Aim: Aminoglycoside resistance is common in Acinetobacter baumannii. We investigated aminoglycoside resistance genes in clinical multidrug-resistant Acinetobacter baumannii strains isolated from the Chinese population.
Methods: One-hundred-and-seven strains of multidrug-resistant Acinetobacter baumannii were isolated from Ruijin Hospital in Shanghai, China. The minimum inhibitory concentrations (MICs) of amikacin, kanamycin, tobramycin, gentamicin, netilmicin and neomycin for these strains were determined with agar dilution method. 16S rRNA methylase genes and eight aminoglycoside modifying enzyme genes were tested via polymerase chain reaction.
Results: We found MICs of amikacin, kanamycin, tobramycin, gentamicin, netilmicin and neomycin in these strains with doses of ≥64 μg/mL, ≥64 μg/mL, ≥128 μg/mL, ≥128 μg/mL, ≥32 μg/mL and ≥8 μg/mL, respectively. Most of those strains showed a high-level resistance to aminoglycosides. ArmA was found in 90% (97/107) of the strains. Six modifying enzyme genes, including aac(6')-Ib, aac(6')-II, aac(3)-II, aac(3)-I, aph(3')-I and ant(3")-I were found with a positive rate of 47%, 50%, 28%, 31%, 93% and 96%, respectively.
Conclusion: Multidrug-resistant Acinetobacter baumannii is highly resistant to aminoglycosides. Resistant genes could coexist in one strain, therefore, strict implementation of infection control measures is essential to avoid the rapid spread or outbreaks of these multidrug-resistant Acinetobacter baumannii in healthcare-associated facilities.