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00925njm 22002777a 4500 dc Ortega, Adriana author Oteo-Iglesias, Jesus author Aranzamendi-Zaldumbide, Maitane author Bartolomé, Rosa M author Bou, Germán author Cercenado, Emilia author Conejo, María Carmen author González-López, Juan José author Marín, Mercedes author Martínez-Martínez, Luis author Merino, María author Navarro, Ferran author Oliver, Antonio author Pascual, Álvaro author Rivera, Alba author Rodríguez-Baño, Jesús author Weber, Irene author Aracil, Belen author Campos, Jose author 2012-07 We conducted a prospective multicenter study in Spain to characterize the mechanisms of resistance to amoxicillin-clavulanate (AMC) in Escherichia coli. Up to 44 AMC-resistant E. coli isolates (MIC ≥ 32/16 μg/ml) were collected at each of the seven participant hospitals. Resistance mechanisms were characterized by PCR and sequencing. Molecular epidemiology was studied by pulsed-field gel electrophoresis (PFGE) and by multilocus sequence typing. Overall AMC resistance was 9.3%. The resistance mechanisms detected in the 257 AMC-resistant isolates were OXA-1 production (26.1%), hyperproduction of penicillinase (22.6%), production of plasmidic AmpC (19.5%), hyperproduction of chromosomic AmpC (18.3%), and production of inhibitor-resistant TEM (IRT) (17.5%). The IRTs identified were TEM-40 (33.3%), TEM-30 (28.9%), TEM-33 (11.1%), TEM-32 (4.4%), TEM-34 (4.4%), TEM-35 (2.2%), TEM-54 (2.2%), TEM-76 (2.2%), TEM-79 (2.2%), and the new TEM-185 (8.8%). By PFGE, a high degree of genetic diversity was observed although two well-defined clusters were detected in the OXA-1-producing isolates: the C1 cluster consisting of 19 phylogroup A/sequence type 88 [ST88] isolates and the C2 cluster consisting of 19 phylogroup B2/ST131 isolates (16 of them producing CTX-M-15). Each of the clusters was detected in six different hospitals. In total, 21.8% of the isolates were serotype O25b/phylogroup B2 (O25b/B2). AMC resistance in E. coli is widespread in Spain at the hospital and community levels. A high prevalence of OXA-1 was found. Although resistant isolates were genetically diverse, clonality was linked to OXA-1-producing isolates of the STs 88 and 131. Dissemination of IRTs was frequent, and the epidemic O25b/B2/ST131 clone carried many different mechanisms of AMC resistance. Antimicrob Agents Chemother. 2012 Jul;56(7):3576-81. doi: 10.1128/AAC.06393-11. Epub 2012 Apr 9. 0066-4804 http://hdl.handle.net/20.500.12105/8587 22491692 10.1128/AAC.06393-11 1098-6596 Antimicrobial agents and chemotherapy Spanish multicenter study of the epidemiology and mechanisms of amoxicillin-clavulanate resistance in Escherichia coli