β-lactamase-mediated resistance in MDR-Pseudomonas aeruginosa from Qatar

Abstract

Background: The distribution of b-lactam resistance genes in P. aeruginosa is often closely related to the distribution of certain high-risk international clones. We used whole-genome sequencing (WGS) to identify the predominant sequence types (ST) and b-lactamase genes in clinical isolates of multidrug-resistant (MDR)-P. aeruginosa from Qatar

Methods: Microbiological identification and susceptibility tests were performed by automated BD PhoenixTM system and manual Liofilchem MIC Test Strips.

Results: Among 75 MDR-P. aeruginosa isolates; the largest proportions of susceptibility were to ceftazidime-avibactam (n=36, 48%), followed by ceftolozane-tazobactam (30, 40%), ceftazidime (n=21, 28%) and aztreonam (n=16, 21.3%). All isolates possessed Class C and/or Class D b-lactamases (n=72, 96% each), while metallo-β-lactamases were detected in 20 (26.7%) isolates. Eight (40%) metallo-β-lactamases producers were susceptible to aztreonam and did not produce any concomitant extended-spectrum b-lactamases. High risk ST235 (n=16, 21.3%), ST357 (n=8, 10.7%), ST389 and ST1284 (6, 8% each) were most frequent. Nearly all ST235 isolates (15/16; 93.8%) were resistant to all tested b-lactams.

Conclusion: MDR-P. aeruginosa isolates from Qatar are highly resistant to antipseudomonal b-lactams. High-risk STs are predominant in Qatar and their associated MDR phenotypes are a cause for considerable concern.