Epidemiology, clinical, phenotypic and genotypic characteristics of multidrug-resistant Acinetobacter baumannii from...

In healthcare, multidrug-resistant (MDR) Acinetobacter baumannii is associated with significant morbidity, mortality and limited treatment options. This study evaluates the epidemiology, clinical, phenotypic, and genotypic characteristics of MDR Acinetobacter baumannii from Qatar.

We conducted a prospective study from 2017 to 2020 of all clinical Acinetobacter baumannii isolates subjected to phenotypic testing. We performed identification and antimicrobial susceptibility testing using MALDI-TOF MS (Billerica, MA, USA) and BD PhoenixTM (BD Diagnostics, Durham, NC, USA), as well as the E test (Liofilchem®, Roseto degli Abruzzi, Italy). We performed whole-genome sequencing and bioinformatics analyses on bacterial isolates.

Out of 536 Acinetobacter baumannii isolates, 62 (11.6%) were MDR, with a decreasing trend. Isolation sites were urinary (42%), respiratory (29%), bloodstream (16%), and skin and soft tissues (13%). Hospital acquisition was recorded in 97% of cases, isolated from older patients with multiple comorbidities and prior antimicrobial exposure, leading to a 30-day mortality of 16%. Phenotypic evaluation revealed extensive antimicrobial resistance to meropenem, ampicillin-sulbactam, ceftazidime-avibactam, ceftolozane-tazobactam, meropenem-vaborbactam and imipenem- relebactam, while the most active agents were tigecycline and cefiderocol. Genomic analysis of 39 isolates revealed predominance of sequence type 2 (n = 27). All resistant Acinetobacter isolates carried AmpC beta-lactamases and the blaOXAAb, (blaOXA-51-like family) family of carbapenem resistance genes. The predominant carbapenemases were blaOXA-23, while 7 isolates carried blaNDM-₁.

Multidrug-resistant A. baumannii was infrequently isolated, predominantly ST2, mainly from elderly patients with multiple risk factors. Extensive resistance profiles limit treatment options, with promising in vitro results for tigecycline and cefiderocol.