Multidrug-Resistant Gram-Negative Bacteria: Inter- and Intradissemination Among Nursing Homes of Residents With Advanced Dementia.

OBJECTIVE: To quantify the extent of inter- and intra-nursing home transmission of multidrug-resistant gram-negative bacteria (MDRGN) among residents with advanced dementia and characterize MDRGN colonization among these residents.

DESIGN: Prospective cohort study.

SETTING: Twenty-two nursing homes in the greater Boston, Massachusetts, area.

PATIENTS: Residents with advanced dementia.

METHODS: Serial rectal surveillance cultures for MDRGN and resident characteristics were obtained every 3 months for 12 months or until death. Molecular typing of MDRGN isolates was performed by pulsed-field gel electrophoresis.

RESULTS: A total of 190 MDRGN isolates from 152 residents with advanced dementia were included in the analyses. Both intra- and inter-nursing home transmission were identified. Genetically related MDRGN strains, recovered from different residents, were detected in 18 (82%) of the 22 nursing homes. The percent of clonally related strains in these nursing homes ranged from 0% to 86% (average, 35%). More than 50% of strains were clonally related in 3 nursing homes. Co-colonization with more than 1 different MDRGN species occurred among 28 residents (18.4%). A total of 168 (88.4%), 20 (10.5%), and 2 (1.0%) of MDRGN isolates were resistant to 3, 4, and 5 different antimicrobials or antimicrobial classes, respectively.

CONCLUSIONS: MDRGN are spread both within and between nursing homes among residents with advanced dementia. Infection control interventions should begin to target this high-risk group of nursing home residents.