
Background: As use of nasal and body decolonization increases, there are periodic reports of mupirocin resistance and CHG non-susceptibility. A large multi-state sample of MRSA and GNR isolates was tested to assess the frequency of non-susceptibility to these agents.
Methods: We studied MRSA and select GNR isolates identified in routine clinical cultures from non-critically ill patients on study units in 53 community hospitals served by 41 laboratories in 15 states. Isolate were collected from March - November 2013, during the baseline period of a large multicenter trial of decolonization in participating HCA-affiliated hospitals. Mupirocin susceptibility was determined by Etest. Low-level mupirocin resistance (LLMR) was defined as a minimum inhibitory concentration (MIC) of mupirocin between 8-64 µg/ml and high-level mupirocin resistance (HLMR) as MIC >256 µg/ml. CHG susceptibility was determined by microtiter dilution. An epidemiologic cut-off approach was used to estimate non-susceptibility to CHG, based on published data and observed results. Breakpoints for CHG non-susceptibility were species-specific: MIC >4 µg/ml for MRSA and Escherichia coli; >16 µg/ml for Serratia marcescens; >32 µg/ml for Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Acinetobacter baumannii; >64 µg/ml for Klebsiella spp.; and >256 µg/ml for Proteus mirabilis.
Results: 4263 isolates (2120 MRSA and 2143 GNR) were collected (facility range 15 - 161). Common GNR isolates were E. coli (48%), Klebsiella pneumoniae (19%), P. aeruginosa (16%), and P. mirabilis (9%).
Six percent (95% CI, 5-7%) of MRSA expressed LLMR and 11% (95% CI, 10-13%) expressed HLMR. Highest percentage LLMR was found in the Midwest (9%) and lowest percentage in the West (3%). Highest percentage HLMR was found in the Southeast (14%) and lowest percentage in the West (7%). CHG non-susceptibility was found in 0% of MRSA and 2.7% (95% CI, 2.0-3.3%) of GNR: 17 (2%) E. coli, 6 (1%) Klebsiella spp, 17 (35%) S. marcescens, 13 (4%) P. aeruginosa and 5 (14%) S. maltophilia (Figure).
Conclusion: Mupirocin resistance in this cohort of community hospitals varied across U.S. regions, with HLMR resistance exceeding 10% in some areas. CHG non-susceptibility was negligible in MRSA and uncommon in most GNR species.

K. Haffenreffer,
Sage Inc.:
Investigative Team Member
,
Contributed product for ABATE Study
Molnlycke:
Investigative Team Member
,
Contributed product for ABATE Study
Molnlycke: Investigative Team Member , Contributed product for ABATE Study
T. Avery, Sage Inc.: Investigative Team Member , Contributed product for ABATE Study
Molnlycke: Investigative Team Member , Contributed product for ABATE Study
R. E. Kaganov, Sage Inc.: Investigative Team Member , Contributed product for ABATE Study
Molnlycke: Investigative Team Member , Contributed product for ABATE Study
L. Shimelman, Sage Inc.: Investigative Team Member , Contributed product for ABATE Study
Molnlycke: Investigative Team Member , Contributed product for ABATE Study
M. V. Murphy, Sage Inc.: Investigative Team Member , Contributed product for ABATE Study
Molnlycke: Investigative Team Member , Contributed product for ABATE Study
J. Moody, Sage Inc.: Investigator , Contributed product for ABATE Study
Molnlycke: Investigator , Contributed product for ABATE Study
C. Bushe, Sage Inc.: Investigator , Contributed product for ABATE Study
Molnlycke: Investigator , Contributed product for ABATE Study
E. Septimus, Sage Inc.: Investigator , Contributed product for ABATE Study
Molnlycke: Investigator , Contributed product for ABATE Study
R. A. Weinstein, Sage Inc.: Investigator , Contributed product for ABATE Study
Molnlycke: Investigator , Contributed product for ABATE Study
J. Hickok, Sage Inc.: Investigator , Contributed product for ABATE Study
Molnlycke: Investigator , Contributed product for ABATE Study
J. Perlin, Sage Inc.: Investigator , Contributed product for ABATE Study
Molnlycke: Investigator , Contributed product for ABATE Study
S. S. Huang, Sage Inc.: Investigator , Contributed product for ABATE Study
Molnlycke: Investigator , Contributed product for ABATE Study
3M: Investigator , Conducting studies in which participating healthcare facilities are receiving product from 3M.
M. K. Hayden, Sage Products, Inc.: Sage provided CHG product at no cost to a study on which I was PI, and on another study on which I am CoI. , Sage provided CHG product at no cost to a study on which I was PI, and on another study on which I am CoI.
Molnlycke: Molnlycke provided CHG product at no charge to facilities participating in a research project on which I am a co-investigator. , Molnlycke provided CHG product at no charge to facilities participating in a research project on which I am a co-investigator.