Susceptibility of the Acinetobacter calcoaceticus–A. baumannii complex to imipenem, meropenem, sulbactam and colistin

Abstract The Acinetobacter calcoaceticus – Acinetobacter baumannii complex includes some of the most clinically relevant species of the genus Acinetobacter due to their capacity to cause epidemic nosocomial outbreaks as well as their increasing resistance to antibiotics. Susceptibility of Acinetobacter strains varies greatly depending on origin, thus highlighting the importance of local analyses of susceptibility profiles. Two hundred twenty-one strains of the A. calcoaceticus – A. baumannii complex were identified using biochemical tests and were biotyped. Strain susceptibility to imipenem, meropenem, colistin and sulbactam was studied using agar dilution. Eight different biotypes were found, type 1 accounting for 69.2% of the strains. MIC 50 and MIC 90 to imipenem, meropenem, colistin and sulbactam were 4 and 8 mg/l, 16 and 32 mg/l, 0.5 and 1 mg/l, and 8 and 16 mg/l, with susceptibility rates of 64.3, 22.6, 98.2 and 73.8%, respectively. Biotype 1 was the most resistant. A statistically significant difference was observed for the mean MIC of the four predominant biotypes to imipenem, meropenem and sulbactam but not to colistin.