Detection of aac(6')-I genes in amikacin-resistant Acinetobacter spp. by PCR

The distribution of aac(6')-I genes in 62 strains of Acinetobacter spp. resistant to amikacin, netilmicin, and tobramycin and susceptible to gentamicin, a phenotype compatible with synthesis of an AAC(6')-I enzyme, was studied by PCR and by DNA hybridization. Both methods gave similar results. Among the 51 Acinetobacter baumannii strains, aac(6')-Ib was found in 19 isolates and aac(6')-Ih was found in the remaining strains. The aac(6')-Ig gene was present in all 10 A. haemolyticus strains studied and was detected only in this species. A pair of degenerate oligonucleotides complementary to conserved regions of aac(6')-Ic, -Id, -If, -Ig, and -Ih enabled detection of these genes and also of aac(6')-Ij, recently recognized in Acinetobacter sp. strain 13.