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J Antimicrob Chemother. 2019 Jul 1;74(7):1825-1835. doi: 10.1093/jac/dkz147.

Spanish nationwide survey on Pseudomonas aeruginosa antimicrobial resistance mechanisms and epidemiology.

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Servicio de Microbiología, Hospital Son Espases, Instituto de Investigación Sanitaria Illes Balears (IdISBa), Palma de Mallorca, España.
Servicio de Microbiología, Hospital Universitario La Coruña, Instituto Investigación Biomédica A Coruña (INIBIC), La Coruña, España.
Unidad de Gestión Clínica de Microbiología, Hospital Reina Sofía, Departamento de Microbiología, Universidad de Córdoba, Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Córdoba, España.



To undertake a Spanish nationwide survey on Pseudomonas aeruginosa molecular epidemiology and antimicrobial resistance.


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.


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.


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.


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