Willmann, MatthiasBezdan, DanielaZapata Ortiz, Luis, 1985-Sušak, Hana, 1985-Vogel, WichardSchröppel, KlausLiese, JanWeidenmaier, ChristopherAutenrieth, Ingo B.Ossowski, StephanPeter, Silke2016-07-222016-07-222015Willmann M, Bezdan D, Zapata L, Susak H, Vogel W, Schröppel K et al. Analysis of a long-term outbreak of XDR Pseudomonas aeruginosa: a molecular epidemiological study. Journal of antimicrobial chemotherapy. 2015;70(5):1322-30. DOI: 10.1093/jac/dku5460305-7453http://hdl.handle.net/10230/27110OBJECTIVES: Here we report on a long-term outbreak from 2009 to 2012 with an XDR Pseudomonas aeruginosa on two wards at a university hospital in southern Germany. METHODS: Whole-genome sequencing was performed on the outbreak isolates and a core genome was constructed for molecular epidemiological analysis. We applied a time-place-sequence algorithm to improve estimation of transmission probabilities. RESULTS: By using conventional infection control methods we identified 49 P. aeruginosa strains, including eight environmental isolates that belonged to ST308 (by MLST) and carried the metallo-β-lactamase IMP-8. Phylogenetic analysis on the basis of a non-recombinant core genome that contained 22 outbreak-specific SNPs revealed a pattern of four dominant clades with a strong phylogeographic structure and allowed us to determine the potential temporal origin of the outbreak to July 2008, 1 year before the index case was diagnosed. Superspreaders at the root of clades exhibited a high number of probable and predicted transmissions, indicating their exceptional position in the outbreak. CONCLUSIONS: Our results suggest that the initial expansion of dominant sublineages was driven by a few superspreaders, while environmental contamination seemed to sustain the outbreak for a long period despite regular environmental control measures.application/pdfeng© Oxford University Press. This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Journal of antimicrobial chemotherapy following peer review. The definitive publisher-authenticated version Willmann M, Bezdan D, Zapata L, Susak H, Vogel W, Schröppel K et al. Analysis of a long-term outbreak of XDR Pseudomonas aeruginosa: a molecular epidemiological study. Journal of antimicrobial chemotherapy. 2015; 70(5): 1322-1330. DOI 10.1093/jac/dku546 is available online at: http://jac.oxfordjournals.org/content/70/5/1322.longBacterisEpidemiologiainfo:eu-repo/semantics/articlehttp://dx.doi.org/10.1093/jac/dku546IMP carbapenemaseOutbreak investigationTransmission analysisWhole-genome sequencinginfo:eu-repo/semantics/openAccess