but not to extended-spectrum β-lactam antibiotics. Many factors can contribute to the resistance of bacteria towards antibiotics. Adaptation of bacteria to stressful environments can result in bacteria adaptation, survival and growth. This could ultimately result in the production of ESBL producers in K. pneumonia (Puspanadan et al, 2013).
đang được dịch, vui lòng đợi..