Colonization with antibiotic-susceptible strains protects against methicillin-resistant Staphylococcus aureus but not vancomycin-resistant enterococci acquisition: a nested case-control study
Authors
Huang, Susan S.Datta, Rupak
Rifas-Shiman, Sheryl L.
Kleinman, Ken P.
Placzek, Hilary
Lankiewicz, Julie
Platt, Richard
Student Authors
Hilary PlaczekAcademic Program
Clinical and Population Health ResearchDocument Type
Journal ArticlePublication Date
2011-09-14Keywords
EnterococcusMethicillin Resistance
Staphylococcal Infections
Staphylococcus aureus
Vancomycin Resistance
Bacterial Infections and Mycoses
Immunology and Infectious Disease
Metadata
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INTRODUCTION: Harboring sensitive strains may prevent acquisition of resistant pathogens by competing for colonization of ecological niches. Competition may be relevant to decolonization strategies that eliminate sensitive strains and may predispose to acquiring resistant strains in high-endemic settings. We evaluated the impact of colonization with methicillin-sensitive Staphylococcus aureus (MSSA) and vancomycin-sensitive enterococci (VSE) on acquisition of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE), respectively, when controlling for other risk factors. METHODS: We conducted a nested case-control study of patients admitted to eight ICUs performing admission and weekly bilateral nares and rectal screening for MRSA and VRE, respectively. Analyses were identical for both pathogens. For MRSA, patients were identified who had a negative nares screen and no prior history of MRSA. We evaluated predictors of MRSA acquisition, defined as a subsequent MRSA-positive clinical or screening culture, compared to those with a subsequent MRSA-negative nares screen within the same hospitalization. Medical records were reviewed for the presence of MSSA on the initial MRSA-negative nares screen, demographic and comorbidity information, medical devices, procedures, antibiotic utilization, and daily exposure to MRSA-positive patients in the same ward. Generalized linear mixed models were used to assess predictors of acquisition. RESULTS: In multivariate models, MSSA carriage protected against subsequent MRSA acquisition (OR = 0.52, CI: 0.29, 0.95), even when controlling for other risk factors. MRSA predictors included intubation (OR = 4.65, CI: 1.77, 12.26), fluoroquinolone exposure (OR = 1.91, CI: 1.20, 3.04), and increased time from ICU admission to initial negative swab (OR = 15.59, CI: 8.40, 28.94). In contrast, VSE carriage did not protect against VRE acquisition (OR = 1.37, CI: 0.54, 3.48), whereas hemodialysis (OR = 2.60, CI: 1.19, 5.70), low albumin (OR = 2.07, CI: 1.12, 3.83), fluoroquinolones (OR = 1.90, CI: 1.14, 3.17), third-generation cephalosporins (OR = 1.89, CI: 1.15, 3.10), and increased time from ICU admission to initial negative swab (OR = 15.13, CI: 7.86, 29.14) were predictive. CONCLUSIONS: MSSA carriage reduced the odds of MRSA acquisition by 50% in ICUs. In contrast, VSE colonization was not protective against VRE acquisition. Studies are needed to evaluate whether decolonization of MSSA ICU carriers increases the risk of acquiring MRSA when discharging patients to high-endemic MRSA healthcare settings. This may be particularly important for populations in whom MRSA infection may be more frequent and severe than MSSA infections, such as ICU patients.Source
Crit Care. 2011 Sep 14;15(5):R210. Link to article on publisher's site 2011 Huang et al.; licensee BioMed Central Ltd.DOI
10.1186/cc10445Permanent Link to this Item
http://hdl.handle.net/20.500.14038/39460PubMed ID
21914221; 21914221Related Resources
Link to Article in PubMedRights
© 2011 Huang et al.; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.ae974a485f413a2113503eed53cd6c53
10.1186/cc10445