Carriage of class 1 integrons and antibiotic resistance in clinical isolates of Acinetobacter baumannii from northern Spain

A collection of 70 clinical isolates of Acinetobacter baumannii from Bilbao in northern Spain was examined by PCR for the presence of class 1 integron structures. The organisms comprised 21 distinct RAPD genotypes, with 10 distinct antibiogram patterns. Four different integron structures were detected in a total of 59 (84%) of the 70 isolates, with two predominant integron structures found in 20 and 30 isolates each. No clear antibiogram differences could be correlated with the presence or absence of integron structures, but sequence analysis of two of the internal integron regions indicated homology with genes encoding ANT(2') adenyltransferase activity and AAC(6')-Ib acetyltransferase activity. Phenotypic analysis of aminoglycoside resistance profiles indicated that many isolates produced a combination of aminoglycoside-modifying enzymes, with most of the observed resistance to amikacin being associated with a gene encoding APH(3')-VI phosphotransferase, as detected by PCR. RAPD analysis indicated that all the Bilbao isolates producing APH(3')-VI were distinct from an epidemic integron-carrying and APH(3')-VI-producing Acinetobacter strain found in other regions of Spain. It is concluded that, although class 1 integrons are widely disseminated amongst clinical isolates of A. baumannii from the Bilbao region of Spain, at present they are not playing a major role in the dissemination of antibiotic resistance genes in this region.