Clustering of Antimicrobial Resistance Outbreaks Across Bacterial Species in the Intensive Care Unit
Clinical Infectious Diseases July 1, 2013 V.57 N.1 P.65-76
Anne L. M. Vlek, Ben S. Cooper, Theodore Kypraios, Andy Cox, Jonathan D. Edgeworth, and Olga Tosas Auguet
1Centre for Clinical Infection and Diagnostics Research, Department of Infectious Diseases, King’s College London and Guy’s and St Thomas’ NHS Foundation Trust, London, United Kingdom
2Medical Microbiology, University Medical Centre Utrecht, the Netherlands
3Centre for Clinical Vaccinology and Tropical Medicine, Nuffield Department of Clinical Medicine, University of Oxford, United Kingdom
4Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
5School of Mathematical Sciences, University of Nottingham
6Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom
here are frequent reports of intensive care unit (ICU) outbreaks due to transmission of particular antibiotic-resistant bacteria. Less is known about the burden of outbreaks of resistance due to horizontal transfer of mobile genetic elements between species. Moreover, the potential of existing statistical software as a preliminary means for detecting such events has never been assessed. This study uses a software package to determine the burden of species and resistance outbreaks in 2 adjacent ICUs and to look for evidence of clustering of resistance outbreaks consistent with interspecies transmission of resistance elements.
A retrospective analysis of data from 2 adjacent 15-bed adult ICUs between 2002 and 2009 was undertaken. Detection of bacterial species-groups and resistance outbreaks was conducted using SaTScan and WHONet-SaTScan software. Resampling and permutation methods were applied to investigate temporal clustering of outbreaks.
Outbreaks occurred for 69% of bacterial species-groups (18/26), and resistance outbreaks were detected against 63% of antibiotics (10/16). Resistance outbreaks against 7 of 10 antibiotics were observed in multiple species-groups simultaneously and there was evidence of inter–species-group dependence for 4 of 7 antibiotics; background temporal changes in resistance did not explain the temporal aggregation of outbreaks in 3 of 7 antibiotics.
Species outbreaks occurred for the majority of bacteria commonly identified in the ICU. There was evidence for frequent temporal clustering of resistance outbreaks consistent with interspecies transmission of resistance elements. Wider application of outbreak detection software combined with targeted sequencing of bacterial genomes is needed to understand the contribution of interspecies gene transfer to resistance emergence. Outbreaks of bacterial species occur for the majority of bacteria commonly identified in the intensive care unit. This study provides evidence for frequent temporal clustering of resistance outbreaks consistent with interspecies transmission of resistance elements.