title: [Beta-lactamases and their role in resistance. PART 2: beta-lactamases in 21st century].
abstract: Resistance to beta-lactam antibiotics continues to increase, mostly due to the presence of various beta-lakta mases. As a result of the ability of the plasmids to acquire additional resistance determinants, many of the beta-lactamase producing pathogens became multidrug resistant. The most important beta-lactamases which compomise the use of beta-lactams nowdays are extended-spectrum beta-lactamases, inhibitor-resistant TEM and SHV beta-lactamases and carbapenemases. Carbapenemases are beta-lactamases which hydrolyse carbapenems. They belong to molecular classes A, B, and D. Class A comprises carbapenemases sensitive to inhibition by clavulanic acid. Most of them are chromosomaly encoded, but some of them are plasmid-mediated such as KPC-1 in Klebsiella pneumoniae and GES-2 in Pseudomonas aeruginosa. The class B carbapenemases are metallo-beta-lactamases of the IMP or VIM group. The class D carbapenemases are the most frequent in Acinetobacter baumannii but confer resistance to carbapenems only if other resistance mechanisms such as porin alterations, are present. Inhibitor resistant beta-lactamases are one of the most important causes of resistance to beta-lactam-inhibitor combinations. The resistance to these formulations can be also due to hyperproduction of TEM-1 beta-lactamase, modifications of the outer membrane proteins or production of OXA-type enzymes. IRT enzymes are derived from parenthal TEM-1 or TEM-2 beta-lactamases by point mutations in the beta-lactamase gene. The frequent use of beta-lactamase inhibitors in hospitals and general practice pose a selection pressure which favours spread of such strains in hospitals and community.
authors.affiliation: Zavod za mikrobiologiju, SNZ A. Stampar, Zagreb.
authors.forename: Branka
authors.initials: B
authors.lastname: Bedenić
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D015780:Carbapenems / Q000494:pharmacology; D018440:beta-Lactam Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D001618:beta-Lactamases