Analysis of a long-term outbreak of XDR Pseudomonas aeruginosa: a molecular epidemiological study

Willmann, Matthias; Bezdan, Daniela; Zapata Ortiz, Luis, 1985-; Sušak, Hana, 1985-; Vogel, Wichard; Schröppel, Klaus; Liese, Jan; Weidenmaier, Christopher; Autenrieth, Ingo B.; Ossowski, Stephan; Peter, Silke

doi:http://dx.doi.org/10.1093/jac/dku546

Analysis of a long-term outbreak of XDR Pseudomonas aeruginosa: a molecular epidemiological study

Citation

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):1322-30. DOI: 10.1093/jac/dku546

Abstract

OBJECTIVES: 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.