doi:10.1093/jac/dkz346engDel Barrio-Tofiño, EsterSánchez-Diener, IrinaZamorano, LauraCortes-Lara, SaraLópez-Causapé, CarlaCabot, GabrielBou, GermánMartínez-Martínez, LuisOliver, Antonioon behalf of the GEMARA-SEIMC/REIPI Pseudomonas study groupCastillo-García, Francisco JavierSeral, CristinaAssociation between Pseudomonas aeruginosa O-antigen serotypes, resistance profiles and high-risk clones: results from a Spanish nationwide surveyART-2019-115376Objectives: To evaluate the correlation of O-antigen serotypes with resistance profiles and high-risk clones in a Spanish nationwide survey. Methods: Up to 30 consecutive healthcare-associated Pseudomonas aeruginosa isolates were collected during October 2017 from each of 51 hospitals (covering all Spanish regions) with a total of 1445 isolates studied. MICs of 13 antipseudomonal agents and MDR/XDR profiles had been previously determined, as well as whole-genome sequences of 185 representative XDR isolates. O-antigen serotypes (O1–O16) were determined by agglutination using serotype-specific antisera (BioRad). The Pseudomonas aeruginosa serotyper (PAst) program was used for in silico serotyping. Results: The most frequent serotypes were O6 (17.8%), O1 (15.4%) and O11 (13.3%). In contrast, the most frequent serotype among XDR isolates (17.3%) was O4 (34.1%), distantly followed by O11 (15.9%). Within serotypes, XDR phenotypes were more frequent for O12 (60.0%) and O4 (57.3%). The most frequent clone among the XDR isolates was ST175 (40.9%), followed by CC235 (10.7%), ST308 (5.2%) and CC111 (3.6%). Up to 81.6%of XDR ST175 isolates typed O4, whereas 18.4% were non-typeable. O4 genotype was detected in all sequenced (n=55) ST175 isolates. On the other hand, CC235 and ST308 were associated with O11, whereas CC111 was linked to serotype O12. Conclusions: O4 serotype is linked to the MDR/XDR profile of widespread ST175 (typically only susceptible to colistin, amikacin and the novel combinations ceftolozane/tazobactam and ceftazidime/avibactam) and therefore, after local validation, its detection in the microbiology laboratory might be useful for guiding semi-empirical antipseudomonal therapies and infection control measures in Spanish hospitals.2019http://zaguan.unizar.es/record/9503510.1093/jac/dkz346http://zaguan.unizar.es/record/95035oai:zaguan.unizar.es:95035info:eu-repo/grantAgreement/ES/ISCIII/PI15-00088info:eu-repo/grantAgreement/ES/ISCIII/PI18-00076info:eu-repo/grantAgreement/ES/MINECO-FEDER/ISCIII-REIPI-RD16-0016The Journal of antimicrobial chemotherapy 74, 11 (2019), 3217-3220All rights reservedhttp://www.europeana.eu/rights/rr-f/info:eu-repo/semantics/openAccess