Frequency of Various Types of Beta-Lactamase Enzymes inEscherichia coliStrains Isolated From Urine Samples in Aliabad, North-east of Iran

Abstract

BackgroundBeta-lactam antibiotics have long been used to treat bacterial infections, but resistance to these antibiotics is now a concern. Overuse and misuse of these antibiotics have caused difficulties in treating many infectious diseases (1). Production of beta-lactamase enzymes among clinical isolates of Escherichia coli is one of these concerns. E. coli is a common cause of urinary tract infections (UTIs) and some nosocomial infections such as sepsis, wound infection, gastroenteritis and neonatal meningitis. Antibiotic resistance of E. coli has been reported worldwide and its resistance to antibiotics has raised a great deal of concern in both developing and developed countries. Therefore, identification of the antibiotic resistance pattern of E. coli is highly important from clinical perspective (2).Production of beta-lactamase enzymes is the most common resistance mechanism in Gram-negative bacteria. This enzyme hydrolyzes beta-lactam drugs such as cephalosporins and penicillins. Over the past two decades, new beta-lactam antibiotics have been developed that are specifically resistant to beta-lactamase enzymes. However, gram-negative bacteria have developed new strategies to inactivate these novel antibiotics by producing new beta-lactamases such as AmpC, extended-spectrum β-lactamases (ESBLs), and metallo-β-lactamases (MBLs). AmpC β-lactamases that are called cephalosporinase are also partially capable of hydrolyzing other betalactams. These enzymes hydrolyze broad-spectrum cephalosporins such as ceftazidime, ceftriaxone, cefepime, and monobactams (i.e., aztreonam and cephamycin), but they are not inhibited by common inhibitors such as clavulanate (3).ESBLs are enzymes that, in addition to resistance to penicillins, mediate the development of resistance to a wide range of cephalosporins (e.g., ceftazidime,

Phenotypic Detection of Beta-lactamases among Proteus mirabilis, Enterobacter cloacae, and Citrobacter freundii Isolates from Urinary Samples in Gorgan, Northeast Iran

“…and E. coli, but they have also been described in other genera, such as Enterobacter, Citrobacter, Proteus, Morganella , Providencia, Salmonella, and Serratia [8]. AmpC β-lactamases are a type of cephalosporins, rendering Enterobacteriaceae resistant to most β-lactams but are not active against cefepime and carbapenems [7,9]. MBLs or carbapenemases are responsible for carbapenem resistance and are increasingly detected among Enterobacteriaceae bacteria [7].…”