Co-colonization with multiple different species of multidrug-resistant gram-negative bacteria

Background: The characteristics of co-colonization with multiple different species of multidrug-resistant gram-negative bacteria (MDRGN) have not been fully elucidated. Quantifying the prevalence of co-colonization and those patients at higher risk of co-colonization may have important implications for strategies aimed at limiting the spread of MDRGN. Methods: To determine the prevalence of MDRGN colonization, rectal swabs were obtained from 212 residents residing in a 600-bed long-term care facility. Co-colonization was defined as colonization with >= 2 different MDRGN species. Co-colonized residents were compared with residents colonized with a single MDRGN species to identify factors associated with an increased risk for co-colonization. Molecular typing was performed to determine the contribution of cross transmission to the co-colonized state. Results: A total of 53 (25%) residents was colonized with >= 1 MDRGN. Among these, 11 (21%) were colonized with >= 2 different species of MDRGN. A global deterioration score of >= 5 representing advanced dementia and an increased requirement for assistance from health care workers was significantly associated with co-colonization (P = .05). Clonally related MDRGN strains were identified among 7 (64%) co-colonized residents. Conclusion: The prevalence of co-colonization with >= 2 different MDRGN is substantial. Cross transmission of MDRGN is a major contributor to the co-colonized state.