Detection of integrons in worldwide nosocomial isolates of Acinetobacter spp.

Objective: To examine the distribution of integrons in genotypically unrelated worldwide multiresistant clinical isolates of Acinetobacter spp.
Methods: The presence and genetic location of class 1, 2 and 3 integrons were examined in a genotypically heterogeneous collection of 25 nosocomial isolates of Acinetobacter spp., from 15 locations in 11 different countries worldwide, by hybridization and PCR-based methods. Class 1 integron structures were characterized genetically by a PCR mapping technique.
Results: Class 1 integrons were detected in 17 of the 25 Acinetobacter isolates examined. Only one isolate contained a class 2 integron. No class 3 integrons were detected. The integrons varied in size and in the number of inserted cassettes, but similar integrons were found in genotypically distinct isolates from different locations worldwide. These structures were integrated into the chromosome in all isolates where they were detected, although some integrons were capable of subsequent transfer or mobilization. Genes coding for aminoglycoside-modifying enzymes formed the predominant cassettes identified within the integrons.
Conclusions: Clinical isolates of Acinetobacter spp. from diverse locations seem to share resistance mechanisms acquired from other genera by a variety of mechanisms, including dissemination of integrons. Once integrons are incorporated into the bacterial genome, Acinetobacter spp. are potentially able to act as a reservoir of resistance genes for other species and genera.