Molecular epidemiology and resistance mechanisms involved in reduced susceptibility to amoxicillin/clavulanic acid in isolates from a chronic care centre

Mar Olga Pérez-Moreno , Maria José Centelles-Serrano , Maria Cortell-Ortolá , Isabel Fort-Gallifa , Joaquim Ruiz (1) , Maria Isabel Llovet-Lombarte , Ester Picó-Plana , Anna Maria Jardí-Baiges

1 IDIBAPS - Institut d'Investigacions Biomèdiques August Pi i Sunyer

The aim of this work was to investigate the molecular epidemiology and mechanisms responsible for reduced susceptibility to amoxicillin/clavulanic acid (AMC) among cefazolin-susceptible isolates from patients admitted to a chronic care institution. In total, 51 (29.8%) of 171 isolates recovered between 2006 and 2008 were non-susceptible to AMC, of which 45 were susceptible to cefazolin. Nucleotide sequencing analysis revealed that 19 produced IRT-11 and the remaining 26 were OXA-1-producers. All of the OXA-1-producing isolates harboured the cassette array, which in 23 isolates was located together with and within a class1 integron and associated with (in 3 cases the integron lacked the Δ and or genes). Genotyping analysis performed by enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR) identified three different patterns among IRT-11-producing isolates (E1 to E3), with E1 being the most prevalent (63.2%), whilst the OXA-1-producing isolates were assigned to patterns E3 and E3a (isolates carrying typical class 1 integrons), E4 (isolates carrying defective integrons) and E5 (isolates without integrons). Genes encoding IRT-11 and OXA-1 were transferred by conjugation, and and were systematically co-transferred with . These results demonstrate that the high prevalence of decreased susceptibility to AMC among isolates from a chronic care hospital was mainly due to the simultaneous spread of two different clones, one of which comprised isolates producing IRT-11 and the other one comprised isolates that had acquired either the gene located in a class 1 integron and linked to or the gene.

Mots clés: Klebsiella pneumoniae; Amoxicillin/clavulanic acid; Resistance; IRT-11; OXA-1; Class 1 integrons

Domaines: Microbiologie et Parasitologie

Mar Olga Pérez-Moreno, Maria José Centelles-Serrano, Maria Cortell-Ortolá, Isabel Fort-Gallifa, Joaquim Ruiz, et al.. Molecular epidemiology and resistance mechanisms involved in reduced susceptibility to amoxicillin/clavulanic acid in isolates from a chronic care centre. International Journal of Antimicrobial Agents, 2011, 37 (5), pp.462. ⟨10.1016/j.ijantimicag.2010.12.010⟩. ⟨hal-00685790⟩