del Barrio-Tofiño, EsterZamorano, LauraCortés-Lara, SaraLópez-Causapé, CarlaSánchez-Diener, IrinaCabot, GabrielBou, GermánMartínez-Martínez, LuisOliver, Antonio2025-09-122025-09-122019-04-15Del Barrio-Tofiño E, Zamorano L, Cortes-Lara S, López-Causapé C, Sánchez-Diener I, Cabot G, Bou G, Martínez-Martínez L, Oliver A; GEMARA-SEIMC/REIPI Pseudomonas study Group. Spanish nationwide survey on Pseudomonas aeruginosa antimicrobial resistance mechanisms and epidemiology. J Antimicrob Chemother. 2019 Jul 1;74(7):1825-1835.0305-7453https://hdl.handle.net/2183/45745[Abstract] Objectives: To undertake a Spanish nationwide survey on Pseudomonas aeruginosa molecular epidemiology and antimicrobial resistance. Methods: Up to 30 consecutive healthcare-associated P. aeruginosa isolates collected in 2017 from each of 51 hospitals were studied. MICs of 13 antipseudomonal agents were determined by broth microdilution. Horizontally acquired β-lactamases were detected by phenotypic methods and PCR. Clonal epidemiology was evaluated through PFGE and MLST; at least one XDR isolate from each clone and hospital (n = 185) was sequenced. Results: The most active antipseudomonals against the 1445 isolates studied were colistin and ceftolozane/tazobactam (both 94.6% susceptible, MIC50/90 = 1/2 mg/L) followed by ceftazidime/avibactam (94.2% susceptible, MIC50/90 = 2/8 mg/L). Up to 252 (17.3%) of the isolates were XDR. Carbapenemases/ESBLs were detected in 3.1% of the isolates, including VIM, IMP, GES, PER and OXA enzymes. The most frequent clone among the XDR isolates was ST175 (40.9%), followed by CC235 (10.7%), ST308 (5.2%) and CC111 (4.0%). Carbapenemase production varied geographically and involved diverse clones, including 16.5% of ST175 XDR isolates. Additionally, 56% of the sequenced XDR isolates showed horizontally acquired aminoglycoside-modifying enzymes, which correlated with tobramycin resistance. Two XDR isolates produced QnrVC1, but fluoroquinolone resistance was mostly caused by QRDR mutations. Beyond frequent mutations (>60%) in OprD and AmpC regulators, four isolates showed AmpC mutations associated with resistance to ceftolozane/tazobactam and ceftazidime/avibactam. Conclusions: ST175 is the most frequent XDR high-risk clone in Spanish hospitals, but this nationwide survey also indicates a complex scenario in which major differences in local epidemiology, including carbapenemase production, need to be acknowledged in order to guide antimicrobial therapy.engAnti-bacterial agentsDrug resistance, bacterialGenotypePseudonomas infectionsPseudonomas aeruginosajournal articleopen access10.1093/jac/dkz147