Carbapenem resistance continues to erode the effectiveness of antibiotics such as imipenem and meropenem in the clinic. Resistance mechanisms can include interplay between porin loss (membrane permeability), mutation of penicillin binding proteins necessary for cell division, and expression of class A, B and D β-lactamases. Bacterial resistance to β-lactams such as penicillin or amoxicillin has...

From the Department of Infectious Diseases, Lahey Clinic, Burlington, Mass., and Harvard Medical School, Boston (G.A.J.); and the Department of Geographic Medicine and Infectious Diseases, Tufts–New England Medical Center and Tufts University School of Medicine, Boston (L.S.M.-P.). Address reprint requests to Dr. Jacoby at Lahey Clinic, 41 Mall Rd., Burlington, MA 01805, or at george.a.jacoby@l...

The use of ?-lactamase inhibitors in combination with ?-lactam antibiotics is an emerging area drug discovery. This strategy allows the restoration therapeutic efficacy these clinical against multiresistant bacteria. These pathogens are resistant because they express enzymes, which prevent antibiotic action by catalyzing hydrolysis ring. enzymes quite diverse both their structural architecture ...

b a ckground: quorum-sensing systems regulate expression of several virulence factors in pseudomonas aeruginosa . this study investigated the relation between expression of the las quorum-sensing system and expression of mexy and ampc in35 clinical isolates of p. aeruginosa . m e t hods: antibiotic susceptibility was determined by the disc diffusion method according to the clinical and laborato...

background: infectious by pseudomonas aeruginosa has spread worldwide and metallo-beta-lactamases (mbl) are being reported with increasing frequency. the aim of this study was to investigate the antibiotic susceptibility and distribution of blavim and blaimp genes in p. aeruginosa isolates from zanjan province of iran. methods: a total of 70 p. aeruginosa isolates were identified from patients ...

Beta-lactamase enzymes (BLs) have become the most worrisome mediators of antimicrobial resistance expressed by gram-negative bacteria (GNB). The multiple families of BLs have in common the ability to hydrolyze the -lactam rings of one or more members of the penicillins, cephalosporins, cephamycins, carbapenems, and monobactams. Extended-spectrum -lactamases (ESBLs) are a subset of BLs that conf...

We constructed a phylogenetic analysis of class A beta-lactamases and found that the blaCTX-Ms have been mobilized to plasmids approximately 10 times more frequently than other class A beta-lactamases. We also found that the blaCTX-Ms are descended from a common ancestor that was incorporated in ancient times into the chromosome of the ancestor of Kluyvera species through horizontal transfer. C...

The beta-lactamase specified by an R(te16) plasmid in Bordetella bronchiseptica was purified 200-fold by carboxymethyl-Sephadex column chromatography and electrofocusing. The enzyme has a molecular weight of 46,000 +/- 3,000 and an isoelectric point of 8.3 and was highly active against phenethicillin, oxacillin, and propicillin. The enzyme activity was inhibited by sodium chloride but not by fe...

background :   ampc β-lactamases are important cephalosporinases chromosomally encoded in many of enterobacteriaceae and a few other organisms where they mediate resistance to cephalothin, cefazolin, cefoxitin and penicillins. the six different families of plasmid-mediated ampc β-lactamases have been described, but no phenotypic test can discriminate among them. ampc multiplex pcr has been succ...