In Vitro Activity of Sulbactam-Durlobactam against Carbapenem-Resistant Acinetobacter baumannii Clinical Isolates: A Multicentre Report from Italy.

In the present study, the in vitro activity of the sulbactam-durlobactam (SUL-DUR) combination was evaluated against 141 carbapenem-resistant A. baumannii (CR Ab ) clinical strains collected from six Italian laboratories. Over half (54.6%) of these isolates were resistant to colistin. The SUL-DUR combination was active against these CR Ab isolates with MIC 50 and MIC 90 values of 0.5 mg/L and 4 mg/L, respectively. Only eleven isolates were resistant to SUL-DUR with MIC values ranging from 8 to 128 mg/L. The SUL-DUR resistant A. baumannii exhibited several antimicrobial resistance genes (ARGs) such as bla OXA-20 , bla OXA-58 , bla OXA-66 , bla ADC-25 , aac(6')-Ib3 and aac(6')-Ib-cr and mutations in gyr A (S81L) and par C (V104I, D105E). However, in these isolates, mutations Q488K and Y528H were found in PBP3. Different determinants were also identified in these CR Ab isolates, including adeABC , adeFGH , adeIJK , abeS , abaQ and abaR , which encode multidrug efflux pumps associated with resistance to multiple antibacterial agents. This is the first report on the antimicrobial activity of SUL-DUR against carbapenem-resistant A. baumannii isolates selected from multiple regions in Italy.